Synthesis and Color Durability of Silver Nanoparticles Immobilized on Silica Particles
K. Araki; N. Yamauchi; S. Tada; Y. Kobayashi, 責任著者
Journal of Cluster Science, 2024年01月, ［査読有り］
Biosorption of Au from Leachates of Waste Printed Circuit Boards by Baker's Yeast
S. Suzuki; H. Iijima; Y. Kobayashi; Y. Yamamoto; H. Shiigi; N. Saitoh; Y. Konishi
Hydrometallurgy, 2024年01月, ［査読有り］
Synthesis of Gold Nanoparticle-Immobilized Biodegradable Polymer Nanoparticles and Their Degradation Properties
K. Akino; A. Takahashi; N. Yamauchi; S. Tada; T. Takase; M. Kimura; S. Nakao; K. Gonda; Y. Kobayashi, 責任著者
Chemical Papers, 2024年01月, ［査読有り］
Low-Temperature CO2 Methanation over Ru Nanoparticles Supported on Monoclinic Zirconia
S. Tada; T. Jinushizono; K. Ishikawa; S. Miyazaki; T. Toyao; K. Shimizu; M. Nishijima; N. Yamauchi; Y. Kobayashi; Ryuji Kikuchi
Energy & Fuels, 2024年01月, ［査読有り］
Fabrication of Glucose-Immobilizing Fluorescent Polymer Particles with High Magnetic ResponsivenessN. Yamauchi; Y. Noshiro; S. Tada; K. Sato; M. Ogata; Y. Kobayashi, Glycan-immobilizing particles are useful for a wide variety of biomedical applications, such as the detection, separation, and purification of proteins, viruses, and bacteria, which can be specifically bound by the glycan moieties. One strategy for the quick and accurate detection of these components is to collect the particles magnetically after binding the components to the particle surface. We fabricated core-shell particles composed of a magnetic core and a thin polymer shell. The shell was incorporated with a fluorescent dye with glucose molecules immobilized on its surface. As the magnetic core, we selected Fe3O4 particles. Taking into consideration its low environmental impact, we adopted soap-free emulsion polymerization to form the polymer shell. Thus, methyl methacrylate was polymerized in the presence of Fe3O4 particles, octyl-beta-d-glucopyranoside, and rhodamine B to generate a glucose-capped fluorescent PMMA thin shell on the Fe3O4 particles. The resulting particles exhibited a saturation magnetization of similar to 53 emu/g. The novelty of this research is that glucose-immobilized polymer particles with excellent magnetic properties that can be collected in 5 s using a magnet can be synthesized with an environmentally friendly method., TAYLOR & FRANCIS INC
Particulate Science and Technology, 2024年01月,
［査読有り］ Controlled Oxidation of Metallic Copper Nanoparticles by a Silica Coating
H. Hayashida; N. Yamauchi; K. Nakashima; Y. Kobayashi
Inorganic and Nano-Metal Chemistry, 2024年01月, ［査読有り］
Atomic arrangement analysis and crystal growth mechanism of HAp nanocrystal synthesized from amorphous calcium phosphateKouichi Nakashima; Sakino Misawa; Yoshio Kobayashi; Toru Ishigaki; Yoshihisa Ishikawa; Shu Yin; Masato Kakihana; Tomoyo Goto; Tohru Sekino, The crystal growth of hydroxyapatite (HAp) using a solvothermal method was investigated under various reaction conditions. The purpose of the present study is the synthesis of HAp nanocrystals with multiple facets and the atomic arrangement for various orientations of the crystal was clarified. HAp nanorods were obtained at 200°C after 24 h using a reaction medium of water. The atomic arrangement in HAp nanorods was examined for a characteristic facet in the direction of [21−13−] and [0110−] incidences and crystal orientation along the c-axis of HAp nanorod was confirmed using electron microscopy. The present study clarifies the HAp crystal growth mechanism, where the adsorption of cations or anions onto the crystal facet determines the HAp crystal shape. The crystals of HAp grew along the c-axis and became rod-shaped suggesting that cations were adsorbed predominantly over anions.
Journal of the American Ceramic Society, 2023年
Development of Gold-Coated Magnetic Nanoparticles as a Theranostic Agent for Magnetic Hyperthermia and CT Imaging Applications
L. Tonthat; M. Kimura; T. Ogawa; N. Kitamura; Y. Kobayashi; K. Gonda; S. Yabukami
AIP Advances, 2023年01月, ［査読有り］
Synthesis and Sintering Properties of Silica-Coated Titanium Nitride Particles
S. Kobayashi; N. Yamauchi; S. Tada; Y. Kobayashi, 責任著者
Advanced Powder Technology, 2023年01月, ［査読有り］
Synthesis of Metallic Titanium Nanoparticles with a Combination of Ultrasonication and Flowing of Electric Current
S. Sato; T. Yonezawa; N. Yamauchi; S. Tada; Y. Kobayashi, 責任著者
Nano-Structures & Nano-Objects, 2023年01月, ［査読有り］
X-ray Irradiation Negatively Affects Immune Responses in the Lymphatic Network
S. Kanabuchi; N. Kitamura; M. Takano-Kasuya; T. Inosea; C. Nishidate; M. Yamanashia; M. Kudo; T. Ito; N. Ito; H. Okamoto; Y. Taniyama; Y. Kobayashi; T. Kamei; K. Gonda
Microvascular Research, 2023年01月, ［査読有り］
Silica-Coating of Ca14Al10Zn6O35:Mn4+ Particles and Their Luminescence Properties
M. Ito; N. Yamauchi; K. Nakashima; H. Okura; Y. Kobayashi, 責任著者
Advanced Powder Technology, 2023年01月, ［査読有り］
Synthesis of Au Nanoparticles Coated with Silica Containing Polyethylene Glycol for Extracorporeally Dischargeable X-Ray Contrast Agents
T. Sakamoto; N. Yamauchi; S. Tada; T. Takase; M. Kimura; C. Nishidate; K. Gonda; Y. Kobayashi, 責任著者
Journal of Nanoparticle Research, 2023年01月, ［査読有り］
Influence of Si/Al Ratio of MOR Type Zeolites for Bifunctional Catalysts Specific to the One-Pass Synthesis of Lower Olefins via CO2 Hydrogenation
S. Tada; D. Li; M. Okazaki; H. Kinoshita; M. Nishijima; N. Yamauchi; Y. Kobayashi; K. Iyoki
Catalysis Today, 2023年01月, ［査読有り］
Precise Tuning of the Properties of MOR-Type Zeolite Nanoparticles to Improve Lower Olefins Selectivity in Composite Catalysts for CO2 Hydrogenation
R. Oishi; D. Li; M. Okazaki; H. Kinoshita; N. Ochiai; N. Yamauchi; Y. Kobayashi; T. Wakihara; T. Okubo; S. Tada; Kenta Iyoki
Journal of CO2 Utilization, 2023年01月, ［査読有り］
Oxidation Control of Metallic Zinc Nanoparticles by Silica Coating
S. Furukawa; N. Yamauchi; K. Nakashima; K. Watanabe; H. Koda; H. Kunigami; H. Kunigami; Y. Kobayashi, 責任著者
Materials Research Innovations, 2023年01月, ［査読有り］
Development of a ZrO2-Coating Technique by a Sol–Gel Process Assisted with Pre-Silica-Coating
A. Miwano; T. Yonezawa; N. Yamauchi; K. Nakashima; Y. Kobayashi, 責任著者
Processes, 2022年01月, ［査読有り］
Fabrication of Metallic Copper Nanoparticles by Utilizing a Difference in Standard Electrode Potential
Y. Suga; N. Yamauchi; K. Nakashima; Y. Kobayashi
Chemical Papers, 2022年01月, ［査読有り］
Fabrication of a Sugar-Immobilized Fluorescent PMMA Shell on a Ni Core Particle via Soap-Free Emulsion Polymerization
N. Yamauchi; K. Yakushiji; A. Tago; R. Saito; Y. Sogame; M. Ogata; Y. Kobayashi
Colloid and Polymer Science, 2022年01月, ［査読有り］
Silica-Coating of Quantum Dots by Using Water Glass and Their Photo-Bleaching Properties
A. Tokumashu; T. Inise; N. Yamauchi; C. Kato; K. Gonda; Y. Kobayashi
International Journal of Materials Science and Engineering, 2022年01月, ［査読有り］
Active sites on ZnxZr1−xO2−x solid solution catalysts for CO2-to-methanol hydrogenation
Tada; Shohei; Ochiai; Nagomu; Kinoshita; Hiroka; Yoshida; Mitsuhiro; Shimada; Natsumi; Joutsuka; Tatsuya; Nishijima; Masahiko; Honma; Tetsuo; Yamauchi; Noriko; Kobayashi; Yoshio; Iyoki; Kenta
ACS Catalysis, 2022年01月, ［査読有り］
Search for Solid Acid Catalysts Aiming at the Development of Bifunctional Tandem Catalysts for the One-Pass Synthesis of Lower Olefins via CO2 Hydrogenation
S. Tada; H. Kinoshita; N. Ochiai; A. Chokkalingam; P. Hu; N. Yamauchi; Y. Kobayashi; K. Iyoki
International Journal of Hydrogen Energy, 2021年01月, ［査読有り］
Optimizing TiO2 through Water-Soluble Ti Complexes as Raw Material for Controlling Particle Size and Distribution of Synthesized BaTiO3 Nanocubes
K. Nakashima; K. Hironaka; K. Oouchi; M. Ajioka; Y. Kobayashi; Y. Yoneda; S. Yin; M. Kakihana; T. Sekino
ACS Omega, 2021年01月, ［査読有り］
Synthesis of Metallic Aluminum Particles by Electrolysis in Aqueous Solution
T. Hosoya; T. Yonezawa; N. Yamauchi; K. Nakashima; Y. Kobayashi
Micro and Nano Systems Letters, 2021年01月, ［査読有り］
〔主要な業績〕Electrolytic Synthesis of Metallic Zinc Nanoparticles
H. Iino; N. Yamauchi; K. Nakashima; K. Watanabe; H. Koda; H. Kunigami; H. Kunigami; Y. Kobayashi, 責任著者
Journal of Nanoparticle Research, 2021年01月, ［査読有り］
〔主要な業績〕PELID を用いた砥粒複合化技術 -複合化砥粒の効率化向上についての検討-
樫村聡、小林武寛、稲澤勝史、小林芳男、大森整、梅津信二郎、伊藤伸英
砥粒加工学会誌, 2021年01月, ［査読有り］
〔主要な業績〕Development of X-ray Contrast Agents Using Single Nanometer-Sized Gold Nanoparticles and Lactoferrin Complex and Their Application in Vascular Imaging
T. Inose; N. Kitamura; M. Takano-Kasuya; M. Tokunaga; N. Une; C. Kato; M. Tayama; Y. Kobayashi; N. Yamauchi; D. Nagao; T. Aimiya; N. Furusawa; Y. Nakano; Y. Kobayashi; K. Gonda
Colloids and Surfaces B: Biointerfaces, 2021年01月, ［査読有り］
〔主要な業績〕Stabilization of Size-Controlled BaTiO3 Nanocubes Via Precise Solvothermal Crystal Growth and Their Anomalous Surface Compositional Reconstruction
K. Nakashima; K. Onagi; Y. Kobayashi; T. Ishigaki; Y. Ishikawa; Y. Yoneda; S. Yin; M. Kakihana; T. Sekino
ACS Omega, 2021年01月, ［査読有り］
〔主要な業績〕Synthesis of Metallic Zinc Nanoparticles by Reduction of Zinc Ions in Protonic Solvent
S. Noda; N. Yamauchi; K. Nakashima; K. Watanabe; H. Koda; H. Kunigami; H. Kunigami; Y. Kobayashi, 責任著者
Journal of Metastable and Nanocrystalline Materials, 2021年01月, ［査読有り］
〔主要な業績〕Fabrication of Gold-Immobilized Quantum Dots/Silica Core-Shell Nanoparticles and Their Multimodal Imaging Properties
M. Tayama; T. Inose; N. Yamauchi; K. Nakashima; M. Tokunaga; C. Kato; K. Gonda and Y. Kobayashi, 責任著者
Particulate Science and Technology, 2021年01月, ［査読有り］
〔主要な業績〕Fabrication and Fluorescence Imaging Properties of Indocyanine Green-Loaded Poly(lactic-co-glycolic acid) Nanoparticles
M. Tayama; T. Inose; N. Yamauchi; K. Nakashima; M. Tokunaga; C. Kato; K. Gonda; Y. Kobayashi, 責任著者
Colloid and Polymer Science, 2021年01月, ［査読有り］
石造りの家に棲むタケウチトゲアワフキの観察記録
荻沼正和、小林芳男、三輪野祥
茨城生物, 2020年01月
Synthesis of Metallic Copper Nanoparticles in Aqueous Solution by Surfactant-Free Reduction and Silica Coating
H. Hayashida; N. Yamauchi; K. Nakashima; Y. Kobayashi
Chemical Papers, 2020年01月, ［査読有り］
Spontaneous Immobilization of Both a Fluorescent Dye and a Functional Sugar During the Fabrication of Submicron-Sized PMMA Particles in an Aqueous Solution
N. Yamauchi; R. Yatabe; H. Iino; M. Nagatsuka; Y. Sogame; M. Ogata; Y. Kobayashi
Colloids and Surfaces A: Physiochemical and Engineering Aspects, 2020年01月, ［査読有り］
Synthesis of Metallic Zinc Nanoparticles by Electrolysis
A. Yoshida; N. Yamauchi; K. Nakashima; K. Watanabe; H. Koda; H. Kunigami; H. Kunigami; Y. Kobayashi
Applied Nanoscience, 2020年01月, ［査読有り］
Low Temperature Synthesis of α-Alumina Based on Sol-Gel Processes
Y. Kobayashi; Y. Yasuda; T. Morita
Advances in Materials and Processing Technologies, 2020年01月, ［査読有り］
Solvothermal synthesis and morphology control of NaNbO3 nanocubes using a reaction medium of water and/or methanolNakashima, Kouichi; Toshima, Yasuharu; Kobayashi, Yoshio; Ishikawa, Yoshihisa; Kakihana, Masato, NaNbO3 particles were prepared by solvothermal synthesis at 230 degrees C in a reaction medium of either water or methanol. Morphological control of the particles was achieved by varying the synthesis conditions, such as the starting material and the reaction medium. The starting material was prepared by a process involving heat treatment of an Nb precursor at 400 degrees C and 800 degrees C. The crystal structure of the starting material depended on the heat treatment temperature, with the preferred orthorhombic Nb2O5 obtained at 800 degrees C. Large particles were obtained when water was used as the reaction medium, whereas fine particles were obtained using methanol. Under appropriate conditions, NaNbO3 nanocubes can be synthesized using orthorhombic Nb2O5 as the starting material and methanol as the reaction medium., TAYLOR & FRANCIS LTD
JOURNAL OF ASIAN CERAMIC SOCIETIES, 2019年10月,
［査読有り］ Fabrication and Surface-Modification of Silica/Gadolinium Compound/Silica Core-Shell Nanoparticles Discovered by Transmission Electron Microscopy
E. Kawamata; T. Inose; Y. Kobayashi, 責任著者
International Journal of Theoretical and Applied Nanotechnology, 2019年, ［査読有り］
Low Temperature Synthesis of α-Alumina Through a Hydrothermal Process Combined with a Seeding Technique
K. Yamamura; Y. Kobayashi; Y. Yasuda; T. Morita, 責任著者
Materials Research Innovations, 2019年, ［査読有り］
Quantitative analyses of amount and localization of radiosensitizer gold nanoparticles interacting with cancer cells to optimize radiation therapyKeiichiro Hatoyama; Narufumi Kitamura; Mayumi Takano-Kasuya; Masayuki Tokunaga; Takahiro Oikawa; Mineto Ohta; Yoh Hamada; Hiroshi Tada; Yoshio Kobayashi; Takashi Kamei; Kohsuke Gonda, Previous studies showed that gold nanoparticles (AuNPs) are useful radiosensitizers which optimize radiation therapy under low-dose radiation. However, the mechanisms of AuNP radiosensitization, including the amount and localization of the AuNPs interacting with cancer cells, has not yet been quantified. To answer these questions, we prepared AuNPs conjugated with anti-human epidermal growth factor receptor type 2 (HER2) antibody via polyethylene glycol (PEG) chains (AuNP-PEG-HER2ab). AuNP-PEG-HER2ab specifically bound to the HER2-expressing cancer cells and entered the cells via endocytosis. Whether endocytosis of AuNP-PEG-HER2ab occurred had no effect on radiosensitization efficacy by AuNP-PEG-HER2ab in vitro. The radiosensitization efficacy in vitro depended on dose of AuNP-PEG-HER2ab or dose of X-ray. Moreover, AuNP-PEG-HER2ab administrated into tumor-bearing mice was localized to both the periphery of the tumor tissue and near the nuclei in cancer cells in tumor deep tissue. The localization of AuNP-PEG-HER2ab in tumor tissues was important factors for in vivo powerful radiosensitization efficacy. (C) 2018 Elsevier Inc. All rights reserved., ACADEMIC PRESS INC ELSEVIER SCIENCE
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS, 2019年01月,
［査読有り］ Effects of raw materials on NaNbO3 nanocube synthesis via the solvothermal methodNakashima, Kouichi; Toshima, Yasuharu; Kobayashi, Yoshio; Kakihana, Masato, A nanocube is a single nanoscale crystal with a cubic shape. Raw materials are an important factor in determining the synthesis of nanocubes. In this study, we investigated various niobium compounds that serve as raw materials, each inducing different effects during nanocube synthesis. Perovskite sodium niobate (NaNbO3) nanocubes were synthesized using a two-step process. The first step in this process, synthesis of the raw materials, was followed by solvothermal synthesis of NaNbO3 nanocubes. The raw material for the first step was obtained by applying heat treatment to a precursor following Nb hydrolysis. The heat treatment was performed at temperatures of 300-1000 degrees C. Nb2O5 was obtained after heat treatment of its precursor, during which its crystalline system morphed into hexagonal, orthorhombic, and monoclinic systems with respective increases in temperature. For the second step, we obtained various NaNbO3 morphologies via the solvothermal method using water, methanol, or ethanol as a reaction medium. NaNbO3 nanocubes were formed by applying the solvothermal method to the synthesized precursor during heat treatment at 800 degrees C. Solvothermal synthesis was performed with methanol as the reaction medium at 200 degrees C, which resulted in the formation of NaNbO3 nanocubes., TAYLOR & FRANCIS LTD
JOURNAL OF ASIAN CERAMIC SOCIETIES, 2019年01月,
［査読有り］ Fabrication of Silica/Platinum Core-Shell Particles by Electroless Metal Plating
Y. Ishii; Y. Kobayashi; K. Watanabe; H. Koda; H. Kunigami; H. Kunigami, 責任著者
Advanced Powder Technology, 2019年, ［査読有り］
Fabrication and Dual-Modal Imaging Properties of Quantum Dot/Silica Core-Shell Particles with Immobilized Single-Nanometer-Sized Gold NanoparticlesM. Tayama; T. Inose; N. Yamauchi; K. Nakashima; M. Tokunaga; C. Kato; K. Hatoyama; T. Kamei; K. Gonda; Y. Kobayashi, 責任著者, This work develops a process for fabricating particles composed of a quantum dot (QD) core, a SiO2 shell, and single-nanometer-sized Au nanoparticles (Au-S) immobilized on the particle surface. The QD nanoparticles were silica-coated with a sol-gel process using tetraethyl orthosilicate (QD/SiO2). A colloidal solution of the Au-S was prepared by reducing Au3+ with tetrakis(hydroxymethyl)phosphonium chloride in an aqueous solution. The QD/SiO2 particles were surface-modified with thiol groups by using (3-mercaptopropyl)trimethoxysilane (QD/SiO2/SH). The Au-S nanoparticles were immobilized on the QD/SiO2/SH particle surface by adding a colloidal Au-S solution to a colloidal QD/SiO2/SH solution (QD/SiO2/SH/Au-S). The QD/SiO2/SH/Au-S particles were surface-modified with thiol-terminated polyethylene glycol (PEG) (QD/SiO2/SH/Au-S/PEG). Fluorescence images and computed tomography (CT) images could be obtained for the colloidal QD/SiO2/SH/Au-S/PEG particle solution. The colloidal QD/SiO2/SH/Au-S/PEG particle solution had a CT value per unit concentration of Au (M) of 6.68 x 10(3) HU/M. The circulation of the QD/SiO2/SH/Au-S/PEG particles was confirmed in a mouse after injection of a colloidal particle solution into its blood vessels, and they accumulated in the heart. A portion of the QD/SiO2/SH/Au-S/PEG particles accumulated in the liver and spleen and remained there., ELSEVIER SCIENCE BV
Colloids and Surfaces A: Physiochemical and Engineering Aspects, 2019年,
［査読有り］ Electron Microscopy Observations of the Au Nanorods and Au Nanorod/SiO2 Nanocapsules
K. Nakashima; T. Inose; T. Oikawa; M. Tokunaga; K. Hatoyama; M. Kakihana; K. Gonda; Y. Kobayashi
Journal of the Japan Society of Powder and Powder Metallurgy, 2019年, ［査読有り］
Au Nanoparticles Coated with ChitosanA. Tokumasu; T. Inose; N. Yamauchi; K. Nakashima; M. Tokunaga; C. Kato; K. Hatoyama; T. Kamei; K. Gonda; Y. Kobayashi, 責任著者, This paper describes a method of coating metallic gold (Au) nanoparticles with chitosan (CS) shells in an aqueous solution. A colloidal solution of Au nanoparticles with a particle size of 16.51.7nm was prepared by reducing the Au ions (III) with sodium citrate in water at 80 degrees C. CS coating was achieved in an aqueous solution containing the Au nanoparticles by using CS as a shell source and sodium hydroxide as a pH adjuster at 25 degrees C. Ultraviolet-visible extinction spectroscopy and transmittance electron microscopy observation revealed that the Au nanoparticles were coated with CS shells. Additionally, the CS shell thickness could be varied in a range up to 2.2nm by changing the CS concentration during the CS-coating process., SPRINGER
Colloid and Polymer Science, 2019年,
［査読有り］ Preparation of High-Concentration Colloid Solutions of Metallic Copper Particles and Their Use in Metal-Metal Bonding Processes
Y. Suga; K. Nakashima; N. Yamauchi; Y. Yasuda; T. Morita; Y. Kobayashi, 責任著者
SN Applied Sciences, 2019年, ［査読有り］
Fe3O4ナノ粒子の疎水性シリカナノコーティングによる磁気特性の保護
山内紀子、五十嵐達也、小林芳男、車田研一
塗装工学, 2019年, ［査読有り］
Silica-Coating of Indium Phosphide Nanoparticles by a Sol-Gel Method and Their Photobleaching Properties
M. Kambayashi; N. Yamauchi; K. Nakashima; M. Hasegawa; Y. Hirayama; T. Suzuki; Y. Kobayashi, 責任著者
SN Applied Sciences, 2019年, ［査読有り］
One-Pot Formation of Sugar-Immobilized Fluorescent Polymer Particles by Soap-Free Emulsion Polymerization
N. Yamauchi; R. Yatabe; H. Iino; M. Ogata; Y. Kobayashi
APCChE 2019 Session 12 Abstracts of the 18th Asian Pacific Confederation of Chemical Engineering Congress (APCChE 2019), 2019年, ［査読有り］
Development of Au-Immobilized Quantum Dots/Silica Core-Shell Nanoparticles for Multimodal Imaging
M. Tayama; T. Inose; N. Yamauchi; K. Nakashima; M. Tokunaga; C. Kato; K. Gonda; Y. Kobayashi, 責任著者
Program & Abstracts of the 8th Asian Conference on Colloid and Interface Science (ACCIS 2019), 2019年, ［査読有り］
Fabrication of Multi-Layered Gold-Silica-Gadolinium Compound Core-Shell Particles and their Applications to X-ray Imaging and Magnetic Resonance Imaging
Y. Shindo; T. Inose; N. Yamauchi; K. Nakashima; M. Tokunaga; C. Kato; K. Gonda; Y. Kobayashi, 責任著者
List of Accepted Abstracts in web site of 2019 Sustainable Industrial Processing Summit and Exhibition (SIPS 2019), 2019年, ［査読有り］
Electron Microscopy of Surface Reconstruction of a SrTiO3 Photocatalyst
K. Nakashima; R. Yamazaki; N. Okouchi; Y. Kobayashi; M. Kakihana; M. Higashi; R. Abe
PACRIM 13 Program Book of the 13th Pacific Rim Conference of Ceramic Societies (PACRIM13), 2019年, ［査読有り］
Detailed Observation of Pt co-Catalyst Morphology and Dispersion on SrTiO3 Photocatalyst
R. Yamazaki; Y. Kobayashi; M. Kakihana; M. Higashi; R. Abe; K. Nakashima
PACRIM 13 Program Book of the 13th Pacific Rim Conference of Ceramic Societies (PACRIM13), 2019年, ［査読有り］
The development of quantum dot/silica particles for fluorescence imaging and medical diagnosticsYoshio Kobayashi; Kohsuke Gonda, This chapter introduces our study on development of core-shell silica particles containing quantum dot (QD) for fluorescence imaging and medical diagnostics and is composed of six sections. The first section is Introduction. The second section describes development of methods for preparing colloid solutions of core-shell particles composed of core of nanoparticles and shell of silica. Two types of methods, both of which are sol-gel methods using raw chemicals such as sodium silicate solution and silicon alkoxide, were successfully performed for silica coating of the nanoparticles. For the method using the silicon alkoxide, an amine-free method, or a method without amine that is usually used as a catalyst for the sol-gel method, could be also developed. The third section describes fabrication of core-shell particles containing QD. QD/silica core-shell particles (QD/SiO2), multilayered core-shell particles composed of QD, silica (inner silica shell), gadolinium compounds (GdC) and silica (outer silica shell) (QD/SiO2/GdC/SiO2), and QD/SiO2 particles with immobilized Au nanoparticles (QD/SiO2/Au) were fabricated by using our amine-free method. The fourth section describes an effect of silica shell on photostability of QD. The silica shell was rigid enough to prevent O2 molecules from reaching surfaces of the QD, which maintained their photostability. In addition, the silica shell produced from silicon alkoxide stabilized their photo-property more effectively. The fifth section describes fluorescence imaging techniques using the core-shell particles containing QD. Various tissues in mouse could be imaged by detecting fluorescence emitted from the QD/SiO2 particle colloid solutions with an in vivo imaging system (IVIS). The QD/SiO2/GdC/SiO2 particle colloid solution simultaneously functioned as a fluorescent marker and high-contrast MRI agent. The colloid solution of QD/SiO2/Au particles functioned as a contrast agent for dual imaging processes based on fluorescence and X-ray absorption. The last section is on Conclusion., Springer International Publishing
Handbook of Sol-Gel Science and Technology: Processing, Characterization and Applications, 2018年07月
Silica-Coating of Quantum Nanorods by a Sol-Gel Process and Their Photo-Bleaching Properties
M. Yokokawa; T. Li; M. Kambayashi; K. Nakashima; Y. Hirayama; H. Okura; M. Hasegawa; S. Dertinger; Y. Kobayashi, 責任著者
Journal of Sol-Gel Science and Technology, 2018年, ［査読有り］
CaF2 nanocrystals synthesis that have a unique shapeKouichi Nakashima; Joji Shibukawa; Yoshio Kobayashi; Masato Kakihana, CaF2 nanocrystals with a clear cubic shape were synthesized using both simple mixing and a hydrothermal method that neither of which required the use of surfactants or dispersants. The concentration and pH of the reaction medium, which in this case was an aqueous HNO3 solution, was found to be very important for determining the morphology of the CaF2 particles., Journal of the Japan Society of Powder and Powder Metallurgy
Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy, 2018年,
［査読有り］ Fabrication of Palladium/Platinum Core-Shell Nanoparticles by Electroless Metal Plating
M. Sakai; S. Noda; Y. Kobayashi; K. Watanabe; H. Koda; H. Kunigami; H. Kunigami, 責任著者
Zaštita Materijala, 2018年, ［査読有り］
Fabrication and Dual Imaging Properties of Quantum Dot/Silica Core-Shell Particles Immobilized with Gold NanoparticlesT. Li; T. Inose; T. Oikawa; M. Tokunaga; K. Hatoyama; K. Nakashima; T. Kamei; K. Gonda; Y. Kobayashi, 責任著者, The present work proposes a preparation method for core-shell nanoparticles composed of quantum dots (QDs), SiO2, large Au nanoparticles (Au-L), and small Au nanoparticles (Au-s). The QDs were silica-coated with a sol-gel method using tetraethyl orthosilicate (QD/SiO2). Au-L and Au-s were fabricated by reducing Au3+ ions with sodium citrate and tetrakis(hydroxymethyl)phosphonium chloride in water, respectively. Amino groups were introduced onto QD/SiO2 surface by using (3-aminopropyl)-triethoxysilane (QD/SiO2/NH2). Both Au-L and Au-s were immobilized on QD/SiO2/ NH2 by successively reacting Au-L and Au-s with QD/SiO2/NH2 (QD/SiO2/NH2/Au-L/Au-s). Surface modification of QD/SiO2/NH2/Au-L/Au-s was performed by using polyethylene glycol (PEG) with a thiol group (QD/SiO2/NH2/Au-L/Au-s/PEG). The QD/SiO2/NH2/Au-L/Au-s/PEG colloid solution could be clearly imaged via its fluorescence. Its computed tomography (CT) value per unit concentration of Au {M) was 1.2 x 10(4) HU/M. The QD/SiO2/NH2/Au-L/Au-S/PEGs were circulated in a mouse through blood vessels, and some of them became trapped and accumulated in the liver and spleen., TAYLOR & FRANCIS LTD
Materials Technology: Advanced Performance Materials, 2018年,
［査読有り］ Synthesis on Aggregation of Colloidal Solutions of ICG-Active Silica Nanoparticles and Their Application in In‐vivo Fluorescence ImagingY. Shindo; T. Inose; Y. Kubota; T. Oikawa; M. Tokunaga; T. Kamei; K. Gonda; Y. Kobayashi, 責任著者, This study reports two findings. The first is a method for preparing a colloidal solution of silica (SiO2) nanoparticles activated with fluorescent dye or fluorescent dye-active SiO2 nanoparticles. Preparation of a colloid solution of spherical SiO2 nanoparticles with an average size of 109.4 +/- 8.6 nm was performed using the sol-gel method at 35 degrees C using 0.2 M tetraethylorthosilicate, 25 M H2O, and 0.01 M NaOH in ethanol. Two kinds of cationic chemicals (poly-diallyldimethylammonium chloride (PDADMAC) and (3-aminopropyl) triethoxysilane (APES) were examined for surface-modification or surface-cationization of the SiO2 nanoparticles (SiO2/PDADMAC and SiO2/APES). To activate the SiO2 nanoparticles with fluorescent dye, indocyanine green (ICG) molecules were fixed on the surface-modified SiO2 nanoparticles by mixing ICG dissolved in albumin aqueous solution and the surface-modified SiO2 nanoparticle colloid solution (SiO2/PDADMAC/ICG and SiO2/APES/ICG) through electrostatic aggregation. The second finding is the verification of the fluorescence ability of the ICGactive SiO2 nanoparticle colloid solutions. Both the ICG-active SiO2 nanoparticle colloid solutions exerted fluorescence even at high ICG concentrations. Mouse tissues could be imaged by injecting the ICG-immobilized SiO2 nanoparticle colloid solution into the tail vein of the mouse and measuring the emitted fluorescence intensity. Pulmonary embolism was avoided in the SiO2/APES/ICG particle colloid solution-injected group, in which the particles reached the tissues more efficiently than in the SiO2/PDADMAC/ICG nanoparticles-injected group., ELSEVIER SCIENCE SA
Materials Chemistry and Physics, 2018年,
［査読有り］ Low Temperature Synthesis of α-Alumina Through a Hydrothermal Process Combined with a Seeding Technique
K. Yamamura; Y. Kobayashi; Y. Yasuda; T. Morita, 責任著者
Materials Research Innovations, 2018年, ［査読有り］
Fabrication of α-Alumina by a Combination of a Hydrothermal Process and a Seeding Technique
K. Yamamura; Y. Kobayashi; Y. Yasuda; T. Morita, 責任著者
Functional Materials Letters, 2018年, ［査読有り］
Synthesis of Core-shell Particle Colloid Solutions andImaging Processes Using Them
E. Kawamata; T. Inose; Y. Kobayashi, 責任著者
Proceedings of the 2nd International Conference of Theoretical and Applied Nanoscience and Nanotechnology (TANN'18), 2018年, ［査読有り］
One-Pot Preparation of Micron-Sized Monodisperse Polymer Particles with Carboxyl Groups on Their Surface
N. Yamauchi; S. Obinata; H. Iino; Y. Kobayashi; K. Kurumada
Program and Abstracts of the 6th International Conference on the Characterization and Control of Interfaces for High Quality Advanced Materials and the 54th Summer Symposium on Powder Technology (ICCCI2018), 2018年, ［査読有り］
Fabrication of Silica/Platinum Core-Shell Particles by Electroless Metal Plating
Y. Ishii; Y. Kobayashi; K. Watanabe; H. Koda; H. Kunigami; H. Kunigami, 責任著者
Program and Abstracts of the 6th International Conference on the Characterization and Control of Interfaces for High Quality Advanced Materials and the 54th Summer Symposium on Powder Technology (ICCCI2018), 2018年, ［査読有り］
Fabrication of Multilayered Gold/Silica/Gadolinium Compound Core-Shell Particles and Their Properties of X-ray Imaging and MRI
Y. Shindo; T. Inose; T. Oikawa; M. Tokunaga; Y. Kubota; K. Gonda; Y. Kobayashi, 責任著者
Programme and The Book of Abstracts of Twentieth Annual Conference of the Yugoslav Materials Research Society (YUCOMAT 2018), 2018年, ［査読有り］
Synthesis of metallic copper nanoparticles and metal-metal bonding process using themYoshio Kobayashi; Hiroaki Nakazawa; Takafumi Maeda; Yusuke Yasuda; Toshiaki Morita, Metallic copper nanoparticles were synthesised by reduction of copper ions in aqueous solution, and metal-metal bonding by using the nanoparticles was studied. A colloid solution of metallic copper nanoparticles was prepared by mixing an aqueous solution of CuCl2 (0.01 M) and an aqueous solution of hydrazine (reductant) (0.2-1.0 M) in the presence of 0.0005 M of citric acid and 0.005 M of n-hexadecyltrimethylammonium bromide (stabilizers) at reduction temperature of 30-80 degrees C. Copper-particle size varied (in the range of ca. 80-165 nm) with varying hydrazine concentration and reduction temperature. These dependences of particle size are explained by changes in number of metallic-copper-particle nuclei (determined by reduction rate) and changes in collision frequency of particles (based on movement of particles in accordance with temperature). The main component in the nanoparticles is metallic copper, and the metallic-copper particles are polycrystalline. Metallic-copper discs were successfully bonded by annealing at 400 degrees C and pressure of 1.2 MPa for 5 min in hydrogen gas with the help of the metallic-copper particles. Shear strength of the bonded copper discs was then measured. Dependences of shear strength on hydrazine concentration and reduction temperature were explained in terms of progress state of reduction, amount of impurity and particle size. Highest shear strength of 40.0 MPa was recorded for a colloid solution prepared at hydrazine concentration of 0.8 M and reduction temperature of 50 degrees C., TECHNO-PRESS
ADVANCES IN NANO RESEARCH, 2017年12月,
［査読有り］ Fabrication of silica-coated gold nanorods and investigation of their property of photothermal conversionTomoya Inose; Takahiro Oikawa; Kyosuke Shibuya; Masayuki Tokunaga; Keiichiro Hatoyama; Kouichi Nakashima; Takashi Kamei; Kohsuke Gonda; Yoshio Kobayashi, This study described the preparation of silica-coated Au nanorods (AuNR/SiO2) in a colloidal solution, assessed their property of photothermal conversion, and investigated their ability to kill cancer cells using photothermal conversion. Au-seed nanoparticles were produced by reducing hydrogen tetrachloroaurate (HAuCl4) with sodium borohydride (NaBH4) in aqueous n-hexadecyltrimethylammonium bromide (CTAB) solution. AuNRs were then fabricated by reducing HAuCl4 and silver nitrate (AgNO3) with L-ascorbic acid in the aqueous CTAB solution in the presence of Au-seed nanoparticles. The as prepared AuNRs were washed by a process composed mainly of centrifugation to remove the CTAB. The washed AuNRs were coated with silica by mixing the AuNR colloidal solution, an aqueous solution of (3-aminopropyl)trimethoxysilane, and tetraethylorthosilicate/ethanol solution with a water/ethanol solution. We found that the addition of AuNR/SiO2 in water, in mice, and in a culture medium with cancer cells, followed by irradiation with a laser, cause an increase in temperature, demonstrating that AuNR/ SiO2 have the ability of photothermal conversion. In addition, the cancer cells in the culture medium were found to be killed due to the increase in temperature caused by the photothermal conversion. (C) 2017 Elsevier Inc. All rights reserved., ACADEMIC PRESS INC ELSEVIER SCIENCE
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS, 2017年03月,
［査読有り］ Effect of peptiser species on crystallisation of alumina gel produced by sol-gel processYoshio Kobayashi; Katsumi Yamamura; Yusuke Yasuda; Toshiaki Morita, The present work reports a study on the effect that a peptiser species has on the crystallisation of alumina gel produced by a sol-gel process to help develop a method for producing alpha-Al2O3 at low temperature. The white precipitate of aluminium hydroxide, which was prepared with a homogeneous precipitation method using aluminium nitrate and urea in an aqueous solution, was peptised using various peptisers at room temperature to form a transparent alumina sol. The alumina gel obtained from the alumina sol, which was produced using formic acid as the peptiser, was most dominantly crystallised into alpha-Al2O3 by annealing at 900 degrees C. The optimal [peptiser]/[Al3+] (P/A) molar ratio for the crystallisation into alpha-Al2O3 was 0.2. The alumina gel began to crystallise into alpha-Al2O3 with annealing at as low as 500 degrees C when formic acid and a P/A ratio of 0.2 were used., TAYLOR & FRANCIS LTD
ADVANCES IN APPLIED CERAMICS, 2017年,
［査読有り］ Fabrication of multilayered Au/silica/gadolinium compound core-shell particles and their imaging propertiesY. Kobayashi; Y. Shindo; T. Oikawa; M. Tokunaga; Y. Kubota; K. Gonda, The present work proposes a preparation method for multilayered Au nanoparticle/silica/gadolinium compound core-shell (Au/SiO2/GdC) particles. Silica-coated Au core-shell (Au/SiO2) particles with a size of 38.0nm were prepared by a sol-gel reaction in the presence of the Au nanoparticles with a size of 15.5nm. Multilayered Au/SiO2/GdC particles with sizes of ca. 35-52 nm were prepared by a homogeneous precipitation reaction in the presence of Au/SiO2 particles. The computed tomography (CT) value of the Au/SiO2/GdC colloid solution containing 4.3x10(-2)M Au was 344.1HU: Its converted CT value (CT divided by Au concentration) was as large as 8.0x10(3)HU/M. The r(1) value of the Au/SiO2/GdC colloid solution was as large as 3.5 mM(-1)s(-1)., TAYLOR & FRANCIS LTD
MATERIALS SCIENCE AND TECHNOLOGY, 2017年,
［査読有り］ Synthesis of nanoparticles composed of silver and copper for metal-metal bondingTakafumi Maeda; Norihisa Matsubara; Yoshio Kobayashi; Yusuke Yasuda; Toshiaki Morita, A metal-metal bonding technique is described that uses nanoparticles composed of silver and copper. Colloid solutions of nanoparticles with an Ag content of 0-100 mol% were prepared by simultaneous reduction of Ag+ and Cu2+ using hydrazine with polyvinylpyrrolidone and citric acid as stabilisers. The nanoparticles ranged in size from 34 to 149nm depending on the Ag content. Copper discs were strongly bonded at 400 degrees C for 5 min under 1.2 MPa pressure in hydrogen gas; the maximum shear strength was as high as 23.9 MPa. The dependence of shear strength on the Ag content was explained by a mismatch between the d-spacings of Cu metal and Ag metal., TAYLOR & FRANCIS LTD
MATERIALS SCIENCE AND TECHNOLOGY, 2017年,
［査読有り］ Development of a Method for Synthesizing Ag/Cu Composite Nanoparticles and Their Bonding Property
T. Maeda; N. Matsubara; Y. Kobayashi; Y. Yasuda; T. Morita, 責任著者
International Journal of Materials Science and Engineering, 2017年, ［査読有り］
Development of a Method for Synthesizing Ag/Cu Composite Nanoparticles and Their Bonding Property
T. Maeda; N. Matsubara; Y. Kobayashi; Y. Yasuda; T. Morita, 責任著者
2017 International Conference on Materials Engineering and Functional Materials (ICMFM 2017) Conference Abstract, 2017年, ［査読有り］
Fabrication of Palladium/Platinum Core-Shell Nanoparticles by Electroless Metal Plating
M. Sakai; S. Noda; Y. Kobayashi; K. Watanabe; H. Koda; H. Kunigami; H. Kunigami, 責任著者
Proceedings of XIX YuCorr Conference, 2017年, ［査読有り］
Synthesis of Core-shell Particle Colloid Solutions andImaging Processes Using Them
Y. Kobayashi; K. Gonda, 筆頭著者
Proceeding of A3 Foresight 9th Meeting, 2017年, ［査読有り］
Metal-metal bonding process using cuprous oxide nanoparticlesYoshio Kobayashi; Takafumi Maeda; Yusuke Yasuda; Toshiaki Morita, This work performs metal-metal bonding by using cuprous oxide (Cu2O) nanoparticles prepared by reduction in aqueous solution. A colloid solution of Cu2O nanoparticles was prepared by mixing Cu(NO3)(2) aqueous solution and NaBH4 aqueous solution. Cu2O nanoparticles with a size of 111 f 34 nm, cubic crystal phase, and crystal size of 21.2 nm were produced at initial concentrations of 0.010M Cu(NO3)(2) and 0.010M NaBH4 at a temperature of 40 degrees C. The Cu2O particles contained not only Cu O bonds but also Cu-0-Cu-0 bonds, which indicated formation of fine cluster-like domains composed of Cu-0-Cu-0 bonds. The shear strength required for separating the metallic Cu discs bonded by using the particles as a filler at 400 degrees C in H-2 gas was as high as 27.9 MPa, which was comparable to the shear strengths of metallic Cu particles and CuO particles reported in our previous works. Metallic Cu single crystallites were produced during the bonding process. The presence of the fine cluster-like domains promoted epitaxial particle growth of the metallic Cu and formation of the micron-sized domains composed of nano-sized and submicron-sized single crystals, which provided the strong bonding. (C) 2016 Brazilian Metallurgical, Materials and Mining Association. Published by Elsevier Editora Ltda., ELSEVIER SCIENCE BV
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 2016年10月,
［査読有り］ Metal-metal bonding using silver/copper nanoparticlesY. Kobayashi; T. Maeda; Y. Yasuda; T. Morita, A method for producing nanoparticles composed of silver and copper and a metal-metal bonding technique using the silver/copper nanoparticles are proposed. The method consists of three steps. First, copper oxide nanoparticles are produced by mixing Cu(NO3)(2) aqueous solution and NaOH aqueous solution. Second, copper metal nanoparticles are fabricated by reducing the copper oxide nanoparticles with hydrazine in the presence of poly(vinylpyrrolidone) (PVP). Third, silver/copper nanoparticles are synthesized by reducing Ag+ ions with hydrazine in the presence of the copper metal nanoparticles. Initial concentrations in the final silver/copper particle colloid, composed of 0.0075 M Cu2+, 0.0025 M Ag+, 1.0 g/L PVP, and 0.6 M hydrazine, produced silver/copper nanoparticles with an average size of 49 nm and a crystal size of 16.8 nm. Discs of copper metal were successfully bonded by the silver/copper nanoparticles under annealing at 400 degrees C and pressurizing at 1.2 MPa for 5 min in not only hydrogen gas but also nitrogen gas. The shear force required to separate the bonded discs was 22.3 MPa for the hydrogen gas annealing and 14.9 MPa for the nitrogen gas annealing (namely, 66.8 % of that for hydrogen gas annealing)., SPRINGER HEIDELBERG
APPLIED NANOSCIENCE, 2016年08月,
［査読有り］ Silica-coating of nitrogen-doped titanium oxide particles and their electrical conductivityY. Kobayashi; T. Iwasaki, The present work investigates effects of concentrations of raw chemicals in a sol-gel process on morphology of partially nitrided titanium oxide (TiON) particles coated with silica shells (TiON/SiO2) and describes their electronic insulation properties. Commercially available TiON particles with an average size of 90.3 +/- 29.9 nm, of which the volume resistivity was 6.27 x 10(-2) Omega m under pressure applied to their powder of 200 kg-f/cm(2), were used as the core particles. The silica-coating of the TiON particles was performed using a sol-gel method using tetraethylorthosilicate (TEOS) at 1.2 x 10(-3)-12.0 x 10(-3) M NaOH and 9-21 M H2O in an ethanol solution containing 1.0 x 10(-1) M TiON particles at 35 degrees C. Optimum concentrations of NaOH and H2O for successful silica-coating were 15 and 9.0 x 10(-3) M, respectively. The silica shell thickness increased in the range of 105 +/- 37-114 +/- 40 nm with increasing TEOS concentrations from 1.0 x 10(-2) to 9.0 x 10(-2) M TEOS. The volume resistivity of a powder of the TiON/SiO2 particles with a silica shell thickness of 4.9 nm was as high as 2.17 x 10(3) Omega m at the applied pressure of 200 kg-f/cm(2); the silica shells were considered to prevent the TiON particles from contacting other TiON particles. (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved., ELSEVIER SCIENCE BV
ADVANCED POWDER TECHNOLOGY, 2016年05月,
［査読有り］ Preparation of high-concentration colloidal solution of silica-coated gold nanoparticles and their application to X-ray imagingYoshio Kobayashi; Kyosuke Shibuya; Masayuki Tokunaga; Yohsuke Kubota; Takahiro Oikawa; Kohsuke Gonda, This study proposes a method for preparing high-concentration silica-coated Au (Au/SiO2) nanoparticles in colloidal solution from 1.5 x 10(-3) M hydrogen tetrachloroaurate (III) trihydrate as the Au source and 1.0 x 10(-2) M sodium citrate as the reducing reagent. The colloidal solution is applied to X-ray computed tomography (CT) imaging of mouse tissue. The Au nanoparticles in the colloidal solution had a diameter of 18.9 nm, and the Au concentration reached 1.5 x 10(-3) M. The Au nanoparticles were silica-coated by modifying their surfaces with (3-aminopropyl)trimethoxysilane (APMS), then depositing silica nuclei generated by a sol-gel reaction of tetraethyl orthosilicate (TEOS) in water/ethanol initiated with sodium hydroxide (NaOH) on the surface modified with APMS. A colloidal solution of Au/SiO2 core-shell particles (silica shell thickness = 19.7 nm) was formed in a final as-prepared solution of 2.7 x 10(-4) M Au, 2.0 x 10(-5) M APMS, 24 M H2O, 1.9 x 10(-3) M NaOH, and 4.1 x 10(-3) M TEOS. The Au in the as-prepared colloidal solution was further concentrated to 0.27 M by salting-out and centrifugation. The CT value of the concentrated Au/SiO2 colloidal solution was 2.52 x 10(3) Hounsfield units, double that of a commercial X-ray contrast agent with the same I concentration as the Au concentration. When injected into mouse tissue, the Au/SiO2 colloidal solution demonstrated good imaging capability., SPRINGER
JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 2016年04月,
［査読有り］ Fabrication of quantum dot/silica core-shell particles immobilizing Au nanoparticles and their dual imaging functionsYoshio Kobayashi; Hiromu Matsudo; Ting-ting Li; Kyosuke Shibuya; Yohsuke Kubota; Takahiro Oikawa; Tomohiko Nakagawa; Kohsuke Gonda, The present work proposes preparation methods for quantum dot/silica (QD/SiO2) core-shell particles that immobilize Au nanoparticles (QD/SiO2/Au). A colloid solution of QD/SiO2 core-shell particles with an average size of 47.0 +/- 6.1 nm was prepared by a sol-gel reaction of tetraethyl orthosilicate in the presence of the QDs with an average size of 10.3 +/- 2.1 nm. A colloid solution of Au nanoparticles with an average size of 17.9 +/- 1.3 nm was prepared by reducing Au3+ ions with sodium citrate in water at 80 degrees C. Introduction of amino groups to QD/SiO2 particle surfaces was performed using (3-aminopropyl)triethoxysilane (QD/SiO2-NH2). The QD/SiO2/Au particles were fabricated by mixing the Au particle colloid solution and the QD/SiO2-NH2 particle colloid solution. Values of radiant efficiency and computed tomography for the QD/ SiO2/Au particle colloid solution were 2.23 x 10(-7) (p/s/cm(2) /sr)/(lW/cm(2)) at a QD concentration of 8 x 10(-7) M and 1180 +/- 314 Hounsfield units and an Au concentration of 5.4 x 10(-2) M. The QD/SiO2/Au particle colloid solution was injected into a mouse chest wall. Fluorescence emitted from the colloid solution could be detected on the skin covering the chest wall. The colloid solution could also be X-ray-imaged in the chest wall. Consequently, the QD/SiO2/Au particle colloid solution was found to have dual functions, i.e., fluorescence emission and X-ray absorption in vivo, which makes the colloid solution suitable to function as a contrast agent for dual imaging processes., SPRINGER HEIDELBERG
APPLIED NANOSCIENCE, 2016年03月,
［査読有り］ Stabilization of silica-coated silver iodide nanoparticles by ethanol-washingYoshio Kobayashi; Tetsuya Ayame; Kyosuke Shibuya; Tomohiko Nakagawa; Yohsuke Kubota; Kohsuke Gonda; Noriaki Ohuchi, Purpose - This paper aims to propose a simple method for stabilizing silica-coated silver iodide (AgI/SiO2) core-shell particles, of which a colloid solution functions as an X-ray contrast agent.
Design/methodology/approach - A colloid solution of AgI nanoparticles was prepared by mixing silver perchlorate and potassium iodide in water. The AgI/SiO2 nanoparticles were fabricated by a sol-gel method using NaOH, H2O and tetraethylorthosilicate in ethanol in the presence of AgI nanoparticles surface-modified with 3-mercaptopropyltrimethoxysilane.
Findings - The silica shells of AgI/SiO2 particles were dissolved near the AgI nanoparticle surface, when they were washed by a process composed of centrifugation, removal of supernatant with decantation, addition of water as a washing solution and a shake with a vortex mixer. In contrast, the shells were not damaged by using ethanol as the washing solution, i. e. ethanol-washing. An X-ray photoelectron spectroscopy spectrum of the silica was changed after the ethanol-washing, which indicated that the ethanol-washing had an effect on the chemical bonds in silica. The effect also acted on the silica shells of AgI/SiO2 particles, which did not damage the core-shell structure, i. e. controlled the dissolution of shell.
Originality/value - The paper demonstrates that the ethanol-washing is quite useful for stabilizing the core-shell structure composed of the silica shells., EMERALD GROUP PUBLISHING LTD
PIGMENT & RESIN TECHNOLOGY, 2016年,
［査読有り］ Effects of seeding with nanocrystallites and addition of inorganic alumina sol on crystallization of alkoxide alumina gelYoshio Kobayashi; Yusuke Mabuchi; Masachika Hama; Katsumi Yamamura; Yusuke Yasuda; Toshiaki Morita, This paper reports a method for producing α-Al2O3 at low temperature from aluminum alkoxide using a combination of seeding of α-Al2O3 nanocryatallites and adding of inorganic alumina sol. An alkoxide alumina sol was obtained by hydrolyzing aluminum isopropoxide in water at 80�C and then peptizing the hydrolyzed aluminum isopropoxide using acetic acid at 80�C. An inorganic alumina sol was obtained by producing aluminum compound with a homogeneous precipitation method using aluminum nitrate and urea in aqueous solution and then peptizing the aluminum compound using acetic acid at room temperature. α-Al2O3 nanocrystallites were added to the alkoxide alumina sol containing the inorganic alumina sol. The addition of inorganic alumina sol provided successful fabrication of a crack-free α-Al2O3-seded alumina film by a spin-coating technique. The sol containing α-Al2O3 nanocrystallites was transformed to an α-Al2O3-seeded alumina gel by drying the sol at room temperature. The non-seeded alumina gel was crystallized into γ-Al2O3 at a temperature below 900�C. In contrast, the alumina seeded at 1% α-Al2O3 nanocrystallites content began to be transformed to α-Al2O3 by annealing at the temperature. The seeding and the adding promoted crystallization of the alumina gel into α-Al2O3. The promotion of crystallization was significant with an increase in α-Al2O3 nanocrystallites content by weight in the final seeded alumina gel., Trans Tech Publications Ltd
Key Engineering Materials, 2016年,
［査読有り］ Effect of Surface-Modification of Indium Tin Oxide Particles on Their Electrical Conductivity
Y. Kobayashi; T. Kurosaka; K. Yamamura; T. Yonezawa; K. Yamasaki, 筆頭著者
International Journal of Chemical, Molecular, Nuclear, Materials and Metallurgical Engineering, 2016年, ［査読有り］
Effect of Hydrothermal Process for Inorganic Alumina Sol on Crystal Structure of Alumina Gel
K. Yamamura; M. Hama; Y. Kobayashi; Y. Yasuda; T. Morita, 責任著者
Journal of Asian Ceramic Societies, 2016年, ［査読有り］
Preparation of a Colloid Solution of Au/Silica Core-Shell Nanoparticles Surface-Modified with Cellulose and Its X-ray Imaging Properties
Y. Kobayashi; R. Nagasu; T. Nakagawa; Y. Kubota; K. Gonda; N. Ohuchi, 筆頭著者
Journal of Nanomaterials & Molecular Nanotechnology, 2016年, ［査読有り］
Recent Advances in the Synthesis of Copper-Based Nanoparticles for Metal-Metal Bonding Processes
Y. Kobayashi; Y. Yasuda; T. Morita, 筆頭著者
Journal of Science: Advanced Materials and Devices, 2016年, ［査読有り］
Preparation of Au/Silica/Cellulose Nanoparticle Colloid Solution and Its Use in X-ray Imaging Process
Y. Kobayashi; R. Nagasu; T. Nakagawa; Y. Kubota; K. Gonda; N. Ohuchi, 筆頭著者
Proceedings of the 7th World Nano Conference (NANO 2016), 2016年, ［査読有り］
Synthesis of Metallic Copper Nanoparticles by Reduction of Copper Ions in Aqueous Solution and Metal-Metal Bonding Process Using Them
Y. Kobayashi; H. Nakazawa; T. Maeda; Y. Yasuda; T. Morita, 筆頭著者
The 23rd International Symposium on Metastable, Amorphous and Nanostructured Materials (ISMANAM 2016) Book of Abstracts, 2016年, ［査読有り］
Effect of Surface-Modification of Indium Tin Oxide Particles on Their Electrical Conductivity
Y. Kobayashi; T. Kurosaka; K. Yamamura; T. Yonezawa; K. Yamasaki, 筆頭著者
World Acedemy of Science, Engineering and Technology Conference Proceedings, 2016年, ［査読有り］
In situ observation of water in a fuel cell catalyst using scanning electron microscopySatoru Ueda; Yoshio Kobayashi; Satoshi Koizumi; Yasuyuki Tsutsumi, To visualize water in the catalyst of polymer electrolyte fuel cells (PEFCs), backscattered electron (BSE) imaging by means of scanning electron microscopy was employed. To confine a wet specimen of catalyst, an environmental wet cell was manufactured with a silicon nitride thin film (similar to 100 nm) as the beam window. By supplying humidified gas into the cell, a change in BSE brightness was detected in the catalyst attached to the silicon nitride window. As humidification proceeded, the BSE image became darker and returned brighter by switching to a dry gas. Monte Carlo simulations were performed to evaluate the energy and number of BSE obtained after passing through water with thickness d. Combining the results of the Monte Carlo simulation successfully converted the change in brightness to the change in thickness from d = 100 nm to d = 3 mu m. This established method of evaluating water with a thickness resolution of the order of Delta d = 100 nm can be applied to in situ observations of the catalyst in a PEFC during operation., OXFORD UNIV PRESS
MICROSCOPY, 2015年04月
Direct immobilization of gadolinium complex on silica particles and their MRI propertiesYoshio Kobayashi; Kyosuke Shibuya; Tomohiko Nakagawa; Yohsuke Kubota; Kohsuke Gonda; Noriaki Ohuchi, This paper proposes a method for fabricating gadolinium diethylenetriamine pentaacetic acid-immobilized silica particles (SiO2/Gd-DTPA). Preparation of a colloid solution of spherical silica particles with an average size of 101.7±11.7 nm was performed by a sol-gel method at 35°C using 0.2 M tetraethylorthosilicate, 25 M H2O and 0.01 M NaOH in ethanol. Amino groups were introduced on the silica particles with 6 × 10-3 M (3-aminopropyl)triethoxysilane (APES) at 35°C (SiO2-NH2), which resulted in their average particle of 80.5±9.7 nm. Gd-DTPA was immobilized on the SiO2-NH2 particle surface with 5 × 10-4 M Gd-DTPA in 50/50 (v/v) water/dimethylformamide solution at 35°C, which provided their average particle of 101.6±12.3 nm. The APES-introduction and the Gd-DTPA-immobilization did not change the spherical structure, and shifted an iso-electric point of particles to higher pH for the APES-introduction and then to lower pH for the Gd-DTPA-immobilization, which indicated that APES and Gd-DTPA were successfully attached on the particle surface with no chemical damage. A relaxivity value for T1-weighted imaging of the SiO2/Gd-DTPA particle colloid solution was 2.7 mM-1 s-1, that was 64% of that for Magnevist., Surface Science Society of Japan
e-Journal of Surface Science and Nanotechnology, 2015年02月
Preparation of Silica-Coated Quantum Dot Nanoparticle Colloid Solutions and Their Application in in-vivo Fluorescence ImagingYoshio Kobayashi; Hiromu Matsudo; Yohsuke Kubota; Tomohiko Nakagawa; Kohsuke Gonda; Noriaki Ohuchi, This paper describes three findings. The first is a method for producing colloidal solutions of quantum dot (QD) nanoparticles with silica shells (QD/SiO2). QD nanoparticles averaging 10.3 +/- 2.1 nm in size were coated with silica via a sol-gel reaction with tetraethyl orthosilicate using NaOH as a catalyst. The QD/SiO2 particle size could be varied by varying the QD concentration. The average particle sizes were 19.1 +/- 3.0 (S-QD/SiO2) and 47.0 +/- 6.1 nm (L-QD/SiO2) for QD concentrations of 6.4 x 10(-9) M (4.6 x 10(11) particles/L) and 6.4 x 10(-10) M (4.6 x 10(10) particles/L), respectively. The second finding is a method to modify the particle surface with poly(ethylene glycol), which is called PEGylation (QD/SiO2/PEG). S-QD/SiO2 and L-QD/SiO2 were PEGylated using methoxy polyethylene glycol silane (S-QD/SiO2/PEG and L-QD/SiO2/PEG, respectively). The third finding is an in-vivo fluorescence imaging technique using the QD/SiO2/PEG particle colloid solutions. Both QD/SiO2/PEG particle colloid solutions fluoresced with intensities comparable with that of the QD colloid solution. Mouse tissues could be imaged by injecting the QD/SiO2/PEG colloid solution into them and measuring the emitted fluorescence intensity. The L-QD/SiO2/PEG particles did not form aggregates in blood, which allowed the particles to reach the tissues more efficiently than the S-QD/SiO2/PEG particles., SOC CHEMICAL ENG JAPAN
JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 2015年02月
Low-Temperature Metal-Metal Bonding Process Using Leaf-Like Aggregates Composed of CuO NanoparticlesTakafumi Maeda; Yoshio Kobayashi; Yusuke Yasuda; Toshiaki Morita, The present study describes a low-temperature metal-metal bonding process using leaf-like CuO aggregates. A CuO nanoparticle colloid solution was prepared at 20 degrees C with a salt-base reaction. Leaf-like CuO aggregates with a longitudinal size of ca. 990 nm and a lateral size of ca. 440 nm composed of CuO nanoparticles with a size of ca. 10 nm were fabricated by aging the CuO particle colloid solution at 80 degrees C. The metal-metal bonding ability of the leaf-like CuO aggregates was examined by pressurizing metallic discs sandwiching the CuO particles as a filler at 1.2 MPa for 5 min under annealing in H-2 gas. The metal-metal bonding could be performed even for an annealing temperature as low as 250 degrees C. A shear strength of 17.0 MPa was recorded for the annealing temperature of 250 degrees C., SOC CHEMICAL ENG JAPAN
JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 2015年01月
Seeding Technique for Lowering Temperature During Synthesis of α-Alumina
Journal of Asian Ceramic Societies, 2015年, ［査読有り］
Preparation of Au/Silica/Poly(ethylene glycol) Nanoparticle Colloid Solution and its Use in X-ray Imaging Process
Nanocomposites, 2015年, ［査読有り］
Fabrication of ITO Particles Using a Combination of a Homogeneous Precipitation Method and a Seeding Technique and Their Electrical Conductivity
Journal of Asian Ceramic Societies, 2015年, ［査読有り］
Fabrication of Gd hydroxide Nanoparticles by a Method Using Ion-Exchange Resin and Their MRI Property
Y. Kobayashi; H. Morimoto; T. Nakagawa; Y. Kubota; K. Gonda; N. Ohuchi
Abstract Booklet of the 2nd International Conference on Surfaces, Coatings and Nanostructured Materials (NANOSMAT-Asia 2015), 2015年, ［査読有り］
Silica-Coating of Nitrogen-Doped Titanium Oxide Particles and Their Electrical Conductivity
Y. Kobayashi; T. Iwasaki
Program and Abstracts of the 5th International Conference on the Characterization and Control of Interfaces for High Quality Advanced Materials and the 51st Summer Symposium on Powder Technology (ICCCI 2015), 2015年, ［査読有り］
Effects of Seeding with Nanocrystallites and Addition of Inorganic Alumina Sol on Crystallization of Alkoxide Alumina GelY. Kobayashi; Y. Mabuchi; M. Hama; Y. Yasuda; T. Morita, 筆頭著者, This paper reports a method for producing α-Al2O3 at low temperature from aluminum alkoxide using a combination of seeding of α-Al2O3 nanocryatallites and adding of inorganic alumina sol. An alkoxide alumina sol was obtained by hydrolyzing aluminum isopropoxide in water at 80�C and then peptizing the hydrolyzed aluminum isopropoxide using acetic acid at 80�C. An inorganic alumina sol was obtained by producing aluminum compound with a homogeneous precipitation method using aluminum nitrate and urea in aqueous solution and then peptizing the aluminum compound using acetic acid at room temperature. α-Al2O3 nanocrystallites were added to the alkoxide alumina sol containing the inorganic alumina sol. The addition of inorganic alumina sol provided successful fabrication of a crack-free α-Al2O3-seded alumina film by a spin-coating technique. The sol containing α-Al2O3 nanocrystallites was transformed to an α-Al2O3-seeded alumina gel by drying the sol at room temperature. The non-seeded alumina gel was crystallized into γ-Al2O3 at a temperature below 900�C. In contrast, the alumina seeded at 1% α-Al2O3 nanocrystallites content began to be transformed to α-Al2O3 by annealing at the temperature. The seeding and the adding promoted crystallization of the alumina gel into α-Al2O3. The promotion of crystallization was significant with an increase in α-Al2O3 nanocrystallites content by weight in the final seeded alumina gel., Trans Tech Publications Ltd
Programme and Abstracts of the 9th International Conference on High-Performance Ceramics (CICC-9), 2015年,
［査読有り］ Fabrication of barium titanate nanoparticles/poly (methylmethacrylate) composite films by a combination of deposition process and spin-coating techniqueYoshio Kobayashi; Aiko Odo, The present work proposes a method for fabricating poly(methylmethacrylate) (PMMA) film containing barium titanate (BT) nanoparticles (BT/PMMA film). BT particles with an average size of 77.6 +/- 30.5 nm and a crystal size of 28.1 nm were synthesized by adding sodium hydroxide aqueous solution to titanium tetraisopropoxide/acetylacetone/i-propanol solution suspending barium hydroxide. A sodium glass plate, of which surface was modified with polyvinylpyrrolidone, was immersed into water suspending the BT particles, which resulted in deposition of the BT particles on the plate. A BT/PMMA film was fabricated by twice performance of a process composed of spin-coating of N-methyl-2-pyrrolidone (NMP) dissolving PMMA on the plate, and then drying the coated plate in the atmosphere at room temperature. Spin-coating of a PMMA/NMP solution with a PMMA concentration of 150 g/L at a rotating speed of 5000 rpm provided fabrication of a BT/PMMA film with a BT volume fraction of 35.5%, a thickness of ca. 300 nm, and a transmittance of ca. 90% in the visible light region. (C) 2014 Brazilian Metallurgical, Materials and Mining Association. Published by Elsevier Editora Ltda., ELSEVIER SCIENCE BV
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 2014年10月,
［査読有り］ Fabrication of nitrogen-doped titanium oxide/silica core-shell particles and their electrical conductivityYoshio Kobayashi; Toshio Iwasaki; Kensuke Kageyama; Shigeki Ishikuro; Kazuhiko Yamasaki; Takehiro Yonezawa; Ai Takenoshita, The present work proposes a method for fabricating partially nitrided titanium oxide (TiON) particles coated with silica shells (TiON/SiO2) using a sol-gel process and describes their electronic insulation properties. Commercially available TiON particles with an average size of 90.3 +/- 29.9 nm were used as the core particles. The silica coating of the TiON particles was performed using a sol-gel method with 15 M tetraethylorthosilicate (TEOS) in H2O and 1.2 x 10(-3) M NaOH in an ethanol solution containing 1.0 x 10(-2) M TiON particles at 35 degrees C. Successful silica coating was confirmed using transmittance electron microscopy, dynamic light scattering, electrophoretic light scattering, X-ray photoelectron spectroscopy and optical spectroscopy. The silica shell thickness increased in the range of 3.6-11.4nm with increasing TEOS concentrations from 2.0 x 10(-3) to 9.0 x 10(-3) M. The volume resistivity of a powder of the TiON/SiO2 particles was larger than 2.8 x 10(6) Omega cm, even under pressure, i.e., it did not decrease remarkably with an increase in pressure applied to the powder from 10 to 200 kg-f/cm(2). The silica shells were hypothesized to prevent the TiON particles from contacting other TiON particles. (C) 2014 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 2014年09月,
［査読有り］ Synthesis of a colloid solution of silica-coated gold nanoparticles for X-ray imaging applicationsYoshio Kobayashi; Ryoko Nagasu; Kyosuke Shibuya; Tomohiko Nakagawa; Yohsuke Kubota; Kohsuke Gonda; Noriaki Ohuchi, This work proposes a method for fabricating silica-coated gold (Au) nanoparticles, surface modified with poly(ethylene glycol) (PEG) (Au/SiO2/PEG), with a particle size of 54.8 nm. X-ray imaging of a mouse is performed with the colloid solution. A colloid solution of 17.9 nm Au nanoparticles was prepared by reducing Au ions (III) with sodium citrate in water at 80 degrees C. The method used for silica-coating the Au nanoparticles was composed of surface-modification of the Au nanoparticles with (3-aminopropyl)-trimethoxysilane (APMS) and a sol-gel process. The sol-gel process was performed in the presence of the surface-modified Au nanoparticles using tetraethylorthosilicate, APMS, water, and sodium hydroxide, in which the formation of silica shells and the introduction of amino groups to the silica-coated particles took place simultaneously (Au/SiO2-NH2). Surface modification of the Au/SiO2-NH2 particles with PEG, or PEGylation of the particle surface, was performed by adding PEG with a functional group that reacted with an amino group in the Au/SiO2-NH2 particle colloid solution. A computed tomography (CT) value of the aqueous colloid solution of Au/SiO2/PEG particles with an actual Au concentration of 0.112 M was as high as 922 +/- 12 Hounsfield units, which was higher than that of a commercial X-ray contrast agent with the same iodine concentration. Injecting the aqueous colloid solution of Au/SiO2/PEG particles into a mouse increased the light contrast of tissues. A CT value of the heart rose immediately after the injection, and this rise was confirmed for up to 6 h., SPRINGER
JOURNAL OF NANOPARTICLE RESEARCH, 2014年07月,
［査読有り］ Fabrication of TiO2/Pt core-shell particles by electroless metal platingYoshio Kobayashi; Yuya Ishii; Hideyuki Yamane; Ken-ichi Watanabe; Hidekazu Koda; Hiroshi Kunigami; Hideki Kunigami, An electroless metal plating method was used to form Pt shells on sub-micrometer-sized titania particles fabricated by a sol-gel method. The electroless metal plating method comprised three steps: (1) surface-modification of titania particles with poly(diallyldimethylammonium chloride) (PDADMAC) (TiO2-PDADMAC), (2) pre-deposition of Pt nuclei or Pt fine particles on the titania particles by reducing Pt ions in the presence of TiO2-PDADMAC particles (TiO2-Pt) and (3) growth of the pre-deposited Pt by immersing the TiO2-Pt particles in a Pt-plating solution. TEM observation and X-ray diffractometry revealed that surface modification with PDADMAC promoted the pre-deposition of Pt and that crystalline Pt shells with a thickness of approximately 25 nm were successfully produced on the titania particles using initial concentrations of 0.8 x 10(-3) M TiO2 and 0.375 x 10(-3) M Pt in the Pt-plating solution. (C) 2014 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 2014年04月,
［査読有り］ A metal-metal bonding process using metallic copper nanoparticles produced by reduction of copper oxide nanoparticlesYoshio Kobayashi; Yuki Abe; Takafumi Maeda; Yusuke Yasuda; Toshiaki Morita, Metal-metal bonding was performed using metallic Cu nanoparticles fabricated from CuO nanoparticles. Colloid solutions of CuO nanoparticles were prepared by the reaction of Cu(NO3)(2) and NaOH in aqueous solution at reaction temperatures (T(CuO)s) of 20, 40, 60 and 80 degrees C. CuO single crystallites with a size of ca. 10 nm were produced, and they formed leaf-like aggregates. The longitudinal and lateral sizes of the aggregates decreased from 522 to 84 nm and from 406 to 23 nm, respectively, with an increase in TCuO. Colloid solutions of metallic Cu nanoparticles were prepared by reducing the CuO nanoparticles with hydrazine in the presence of cetyltrimethylammonium bromide. The size of the metallic Cu nanoparticles decreased from 92 to 73 nm with increasing TCuO. Metallic copper discs were bonded with the metallic Cu nanoparticles by annealing at 400 degrees C and 1.2 MPa for 5 min in H2 gas. The shear strength required to separate the bonded discs increased with increasing T-CuO. A maximum shear strength of 39.2 MPa was recorded for a T-CuO of 80 degrees C. (C) 2014 Brazilian Metallurgical, Materials and Mining Association. Published by Elsevier Editora Ltda., ELSEVIER SCIENCE BV
JOURNAL OF MATERIALS RESEARCH AND TECHNOLOGY-JMR&T, 2014年04月,
［査読有り］ Metal-Metal Bonding Properties of Copper Oxide NanoparticlesT. Maeda; Y. Kobayashi; Y. Yasuda; T. Morita, The present study performs production of copper oxide particles, and examines the particles as a filler in metalmetal bonding. Leaf-like aggregates with a longitudinal size of ca. 600-950 nm and a lateral size of ca. 280-380 nm, which were composed of particles with a size of ca. 10 nm, were produced with a salt-base reaction using a Cu(NO3)2 aqueous solution and an NaOH aqueous solution. Copper discs were bonded by pressurizing them, between which the particles were sandwiched, at 1.2 MPa for 5 min in H2 gas under annealing at 400°C. Bonding properties of particles were evaluated by measuring shear strength, which was required to separate the discs. The shear strengths were as large as ca. 23 MPa at NaOH/Cu(NO3)2 ratios of 1.9 and 2.0, since CuO particles that contained nether Cu 2(OH)3NO3 nor impurity based on the addition of NaOH were produced at the ratios. © 2014 The Surface Science Society of Japan., Surface Science Society of Japan
e-Journal of Surface Science and Nanotechnology, 2014年,
［査読有り］ Imaging Processes Using Core-Shell Particle Colloid Solutions for Medical Diagnosis
Y. Kobayashi; K. Gonda; N. Ohuchi
Athens Journal of Natural & Formal Sciences, 2014年, ［査読有り］
Effects of Reductant Concentration and Reduction Temperature in Synthesis of Copper Nanoparticles on Their Metal-Metal Bonding Properties
T. Maeda; H. Nakazawa; Y. Kobayashi; Y. Yasuda; T. Morita
Science Letters, 2014年, ［査読有り］
Effects of Reductant Concentration and Reduction Temperature in Synthesis of Copper Nanoparticles on Their Metal-Metal Bonding Properties
T. Maeda; H. Nakazawa; Y. Kobayashi; Y. Yasuda; T. Morita
International Metallurgy and Welding Technology (ISMWT 2014) in 9th International Materials Technology Conference & Exhibition (IMTCE 2014) Book of Abstracts, 2014年, ［査読有り］
Preparation of Au/Silica/Poly(ethylene glycol) Nanoparticle Colloid Solution and X-ray Imaging Using It
Y. Kobayashi; R. Nagasu; T. Nakagawa; Y. Kubota; K. Gonda; N. Ohuchi
9th International Conference on Surfaces, Coatings and Nanostructured Materials (NANOSMAT 2014) Abstracts Book, 2014年, ［査読有り］
Direct Immobilization of Gadolinium Complex on Silica Particles and Their MRI Properties
Y. Kobayashi; K. Shibuya; T. Nakagawa; Y. Kubota; K. Gonda; N. Ohuchi
Program/Abstracts of the 7th International Symposium on Surface Science (ISSS-7), 2014年, ［査読有り］
X-ray imaging technique using colloid solution of Au/silica/poly(ethylene glycol) nanoparticlesY. Kobayashi; H. Inose; R. Nagasu; T. Nakagawa; Y. Kubota; K. Gonda; N. Ohuchi, This work describes X-ray imaging of mouse using colloid solution of silica coated Au (Au/SiO2) nanoparticles surface modified with poly(ethylene glycol) (PEG) (Au/SiO2/PEG). A colloid solution of Au nanoparticles was prepared by reducing Au ions (III) with sodium citrate. Au/SiO2 nanoparticles were fabricated by a sol-gel method using tetraethylorthosilicate, water and sodium hydroxide in ethanol in the presence of Au nanoparticles surface modified with (3-aminopropyl)- trimethoxysilane. A computed tomography value of the Au/SiO2 colloid solution with an Au concentration of 0.083M was as high as 1421.2 Hounsfield units, which was higher than that of a commercial X-ray contrast agent with the same iodine concentration. Surface modification of the Au/SiO2 particles with PEG, or PEGylation of the particle surface, was performed using (3- aminopropyl)trimethoxysilane and PEG for the Au/SiO2 particles. Tissues of mouse could be imaged by injecting the colloid solutions of Au/SiO2 particles or Au/SiO2/PEG particles into it. The PEGylation provided an increase in residence time of particles in the mouse. © W. S. Maney &
Son Ltd. 2013.
Materials Research Innovations, 2013年11月
Metal-Metal Bonding Process Using Cu+Ag Mixed NanoparticlesJianfeng Yan; Guisheng Zou; Yingchuan Zhang; Jiaxin Li; Lei Liu; Aiping Wu; Y. Norman Zhou, The Cu+Ag mixed nanoparticles were prepared based on the chemical reduction method. The polymer coated on the Cu+Ag mixed nanoparticles can protect Cu nanoparticles from oxidation. The metal-metal joint of silver plated Cu bulks was investigated with the use of Cu+Ag mixed nanoparticles. The bonding experiments show that joint with shear strength about 20 MPa was formed at the bonding temperature above 250 degrees C under 5 MPa using Cu+Ag mixed nanoparticles. The strength of bonding using Cu+Ag mixed nanoparticles is lower than that of bonding using pure Ag nanoparticles. This may be due to the fact that the sintering between the Cu nanoparticles and Ag nanoparticles is more difficult than the sintering between Ag nanoparticles., JAPAN INST METALS
MATERIALS TRANSACTIONS, 2013年06月,
［査読有り］ Fabrication of transparent self-supporting alumina films by homogeneous precipitation processKazuhiro Inoue; Hidemi Kurebayashi; Masachika Hama; Yoshio Kobayashi; Yusuke Yasuda; Toshiaki Morita, This paper reports fabrication of transparent self-supporting alumina films by using homogeneous precipitation and peptization processes. White precipitate of aluminum hydroxide was prepared with a homogeneous precipitation method using aluminum nitrate and urea in aqueous solution. The obtained aluminum hydroxide precipitate was peptized by using acetic acid at room temperature, which resulted in production of a transparent alumina sol. The alumina sol was transformed to an alumina gel film by drying the sol at room temperature. The alumina film was amorphous or fine crystallites even after annealed at a temperature as high as 500 degrees C, and was crystallized to gamma-Al2O3 at 900 degrees C. (C) 2013 The Ceramic Society of Japan. All rights reserved., CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
JOURNAL OF THE CERAMIC SOCIETY OF JAPAN, 2013年06月,
［査読有り］ Interfacial Nanostructure of the Polymer Electrolyte Fuel Cell Catalyst Layer Constructed with Different Ionomer ContentsKoki Baba; Kenta Iwasawa; Mika Eguchi; Yoshio Kobayashi; Maya Kobori; Mikka Nishitani-Gamo; Toshihiro Ando, Fibrous carbon materials such as carbon nanotubes (CNTs) and carbon nanofilaments (CNFs) have attracted attention for use in the polymer electrolyte fuel cells (PEFCs). We have applied one type of fibrous carbon materials named Marimo carbon (MC) as the catalyst support. The modified nanocolloidal method was used preparing the Marimo carbon supported Pt catalyst (Pt/MC). And then, ionomer/carbon ratio in the cathode catalyst layer of the PEFC has been investigated for its effect on performance and structure of the membrane electrode assembly (MEA). The morphologies and cell performance of cathode catalyst layer using Marimo carbon changed dramatically with ionomer content. In case of excess ionomer, the air volume between CNFs was plugged up by ionomer, and blocked supply fuel gas diffusion caused decrease cell performance. PEFC cell performance was increase with decreasing ionomer content. (c) 2013 The Japan Society of Applied Physics, JAPAN SOC APPLIED PHYSICS
JAPANESE JOURNAL OF APPLIED PHYSICS, 2013年06月,
［査読有り］ In-vivo fluorescence imaging technique using colloid solution of multiple quantum dots/silica/poly(ethylene glycol) nanoparticlesYoshio Kobayashi; Hiromu Matsudo; Tomohiko Nakagawa; Yohsuke Kubota; Kohsuke Gonda; Noriaki Ohuchi, This paper describes a method for producing silica particles containing multiple quantum dots (QD/SiO2), a method for surface-modifying the particles with poly(ethylene glycol) (QD/SiO2/PEG), and an in vivo fluorescence imaging technique using colloid solution of the QD/SiO2/PEG particles. The QDs used were ZnS-coated CdSexTe1-x nanoparticles surface-modified with carboxyl groups, and had an average size of 10.3 +/- A 2.1 nm. The QD/SiO2 particles were fabricated by performing sol-gel reaction of tetraethyl orthosilicate using NaOH as a catalyst in the presence of the QDs. The produced particles formed core-shell structure composed of multiple QDs and silica shell, and had an average size of 50.2 +/- A 17.9 nm. Surface-modification of the QD/SiO2 particles with PEG, or PEGylation of the particle surface, was performed by using methoxy polyethylene glycol silane. Fluorescence of QD colloid solution was not quenched even through the silica-coating and the PEGylation. Tissues of a mouse could be imaged by injecting the concentrated colloid solution into it and measuring fluorescence intensity emitted from the tissues., SPRINGER
JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 2013年04月,
［査読有り］ Characterization of polymer electrolyte fuel ceils by neutron scattering during operation in a segmented electrode cellSatoru Ueda; Mika Eguchi; Yoshio Kobayashi; Yasuyuki Tsutsumi; Ananda Putra; Daisuke Yamaguchi; Satoshi Koizumi, Small-angle neutron scattering (SANS) is a powerful technique to visualize the swelling behavior of a polymer electrolyte membrane (Nafion) during cell operation. Using a small incident beam with 10 mm in diameter, we monitored the inhomogeneous swelling and ion-cluster size distribution in a membrane along a serpentine gas flow channel as a function of current density. To determine the local cell voltage, corresponding to SANS observation, we developed a segmented electrode that was incorporated in a shunt resistance circuit. Using the segmented electrode, we quantitatively determined local cell resistance and cell voltage during operation. © 2013, The Society of Polymer Science.
Kobunshi Ronbunshu, 2013年03月
Characterization of Polymer Electrolyte Fuel Cells by Neutron Scattering During Operation in a Segmented Electrode CellSatoru Ueda; Mika Eguchi; Yoshio Kobayashi; Yasuyuki Tsutsumi; Ananda Putra; Daisuke Yamaguchi; Satoshi Koizumi, Small-angle neutron scattering (SANS) is a powerful technique to visualize the swelling behavior of a polymer electrolyte membrane (Nafion) during cell operation. Using a small incident beam with 10 mm in diameter, we monitored the inhomogeneous swelling and ion-cluster size distribution in a membrane along a serpentine gas flow channel as a function of current density. To determine the local cell voltage, corresponding to SANS observation, we developed a segmented electrode that was incorporated in a shunt resistance circuit. Using the segmented electrode, we quantitatively determined local cell resistance and cell voltage during operation., SOC POLYMER SCIENCE JAPAN
KOBUNSHI RONBUNSHU, 2013年
中性子線と分割電極セルの組合せによる固体高分子形燃料電池の水計測技術
上田悟、江口美佳、小林芳男、堤泰行、プトラアナンダ、山口大輔、小泉智
高分子論文集, 2013年, ［査読有り］
Electroless Deposited Gold Nanoparticles on Glass Plates as Sensors for Measuring the Dielectric Constant of Solutions
Y. Kobayashi; Y. Ishii
Journal of Nanoparticles, 2013年
Preparation of Gd Complex-Immobilized Silica Particles and Their Application to MRI
Y. Kobayashi; H. Morimoto; T. Nakagawa; Y. Kubota; K. Gonda; N. Ohuchi
ISRN Nanotechnology, 2013年, ［査読有り］
Fabrication of Hollow Particles Composed of Silica Containing Gadolinium Compound and Magnetic Resonance Imaging Using Them
Y. Kobayashi; H. Morimoto; T. Nakagawa; Y. Kubota; K. Gonda; N. Ohuchi
Journal of Nanostructure in Chemistry, 2013年, ［査読有り］
Preparation of Copper Nanoparticles and Metal-Metal Bonding Process Using Them
Y. Kobayashi; S. Ishida; K. Ihara; Y. Yasuda; T. Morita
World Journal of Engineering, 2013年, ［査読有り］
Fabrication of Multilayered Au/Silica/Gadolinium Compound/Silica Core-Shell Particles
Y. Kobayashi; H. Inose; T. Nakagawa; Y. Kubota; K. Gonda; N. Ohuchi
Materials Focus, 2013年, ［査読有り］
Preparation of AgI/Silica/Poly(ethylene glycol) Nanoparticle Colloid Solution and X-ray Imaging Using It
Y. Kobayashi; T. Ayame; T. Nakagawa; Y. Kubota; K. Gonda; N. Ohuchi
ISRN Nanomaterials, 2013年, ［査読有り］
X-ray Imaging Technique Using Colloid Solution of Au/Silica Core-Shell Nanoparticles
Y. Kobayashi; H. Inose; T. Nakagawa; Y. Kubota; K. Gonda; N. Ohuchi
Journal of Nanostructure in Chemistry, 2013年, ［査読有り］
SYNTHESIS OF SILVER/COPPER NANOPARTICLES AND THEIR METAL-METAL BONDING PROPERTYY. Kobayashi; T. Shirochi; Y. Yasuda; T. Morita, The present paper describes a metal-metal bonding technique using Cu nanoparticles containing Ag nanoparticles (Ag/Cu nanoparticles). The Ag/Cu nanoparticles with particle sizes of 30-85 nm and crystal sizes of 9.3 nm for Cu and 8.1 nm for Ag were produced by reducing 5.0x10(-3) M Ag+ (AgClO4) and 5.0x10(-3) M Cu2+ (Cu(NO3)(2)) simultaneously with 1.0 M hydrazine in aqueous solution containing 1.0 g/L poly(vinylpyrrolidone) as dispersing agent and 5x10(-3) M citric acid as stabilizer at room temperature. Discs of metallic Cu or metallic Ag were successfully bonded under annealing at 400 degrees C and pressurizing at 1.2 MPa for 5 min in H-2 gas with help of the Ag/Cu particles. The shear strengths required for separating the bonded discs were as large as 19.7 for the Cu discs and 16.0 MPa for the Ag discs, TECHNICAL FACULTY, BOR-SERBIA
JOURNAL OF MINING AND METALLURGY SECTION B-METALLURGY, 2013年,
［査読有り］ Preparation of Silica-Coated Gadolinium Compound Particle Colloid Solution and Its Application in Imaging
Y. Kobayashi; H. Morimoto; T. Nakagawa; K. Gonda; N. Ohuchi
Advances in Nano Research, 2013年, ［査読有り］
Preparation of Metallic Copper Nanoparticles by Reduction of Copper Ions in Aqueous Solution and Their Metal-Metal Bonding Properties
Y. Kobayashi; T. Shirochi; Y. Yasuda; T. Morita
International Journal of Physical, Natural Science and Engineering, 2013年, ［査読有り］
Low Temperature Synthesis of α-Alumina with a Seeding Technique
K. Inoue; M. Hama; Y. Kobayashi; Y. Yasuda; T. Morita
ISRN Ceramics, 2013年, ［査読有り］
Fabrication of TiO2/Pt Core-Shell Particles by Electroless Metal Plating
Y. Kobayashi; Y. Ishii; H. Yamane; K. Watanabe; H. Koda; H. Kunigami; H. Kunigami
Colloids and Surfaces A: Physiochemical and Engineering Aspects, 2013年, ［査読有り］
Imaging Processes Using Core-Shell Particle Colloid Solutions for Medical Diagnosis
Y. Kobayashi; T. Shirochi; Y. Yasuda; T. Morita
1st Annual International Conference On Physics And Chemistry Abstracts, 2013年, ［査読有り］
Preparation of Metallic Copper Nanoparticles by Reduction of Copper Ions in Aqueous Solution and Their Metal-Metal Bonding Properties
Y. Kobayashi; T. Shirochi; Y. Yasuda; T. Morita
World Academy of Science, Engineering and Technology (Conference proceedings of the 2013 International Conference on Nanotechnology, Optoelectronics and Photonics (ICNOP 2013)), 2013年, ［査読有り］
Metal-Metal Bonidng Properties of Copper Oxide Nanoparticles
T. Maeda; Y. Kobayashi; Y. Yasuda; T. Morita
12th International Conference on Atomically Controlled Surfaces, Interfaces and Nanostructures in conjunction with 21st International Colloquium on Scanning Probe Microscopy (ACSIN-12 & ICSPM21) Abstracts Book, 2013年, ［査読有り］
Fabrication of Gold Nanoparticles-Deposited Glass Plate by Electroless Metal Plating Technique and Immobilization of Proteins on It
Y. Kobayashi; Y. Ishii
IIE Int’l Conference Proceedings of International Conference on Innovations in Engineering and Technology (ICIET'2013), 2013年, ［査読有り］
Influence of Ionomer/Carbon Ratio on the Performance of a Polymer Electrolyte Fuel CellMika Eguchi; Koki Baba; Takamitsu Onuma; Kazuma Yoshida; Kenta Iwasawa; Yoshio Kobayashi; Katsuhiro Uno; Keishiro Komatsu; Maya Kobori; Mikka Nishitani-Gamo; Toshihiro Ando, We have used fibrous carbon materials as polymer electrolyte fuel cell (PEFC) electrodes. We have examined the influence of the ionomer/carbon ratio on the performance of the PEFCs. The Marimo carbon is a kind of carbon with a spherical shape, and consists of carbon nanofilaments. Fibrous carbon materials have large specific surface areas without fine pores. The reactant gases and generated water can easily diffuse among the nanofilaments. The ionomer plays two roles; one is a proton transfer activity, and the other is binding the catalyst electrodes. An excess ionomer interferes with the diffusion of gases. The ionomer/carbon ratio should affect the performance of the PEFC, especially at a high current density., MDPI AG
POLYMERS, 2012年12月,
［査読有り］ Development of Silica-Coated Silver Iodide Nanoparticles and Their BiodistributionYu Sakurai; Hiroshi Tada; Kohsuke Gonda; Motohiro Takeda; Liman Cong; Masakazu Amari; Yoshio Kobayashi; Mika Watanabe; Takanori Ishida; Noriaki Ohuchi, Nanomaterials have great potential in the field of medicine and have been studied extensively. In a previous study, we addressed the potential of silver iodide (AgI) as X-ray contrast media, because it possessed high imaging ability in the measurement by X-ray computed tomography (X-CT) in vitro, and its surface can be modified with many functional groups. We developed the method of silica coating to make AgI nanoparticles more stable and uniform in size. However, the safety and metabolism of nanoparticles in vivo remains to be determined. The objective of the present study was to evaluate the in vivo biodistribution of silica-coated AgI nanoparticles (SAgINPs). X-CT, transmission electron microscopy (TEM), and inductively coupled plasma atomic emission spectrometry (ICP-AES) were performed prior to and at intervals following the intravenous administration of SAgINPs to rats and rabbits. ICP-AES is a spectral technique that can determine the presence and concentrations of metal samples. The X-CT study showed long-period enhancement in the liver and spleen, but not in the bladder of rats. The TEM study demonstrated that SAgINPs were found in hepatocytes. Using ICP-AES, Ag was detected in the bile juice of rabbits, but not found in the urine of these animals, suggesting that SAgINPs are excreted via the liver. This study shows the quantitative biodistribution of silica-coated nanoparticles for the first time, indicating that our silica coating technique is useful for development of nanoparticles with hepatic excretion. In conclusion, the SAgINPs may provide X-ray contrast media with high imaging ability and biocompatibility., TOHOKU UNIV MEDICAL PRESS
TOHOKU JOURNAL OF EXPERIMENTAL MEDICINE, 2012年12月,
［査読有り］ Metal-metal bonding process using copper oxide nanoparticlesT. Maeda; Y. Kobayashi; Y. Yasuda; T. Morita, This work performs metal-metal bonding using CuO nanoparticles prepared with salt base reaction in aqueous solution. A colloid solution of CuO nanoparticles was prepared by mixing Cu(NO3)(2) aqueous solution and NaOH aqueous solution. Submicrometre sized leaf-like aggregates composed of CuO nanoparticles were produced at a Na/Cu ratio of 1.7 and at 20 degrees C, though Cu-2(OH)(3)NO3 was also obtained. An aging process, which is a process composed of preparation of the particles at 20 degrees C and then aging them at 80 degrees C, provided transformation from Cu-2(OH)(3)NO3 to CuO with no damage of the leaf structure. The shear strength, which was required for separating discs bonded using the particles as a filler at 400 degrees C in H-2 gas, was 32.5 MPa at the maximum for the particles prepared at the Na/Cu ratio of 1.7 with the aging process. These results indicated that the formation of leaf-like aggregates of CuO particles with high purity led to efficient metal-metal bonding., MANEY PUBLISHING
SCIENCE AND TECHNOLOGY OF WELDING AND JOINING, 2012年10月,
［査読有り］ Luminescence enhancement of Eu-doped amorphous barium titanate films with crystalline BaTiO3 nanoparticle incorporationDaisuke Nagao; Hirobumi Saito; Haruyuki Ishii; Yoshio Kobayashi; Mikio Konno, Crystalline barium titanate (BT) nanoparticles were incorporated into Eu-doped amorphous BT films to examine the influence of local permittivity around Eu ions on their luminescent properties in the BT films. The BT nanoparticles were synthesized by hydrolysis of a BT complex alkoxide in 2-methoxyethanol/ethanol cosolvent, and then incorporated into the Eu-doped films at Eu/(Eu + BT) ratio of 10 mol%. The emission intensities of Eu3+ in the film were linearly raised with volume of the nanoparticles incorporated, while dielectric constant of the film also increased with the nanoparticle volume. This indicates that the incorporation of crystalline nanoparticles is effective to enhance the luminescence of Eu ions in the amorphous film. (C) 2012 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 2012年09月
Synthesis of metallic copper nanoparticles using copper oxide nanoparticles as precursor and their metal-metal bonding propertiesT. Maeda; Y. Abe; Y. Kobayashi; Y. Yasuda; T. Morita, This work proposes a method for preparing metallic Cu nanoparticles using CuO nanoparticles as a precursor, and performs metal-metal bonding by using the metallic Cu nanoparticles. Colloid solution of CuO nanoparticles with a longitudinal particle size of 13.0 +/- 3.0, a lateral particle size of 8.4 +/- 2.2 and a crystal size of 7.8 nm was prepared with salt base reaction using Cu(NO3)(2) aqueous solution and NaOH aqueous solution. Preparation of the metallic Cu particle colloid solution was performed in water using the CuO nanoparticles, hydrazine and cetyltrimethylammonium bromide, which resulted in production of the metallic Cu nanoparticles with a particle size of 50.6 nm and a crystal size of 30.5 nm. Metallic copper discs could be bonded using the metallic Cu nanoparticles under annealing at 400 degrees C and pressurising at 1.2 MPa for 5 min in H-2 gas. A shear strength required for separating the bonded discs was recorded as high as 39.6 MPa., MANEY PUBLISHING
SCIENCE AND TECHNOLOGY OF WELDING AND JOINING, 2012年08月,
［査読有り］ Synthesis of High Concentration Colloid Solution of Silica-Coated AgI NanoparticlesYoshio Kobayashi; Marie Minato; Kazuaki Ihara; Tomohiko Nakagawa; Kohsuke Gonda; Motohiro Takeda; Noriaki Ohuchi; Atsuo Kasuya, Methods for high concentration silica-coated silver iodide (AgI/SiO2) particles, which could be practically used as X-ray contrast agent, were examined. The first was a single-step method, which was to prepare AgI nanoparticles at an AgI concentration of 5 x 10(-3) M and coat the AgI nanoparticles with silica shell by a Stober method. The second was a multiple-step method, which was to repeat a step for preparing a AgI/SiO2 particle colloid solution with 10(-3) M AgI 5 times for adjusting a final AgI concentration to 5 x 10(-3) M. In the two methods, dominant particle aggregation took place, though core-shell particles were also produced. The third was a salting-out method, which was to salt out AgI/SiO2 particles in their colloid solution prepared at an AgI concentration of 10(-3) M, remove supernatant by decantation, and redisperse the particles in a fresh solvent. Consequently, AgI/SiO2 particles with an AgI concentration as high as 0.05 M were successfully prepared with the salting-out method, and their core shell structure was not damaged during the salting-out., AMER SCIENTIFIC PUBLISHERS
JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 2012年08月,
［査読有り］ Metal-metal bonding process using metallic copper nanoparticles prepared in aqueous solutionY. Kobayashi; T. Shirochi; Y. Yasuda; T. Morita, A method for preparing metallic Cu nanoparticles in aqueous solution is proposed, and metal-metal bonding with the use of the nanoparticles is demonstrated. The metallic Cu nanoparticle colloid solution was prepared by mixing a 0.01 M aqueous solution of copper salt (copper chloride (CuCl2), copper nitrate (Cu(NO3)(2)), or copper acetate ((CH3COO)(2)Cu) (copper source) and a 0.2-1.0 M hydrazine aqueous solution (reducing reagent) in the presence of 0.0005 M citric acid and 0.005 M cetyltrimethy-lammonium bromide (stabilizers). The metallic Cu nanoparticles with average sizes in the range of 54-64 nm were prepared for all the copper salts and the hydrazine concentrations examined. A stage and a plate of metallic Cu were successfully bonded under annealing at 400 degrees C and pressurizing at 1.2 MPa for 5 min in H-2 gas with the help of the metallic Cu particles. The shear strength with the use of (CH3COO)(2)Cu was large compared to CuCl2 and Cu(NO3)(2). A shear strength required for separating the bonded Cu substrates reached the maximum value at a hydrazine concentration of 0.6 M, and it decreased beyond the concentration. Consequently, the largest shear strength of 37.7 MPa was achieved using (CH3COO)(2)Cu at the 0.6 M hydrazine concentration. (C) 2011 Elsevier Ltd. All rights reserved., ELSEVIER SCI LTD
INTERNATIONAL JOURNAL OF ADHESION AND ADHESIVES, 2012年03月,
［査読有り］ Synthesis of Au-silica core-shell particles by sol-gel processY. Kobayashi; H. Inose; T. Nakagawa; K. Gonda; M. Takeda; N. Ohuchi; A. Kasuya, This paper describes an amine free sol-gel method for silica coating of Au nanoparticles and shows an X-ray image of a colloid solution of the silica coated Au (Au-SiO2) particles. The Au nanoparticles that had a size of 16.9 +/- 1.2 nm were prepared through a conventional citrate reduction method. The silica coating was performed with a sol-gel reaction of tetraethylorthosilicate (TEOS) catalysed with NaOH in the presence of Au nanoparticles. The silica shell thickness was varied from 37 to 68 nm for TEOS concentrations of 1 x 10(-3)-20 x 10(-3)M at 4.3 x 10(-5)M of Au, 10.7M of H2O and 1.0 x 10(-3)M of NaOH. The optical properties of the Au-SiO2 particle colloid solution were related to the refractive index around the Au particles and the intensity of scattering from silica shells. The as prepared colloid solution could be concentrated up to an Au concentration of 4.3 x 10(-2) M with salting out. The concentrated colloid solution showed a high contrast X-ray image., MANEY PUBLISHING
SURFACE ENGINEERING, 2012年03月,
［査読有り］ Fabrication and fluorescence properties of multilayered core-shell particles composed of quantum dot, gadolinium compound, and silicaYoshio Kobayashi; Takuya Nozawa; Tomohiko Nakagawa; Kohsuke Gonda; Motohiro Takeda; Noriaki Ohuchi, A preparation method for multilayered quantum dot/silica/gadolinium compound/silica (QD/Si/Gd/Si) core-shell particles is proposed. Silica (Si)-coated quantum dot (QD/Si) core-shell particles were prepared by a Stober method at room temperature in water/ethanol solution with TEOS and NaOH in the presence of QD nanoparticles. Succeeding gadolinium compound (Gd)-coating of the QD/Si core-shell particles was performed by a homogeneous precipitation method using Gd(NO3)(3), urea, and polyvinylpyrrolidone in the presence of the QD/Si particles, which resulted in production of multilayered QD/silica/gadolinium compound (QD/Si/Gd) core-shell particles. For Si-coating of the QD/Si/Gd particles, the Stober method was performed at room temperature in water/ethanol solution with TEOS and NaOH in the presence of the QD/Si/Gd particles. Consequently, Si-coated QD/Si/Gd, i.e., multilayered QD/Si/Gd/Si, core-shell particles were obtained. The QD/Si/Gd/Si particles revealed strong fluorescence, which was almost comparable to the QD particles with no shells. These particles are expected to be harmless to living bodies, and have dual functions of magnetic resonance imaging and fluorescence., SPRINGER
JOURNAL OF MATERIALS SCIENCE, 2012年02月,
［査読有り］ Low-Temperature Synthesis of Crystalline Barium Titanate Nanoparticles by Reaction of Barium Hydroxide with Titanium Alkoxide
Y. Kobayashi; T. Gunji
Materials Focus, 2012年, ［査読有り］
X-ray Imaging Technique Using Colloid Solution of AgI/Silica/Poly(ethylene glycol) Nanoparticles
Y. Kobayashi; T. Ayame; T. Nakagawa; K. Gonda; N. Ohuchi
Materials Focus, 2012年, ［査読有り］
Rapid one-step synthesis, characterization and functionalization of silica coated gold nanoparticlesNewaz Mohammed Bahadur; Shun Watanabe; Takeshi Furusawa; Masahide Sato; Fumio Kurayama; Iqbal Ahmed Siddiquey; Yoshio Kobayashi; Noboru Suzuki, This paper describes a rapid, simple and one-step method for preparing silica coated gold (Au@SiO(2)) nanoparticles with fine tunable silica shell thickness and surface functionalization of the prepared particles with different groups. Monodispersed Au nanoparticles with a mean particle size of 16 nm were prepared by citrate reduction method. Silica coating was carried out by mixing the as prepared Au solution, tetraethoxysilane (TEOS) and ammonia followed by microwave (MW) irradiation. Although there are several ways of coating Au nanoparticles with silica in the literature, each of these needs pre-coating step as well as long reaction duration. The present method is especially useful for giving the opportunity to cover the colloidal Au particles with uniform silica shell within very short time and forgoes the use of a silane coupling agent or pre-coating step before silica coating. Au@SiO(2) nanoparticles with wide range of silica shell thickness (5-105 nm) were prepared within 5 min of MW irradiation by changing the concentration of TEOS only. The size uniformity and monodispersity were found to be better compared to the particles prepared by conventional methods, which were confirmed by dynamic light scattering and transmission electron microscopic techniques. The prepared Au@SiO(2) nanoparticles were further functionalized with amino, carboxylate, alkyl groups to facilitate the rapid translation of the nanoparticles to a wide range of end applications. The functional groups were identified by XPS, and zeta potential measurements. (C) 2011 Elsevier BM. All rights reserved., ELSEVIER SCIENCE BV
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 2011年12月,
［査読有り］ Preparation of CuO nanoparticles by metal salt-base reaction in aqueous solution and their metallic bonding propertyY. Kobayashi; T. Maeda; K. Watanabe; K. Ihara; Y. Yasuda; T. Morita, This article describes a method for preparing CuO nanoparticles in aqueous solution, and a demonstration of feasibility of metallic bonding with the use of the CuO particles. Colloid solution of CuO nanoparticles was prepared from Cu(NO3)(2) aqueous solution (0.01 M) and NaOH aqueous solution (0.019 M) at 5-80 A degrees C. Leaf-like aggregates with an average size of 567 nm composed of CuO nanoparticles were produced at 20 A degrees C. The size of leaf-like aggregates decreased with increasing reaction temperature. Metallic copper discs could be bonded using the CuO nanoparticles under annealing at 400 A degrees C and pressurizing at 1.2 MPa for 5 min in H-2 gas. A shear strength required for separating the bonded discs was 25.4 MPa for the CuO nanoparticles prepared at 20 A degrees C, whose aggregates were the largest among the CuO particles examined. These results indicated that the formation of leaf-like aggregates of CuO nanoparticles led to efficient metallic bonding., SPRINGER
JOURNAL OF NANOPARTICLE RESEARCH, 2011年10月,
［査読有り］ Preferred test conditions for measuring flow rate distribution between cells in a polymer electrolyte fuel cell stackFumiaki Sekine; Mika Eguchi; Yoshio Kobayashi; Yasuyuki Tsutsumi, A new and practical testing technique was developed for measuring the flow rate distribution between cells in a stack that did not contain any internal sensors. The flow rate distribution is obtained by measuring the hydrogen limiting current of each cell in the stack while a mixed gas of hydrogen and dimethyl ether is supplied to the anode and hydrogen to the cathode. In order to measure large flow rate deviations between cells, it is necessary to decrease the flow rate of the anode hydrogen and to sufficiently humidify the cells. The faster the increasing rate of the current, the more the apparent hydrogen limiting current increases than the theoretical electrochemical equivalent current. However, the relative flow rate deviations between cells can be obtained by a practical accuracy using the ratio of the apparent hydrogen limiting current. Humidification of the cell is indispensable for the measurement and a method using dry anode gas and humidified cathode gas is recommended. The preferred test conditions for measuring the flow rate distribution between cells in a PEFC stack are proposed. (C) 2011 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
JOURNAL OF POWER SOURCES, 2011年10月,
［査読有り］ X-ray imaging of newly-developed gadolinium compound/silica core-shell particlesHikaru Morimoto; Marie Minato; Tomohiko Nakagawa; Masahide Sato; Yoshio Kobayashi; Kohsuke Gonda; Motohiro Takeda; Noriaki Ohuchi; Noboru Suzuki, A preparation method for gadolinium compound (Gd) nanoparticles coated with silica (Gd/SiO2) is proposed. Gd nanoparticles were prepared with a homogeneous precipitation method at 80 A degrees C using 1.0 x 10(-3) M Gd(NO3)(3) and 0.5 M urea in the presence of 1.0 g/L stabilizer. Among stabilizers examined. Sodium n-dodecyl sulfate (SDS) was suitable as the stabilizer for preparing small Gd nanoparticles, and consequently Gd nanoparticles with a size of 46.2 +/- A 12.4 nm were prepared using the SDS. Silica-coating of the Gd nanoparticles was performed by a Stober method at room temperature using 0.013 M TEOS and 2.0 x 10(-3) M NaOH in water/1-propanol solution in the presence of 1.0 x 10(-3) M Gd nanoparticles, which resulted in production of Gd/SiO2 particles with an average size of 64.2 +/- A 14.4 nm. The Gd/SiO2 particles were surface-modified with 3-aminopropyltrimethoxysilane and succinic anhydride. It was confirmed by measurement of electrophretic light scattering that amino group or carboxyl group was introduced onto the Gd/SiO2 particles. The gadolinium concentration of 1.0 x 10(-3) M in the as-prepared colloid solution was increased up to a gadolinium concentration of 0.4 M by centrifugation. The core-shell structure of Gd/SiO2 particles was undamaged, and the colloid solution was still colloidally stable, even after the concentrating process. The concentrated Gd/SiO2 colloid solution showed an X-ray image with contrast as high as a commercial Gd complex contrast agent. Internal organs in a mouse could be imaged injecting the concentrated colloid solution into it., SPRINGER
JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 2011年09月,
［査読有り］ Fabrication of BaTiO3-Y:Eu composite micropatterns by combination of laser induced pyrolysis method and nanocrystalline seeding techniqueY. Kobayashi; N. Shimizu; D. Nagao; A. Watanabe; M. Konno, This paper describes a method for fabricating dielectric BaTiO3 (BT) micropatterns seeded with BT nanocrystalline particles and Y:Eu compound nanoparticles. The method is a combination of a laser induced pyrolysis method and a nanocrystalline seeding technique. The BT particles were prepared by hydrolysis of BT complex alkoxide with polyvinylpyrollidone (PVP). The Y: Eu particles were prepared by homogeneous precipitation of Y(NO3)(3) and Eu(NO3)(3) with PVP. A precursor film was fabricated spin-coating a solution containing BT complex alkoxide, the BT particles, the Y:Eu particles and PVP on Pt substrate. A micropattern with a line width of about 1-2 mu m was fabricated by irradiating an Ar+ laser beam on the film, and then stripping laser unirradiated region with HCl aqueous solution. The micropattern containing 5 vol.-% BT particles and 5 vol.-% Y: Eu particles revealed luminescence at 614 nm derived from Eu3+. Its dielectric constant and dissipation factor attained 21.2 and 0.089 respectively., MANEY PUBLISHING
SURFACE ENGINEERING, 2011年07月,
［査読有り］ Control of shell thickness in silica-coating of Au nanoparticles and their X-ray imaging propertiesYoshio Kobayashi; Hiromitsu Inose; Tomohiko Nakagawa; Kohsuke Gonda; Motohiro Takeda; Noriaki Ohuchi; Atsuo Kasuya, This paper describes a performance of precise control of shell thickness in silica-coating of Au nanoparticles based on a sol-gel process, and an investigation into X-ray imaging properties for the silica-coated Au (Au/SiO(2)) particles. The Au nanoparticles with a size of 16.9 +/- 1.2 nm prepared through a conventional citrate reduction method were used as core particles. The Au nanoparticles were silica-coated with a sol-gel reaction using tetraethylorthosilicate (TEOS) as a silica source, sodium hydroxide (NaOH) as a catalyst, and (3-aminopropyl) trimethoxysilane (APMS) as a silane coupling agent. An increase in TEOS concentration resulted in an increase in shell thickness. Under certain concentrations of Au, H(2)O, NaOH, and APMS, the Au/SiO(2) particles with silica shell thickness of 6.0-61.0 nm were produced with varying TEOS concentration. Absorption peak wavelength of surface plasmon resonance of the Au/SiO(2) colloid solution depended on silica shell thickness, which agreed approximately with the predictions by Mie theory. The as-prepared colloid solution could be concentrated up to an Au concentration of 0.19 M with salting-out and centrifugation. The concentrated colloid solution showed an X-ray image with high contrast, and a computed tomography value for the colloid solution with an Au concentration of 0.129 M was achieved 1329.7 +/- 52.7 HU. (C) 2011 Elsevier Inc. All rights reserved., ACADEMIC PRESS INC ELSEVIER SCIENCE
JOURNAL OF COLLOID AND INTERFACE SCIENCE, 2011年06月,
［査読有り］ Preparation of silica-coated AgI nanoparticles by an amine-free process and their X-ray imaging propertiesTetsuya Ayame; Yoshio Kobayashi; Tomohiko Nakagawa; Kohsuke Gonda; Motohiro Takeda; Noriaki Ohuchi, AgI nanoparticles coated with silica shell (AgI/SiO2) were prepared with an amine-free process, i.e. a modified Stober method. A colloid solution of 3.9 x 10(-4) M AgI nanoparticles was prepared mixing silver perchlorate at 3.9 x 10(-4) M and potassium iodide at 7.8 x 10(-4) M. A silica-coating was performed at 4.5 x 10(-6) M 3-mercaptopropyltrimethoxysilane, 0.1 x 10(-3)-2.0 x 10(-3) M NaOH, 11-25 M H2O, and 0.4 x 10(-3)-80 x 10(-3) M tetraethylorthosilicate (TEOS) in the presence of 1.0 x 10(-4) M AgI nanoparticles in ethanol. The AgI/SiO2 particles with a size of 53.2 +/- 9.3 nm and an AgI core size of 13.5 +/- 4.2 nm were prepared at 1.2 x 10(-3) M NaOH, 15 M H2O, and 4.0 x 10(-3) M TEOS. The AgI concentration of 1.0 x 10(-4) M in the as-prepared colloid solution was increased up to an AgI concentration of 0.32 M by salting-out and centrifugation. The core-shell structure of AgI/SiO2 particles was undamaged, and the colloid solution was still colloidally stable, even after the condensation. The concentrated AgI/SiO2 colloid solution showed a high-contrast X-ray image, and its computed tomography value was 2908 +/- 37 HU. Internal organs in a mouse could be imaged injecting the concentrated colloid solution into it. (C) 2011 The Ceramic Society of Japan. All rights reserved., CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
JOURNAL OF THE CERAMIC SOCIETY OF JAPAN, 2011年06月,
［査読有り］ Preparation of metallic copper nanoparticles in aqueous solution and their bonding propertiesY. Kobayashi; T. Shirochi; Y. Yasuda; T. Morita, This paper describes a method for preparing metallic Cu nanoparticles in aqueous solution, and a bonding technique using the nanoparticles. Preparation of the Cu particle colloid solution was performed in water at room temperature in air using a copper source (0.01 M CuCl2), a reducing reagent (0.1-1.0 M hydrazine), and stabilizers (0-1.5 x 10(-3) M citric acid and 5.0 x 10-3 M cetyltrimethylammonium bromide). The metallic Cu nanoparticles with a size of 71 +/- 14 nm were prepared at 0.4 M hydrazine and 5 x 10(-4) M citric acid. A stage and a plate of metallic Cu were successfully bonded under annealing at 400 degrees C and pressurizing at 1.2 MPa for 5 min in H-2 gas with help of the metallic Cu particles. A shear strength required for separating the bonded Cu substrates was as high as 28.6 MPa. (C) 2010 Elsevier Masson SAS. All rights reserved., ELSEVIER SCIENCE BV
SOLID STATE SCIENCES, 2011年03月,
［査読有り］ Low temperature fabrication of barium titanate hybrid films and their dielectric propertiesYoshio Kobayashi; Hirobumi Saito; Takafumi Kinoshita; Daisuke Nagao; Mikio Konno, A method for incorporating BT nano-crystalline into barium titanate (BT) films is proposed for a low temperature fabrication of high dielectric constant films. BT nanoparticles were synthesized by hydrolysis of a BT complex alkoxide in 2-methoxyethanol (ME)/ethanol cosolvent. As the ME volume fraction in the cosolvent (ME fraction) increased from 0 to 100%, the particle and crystal sizes tended to increase from 13.4 to 30.2 nm and from 15.8 to 31.4 nm, respectively, and the particle dispersion in the solution became more improved. The BT particles were mixed with BT complex alkoxide dissolved in an ME/ethanol cosolvent for preparing a precursor solution that was then spin-coated on a Pt substrate and dried at 150 degrees C. The dielectric constant of the spin-coated BT hybrid film increased with an increase in the volume fraction of the BT particles in the film. The dissipation factor of the hybrid film tended to decrease with an increase in the ME fraction in the precursor solution. The hybrid film fabricated at a BT fraction of 30% and an ME fraction of 25% attained a dielectric constant as high as 94.5 with a surface roughness of 14.0 nm and a dissipation factor of 0.11. (C) 2010 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE SA
THIN SOLID FILMS, 2011年01月,
［査読有り］ Characterization of Multi-Walled Carbon Nanotube-Supported Pt Catalyst Prepared by Metal Nanocolloidal Solution For a Polymer Electrolyte Fuel Cell Catalyst
M. Eguchi; S. Yamamoto; T. Aoki; M. Kikuchi; K. Uno; Y. Kobayashi; M. Nishitani-Gamo; T. Ando
Journal of the Surface Finishing Society of Japan, 2011年, ［査読有り］
Metal-Metal Bonding Process Using Copper Nanoparticles
Y. Kobayashi; S. Ishida; K. Ihara; Y. Yasuda; T. Morita
Proceedings of the 19th International Conference on Composites Engineering or Nano Engineering (ICCE-19), 2011年, ［査読有り］
Preparation of Activated-Carbon-Supported Iron Oxide by Homogeneous Precipitation TechniqueEiichi F. Mine; Yuka Kikuchi; Yoshio Kobayashi; Hiroshi Ueno, Iron oxide supported on activated carbon (IO/C) was prepared by a process based on homogeneous precipitation. The iron oxide content and specific surface area of the IO/C were varied by varying the ratio between initial amounts of activated carbon and iron(II) chloride tetrahydrate. Citric acid was used as a dispersant of iron oxide particles on activated carbon. The size of the magnetite particles in the IO/C prepared in the presence of citric acid was decreased with an increase in the concentration of citric acid at a constant magnetite content. The saturation magnetization of the IO/C varied from 0.5 to 39.9 emu/g according to the composition, content, and size of the iron oxide particles., SOC CHEMICAL ENG JAPAN
JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 2011年,
［査読有り］ Synthesis of Silica-Coated AgI Nanoparticles and Immobilization of Proteins on ThemYoshio Kobayashi; Marie Minato; Kazuaki Ihara; Masahide Sato; Noboru Suzuki; Motohiro Takeda; Noriaki Ohuchi; Atsuo Kasuya, This paper describes a method for preparing silica-coated silver iodide (AgI/SiO(2)) particles and immobilizing proteins on the AgI/SiO(2) particles. Colloid solution of AgI particles was prepared by mixing AgClO(4) aqueous solution and KI aqueous solution. Silica-coating of the AgI particles was performed by adding 3-mercaptopropyltrimethoxysilane, tetraethylorthosilicate/ethanol solution and NaOH aqueous solution successively to the AgI colloid solution. TEM observation revealed that the AgI nanoparticles were coated with uniform silica shell. The AgI/SiO(2) particles were surface-modified with 3-aminopropyltrimethoxysilane and succinic anhydride. It was confirmed by XPS measurement that amino group or carboxyl group was introduced onto the AgI/SiO(2) particles. Protein-immobilization was performed in aqueous solution with bovine serum albumin (BSA) in the presence of the surface-modified AgI/SiO(2) particles. UV-VIS absorption spectroscopy revealed that the BSA was adsorbed on the surface-modified particles., AMER SCIENTIFIC PUBLISHERS
JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 2010年11月,
［査読有り］ A durable PtRu/C catalyst with a thin protective layer for direct methanol fuel cellsYuzuru Shimazaki; Sho Hayasaka; Tsubasa Koyama; Daisuke Nagao; Yoshio Kobayashi; Mikio Konno, A methanol oxidation catalyst with improved durability in acidic environments is reported. The catalyst consists of PtRu alloy nanoparticles on a carbon support that were stabilized with a silane-coupling agent. The catalyst was prepared by reducing ions of Pt and Ru in the presence of a carbon support and the silane-coupling agent. The careful choice of preparatory conditions such as the concentration of the silane-coupling agent and solution pH resulted in the preparation of catalyst in which the PtRu nanoparticles were dispersively adsorbed onto the carbon support. The catalytic activity was similar to that of a commercial catalyst and was unchanged after immersion in sulfuric acid solution for 1000 h, suggesting the high durability of the PtRu catalyst for the anode of direct methanol fuel cells. (C) 2010 Elsevier Inc. All rights reserved., ACADEMIC PRESS INC ELSEVIER SCIENCE
JOURNAL OF COLLOID AND INTERFACE SCIENCE, 2010年11月,
［査読有り］ Uniform Silica Coated Fluorescent Nanoparticles: Synthetic Method, Improved Light Stability and Application to Visualize Lymph Network TracerLiman Cong; Motohiro Takeda; Yohei Hamanaka; Kohsuke Gonda; Mika Watanabe; Masutaka Kumasaka; Yoshio Kobayashi; Masaki Kobayashi; Noriaki Ohuchi, Background: The sentinel lymph node biopsy (SLNB) was developed as a new modality in the surgical diagnosis of lymph node metastases. Dye and radioisotope are major tracers for the detection of sentinel lymph nodes (SLN). Dye tends to excessively infiltrate into the interstitium due to their small size ( less than several nanometers), resulting in difficulties in maintaining clear surgical fields. Radioisotopes are available in limited number of hospitals. Fluorescent nanoparticles are good candidates for SLN tracer to solve these problems, as we can choose suitable particle size and fluorescence wavelength of near-infrared. However, the use of nanoparticles faces safety issues, and many attempts have been performed by giving insulating coats on nanoparticles. In addition, the preparation of the uniform insulating layer is important to decrease variations in the quality as an SLN tracer.
Methodology/Principal Findings: We herein succeeded in coating fluorescent polystyrene nanoparticles of 40 nm with uniform silica layer of 13 nm by the modified Stober method. The light stability of silica coated nanoparticles was 1.3-fold greater than noncoated nanoparticles. The popliteal lymph node could be visualized by the silica coated nanoparticles with injection in the rat feet.
Conclusions/Significance: The silica coated nanoparticles in lymph nodes could be observed by transmission electron microscope, suggesting that our silica coating method is useful as a SLN tracer with highly precise distribution of nanoparticles in histological evaluation. We also demonstrated for the first time that a prolonged enhancement of SLN is caused by the phagocytosis of fluorescent nanoparticles by both macrophages and dendritic cells., PUBLIC LIBRARY SCIENCE
PLOS ONE, 2010年10月,
［査読有り］ Measuring method for flow rate distribution between cells in a polymer electrolyte fuel cell stackFumiaki Sekine; Mika Eguchi; Yoshio Kobayashi; Yasuyuki Tsutsumi, The fuel cell transmogrified from a single cell that was the research object to stack is used in various fields such as cars, portable power sources, and fuel-cell cogeneration systems. It is preferable in the stack for the flow rate distribution between cells to be uniform because of the performance gain in power generation efficiency and longevity. As for the flow rate distribution between cells, the method for measuring using smoke in the measuring method and making visible the heat distribution in the stack is reported. However, a research stack was used with these measures, not a stack for practical use. In this report, a method for measuring the flow rate distribution between cells which can also be used for a cell that uses hydrogen limiting current in practical use was examined. (C) 2009 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
JOURNAL OF POWER SOURCES, 2010年09月,
［査読有り］ Preparation of catalyst for a polymer electrolyte fuel cell using a novel spherical carbon supportMika Eguchi; Atsuhiko Okubo; Shun Yamamoto; Mayuko Kikuchi; Katsuhiro Uno; Yoshio Kobayashi; Mikka Nishitani-Gamo; Toshihiro Ando, In this study, the support Pt catalyst was supported by a novel spherical carbon using a convenient technique. Two different preparation methods utilizing a nanocolloidal solution method without heat treatment were developed (methods 1 and 2). The scanning electron microscope (SEM) and transmission electron microscope (TEM) observations showed that the Pt nanoparticles (particle size) were supported, with higher dispersion being achieved with method 2 than method 1. The peak of the Pt metal was confirmed from the X-ray diffraction (XRD) measurement. Based on the inductively coupled plasma mass spectrometry (ICP-MS) measurements, Pt loading was 19.5 wt.% in method 1 and approximately 50 wt.% in method 2. The Pt specific surface area of the Pt/novel spherical carbon catalyst calculated from the cyclic voltammetry (CV) measurement result was larger than that of the commercially available Pt/Ketjen catalyst. These results indicated that the Pt nanoparticles were supported in high dispersion without heat treatment using novel spherical carbon as a carbon support. (C) 2010 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
JOURNAL OF POWER SOURCES, 2010年09月,
［査読有り］ Direct coating of quantum dots with silica shellYoshio Kobayashi; Takuya Nozawa; Tomohiko Nakagawa; Kohsuke Gonda; Motohiro Takeda; Noriaki Ohuchi; Atsuo Kasuya, This paper describes a method for direct coating of fluorescent semiconductor nanoparticles with silica shell. The fluorescent semiconductor nanoparticles used were CdSe (x) Te(1-x) nanoparticles coated with ZnS and succeedingly surface-modified with carboxyl groups, or quantum dots (Q-dots). The Q-dots were silica-coated by performing sol-gel reaction of tetraethyl orthosilicate (TEOS) using NaOH as a catalyst in the presence of the Q-dots. Quasi-perfect Q-dots/silica core-shell particles were formed at 5.0 M H(2)O and 4.0 x 10(-4) M NaOH. Under these concentrations of H(2)O and NaOH, the particle size of Q-dots/silica particles could be varied from 20.1 to 38.1 nm as the TEOS concentration increased from 2.5 x 10(-4) to 50 x 10(-4) M. The Q-dots/silica particles showed fluorescence as well as the uncoated Q-dots., SPRINGER
JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 2010年07月,
［査読有り］ Electrolyte-Added One-Pot Synthesis for Producing Monodisperse, Micrometer-Sized Silica Particles up to 7 μmH. Nakabayashi; A. Yamada; M. Noba; Y. Kobayashi; M. Konno; D. Nagao, A facile one-pot synthesis to produce micrometer-sized silica particles with low polydispersity was examined in a semibatch process where an ethanol solution of tetraethyl orthosilicate (TEOS) was continuously supplied to another ethanol solution of water and ammonia containing an electrolyte of LiCl, NaCl, or KCl. Supply rates of the TEOS solution was ranged with the water and electrolyte concentrations, which indicated that the addition of KCl at a low water concentration was effective to increase size of silica particles in a micrometer range. Highly monodisperse silica particles with an average size of 6.6 mu m were successfully produced at 3 mol/m(3) KCl and 5 kmol/m(3) water. The efficiency of KCl addition for producing the lame particles is interpreted by the previously proposed nucleation and growth mechanism that expects rapid particle coagulation in early reaction stage for particles which have reduced surface potential by the adsorption of cations with a large ionic radius. It is confirmed from competitive growth reactions that the silica particle growth follows the reaction-limited mechanism even in the semibatch process., AMER CHEMICAL SOC
Langmuir, 2010年05月,
［査読有り］ Fabrication of BaTiO3 Micropatterns by a Combination of Laser-Induced Pyrolysis Method and Nano-Crystalline Seeding Technique and Their Dielectric PropertiesYoshio Kobayashi; Naoki Shimizu; Daisuke Nagao; Akira Watanabe; Mikio Konno, This paper describes a method for fabricating dielectric BaTiO3 (BT) micropatterns. The method used in the present work is a combination of a laser-induced pyrolysis method and a nano-crystalline seeding technique. BT nano-crystalline particles used for the seeding are prepared by hydrolysis of a BT complex alkoxide. A precursor solution of a BT complex alkoxide containing the BT nano-crystalline particles and polyvinylpyrollidone (PVP) is spin-coated on a Pt substrate. Micropatterns with a line width of ca. 1-2 mu m are fabricated by irradiating an Ar+ laser beam with a beam waist diameter of 0.74 mu m at a laser energy density of 27 MW/cm(2) and a scanning speed of 25 mu m/s on the spin-coated BT films, and then stripping laser-unirradiated regions on the films with an HCl aqueous solution. The use of BT particles prepared in the presence of PVP with a small molecular weight provides clear micropatterns and high dielectric constant. The dielectric constant and dissipation factor of the micropattern fabricated at 20 vol% BT particles with an average size of 12.9 nm prepared in the presence of PVP with a molecular weight of 10000 attain 78.7 and 0.089, respectively, for a measurement frequency of 100 kHz., SOC CHEMICAL ENG JAPAN
JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 2010年,
［査読有り］ Direct Silica-Coating of Quantum DotsYoshio Kobayashi; Takuya Nozawa; Motohiro Takeda; Noriaki Ohuchi; Atsuo Kasuya, A method for direct silica-coating of fluorescent semiconductor nanoparticles is proposed. The fluorescent semiconductor nanoparticles used are quantum dots (Q-dots), which are CdSe(x)Te(1-x) nanoparticles coated with ZnS and succeedingly surface-modified with amino groups. The silica-coating was performed in the presence of the Q-dots in 1-15M H(2)O, 0.4 x 10(-4)-40 x 10(-4) M NaOH and 0.5 x 10(-4)-50 x 10(-4) M tetraethyl orthosilicate (TEOS). Silica shells were formed at 5M H(2)O and 4 x 10(-4) M NaOH. Under these concentrations of H(2)O and NaOH, the particle size of silica-coated Q-dots could be varied from 15.8 to 31.7 nm as the TEOS concentration was increased from 2.5 x 10(-4) to 50 x 10(-4) M. The silica-coated Q-dots showed fluorescence as well as the uncoated Q-dots., SOC CHEMICAL ENG JAPAN
JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 2010年,
［査読有り］ METALLIC BONDING WITH THE USE OF COPPER COMPOUND POWDERSKazuaki Ihara; Y. Kobayashi; N. Shibamiya; M. Minato; Y. Yasuda; T. Morita; S. Yamada, This paper describes a method for preparing CuI nanoparticles in aqueous solution, and demonstrates the feasibility of metallic bonding using Cul nanoparticles. A colloidal solution of CuI nanoparticles with an average size of 128 nm was prepared from CuCl2 (0.01 M), KI (0.01 M), and a reducing reagent, Na2SO3 (0.05 M), in water at room temperature. A metallic Cu stage and plate were successfully bonded by annealing at 400 degrees C and pressurizing at 1.2 MPa for 5 min in H-2 gas with the help of CuO obtained by pre-annealing the CuI particles in air at 400 degrees C. The shear strength required to separate the bonded Cu substrates was 14.8 MPa., AMER CERAMIC SOC
CHARACTERIZATION AND CONTROL OF INTERFACES FOR HIGH QUALITY ADVANCED MATERIALS III, 2010年,
［査読有り］ Fabrication of Barium Titanate Nanoparticles-Epoxy Resin Composite Films and Their Dielectric PropertiesY. Kobayashi; A. Kurosawa; D. Nagao; M. Konno, A method for fabricating epoxy resin films dispersing the surface-modified barium titanate (BT) particles (BTepoxy resin composite films) are proposed. BT particles with a size of 7.8 nm and a crystal size of 8.6 nm were synthesized with a complex alkoxide method. To introduce epoxy groups on the BT particle surface, the BT particles were surface-modified with 2-(3,4-epoxycyclohexyl)- ethyltrimethoxysilane. A precursor solution, which was prepared by prereacting 2,2-bis(4-glycidyloxyphenyl) propane (BGPP) and phthalic anhydride in 4-butyrolactone and adding the surface-modified BT particles to the prereacting solution, was spin-coated on glass substrates to fabricate the composite films. An increase in BT volume fraction in film increased dielectric constant of the composite film while keeping dissipation factor below 0.03. The dielectric constant attained 10.8 at a BT volume fraction of 30% in film that was around twice higher than pure epoxy resin film. © 2009 Society of Plastics Engineers.
Polymer Composites, 2010年,
［査読有り］ Silica coating of Co–Pt alloy nanoparticles prepared in the presence of poly(vinylpyrrolidone)Yoshio Kobayashi; Hidekazu Kakinuma; Daisuke Nagao; Yasuo Ando; Terunobu Miyazaki; Mikio Konno, This article describes a method for silica coating of Co-Pt alloy nanoparticles prepared in the presence of poly(vinylpyrrolidone) (PVP) as a stabilizer. The Co-Pt nanoparticles were prepared in an aqueous solution at 25-80 A degrees C from CoCl(2) (3.0 x 10(-4) M), H(2)PtCl(6) (3.0 x 10(-4) M), PVP (0-10 g/L), and NaBH(4) (4.8 x 10(-3)-2.4 x 10(-2) M). The silica coating was performed for the Co-Pt nanoparticle colloid containing the PVP ([Co] = [Pt] = 3.0 x 10(-5) M) at 25 A degrees C in (1/4) (v/v) water/ethanol solution with tetraethoxyorthosilicate (TEOS) (7.2 x 10(-5)-7.2 x 10(-3) M) and ammonia (0.1-1.0 M). Silica particles, which had an average size of 43 nm and contained multiple cores of Co-Pt nanoparticles with a size of ca. 8 nm, were produced at 1.4 x 10(-3) M TEOS and 0.5 M ammonia after the preparation of Co-Pt nanoparticles at 80 A degrees C, 5 g/L PVP, and 2.4 x 10(-2) M NaBH(4). Their core particles were fcc Co-Pt alloy crystallites. Their saturation magnetization was 2.0-emu/g sample, and their coercive field was 12 Oe., SPRINGER
J Nanopart Res., 2009年10月,
［査読有り］ Dynamics of different-sized solid-state nanocrystals as tracers for a drug-delivery system in the interstitium of a human tumor xenograftMasaaki Kawai; Hideo Higuchi; Motohiro Takeda; Yoshio Kobayashi; Noriaki Ohuchi, Introduction: Recent anticancer drugs have been made larger to pass selectively through tumor vessels and stay in the interstitium. Understanding drug movement in association with its size at the single-molecule level and estimating the time needed to reach the targeted organ is indispensable for optimizing drug delivery because single cell-targeted therapy is the ongoing paradigm. This report describes the tracking of single solid nanoparticles in tumor xenografts and the estimation of arrival time.Methods: Different-sized nanoparticles measuring 20, 40, and 100 nm were injected into the tail vein of the female Balb/c nu/nu mice bearing human breast cancer on their backs. The movements of the nanoparticles were visualized through the dorsal skin-fold chamber with the high-speed confocal microscopy that we manufactured.Results: An analysis of the particle trajectories revealed diffusion to be inversely related to the particle size and position in the tumor, whereas the velocity of the directed movement was related to the position. The difference in the velocity was the greatest for 40-nm particles in the perivascular to the intercellular region: difference = 5.8 nm/s. The arrival time of individual nanoparticles at tumor cells was simulated. The estimated times for the 20-, 40-, and 100-nm particles to reach the tumor cells were 158.0, 218.5, and 389.4 minutes, respectively, after extravasation.Conclusions: This result suggests that the particle size can be individually designed for each goal. These data and methods are also important for understanding drug pharmacokinetics. Although this method may be subject to interference by surface molecules attached on the particles, it has the potential to elucidate the pharmacokinetics involved in constructing novel drug-delivery systems involving cell-targeted therapy. © 2009 Kawai et al.
licensee BioMed Central Ltd.
Breast Cancer Research, 2009年07月,
［査読有り］ Fabrication of barium titanate nanoparticles- polymethylmethacrylate composite films and their dielectric propertiesY. Kobayashi; A. Kurosawa; D. Nagao; M. Konno, A method for incorporating barium titanate (BT) nanoparticles into polymethylmethacrylate (PMMA) is proposed to prepare composite films with a high dielectric constant and high transparency. BT particles with particle sizes of 7.8-24.0 nm and crystal sizes of 8.60-17.7 nm were synthesized with a complex alkoxide method. Surface of the BT particles was modified with 3-methacryloxypropyltrimethoxysilane to introduce double bonds that was grafted with PMMA. The PMMA-grafted BT particles were suspended in PMMA/N-methyl-2- pyrrodinone solution and spin-coated onto glass substrates to prepare the PMMA/BT composite films. The surface modification gave composite films having smooth surfaces and high transparency. An increase in BT particle size and BT volume fraction in the film tended to increase the dielectric constant while keeping the dissipation factor around 5%. The dielectric constant of the film prepared for a particle size of 24.0 nm at 39 vol% attained a value of 19.8 that was around four times higher than that of the pure PMMA film. The dielectric constants of the BT particles estimated by the application of Lichtenecker's mixing model to the composite films were 75.3, 105.1, and 166.3 for particle sizes of 7.8, 11.0, and 24.0 nm, respectively. POLYM. ENG. SCI., 49:1069-1075, 2009. © 2009 Society of Plastics Engineers.
Polymer Engineering and Science, 2009年06月,
［査読有り］ Fabrication of monodispersed, multilayered silica-Y:Eu-silica core-shell particles and their photonic crystalsYoshio Kobayashi; Jun-Ichi Imai; Daisuke Nagao; Mikio Konno, Methods for preparing monodispersed, multilayered silica-Y:Eu-silica core-shell particles and for fabricating their colloidal photonic crystals are proposed. Silica-Y:Eu core-shell particles with a size of 360 nm were synthesized with a homogeneous precipitation method at 80°C in a 50/50 (v/v) water/propanol solution at 0.0009 mol/dm3 Y(NO3)3, 0.0001 mol/dm3 Eu(NO3)3 0.5 mol/dm3 urea, I g/dm3 polyvinylpyrrolidone (PVP) and 0.01 vol% suspension of silica particles with an average size of 330 nm. Succeeding silica-coating of the silica-Y:Eu core-shell particles was performed in ethanol at 10 mmol/dm3 tetraethylorthosilicate, 11 mol/dm3 H2O, 0.5 mol/dm3 ammonia, 5 mmol/dm3 acetic acid, 1 g/dm3 PVP and 0.001 vol% suspension of silica:Eu core-shell particles. Consequently, multilayered silica-Y:Eu-silica core-shell particles with an average size of 460 nm and a coefficient of variation as low as 3.0% could be obtained. Colloidal crystals composed of these particles exhibited both reflection based on Bragg diffraction and luminescence of Y:Eu. Copyright © 2009 The Society of Chemical Engineers.
Journal of Chemical Engineering of Japan, 2009年,
［査読有り］ Y. Kobayashi, J. Imai, D. Nagao, M. Konno
Fabrication of; Monodispesed; Multilayered Silica-Y; Eu-Silica Core-Shell Particles; d Their Photonic Crystals
Journal of Chemical Engineering of Japan, 2009年, ［査読有り］
Y. Kobayashi, A. Kurosawa, D. Nagao, M. Konno
Fabrication of; Barium Titanate Nanoparticles-Polymethylmethacrylate Composite Films; Their Dielectric Properties
Polymer Engineering & Science, 2009年, ［査読有り］
Y. Kobayashi, H. Kakinuma, D. Nagao, Y. Ando, T. Miyazaki, M. Konno
Silica-coating of Co-P; alloy nanoparticles prepared in the; presence of poly; lidone
Journal of Nanoparticle Research, 2009年, ［査読有り］
Y. Kobayashi, S. Ishida, K. Ihara, Y. Yasuda, T. Morita, S. Yamada
Synthesis of Metallic Copper Nanoparticles Coated with Polypyrrole
Colloid and Polymer Science, 2009年, ［査読有り］
M. Kawai, H. Higuchi, M. Takeda, Y. Kobayashi, N. Ohuchi
Dynamics of Different; Sized Solid; State Nanocrystals as Tracers for a; Drug Delivery; System in; the Interstitium of; a; Human Tumor; Xenograft
Breast Cancer Research, 2009年, ［査読有り］
Fabrication of high concentration barium titanate/polyvinylpyrrolidone nano-composite thin films and their dielectric propertiesY. Kobayashi; A. Kosuge; M. Konno, A simple method for fabricating polyvinylpyrrolidone (PVP) thin films containing barium titanate (BT) nanoparticles on electrodes is proposed. The BT particles that had an average size of ca. 8 nm and a tetragonal crystalline phase were prepared with complex alkoxide methods in the presence of PVP. PVP/ ethanol/water solutions containing the BT particles, which were suspended with sonication for 0-12 h, and were spin-coated on ITO glass substrates. Surface roughness was low at a sonication time longer than 4 h. As a BT concentration for the film increased from 0 to 85 wt%, its dielectric constant increased from 7 to 30 with dissipation factors below 0.12. The present method can be used to prepare high capacitance films at low temperatures, which have favorable electrical properties or characteristics. (C) 2008 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
APPLIED SURFACE SCIENCE, 2008年12月,
［査読有り］ Synthesis of highly monodisperse particles composed of a magnetic core and fluorescent shellDaisuke Nagao; Mikio Yokoyama; Noriko Yamauchi; Hideki Matsumoto; Yoshio Kobayashi; Mikio Konno, Highly monodisperse particles composed of a magnetic silica core and fluorescent polymer shell were synthesized with a combined technique of heterocoagulation and soap-free emulsion polymerization. Prior to heterocoagulation, monodisperse, submicrometer-sized silica particles were prepared with the Stober method, and magnetic nanoparticles were prepared with a modified Massart method in which a cationic silane coupling agent of N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride was added just after coprecipitation of Fe2+ and Fe3+. The silica particles with negative surface potential were heterocoagulated with the magnetic nanoparticles with positive surface potential. The magnetic silica particles obtained with the heterocoagulation were treated with sodium silicate to modify their surfaces with silica. In the formation of a fluorescent polymer shell onto the silica-coated magnetic silica cores. an amphoteric initiator of 2,2'-azobis[N-(2-carboxyethyl)-2-2-methylpropionamidine] (VA-057) was used to control the colloidal stability of the magnetic cores during the polymer coating. The polymerization of St in the presence of a hydrophobic fluorophore of pyrene Could coat the cores with fluorescent polymer shells, resulting in monodisperse particles with a magnetic silica core and fluorescent polymer shell. Measurements of zeta potential for the composite particles in different pH values indicated that the composite particles had an amphoteric property originating from VA-057 initiator., AMER CHEMICAL SOC
LANGMUIR, 2008年09月,
［査読有り］ Preparation of composite particles with magnetic silica core and fluorescent polymer shellDaisuke Nagao; Mikio Yokoyama; Shu Saeki; Yoshio Kobayashi; Mikio Konno, Dual functions of magnetic and fluorescent properties were created in composite particles that incorporated magnetite (Fe(3)O(4)) nanoparticles in particle cores of silica and fluorescent pyrene in particle shells of polystyrene. The Fe(3)O(4) nanoparticles were prepared with a conventional homogeneous precipitation method and surface modified with a coupling agent of carboxyethylsilanetriol. The silica particles incorporating Fe(3)O(4) nanoparticles were synthesized with a modified Stober method in which the Fe(3)O(4) nanoparticles were added to a system of tetraethylorthosilicate (TEOS)/ammonia/water/ethanol. Then, the magnetite/silica composite particles were coated with the pyrene/polystyrene shell in a soap-free emulsion polymerization, which was conducted in the presence of pyrene in a mixed solvent of water/ethanol. The composite particles prepared in the mixed solvent had both magnetic and fluorescent properties. The fluorescent spectrum of the particles with Fe(3)O(4) was very similar to that without Fe(3)O(4), indicating that the magnetic component within the core particles scarcely interfered with the fluorescent emission from the polymer shell., SPRINGER
COLLOID AND POLYMER SCIENCE, 2008年08月,
［査読有り］ Fabrication of Eu-coated silica particles by homogeneous precipitation methodY. Kobayashi; J. Imai; D. Nagao; M. Konno, This paper describes a method for Eu-coating of submicron-sized silica particles. The core silica particles with an average size of 333 nm were prepared with Stober method. The Eu-coating was performed in a water/propanol solvent in the presence of silica particles and europium acetate with a homogeneous precipitation method with the use of urea. Transmission electron microscopy (TEM) observation and measurements of zeta-potentials revealed that the silica particles were successfully coated with Eu shell. Eu shell size of the Eu-silica particles ranged from 5 to 38 nm with varying concentration of silica particles. (C) 2008 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 2008年08月,
［査読有り］ Synthesis and properties of Co-Pt alloy silica core-shell particlesY. Kobayashi; H. Kakinuma; D. Nagao; Y. Ando; T. Miyazaki; M. Konno, This paper describes a method for fabrication of silica-coated Co-Pt alloy nanoparticles in a liquid phase process. The Co-Pt nanoparticles were prepared from CoCl(2) (4.2 x 10(-5) M), H(2)PtCl(6) (1.8 x 10(-5) M), citric acid (4 x 10(-4) M) and NaBH(4) (1.2 x 10(-2) M) with a Co:Pt mole ratio of 7:3. The silica coating was performed in water/ethanol solution with a silane coupling agent, 3-aminopropyltrimethoxysilane (8 x 10(-5) M), and a silica source, tetraethoxyorthosilicate (7.2 x 10(-4) M) in the presence of the Co-Pt nanoparticles. Observations with a transmittance electron microscope and a scanning transmission electron microscope revealed that the Co-rich and Pt-rich nanoparticles were coated with silica. According to X-ray diffraction measurements, core particles were crystallized to metallic Co crystallites and fcc Co-Pt alloy crystallites with annealing in air at 300-500 degrees C. Magnetic properties of the silica-coated particles were strongly dependent on annealing temperature. Maximum values of 11.4 emu/g-sample for saturation magnetization and 365 Oe for coercive field were obtained for the particles annealed at 300 and 500 degrees C, respectively. Annealing at a temperature as high as 700 degrees C destroyed the coating structures because of crystallization of silica shell, resulting in reduction in saturation magnetization and coercive field., SPRINGER
JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 2008年07月,
［査読有り］ Preparation and Properties of Silica-Coated AgI Nanoparticles with a Modified Stöber MethodY. Kobayashi; K. Misawa; M. Takeda; N. Ohuchi; A. Kasuya; M. Konno, In recent years, the authors studied on fabrication of silica-coated AgI (AgI-SiO2) nanoparticles with a Stober method toward new X-ray contrast agents. In the Stober method, amines are often used as catalysts for silica formation, so that it is probable that amine is left in the silica-coated particles. Since amines are harmful to the human body, amine free particles are desired for medical use. From this viewpoint, amine free AgI-SiO2 nanoparticles were prepared with a modified Stober method using NaOH as a catalyst instead of amine in the present work. The AgI nanoparticles were prepared from AgClO4 and KI with the use of 3-mercaptopropyltrimethoxy-silane ( MPS) as a silane coupling agent and NaOH catalyst for alkoxide hydrolysis. The silicacoating was performed at 4.5 x 10(-5) M MPS, 15-22.5M water, 0.0008-0.0024M NaOH and 0.0004-0.009M tetraethylorthosilicate at an AgI concentration of 0.001M. AgI-SiO2 particles as small as ca. 30 nm could be successfully fabricated at the concentrations of 4.5 x 10(-5)M MPS, 20M water, 0.0011M NaOH, 0.001M AgI and 0.004M tetraethylorthosilicate., MANEY PUBLISHING
Materials Research Society Symposium Proceedings, 2008年07月,
［査読有り］ Preparation of Amine-Free Silica-Coated AgI Nanoparticles with Modified Stöber MethodY. Kobayashi; N. Shimizu; K. Misawa; M. Takeda; N. Ohuchi; A. Kasuya; M. Konno, In recent years, the authors studied on fabrication of silica-coated AgI (AgI-SiO2) nanoparticles with a Stober method toward new X-ray contrast agents. In the Stober method, amines are often used as catalysts for silica formation, so that it is probable that amine is left in the silica-coated particles. Since amines are harmful to the human body, amine free particles are desired for medical use. From this viewpoint, amine free AgI-SiO2 nanoparticles were prepared with a modified Stober method using NaOH as a catalyst instead of amine in the present work. The AgI nanoparticles were prepared from AgClO4 and KI with the use of 3-mercaptopropyltrimethoxy-silane ( MPS) as a silane coupling agent and NaOH catalyst for alkoxide hydrolysis. The silicacoating was performed at 4.5 x 10(-5) M MPS, 15-22.5M water, 0.0008-0.0024M NaOH and 0.0004-0.009M tetraethylorthosilicate at an AgI concentration of 0.001M. AgI-SiO2 particles as small as ca. 30 nm could be successfully fabricated at the concentrations of 4.5 x 10(-5)M MPS, 20M water, 0.0011M NaOH, 0.001M AgI and 0.004M tetraethylorthosilicate., MANEY PUBLISHING
Surface Engineering, 2008年07月,
［査読有り］ In vivo single molecular imaging and sentinel node navigation by nanotechnology for molecular targeting drug-delivery systems and tailor-made medicineMotohiro Takeda; Hiroshi Tada; Hideo Higuchi; Yoshio Kobayashi; Masaki Kobayashi; Yuu Sakurai; Takanori Ishida; Noriaki Ohuchi, The recent advances in nanotechnology have a great potential to improve the prevention, diagnosis, and treatment of human diseases. Nanomaterials for medical applications are expected to grasp pharmacokinetics and the toxicity for application to medical treatment on the aspect of safety of the nanomaterials and nanodevices. We describe a generation of CdSe nanoparticles [quantum dots (QDs)] conjugated with monoclonal anti-HER2 antibody (Trastuzumab), for single molecular in vivo imaging of breast cancer cells. We established a high-resolution in vivo 3D microscopic system for a novel imaging method at the molecular level. The cancer cells expressing HER2 protein were visualized by the nanoparticles in vivo at subcellular resolution, suggesting future utilization of the system in medical applications to improve drug-delivery systems to target the primary and metastatic tumors for made-to-order treatment. We also describe sentinel node navigation using fluorescent nanoparticles for breast cancer surgery in experimental model, which have shown the potential to be an alternative to existing tracers in the detection of the sentinel node if we select the appropriate particle size and wavelength. Future innovation in cancer imaging by nanotechnology and novel measurement technology will provide great improvement, not only in the clinical field but also in basic medical science for the development of medicine., SPRINGER TOKYO
BREAST CANCER, 2008年04月,
［査読有り］ Single- and multi-layered patterns of polystyrene and silica particles assembled with a simple dip-coatingDaisuke Nagao; Ryoji Kameyama; Hideki Matsumoto; Yoshio Kobayashi; Mikio Konno, A simple dip-coating method was examined to fabricate two-dimensional particle arrays on glass substrate with the use of submicron-sized, highly monodisperse particles of silica and polystyrene (PSt). This method was demonstrated to be applicable to the fabrication of particle monolayer with high regularity. The monolayer of PSt particles arranged with the dip-coating could be separated from the substrate by immersing it into water, leading to formation of a mono-layered film of the PSt particles. Repetition of the dip-coating was also applicable to multi-layering with silica and PSt particles. A dip-coating with 520 nm PSt particles accompanied by a dip-coating with 233 nm silica particles formed Kagome lattice composed of the silica particles under the monolayer of hexagonally arranged PSt particles. The lattice formation indicated that the silica particles crept under the monolayer of PSt particle in the second coating with the silica particle suspension. Double dip-coatings with different silica particle sizes in the second coating were performed to examine the effect of particle size on creeping under the monolayer. Silica particles much smaller than the PSt particles were gathered in a void between the substrate and the monolayer of PSt particles hexagonally arranged. A high concentration of the small silica particles in the second dip-coating could form hemi-sphere-typed inverse opal with little defects of silica particles after heat treatment at 600 degrees C. (c) 2007 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 2008年03月
Silica-coating of metallic copper nanoparticles in aqueous solutionY. Kobayashi; T. Sakuraba, This paper describes a method for silica-coating of metallic Cu nanoparticles in aqueous solution. Colloid solution of Cu nanoparticles was prepared from CuCl2 (0.001 M), a reducing reagent, hydrazine (0.1 M), and stabilizers, citric acid (0.005 M) and cetyltrimethylammonium bromide (0.0005 M), in water in air, The silica-coating was performed in aqueous solution with a silane coupling agent, (3-aminopropyl)trimethoxysilane (0.0001 M), and a silica source, sodium silicate solution (0.144 M), in the presence of the Cu nanoparticle colloid. UV-vis absorption measurements, TEM observation and X-ray diffraction measurements revealed that the metallic Cu nanoparticles with a size of 51.2 +/- 23.6 nm were coated with silica. (C) 2007 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 2008年03月,
［査読有り］ Fabrication and dielectric properties of the BaTiO3-polymer nano-composite thin filmsY. Kobayashi; T. Tanase; T. Tabata; T. Miwa; M. Konno, To prepare high dielectric thin film of polymer-based materials, nanometer sized barium titanate (BaTiO3) particles, which should have high dielectric coefficients and low energy dissipation factors due to nano-size effects, were dispersed in polyvinylidene fluoride (PVDF) or siloxane-modified polyamideimide (SPAI). The BaTiO3 particles with crystal sizes of 10.5-34.6nm were synthesized with a complex alkoxide method. Polymer/N-methyl-2-pyrrodinone solution suspending the BaTiO3 particles was spin-coated on ITO glass substrates to prepare polymer-based composite films with thickness of submicron meters. The BaTiO3 particles were dispersed more homogeneously in the PVDF film than in the SPAI film. The good dispersion of the particles in the PVDF film brought about a smooth surface of the film that had a root mean square roughness less than 20 nm at a particle volume fraction of 30%. The roughness was less than one-tenth of the roughness of the SPAI composite film. An increase in the BaTiO3 crystal size from 10.5 to 34.6 nm in the PVDF film at a particle volume fraction of 30% increased the dielectric constant of the film from 20.1 to 31.8. The BaTiO3-PVDF composite film attained high dielectric constant that had more than twice the dielectric constant of the BaTiO3-SPAI composite film. The dissipation factor of the PVDF composite film was as low as 0.05 at 10(4) Hz. (c) 2007 Elsevier Ltd. All rights reserved., ELSEVIER SCI LTD
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 2008年,
［査読有り］ Synthesis of spherical submicron-sized magnetite/silica nanocomposite particlesY. Kobayashi; S. Saeki; M. Yoshida; D. Nagao; M. Konno, This paper describes a method for fabricating spherical submicron-sized silica particles that contained magnetite nanoparticles (magnetite/silica composite particles). The magnetite nanoparticles with a size of ca. 10 nm were prepared according to the Massart method, and were surface-modified with carboxyethylsilanetriol. The fabrication of magnetite/silica composite particles was performed in water/ethanol solution of tetraethoxyorthosilicate with ammonia catalyst in the presence of the surface-modified magnetite nanoparticles. The magnetite/silica composite particles with a size of ca. 100 nm were successfully prepared at 0.05 M TEOS, 15 M water, and 0.8 M ammonia with injection of the magnetite nanoparticle colloid at 2 min after the initiation of hydrolysis reaction of TEOS. Magnetite concentration in the composite particles could be raised to 17.3 wt.% by adjustment of the injected amount of the magnetite colloid, which brought about the saturation magnetization of 7.5 emu/g for the magnetite/silica composite particles., SPRINGER
JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 2008年01月,
［査読有り］ 新規開発ナノサイズヨウ化銀ビーズを用いたX線CT造影効果および体内動態の検討
武田元博、桜井遊、叢莉蔓、小林芳男、菅原旭浩、大内憲明
乳癌基礎研究, 2008年, ［査読有り］
Multiformity of particle arrays assembled with a simple dip-coatingDaisuke Nagao; Ryoji Kameyama; Yoshio Kobayashi; Mikio Konno, A simple dip-coating method was examined to fabricate two-dimensional ordered structures of particles on glass substrate with the use of submicron sized, highly monodisperse particles of silica and polystyrene. This method was demonstrated to be applicable to the fabrication of particle mono-layer with high regularity. Multi-layers of the polystyrene particles were fabricated by the repetition of the dip-coating. The polystyrene particle layers could be separated by immersing the substrate into water, leading to formation of mono- and multi-layered films of the polystyrene particles. Repetition of the dip-coating was also applicable to multi-layering of particles with different sizes. A honeycomb structure of 233 nm silica particles under the mono-layer of hexagonally arranged 520 nm polystyrene particles was made by the coating with the polystyrene particles accompanied by the coating with the silica particles. It was indicated that the silica particles crept under the polystyrene particle layer after the coating with the silica particle suspension. A network structure of 233 nm silica particles on mono-layer of hexagonally arranged 590 nm silica particles was formed with the double coating method. Double layer of 175 and 520 nm polystyrene particles was also fabricated with this coating method. (c) 2007 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 2007年12月,
［査読有り］ アルコキシド法により調製したチタン酸バリウムの粒子径及び結晶子径に対する各種実験条件の影響(<特集>希土類系物質の精密合成,形態制御および機能物性)小林 芳男; 棚瀬 智和; 長尾 大輔; 今野 幹男, Barium titanate nanoparticles were synthesized in water/alcohol solutions by the hydrolysis of complex alkoxide precursor that was prepared by reflux of metallic barium and tetraethylorthotitanate in the alcohol. The alcohols employed were ethanol, 1-butanol and 1-octanol, which have different chain lengths. High hydrolysis reaction temperature produced small particles with small crystallite sizes. Particle and crystallite sizes were also dependent on alcohol species. For ethanol, crystallite size increased from 10.3 to 21.0 nm with an increase in water concentration. The crystallite size also increased from 13.0 to 42.9 nm for 1-butanol and from 26.6 to 52.9 nm for 1-octanol, respectively, with an increase in water concentration. Amorphous or low crystallinity products were formed for the 1-butanol and the 1-octanol at high water concentrations., 公益社団法人日本セラミックス協会
日本セラミックス協会学術論文誌 : Nippon Seramikkusu Kyokai gakujutsu ronbunshi = Journal of the Ceramic Society of Japan, 2007年10月
Preparation of multilayered silica-Gd-silica core-shell particles and their magnetic resonance imagesYoshio Kobayashi; Junichi Imai; Daisuke Nagao; Motohiro Takeda; Noriaki Ohuchi; Atsuo Kasuya; Mikio Konno, A preparation method for multilayered silica-Gd-silica core-shell particles is proposed. Silica particles with an average size of 30.9 nm were prepared by the Stober method. Silica-Gd core-shell particles with a size of 57.4 nm were synthesized by a homogeneous precipitation method at 80 degrees C in water/propanol solution with 27.7 M H2O, 0.001 M Gd(NO3)(3), 0.5 M urea and 1 g/l polyvinylpyrrolidone in the presence of 0.001 vol.% suspension of the silica particles. Succeeding silica-coating of the silica-Gd core-shell particles was performed with 0.0133 M TEOS and 0.002 M NaOH in the presence of a suspension of silica-Gd core-shell particles. Consequently, multilayered silica-Gd-silica core-shell particles with an average size of 71.2 nm could be obtained. These particles exhibited clear enhancement in magnetic resonance images. These nanoparticles are expected to a novel magnetic resonance contrast agents. (c) 2007 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 2007年10月,
［査読有り］ Sonochemical preparation of gold nanoparticles: Comparison with the thermal reduction systemYuzuru Shimazaki; Chiyoko Ando; Shu Saeki; Yoshio Kobayashi; Mikio Konno, Comparison was made for the citrate stabilized gold colloids prepared sonochemically and thermally. In the sonochemical reduction system, purge gas had large influence on the formation of gold nanoparticles, while little effect was observed for the thermal reduction system. The average diameter of sonochemically prepared gold nanoparticles was smaller than that of thermally prepared gold nanoparticles when prepared at the same concentrations of HAuCl4 and Na-3 citrate. The average diameter of the sonochemically prepared gold nanoparticles was increased with an increase in the HAuCl4 concentration ([Na-3 citrate]/[HAuCl4 = 7), while the average diameter of the thermally prepared gold colloid was independent of the HAuCl4 concentration. These results were explained by the difference in the reduction rate of gold ions., SOC CHEMICAL ENG JAPAN
JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 2007年10月,
［査読有り］ Influence of different parameters on the particle and crystallite sizes of barium titanate prepared by an alkoxide sol-gel methodYoshio Kobayashi; Tomokazu Tanase; Daisuke Nagao; Nlikio Konno, Barium titanate nanoparticles were synthesized in water/alcohol solutions by the hydrolysis of complex alkoxide precursor that was prepared by reflux of metallic barium and tetraethylorthotitanate in the alcohol. The alcohols employed were ethanol, 1-butanol and 1-octanol, which have different chain lengths. High hydrolysis reaction temperature produced small particles with small crystallite sizes. Particle and crystallite sizes were also dependent on alcohol species. For ethanol, crystallite size increased from 10.3 to 21.0 nm with an increase in water concentration. The crystallite size also increased from 13.0 to 42.9 nm for 1-butanol and from 26.6 to 52.9 run for 1-octanol, respectively, with an increase in water concentration. Amorphous or low crystallinity products were formed for the 1-butanol and the I-octanol at high water concentrations., CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
JOURNAL OF THE CERAMIC SOCIETY OF JAPAN, 2007年10月,
［査読有り］ Direct coating of particles by a liquid phase processYoshio Kobayashi; Shunchao Gu; Daisuke Nagao; Mikio Konno, This review describes our studies on preparation of core-shell particles with a direct coating technique based on a liquid phase process and their several properties. Various particles were successfully silica-coated with surface modification agents and alkoxide. For Au and Ag nanoparticles, optical spectra of the coated particles agreed with predictions by Mie theory. For metallic Co nanoparticles, crystallization ofthe Co was promoted with annealing in air with no oxidation of the Co, and the crystallized particles revealed magnetic properties. The silica-coated fluorescence polystyrene microspheres showed more stable fluorescence to laser-irradiation than uncoated microspheres. Besides, silica-coating of AgI, Fe(3)O(4), CoPt and PtRu particles were also successfully performed. Polystyrene and titania could be also used as shell materials. With the use of titania-coated polystyrene particles as precursor, hollow titania spheres could be fabricated by removing polystyrene core from the coated particles with annealing in air. Jingle bell-shaped hollow spheres were fabricated with removal of polystyrene from multilayered particles composed of a silica core, a polystyrene inner shell, and a titania outer shell by immersing them in tetrahydrofuran. Titania-coated silica particles were used for fabrication of colloidal crystals., BENTHAM SCIENCE PUBL LTD
CURRENT NANOSCIENCE, 2007年08月,
［査読有り］ Effect of ultrasonic irradiation on carbon-supported Pt-Ru nanoparticles prepared at high metal concentrationDaisuke Nagao; Yuzuru Shimazaki; Shu Saeki; Yoshio Kobayashi; Mikio Konno, Effect of ultrasonic irradiation during the preparation of carbon-supported Pt-Ru nanoparticles was studied to obtain the aqueous dispersion of catalyst at higher concentrations. The nanoparticles formed through the reduction of Pt and Ru ions with sodium borohydride were impregnated on carbon powder (Vulcan XC72R). TEM observation revealed that the sample prepared with ultrasonic irradiation had single-nanometer-sized Pt-Ru particles on the carbon support, while aggregated Pt-Ru particles were observed in the non-irradiated sample. Methanol oxidation current for the catalysts prepared under ultrasonic irradiation was higher than that for the catalysts prepared without irradiation. This promotive effect of ultrasonic irradiation on the catalytic activity was also confirmed at concentrations of Pt, Ru and carbon support as high as 3.0 mM, 1.2 mM, and 1065 mg/l, respectively. (C) 2007 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 2007年07月,
［査読有り］ Direct micropatterning of high dielectric BaTiO3 films by laser-induced pyrolysis with a nano-crystalline seeding techniqueYoshio Kobayashi; Kenshi Miyajima; Daisuke Nagao; Akira Watanabe; Shinji Yamada; Takao Miwa; Mikio Konno, A direct patterning method of dielectric BaTiO3 (BT) films is proposed, which applies laser-induced pyrolysis in combination with nanocrystalline seeding technique. A precursor solution of a BT complex alkoxide containing BT nano-crystal line particles with polyvinylpyrollidone (PVP) as dispersion stabilizer was spin-coated on Pt substrate. An Ar+ laser beam was focused and scanned on spin-coated BT films, which induced pyrolysis and crystallization of the films with spatial selectivity. Micropatterns were obtained by striping laser-unirradiated regions on the films with HCl aqueous solution. Raman spectra of the micropattern confirmed that the structures were tetragonal crystalline BT. Clear micropatterns with a line width of ca. 3 mu m and an interval of 5 mu m were formed at PVP concentrations of 25 and 50 kg/m(3). The dielectric constant and dissipation factor of the film fabricated at a laser energy density of 27 MW/cm(2) and a scanning speed of 25 mu m/s attained 76.2 and 0.07, respectively, for a measurement frequency of 100 kHz. (c) 2006 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
APPLIED SURFACE SCIENCE, 2007年04月,
［査読有り］ Photoluminescence of CdSe and CdSe/CdO•nH2O Core/Shell Nanoparticles Prepared in Aqueous SolutionX. Zhou; Z. Shao; Y. Kobayashi; X. Wang; N. Ohuchi; M. Takeda; A. Kasuya, Case sols with different colors were prepared by simply mixing CdSO4 and NaSSeO3 solutions under [Cd2+]/[Se2-] ratios of 2.0-0.4 at room temperature. The nanoparticles, with average sizes of 1.8-3.6 nm, showed relatively narrow photoemission peaks at 522-556 nn. The strongest photoluminescence with a FWHM of 35 nm was obtained under [Cd2+]/[Se2-] ratio of 1.2. The possible mechanism for achieving the strongest photoluminescence was proposed. Photoluminescence of these particles was greatly increased by surface modification of cadmium (II) hydrous oxide. The photoluminescence of these core-shell particles was kept constant in the pH range of 8.010.0, but dramatically decreased with an obvious blue-shifted peak while the pH was lower than 8.0. In addition, the photochemical oxidation of Cdse nanoparticles was markedly inhibited after they were modified with cadmium hydrous oxide. (c) 2006 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
Optical Materials, 2007年04月,
［査読有り］ Direct drawing of submicrom wiring by laser-induced pyrolysis of film prepared from liquid-dispersed metal nanoparticlesAkira Watanabe; Yoshio Kobayashi; Mikio Konno; Shinji Yamada; Takao Miwa, The direct- drawing of submicron Ag wiring was achieved by laser- induced pyrolysis ( LIP) of a precursor film prepared from liquid-dispersed Ag nanoparticles. This new method provided the micro-wiring by wet and maskless process toward printed electronics. The linewith of the Ag wiring was easily controlled by changing the objective lens magnifications and the focusing point. The resistivity of the Ag wiring fabricated by this technique ( 1.9 x 10(-6) Omega cm) is comparable with that of bulk Ag ( 1.6 x 10(-6) Omega cm)., TAYLOR & FRANCIS LTD
MOLECULAR CRYSTALS AND LIQUID CRYSTALS, 2007年03月,
［査読有り］ SYNTHESIS OF SiO2-COATED MAGNETITE NANOPARTICLES AND IMMOBILIZATION OF PROTEINS ON THEMYoshio Kobayashi; Mayumi Yoshida; Daisuke Nagao; Yasuo Ando; Terunobu Miyazaki; Mikio Konno, This paper describes a method for silica-coating of magnetite nanoparticles and immobilization of proteins on the silica-coated particles. The magnetite nanoparticles were prepared according to the Massart method. The silica-coating was performed in aqueous/ethanolic solution with tetraethoxyorthosilicate and ammonia aqueous solution in the presence of the magnetite nanoparticles. TEM observation revealed that the nanoparticles were coated with silica shell. Saturation magnetization of the SiO2-coated particles was 52.4 emu/g-Fe3O4, which indicated that the magnetite nanoparticles were chemically undamaged during the silica-coating. The protein immobilization was performed in aqueous solution with bovine serum albumin in the presence of the silica-coated particles surface-modified with 3-aminopropyltrimethoxysilane and glutaraldehyde. UV-VIS absorption spectroscopy revealed that the BSA was adsorbed on the surface-modified particles., AMER CERAMIC SOC
CHARACTERIZATION AND CONTROL OF INTERFACES FOR HIGH QUALITY ADVANCED MATERIALS II, 2007年,
［査読有り］ SILICA-COATING OF BARIUM TITANATE PARTICLESHideki Matsumoto; Daisuke Nagao; Yoshio Kobayashi; Mikio Konno, Barium titanate (BT) particles were coated with silica to improve their stability in water. The BT particles were prepared using a sol-gel method in a mixed solvent of ethanol and acetonitrile (weight ratio = 25/75) with additives of methylamine (MA) and acetylacetone. The silica coating was produced with the hydrolysis of tetraethylorthosilicate (TEOS) in the mixed solvent using a MA catalyst in the presence of the BT particles. TEM observation showed that the BT particles are spherical and have silica shells. The Zeta-potential measured for the coated BT particles with thick silica shells revealed that isoelectric point of the coated particles was almost consistent with that of silica particles. The size distribution of the coated particles was measured with dynamic light scattering (DLS) to examine the colloidal stability of the coated particles in water. The high stability of the coated particles was confirmed in the DLS measurement, and the averaged diameter of the coated particles obtained in this measurement was close to that obtained by TEM. Annealing of the coated particles produced fresnoite (Ba(2)TiSi(2)O(8)) crystallite particles., AMER CERAMIC SOC
CHARACTERIZATION AND CONTROL OF INTERFACES FOR HIGH QUALITY ADVANCED MATERIALS II, 2007年,
［査読有り］ FABRICATION OF COLLOIDAL PHOTONIC CRYSTALS FROM SUBMICRON-SIZED SPHERESDaisuke Nagao; Mitsuaki Hirose; Ryoji Kameyama; Hideki Matsumoto; Yoshio Kobayashi; Mikio Konno, A number of colloidal methods were examined to rapidly fabricate photonic crystals from well-ordered polystyrene (PSt) or silica particles with controlled layers. Using evaporation methods, colloidal solvent was evaporated under a condition to control the deposition of the well-ordered particles on a substrate. However, the time required to produce well-ordered particle arrays was long, with the deposition rates for PSt particles less than 0.02 mu m/sec. To increase the deposition rate, the substrates were lifted up from the suspensions at a constant speed. Although slow fill up of the substrates resulted in the fabrication of a close-packed structure on the substrates, the number of layers on the substrates was relatively high. A simple dip-coating method proposed by the authors can fabricate close-packed particles in a single layer. Repetition of the dip-coating can fabricate a double-layer of PSt particles on a substrate and a PSt particle mono-layer on a silica particle mono-layer. The fabrication of well-ordered structures shows that the dip-coating is a possible way to rapidly fabricate well-ordered particle arrays with a small number of layers., AMER CERAMIC SOC
CHARACTERIZATION AND CONTROL OF INTERFACES FOR HIGH QUALITY ADVANCED MATERIALS II, 2007年,
［査読有り］ Deposition of Gold Nanoparticles on Polystyrene Spheres by Electroless Metal Plating Technique
Y. Kobayashi; Y. Tadaki; D. Nagao; M Konno
Journal of Physics: Conference Series, 2007年, ［査読有り］
Control of shell thickness in silica-coating of Agl nanoparticlesY. Kobayashi; K. Misawa; M. Takeda; N. Ohuchi; A. Kasuya; M. Konno, Silica-coating of Agl nanoparticles with a Stober method was carried out to find out reaction conditions for control of the shell thickness. The Agl nanoparticles were prepared from AgClO4 and KI with the use of 3-mercaptopropyltrimethoxysilane (MPS) as a silane coupling agent and dimethylamine (DMA) catalyst for alkoxide hydrolysis. The silica-coating was performed at 4.5 x 10(-6)-4.5x10(-5) M MPS, 11-20 M water, 0.002-0.1 M DMA and 0.005-0.04 M tetraethylorthosilicate at Agl concentrations of 0.1-1 mM. Consequently, Agl-silica core-shell particles could be prepared with the use of 4.5 x 10(-5) M MPS, 20 M water, 0.01 M DMA and 1 mM Agl. Silica shell thickness could be varied from 15 to 28 nm with an increase in the TEOS concentration from 0.005 to 0.04 M., TRANS TECH PUBLICATIONS LTD
ADVANCED MATERIALS AND PROCESSING IV, 2007年,
［査読有り］ X-ray absorption of gold nanoparticles with thin silica shellYeon-Su Park; Luis M. Liz-Marzan; Atsuo Kasuya; Yoshio Kobayashi; Daisuke Nagao; Mikio Konno; Sergiy Mamykin; Andriy Dmytruk; Motohiro Takeda; Noriaki Ohuchi, Silica-coated gold (Au) nanoparticles were prepared and their morphological and X-ray absorption properties were investigated. These core-shell type nanoparticles are very stable in aqueous media and may be suitable for an X-ray contrast agent in biological systems. Transmission electron micrographs confirmed well-separated and relatively homogeneous morphology of the nanoparticles in highly concentrated colloids. Peak position for Au plasmon resonance was red-shifted with increasing shell thickness. X-ray absorption by the colloids of silica-coated Au nanoparticles was stronger than that by those of silica-coated Agl nanoparticles, a recently investigated X-ray contrast agent, at similar experimental conditions., AMER SCIENTIFIC PUBLISHERS
JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 2006年11月,
［査読有り］ Preparation and characterization of long-lived anode catalyst for direct methanol fuel cellsYuzuru Shimazaki; Yoshio Kobayashi; Masatoshi Sugimasa; Shinji Yamada; Takeyuki Itabashi; Takao Miwa; Mikio Konno, Entry of direct methanol fuel cells into the market requires anode catalyst with stable activity. This paper presents a novel method for stabilizing the activity by immobilizing silica on the catalytic PtRu nanoparticles. Characterization was performed by STEM-EDX, XRD, and ICP. The silica-immobilized PtRu nanoparticles showed high and stable activity toward methanol oxidation. The activity was maintained for 1000 h in sulfuric acidic solution, while the activity of the catalyst with "bare" PtRu nanoparticles decayed after 100 h, showing high durability of the silica-immobilized PtRu nanoparticles catalyst in quasi-anodic acidic environment. (c) 2006 Elsevier Inc. All rights reserved., ACADEMIC PRESS INC ELSEVIER SCIENCE
JOURNAL OF COLLOID AND INTERFACE SCIENCE, 2006年08月,
［査読有り］ Preparation of palladium catalysts by pretreatment steps in electroless plating toward partial oxidation of methanol with steam reformingYoshio Kobayashi; Yohei Tadaki; Katsumi Takahashi; Mikio Konno, A previously proposed method for depositing Ag nanoparticles on silica particles was extended to the preparation of ZnO-supported Pd (Pd/ZnO) catalysts. The method presented in this work consists of two steps: (1) Sn2+ ions are adsorbed on the surfaces of ZnO particles, and (2) Pd2+ ions added are reduced by oxidization of Sn2+ to Sn4+ and simultaneously adsorbed on the surface. TEM observations revealed that Pd nanoparticles. with an average size of 2-3 nm were formed on the 20 nm ZnO particles. The Pd nanoparticles were transformed into a Pd-Zn alloy by partial oxidation and steam reforming of methanol, and consequently the Pd/ZnO attained CH3OH conversion efficiencies of 35-50% at reaction temperatures of 310-370 degrees C., CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
JOURNAL OF THE CERAMIC SOCIETY OF JAPAN, 2006年07月,
［査読有り］ Preparation of highly monodisperse poly(methyl methacrylate) particles incorporating fluorescent rhodamine 6G for colloidal crystalsD Nagao; N Anzai; Y Kobayashi; SC Gu; M Konno, Soap-free emulsion polymerization was extended to reparation of monodisperse poly(methyl methacrylate) (PMMA) particles incorporating rhodarnine 6G (MG) fluorescent molecules. The polymerization was conducted in the presence of an anionic monomer, p-styrenesulfonate (NaSS), which improved dispersion stability of the polymer particles. NaSS concentrations was ranged up to 2 mol/m(3) H2O in the polymerization at 0.5 kmol/m(3) H2O methyl methacrylate (MMA) monomer and 5 mol/m(3) H2O potassium persulfate (KPS) initiator for R6G concentrations from 0.1 to 10 mol/m(3)-polymer. At R6G concentrations lower than 1.0 mol/m(3)-polymer, PMMA particles were highly monodisperse and incorporated most R6G molecules. The average sizes of PMMA particles were in a rage of 160-300 nm, and decreased with the concentration of NaSS. The high monodispersity of the particles enabled the fabrication of colloidal crystals of the particles with a vertical deposition method. (c) 2005 Elsevier Inc. All rights reserved., ACADEMIC PRESS INC ELSEVIER SCIENCE
JOURNAL OF COLLOID AND INTERFACE SCIENCE, 2006年06月,
［査読有り］ Synthesis of submicron-sized titania-coated silica particles with a sol-gel method and their application to colloidal photonic crystalsE Mine; M Hirose; M Kubo; Y Kobayashi; D Nagao; M Konno, A previously proposed method for preparing monodispersed titania particles was extended to preparation of titania-coated silica spherical particles. The core silica particles with an average size of 264 nm were prepared with Stober method. The titania-coating was performed in ethanol/acetonitrile solvent in the presence of silica particles by a sol-gel method with the use of titanium tetraisopropoxide (TTIP) and methylamine (MA) catalyst. Average size of the silica-titania particles decreased from 457 to 292 nm with an increase in concentration of silica particles. Coefficient of variation for the particle size was less than 5%. Colloidal crystals could be fabricated with a dip-coating technique and a sedimentation process, respectively. Measurements of reflectance revealed peaks based on the Bragg diffraction. Those peaks red-shifted with an increase in titania shell thickness because of a high refractive index of titania. Annealing at high temperature transformed crystal structure of titania shell from amorphous to anatase (500 degrees C) and rutile (1000 degrees C), which led to red-shift of reflection peak because of an increase in refractive index of titania due to the crystallization., SPRINGER
JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 2006年04月,
［査読有り］ Synthesis of Pt-Ru nanoparticles with a bifunctional stabilizerD Nagao; Y Shimazaki; Y Kobayashi; M Konno, A synthetic method for bimetallic Pt-Ru nanoparticles with a bifunctional stabilizer, (3-aminopropyl)trimethoxysilane (APS), is proposed. Sodium borohydride was used to induce simultaneous reduction of platinum and ruthenium ions in the presence of APS. The concentration of each metal ion was 0.06 mM, and sodium borohydride concentration was 10 times higher than the total metal ion concentration. X-ray diffraction measurement showed that the nanoparticles formed by the reduction contained alloy of Pt and Ru. Comparison of the Pt-Ru nanoparticles prepared in the presence of APS with those in the absence of APS confirmed that APS played a role of stabilizer in synthesis of the nanoparticles. The number-averaged size of Pt-Ru nanoparticles could be varied in the range of 2.1-3.7nm at APS concentrations of 0.13-0.26mm, and the narrowest size distribution of Pt-Ru nanoparticles appeared with the minimum average size (2.1 nm) around an APS concentration of 0.1 mM. (c) 2005 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 2006年02月,
［査読有り］ 新規ナノサイズヨウ化銀ビーズを用いた造影効果とX線センチネルリンパ節生検への応用
桜井遊、武田元博、小林芳男、中島護雄、亀井尚、粕谷厚生、川添良幸、大内憲明
乳癌基礎研究, 2006年, ［査読有り］
Preparation and characterization of aqueous colloids of Pt-Ru nanoparticlesY Shimazaki; Y Kobayashi; S Yamada; T Miwa; M Konno, A synthetic method for platinum-ruthenium (PtRu) nanoparticles in aqueous media is proposed. This method employs citric acid as a capping agent and NaBH4 as a reducing agent with the aid of pH control. The number-averaged size of the PtRu nanoparticles was ca. 2 nm. The crystal phase and chemical composition of the nanoparticles was investigated by X-ray diffraction measurement and scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy analysis, which indicated that the nanoparticles mainly consisted of an alloy of Pt and Ru. Electrochemical measurement showed that the PtRu nanoparticles had catalytic activity for methanol oxidation. (c) 2005 Elsevier Inc. All rights reserved., ACADEMIC PRESS INC ELSEVIER SCIENCE
JOURNAL OF COLLOID AND INTERFACE SCIENCE, 2005年12月,
［査読有り］ Synthesis of submicrometer-sized titania spherical particles with a sol-gel method and their application to colloidal photonic crystalsE Mine; M Hirose; D Nagao; Y Kobayashi; M Konno, A synthetic method for preparing submicrometer-sized titania particles is proposed, which is based on hydrolysis of titanium alkoxide with the use of a cosolvent and an amine catalyst for alkoxide hydrolysis. The preparation was performed with different amines of ammonia, methylamine (MA), and dimethylamine (DMA) in different solvents of ethanol/acetonitrile, ethanol/methanol, ethanol/acetone, ethanol/acetonitrile, and ethanol/formamide for 0.1-0.3 M water and 0.03 M titanium tetraisopropoxide (TTIP) at temperatures of 10-50 degrees C. The use of the ethanol/acetonitrile solvent with MA was required for preparing monodispersed, spherical particles. The number average of the titania particle sizes and their coefficient of variation were varied from 143 to 551 nm and from 5.7 to 20.6%, respectively, with reaction temperature and concentrations of water and MA. Colloidal crystals of titania particles fabricated with a sedimentation method revealed reflection peaks attributed to Bragg's diffraction. Annealing at 100-1000 degrees C led to shrinkage and crystallization of titania particles followed by an increase in the refractive index of titania particles. (c) 2005 Elsevier Inc. All rights reserved., ACADEMIC PRESS INC ELSEVIER SCIENCE
JOURNAL OF COLLOID AND INTERFACE SCIENCE, 2005年11月,
［査読有り］ Solvent effects on particle formation in hydrolysis of tetraethyl orthosilicateE Mine; D Nagao; Y Kobayashi; M Konno, Particle formation in ammonia-catalyzed hydrolysis of tetraethyl orthosilicate (TEOS) was studied in aqueous solvents that contained ethanol, 1-propanol or 1-butanol. The reactions were performed at a TEOS concentration of 0.2 kmol/m(3), a H2O concentration of 5 kmol/m(3) and a NH3 concentration of 1 kmol/m(3). Average particle size was the largest for 1-butanol and the smallest for ethanol. No specific relation of the average diameter to hydrolysis rate was observed in the reactions. Difference in dielectric constant of the solvent and particle surface potential in the reactions indicated that the magnitudes of interpartide repulsion in the solvents corresponded with the order of the average particle sizes. This suggested that the particle sizes were dominated by the interparticle repulsion., SPRINGER
JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 2005年09月,
［査読有り］ Preparation of fluorescent polymer particles by emulsion polymerizationSC Gu; N Anzai; D Nagao; Y Kobayashi; M Konno, Core-shell type fluorescent polymer particles were produced in multi-step polymerization. Cross-linking was introduced to the shell to suppress leakage of fluorescent dyes contained in the core particles. First, fluorescent polymer particles were synthesized by emulsion copolymerization of styrene (St) and butyl acrylate (BA) with an anionic surfactant (SE1025A) initiated by ammonium persulfate (APS) in the presence of pyrene. The concentrations of St, BA,SE1025A and APS were 550, 89, 8.2 and 5 mol/m(3) water, respectively. Then the fluorescent particles were covered wit cross-linked polymer by emulsion copolymerization of St, BA and divinylbenzene (DVB) wit SE1025A emulsifier. In the polymerization, a mixture of St, BA, SE1025A and DVB was added dropwise to the reaction system. The average size of cross-linked fluorescent particles ranged from 50 to 70 nm. The fluorescence intensity of the particles prepared in a pyrene concentration range of 8 - 20 mol/m(3) water increased linearly with pyrene concentration. Fluorescence intensities of the particles prepared with and without DVB were also measured. The cross-linked polymer formed by DVB addition drastically suppressed the intensity drop caused by dye leakage almost to one-third of the intensity drop measured for particles prepared without DVB addition., EUROPEAN POLYMER FEDERATION
E-POLYMERS, 2005年09月,
［査読有り］ Preparation and colloidal stability of monodisperse magnetic polymer particlesSC Gu; JY Onishi; Y Kobayashi; D Nagao; M Konno, A previously proposed method was examined for producing monodisperse, submicrometer-sized magnetic polymer particles. The method applies soap-free emulsion polymerization during which Fe3O4 magnetic nanoparticles are heterocoagulated onto precipitated polymer nuclei. To chemically fix the magnetic particles to the polymer nuclei, vinyl groups were introduced on the Fe3O4 particles in a preliminary surface modification reaction with methacryloxypropyltrimethoxysilane, and methacryloxypropyldimethoxysilane (MPDMS) was added to reaction systems of the soap-free emulsion polymerization. The colloidal dispersion stability of magnetic polymer particles was improved by the addition of an ionic monomer, sodium p-styrenesulfonate (NaSS), during the polymerization. The polymerizations were carried out with styrene monomer and potassium persulfate initiator in ranges of NaSS concentrations (0-2.4 x 10(-3) M), NaSS addition times (60-80 min), and monomer concentrations (0.3-0.6 M) at fixed concentrations of 1.6 x 10(-2) M initiator and 1.3 x 10(-2) M MPDMS for pH 4.5 adjusted with a buffer system of [CH3COOH]/[NaOH]. The addition of NaSS during the polymerization could maintain the dispersion stability of magnetic polymer particles during the polymerization. Selection of the reaction conditions enabled the preparation of colloidally stable, submicrometer-sized magnetic polymer particles that had coefficients of variation of distribution smaller than the standard criterion for monodispersity, 10%. (c) 2005 Elsevier Inc. All rights reserved., ACADEMIC PRESS INC ELSEVIER SCIENCE
JOURNAL OF COLLOID AND INTERFACE SCIENCE, 2005年09月,
［査読有り］ Fabrication and dielectric properties of barium strontium titanate nano-particles/amorphous lead zirconate titanate composite thin filmT Tanase; Y Kobayashi; T Miwa; M Konno, A low temperature synthetic method, which combines metal-organic decomposition and a rim-seeding technique, was applied to the fabrication of barium strontium titanate (BST) nano-particle/amorphous lead zirconate titanate (PZT) composite thin films. A metal-organic solution of PZT was mixed with a suspension of BST nano-crystalline particles to prepare a precursor solution. The mixed solution was spin-coated on a Pt/Ti/SiO2/Si substrate and annealed at various temperatures to prepare composite thin films with a thickness around 300 nm. Organic components in the films decomposed at 350 degrees C, and the composite film of PZT amorphous and BST nano-crystalline particles could be prepared at this temperature. The film had smooth surface with a root mean square roughness less than 20 mm. The dielectric constant and dissipation factor of the composite thin films at 10 kHz obtained 70 and 0.036, respectively. (c) 2005 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE SA
THIN SOLID FILMS, 2005年08月,
［査読有り］ Silica-coating of Fluorescent Polystyrene Microspheres by a Modified Stöber Method and their Stability against Photo-BleachingY. Kobayashi; K. Misawa; M. Kobayashi; M. Takeda; M. Konno; M. Satake; Y. Kawazoe; Noriaki Ohuchi; A. Kasuya, Submicron-sized polystyrene spheres incorporating fluorescence dyes (fluorescent microspheres) were coated with silica by means of a seeded polymerization technique based on the Stober method. Silica-coating of the fluorescent microspheres with a size of 100 nm was performed in the presence of 0-10 g/l polyvinylpyrrolidone (PVP), 1-13 mol/l water, 1-0.8 mol/l aq. ammonia and 0.00038-0.2 mol/l tetraethoxyorthosilicate (TEOS). the addition of PVP was found to suppress the generation of free silica particles and produced no shell-free fluorescent microspheres improving the uniformity of shell thickness of silica-coated fluorescent microspheres. Silica shell thickness increased from 11 to 63 nm with increasing TEOS concentration at 10 g/l PVP, 0.4 mol/l aq. ammonia and 11 mol/l water. Silica-coated fluorescent microspheres showed more stable fluorescence to laser-irradiation than uncoated fluorescent microspheres., EUROPEAN POLYMER FEDERATION
e-Polymers, 2005年08月,
［査読有り］ Strong luminescing CdSe nanoparticles by surface modification with cadmium (II) hydrous oxideXP Zhou; Y Kobayashi; N Ohuchi; M Taketa; A Kasuya, CdSe nanoparticles were prepared by simply mixing Na2SSeO3 solution with CdSO4 solution under [Cd2+]/[Se2-] (Cd/Se) ratio of 1.2 at room temperature. The nanoparticles had an average size of 2.3 nm and showed fairly strong photoluminescence (PL) with a peak at 539 nm. Deposition of cadmium (II) hydrous oxide on the CdSe nanoparticles increased photoluminescence quantum yield from 3.1 to 34.8%, in comparison to Rhodamine 6G aqueous solution. Both of the CdSe nanoparticles and the cadmium (II) hydrous oxide deposited on CdSe nanoparticles were characterized as of cubic structure from XRD data and the electron diffraction (ED) patterns. Also, the reason for the photoluminescence enhancement was simply elucidated., WORLD SCIENTIFIC PUBL CO PTE LTD
INTERNATIONAL JOURNAL OF MODERN PHYSICS B, 2005年07月,
［査読有り］ Preparation of silica encapsulated CdSe quantum dots in aqueous solution with the improved optical propertiesXP Zhou; Y Kobayashi; Romanyuk, V; N Ochuchi; M Takeda; S Tsunekawa; A Kasuya, Silica encapsulated CdSe quantum dots (QDs) have been prepared by the use of 3-mercaptopropyl trimethoxysilane (MPS) in a weak alkaline solution in ambient atmosphere at room temperature. The average size of the multicore-shell structured CdSe/SiO2 is 28.0 nm and that of the CdSe QDs is 3.4 nm from the observation of the transmission electron micrographs (TEMs). The enhanced photoluminescence (PL) intensity of the QDs has been observed by passivation of silica shell. The increased photochemical and -physical stability of the encapsulated CdSe/SiO2 QDs has also been demonstrated. (c) 2004 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE BV
APPLIED SURFACE SCIENCE, 2005年04月,
［査読有り］ Silica Coating of Silver Nanoparticles Using a Modified Stöber MethodY. Kobayashi; H. Katakami; E. Mine; D. Nagao; M. Konno; L. M. Liz-Marzán, Silver nanoparticles prepared through a borohydride-reduction method were directly coated with silica by means of a seeded polymerization technique based on the Stober method. Various amine catalysts were used for initialization of a sol-gel reaction of TEOS with no need for a prior surface modification. Use of dimethylamine (DMA) as a catalyst was found to be necessary to obtain a proper coating. The silica shell thickness was varied from 28 to 76 nm for TEOS concentrations of 1-15 mM at 11.1 M water and 0.8 M DMA. The optical spectra of the core-shell silver-silica composite particles show a qualitative agreement with predictions by Mie theory. (C) 2004 Elsevier Inc. All rights reserved., ACADEMIC PRESS INC ELSEVIER SCIENCE
Journal of Colloid and Interface Science, 2005年03月,
［査読有り］ Deposition of gold nanoparticles on silica spheres by electroless metal plating techniqueY Kobayashi; Y Tadaki; D Nagao; M Konno, A previously proposed method for metal deposition with silver [Kobayashi et al., Chem. Mater. 13 (2001) 1630] was extended to uniform deposition of gold nanoparticles on submicrometer-sized silica spheres. The present method consisted of three steps: (1) the adsorption of Sn2+ ions took place on surface of silica particles, (2) Ag+ ions added were reduced and simultaneously adsorbed to the surface, while Sn2+ was oxidized to Sn4+, and (3) Au+ ions added were reduced and deposited on the Ag surface. TEM observation, X-ray diffractometry, and UV-vis absorption spectroscopy revealed that gold metal nanoparticles with an average particle size of 13 nut and a crystal size of 5.1 nm were formed on the silica spheres with a size of 273 nm at an Au concentration of 0.77 M. (C) 2004 Elsevier Inc. All rights reserved., ACADEMIC PRESS INC ELSEVIER SCIENCE
JOURNAL OF COLLOID AND INTERFACE SCIENCE, 2005年03月,
［査読有り］ Low-temperature synthesis of single-phase barium strontium titanate thin film with a nm-seeding technique and its dielectric propertiesY Kobayashi; Y Iizuka; T Tanase; M Konno, Dielectric barium strontium titanate (Ba0.5Sr0.5TiO3, BST) thin films containing crystalline seeds of BST nanoparticles were prepared on indium titanium oxide (ITO) glass electrodes with a complex alkoxide precursor method. BST precursor solution that dispersed the BST particles was spin-coated on the electrode and annealed at various temperatures. Thickness of the film was about 300 nm, and BST particle concentration in the film was varied from 0 to 17 mol%. An unseeded BST film was crystallized into a perovskite structure by annealing at 600 degrees C, while the seeding with the 17 mol%-BST particles promoted crystalline growth of BST perovskite and lowered crystallization temperature of the films to 525 degrees C. Measurement of dielectric properties at 1 kHz showed that the 4.9 mol% BST-seeded film annealed at 600 degrees C had a relative dielectric constant of 303, which was higher than that of the unseeded BST film., SPRINGER
JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 2005年03月,
［査読有り］ Direct drawing of Ag micro-wiring by laser-induced pyrolysis of the film prepared from liquid-dispersed nanometal particles
Akira Watanabe; Kenji Miyajima; Yoshio Kobayashi; Mikio Konno; Shinji Yamada; Takao Miwa, Ag micro-wiring with submicron resolution was fabricated by the laser-induced pyrolysis of the film prepared from liquid-dispersed Ag nanoparticles. Linewidth of the wiring in this laser direct-write maskless technique can be controlled flexibly by the laser beam focusing conditions. The resistivity of the Ag wiring film by this technique (1.9 × 10 -6 Ω cm) is comparable with that of bulk Ag (1.6 × 10 -6 Ω cm).
Polymer Preprints, Japan, 2005年
Dielectric properties of lead zirconate titanate thin films seeded with barium strontium titanate nanoparticlesT Tanase; Y Kobayashi; T Nabatame; T Miwa; M Konno, dA low temperature synthetic method recently proposed by the authors was applied to the fabrication of lead zirconate titanate (PZT) thin films containing crystalline seeds of barium strontium titanate (BST) nanoparticles. PZT precursor and the BST particles were prepared with complex alkoxide methods. Precursor solution suspending the BST particles was spin-coated on Pt/Ti/SiO2/Si substrate to film thickness of 500-800 nm at particle concentrations of 0-25.1 mol%, and annealed at various temperatures. Seeding of BST particles prevented the formation of pyrochlore phases, which appeared at temperatures above 400 degreesC in unseeded PZT films, and induced crystallization of PZT into perovskite structures at 420 degreesC, which was more than 100 degreesC below the crystallization temperature of the unseeded PZT films. Measurement of dielectric properties at 1 kHz showed that the 25.1 mol% BST-seeded PZT films annealed at 450 degreesC had a dielectric constant as high as 300 with a dissipation factor of 0.05. Leakage current density of the film was less than 1 X 10(-6) A/cm(2) at applied electric field from 0 to 64 kV/cm. (C) 2004 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE SA
THIN SOLID FILMS, 2005年01月,
［査読有り］ Preparation of alumina films by the sol-gel methodY Kobayashi; T Ishizaka; Y Kurokawa, This review describes our study on preparation of alumina films by a sol-gel process and their several applications that have been investigated since 1986. Alumina films were prepared from alkoxide or inorganic salt. Both as-prepared alumina films were transparent in ultraviolet, visible and near infrared regions. The alumina from inorganic salt (inorganic alumina) was structureless even after annealed at 300-700degreesC in air, while the alumina from alkoxide (alkoxide alumina) was in pseudo-boehmite at an annealing temperature lower than 400degreesC and was in gamma- or delta-type at 400-700degreesC. Both alumina films became opaque after annealed at temperatures above 1000degreesC. The inorganic alumina film annealed at 800degreesC showed a gas permeability that was influenced by physico-chemical properties of penetrant and alumina. Composite films of alumina and poly(vinyl alcohol) (PVA) were hydrophilic but insoluble in water, and removal of PVA from the composite films by annealing at 600degreesC led to formation of transparent alumina films. Such properties enabled us to use a counter diffusion method for fabricating gamma-Fe2O3-doped alumina films. Alumina films doped with organic dyes such as laser dyes, hole-burning dyes and non-linear optical dyes, which were fabricated by gelation of dye-added alumina sol, exhibited laser emission, hole-spectra and second- or third-harmonic generation properties, respectively. Hydrogenation of alkene was catalyzed by Ni nanoparticles doped alumina films that were prepared by gelation of Ni2+ solution-added alumina sol and annealing the Ni2+-doped alumina gel in hydrogen gas. Nonlinear optical properties were observed for alumina films doped with CdS, Au and Ag nanoparticles, which were fabricated by gelation of Cd2+, HAuCl4 and AgNO3 solution-added alumina sols and annealing the Cd2+-doped alumina gel in H2S gas and the Ag+- and Au3+-doped alumina gels in H-2 gas. Rare earth metal ion-doped alumina films, which were prepared by gelation of rare earth metal ion solution-added alumina sol and annealed the ion-doped alumina gel, exhibited not only normal luminescence but also up-conversion emission, energy transfer type luminescence and long lasting luminescence. (C) 2005 Springer Science + Business Media, Inc., SPRINGER
JOURNAL OF MATERIALS SCIENCE, 2005年01月,
［査読有り］ Fabrication of High Capacitance Ceramic-Polymer Nano-Composite Films
Y. Kobayashi; A. Kosuge; T. Tanase; D. Nagao; M. Konno
Materials Forum, 2005年, ［査読有り］
Direct drawing of Ag microwiring by laser-induced pyrolysis of film prepared from liquid-dispersed metal nanoparticlesA Watanabe; Y Kobayashi; M Konno; S Yamada; T Miwa, Ag microwiring with submicron resolution was fabricated by the laser-induced pyrolysis of a film prepared from liquid-dispersed Ag nanoparticles. The linewidth of the wiring fabricated by this laser direct-write maskless technique can be controlled flexibly by the laser beam focusing conditions. The resistivity of the Ag wiring fabricated by this technique (1.9 x 10(-6) Omega cm) is comparable with that of bulk Ag (1.6 x 10(-6) Omega cm)., INST PURE APPLIED PHYSICS
JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS, 2005年,
［査読有り］ チタン酸ストロンチウムバリウム粒子分散系のエレクトロレオロジー効果と粒子表面状態の関係小林芳男、森本龍介、森山晃司、佐藤友章、今野幹男, Electrorheological response of barium strontium titanate (BST)/silicone oil suspension was experimentally studied with measurements of generated shear stress in a range of field frequency (200-4000 Hz) under steady shear. The BST particles were synthesized by the hydrolysis of complex alkoxide precursor that was prepared in a reflux of metallic barium, metallic and tetraethylorthotitanate in solvent. The hydrolysis was performed by the addition of water/ethanol solution to the precursor solution. Generated shear stress of as-prepared (unannealed) BST particles system decreased with an increase in frequency, while that for 1100 °C-annealed BST system increased with frequency. XPS measurements revealed that alkoxyl groups that were derived from unreacted alkoxide were on surface of the as-prepared BST particles, and the annealing at 1100 °C decomposed the alkoxyl groups to hydroxyl groups. Difference in electric conductivities of the surfaces is considered to be responsible for the different shear stress behaviors of the as-prepared and annealed particles., The Society of Rheology, Japan
日本レオロジー学会誌, 2005年,
［査読有り］ Particle formation in the hydrolysis of tetraethyl orthosilicate in pH buffer solutionD Nagao; H Osuzu; A Yamada; E Mine; Y Kobayashi; M Konno, Particle formation in the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) was studied by varying pH (9.5-11) with the basic catalysts NH3, methylamine (MA), and dimethylamine (DMA) in the presence of 5 mol/m(3) CH3COOH, which was chosen to suppress time variations of pH and ionic strength during the reaction. Spherical particles were formed for MA and DMA at catalyst concentrations of 0.02-0.2 kmol/m(3) and for NH3 at catalyst concentrations of 0.1-1.5 kmol/m(3). In a common range of catalyst concentrations for spherical particle formation, average particle size was largest for DMA and smallest for NH3. Hydrolysis rate of TEOS Could be quantified by the use of buffer systems as a function of TEOS and OH- concentrations. A specific relation was not found between the hydrolysis and the particle size. The zeta potential of silica particles measured in the reaction solvent was in the order DMA < MA < NH3, and ionic strength, estimated from pH in the reactions, was in the order DMA congruent to MA > NH3. This Suggested that the particle sizes were controlled by electrostatic particle interactions. (C) 2004 Elsevier Inc. All rights reserved., ACADEMIC PRESS INC ELSEVIER SCIENCE
JOURNAL OF COLLOID AND INTERFACE SCIENCE, 2004年11月,
［査読有り］ Fabrication of sub-micrometer-sized jingle bell-shaped hollow spheres from multilayered core-shell particlesSC Gu; T Kondo; E Mine; D Nagao; Y Kobayashi; M Konno, Jingle bell-shaped hollow spheres were fabricated starting from multilayered particles composed of a silica core, a polystyrene inner shell, and a titania outer shell. Composite particles of silica core-polystyrene shell, synthesized by coating a 339-nm-sized silica core with a polystyrene shell of thickness 238 nm in emulsion polymerization, were used as core particles for a succeeding titania-coating. A sol-gel method was employed to form the titania outer shell with a thickness of 37 nm. The inner polystyrene shell in the multilayered particles was removed by immersing them in tetrahydrofuran. These successive procedures could produce jingle bell-shaped hollow spheres that contained a silica core in the titania shell. (C) 2004 Elsevier Inc. All rights reserved., ACADEMIC PRESS INC ELSEVIER SCIENCE
JOURNAL OF COLLOID AND INTERFACE SCIENCE, 2004年11月,
［査読有り］ Preparation of multilayered gold-silica-polystyrene core-shell particles by seeded polymerizationS Gu; J Onishi; E Mine; Y Kobayashi; M Konno, A preparation method for multilayered gold-silica-poly styrene core-shell composite particles is proposed. The gold-silica core-shell particles of 192-nm-sized, synthesized by coating the 18-nm-sized gold particles with silica by a seeded growth technique, were used as cores for succeeding polystyrene coating. After surface modification of gold-silica composite particles by methacryloxypropyltilmethoxysitane (MPTMS), polymerizations of styrene (0.16-0.4 M) were conducted with 8 x 10(-3) M of potassium persulfate initiator in the presence of 1 x 10(-3) M of sodium p-styrenesulfonate anionic monomer. Multilayered core-shell gold-silica-polystyrene particles that contained a single core could be obtained. The coefficient of variation of size distribution (C-V) of the composite particles was less than 7%, and polystyrene shell thickness was in a range of 193 to 281 nm. (C) 2004 Elsevier Inc. All rights reserved., ACADEMIC PRESS INC ELSEVIER SCIENCE
JOURNAL OF COLLOID AND INTERFACE SCIENCE, 2004年11月,
［査読有り］ Preparation of micrometer-sized poly(methyl methacrylate) particles with amphoteric initiator in aqueous mediaSC Gu; H Akama; D Nagao; Y Kobayashi; M Konno, A previously proposed method based on soap-free emulsion polymerization with an amphoteric initiator for producing micrometer-sized polystyrene particles was extended to application with methyl methacrylate (MMA). The aggregation and dispersion stability of polymer particles, which have ionizable groups arising from initiator radicals, can be controlled by adjusting the pH of the reaction system accompanied with the addition of ionic monomer. Polymerizations were carried out with 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] tetrahydrate amphoteric initiator, NH3/NH4Cl pH buffer, and sodium p-styrenesulfonate anionic monomer (NaSS) in ranges of MMA concentration (0.58-2.32 kmol/M-3 H2O) and NH3 concentration (2.5-20 mol/m(3) H2O) at fixed concentrations of 5 mol/m(3) H2O initiator, 10 mol/m(3) H2O NH4Cl, and 1 mol/m(3) H2O NaSS at 65 degreesC. The addition of NaSS during the polymerization could improve stability in dispersion of particles, which coagulated in the absence of NaSS after the disappearance of monomer drops. An increase in the monomer concentration in the present method could enlarge the particle size without lowering the monodispersity of the particle size distribution. On the other hand, an increase in NH3 concentration decreased the particle size. The highest monodispersity of particle sizes was obtained at a NH3 concentration of 5 mol/m(3) H2O, which gave an average size of 1.5 mum and a coefficient of variation of particle size distribution of 2.2% that was much smaller than the standard criterion for monodispersity, 10%., AMER CHEMICAL SOC
LANGMUIR, 2004年09月,
［査読有り］ Fabrication of sub-micron sized titania hollow spheresY Kobayashi; SC Gu; T Kondo; E Mine; D Nagao; M Konno, Sub-micron sized hollow spheres were fabricated starting from core-shell particles. Polystyrene particles with a size of 345 nm were coated with a titania shell of 15 nm thickness by a sol-gel method. The core-shell particles prepared were annealed at 500degreesC in air to remove the polystyrene core and crystallize the titania shell. The crystal structure of the hollow titania shell was anatase and its surface area was 91.0 m(2)/g., SOC CHEMICAL ENG JAPAN
JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 2004年07月,
［査読有り］ Synthesis of silica particles in the hydrolysis of tetraethyl orthosilicate with amine catalystsD Nagao; E Mine; Y Kobayashi; M Konno, Methylamine (MA) and dimethylamine (DMA) were examined as catalysts for the hydrolysis of tetraethyl orthosilicate (TEOS) to synthesize monodispersed silica particles. Experimental results were compared with those in ammonia-catalyzed hydrolysis of TEOS. The hydrolysis reactions were carried out at a water concentration of 11 kmol/m(3) in ranges of catalyst concentration (0.01-1.5 kmol/m(3)) and TEOS concentration (0.02-0.2 kmol/m(3)). Spherical particles were formed at catalyst concentrations lower than 1.5 kmol/m(3) for NH3 and lower than 0.2 kmol/m(3) for MA and DMA. Comparison of the coefficient of variation (C-v) for monodisperse spherical particles indicated that silica particles obtained with the amine catalysts were more highly monodisperse than those obtained with NH3 catalyst., SOC CHEMICAL ENG JAPAN
JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 2004年07月,
［査読有り］ Preparation of lead zirconate titanate thin films with a combination of self-assembly and spin-coating techniquesT Tanase; Y Kobayashi; M Konno, A low-temperature synthetic method for preparing lead zirconate titanate (PZT) perovskite film on a Pt substrate is proposed. The method consists of the self-assembly of PZT particles on a substrate and successive spin coating with a precursor of PZT. The PZT particles that had sub-micron sizes and perovskite structures were prepared by annealing amorphous PZT particles formed from a complex alkoxide precursor. The PZT particles were deposited on a Pt substrate that was surface-modified with (3-mercaptopropyl) trimethoxysilane to chemically fix the particles on the substrate. Another PZT precursor solution was used for the spin-coating on the PZT-deposited substrate, and then the spin-coated film was annealed at 350 degreesC to remove organic residues left in the film. The spin-coated PZT film prepared at 350 degreesC had a dielectric constant of 118 at a frequency of 1000 Hz. (C) 2003 Elsevier B.V. All rights reserved., ELSEVIER SCIENCE SA
THIN SOLID FILMS, 2004年06月,
［査読有り］ Structural transformation of template-synthesized mesoporous silica with addition of chloroformY Kobayashi; MM Collinson, M41S family mesoporous silica materials were synthesized via the hydrolysis and condensation of tetraethylorthosilicate (TEOS) using cetyltrimethylammonium bromide (CTAB) as a template and sodium hydroxide as a catalyst. MCM-48 and MCM-41 were prepared in the absence and in the presence of chloroform, respectively. The addition of chloroform likely changed both aggregation and swelling behavior of CTAB micelles and consequently hexagonal mesoporous structures were formed., CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
JOURNAL OF THE CERAMIC SOCIETY OF JAPAN, 2004年06月,
［査読有り］ Micro-patterning of lead zirconate titanate thin films seeded with barium strontium titanate nano-crystalline particles by photoirradiationT Tanase; A Watanabe; Y Kobayashi; M Konno; T Miwa, Lead zirconate titanate (PZT) thin films seeded with barium strontium titanate (BST) nano-crystalline particles were fabricated on a Si wafer with a spin-coating technique. The BST particles synthesized with a sol-gel method were dispersed in an acetylacetone (chelating reagent) modified PZT precursor solution of complex alkoxides for the fabrication. The micro-patterns of the PZT film containing 50 mol% BST particles could be obtained by the direct photo-irradiation to the fabricated films for 40 min without any pre-heating treatments, while the PZT films in the absence of the BST particles required pre-heating treatment at 200degreesC for 10 s before the photo-irradiation. This suggested that the BST crystallines accelerated decomposition of the chelate compounds and subsequent polycondensation of PZT alkoxides., SOC CHEMICAL ENG JAPAN
JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 2004年05月,
［査読有り］ Fabrication of mono- and multi-layers of submicron-sized spheres by a dip-coating technique and their transmittance propertyY Kobayashi; H Miyauchi; SC Gu; D Nagao; M Konno, This paper describes fabrication of well-ordered mono- and multi-layers of submicron-sized silica or polystyrene (PSt) spheres. The mono-layers of spheres were fabricated on glass plates by a dip-coating technique at various concentrations of KCl, HCl and KOH in colloidal suspension. The mono-layer of spheres in a close-packed hexagonal structure showed an extinction peak in the visible wavelength attributed to a secondary Bragg diffraction. Full width at half maximum (FWHM) of the extinction peak was the lowest at low ionic strength and at neutral pH. Different types of multi-layers of spheres were fabricated by repeating the dip-coating processes. Silica spheres with a size of 589 urn could be mono-layered in the close-packed hexagonal structure on the mono-layer of the 404-nm-PSt spheres. PSt spheres with a size of 404 nm could be layered on the mono-layer of 500-nm-PSt spheres in such a way that the 404-nm-PSt spheres occupied void spaces among three 500-nm-PSt spheres. Silica spheres with a size of 233 nm could be assembled in a two-dimensional network structure on mono-layered 589-nm-silica spheres., SOC CHEMICAL ENG JAPAN
JOURNAL OF CHEMICAL ENGINEERING OF JAPAN, 2004年05月,
［査読有り］ 蛍光ビーズを用いたセンチネルリンパ節生検法の検討
中島 護雄; 武田 元博; 小林 正樹; 鈴木 聡; 小林 芳男; 川添 良幸; 粕谷 厚生; 多田 寛; 大内 憲明, (一社)日本外科学会
日本外科学会雑誌, 2004年03月
クロロホルム添加による鋳型合成メソポーラスシリカの構造変化小林 芳男; Collinson Maryanne M., M41S family mesoporous silica materials were synthesized via the hydrolysis and condensation of tetraethylor-thosilicate (TEOS) using cetyltrimethylammonium bromide (CTAB) as a template and sodium hydroxide as a catalyst. MCM-48 and MCM-41 were prepared in the absence and in the presence of chloroform, respectively. The addition of chloroform likely changed both aggregation and swelling behavior of CTAB micelles and consequently hexagonal mesoporous structures were formed., 公益社団法人日本セラミックス協会
日本セラミックス協会学術論文誌 : Nippon Seramikkusu Kyokai gakujutsu ronbunshi, 2004年,
［査読有り］ Size effect on crystal structures of barium titanate nanoparticles prepared by a sol-gel methodY Kobayashi; A Nishikata; T Tanase; M Konno, Barium titanate nanoparticles were synthesized by the hydrolysis of complex alkoxide precursor that was prepared in a reflux of metallic barium and tetraethylorthotitanate in solvent. The hydrolysis was performed by the addition of water/ethanol solution to the precursor solution. As reflux time increased, particle sizes, which were measured with transmittance electromicroscopy, became smaller followed by sharpening of size distribution. As water concentration and benzene content in the hydrolysis increased, the particle size increased with crystallite size that was determined with X-ray diffractometry. No significant difference was observed between the particle and crystallite sizes up to 30 nm. Over the size of 30 nm, the particle size was larger than the crystallite size because of generation of polycrystallites. Annealing treatments in air at 400 and 1000degreesC also increased both the particle and crystallite sizes. The crystallite sizes estimated from the (111) peaks were smaller than those from (110) peaks in a range of sizes larger than 40 nm, which indicated that the critical crystallite size of transformation from cubic to tetragonal structures was approximately 40 nm., SPRINGER
JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY, 2004年01月,
［査読有り］ Direct coating of gold nanoparticles with silica by a seeded polymerization techniqueE Mine; A Yamada; Y Kobayashi; M Konno; LM Liz-Marzan, Gold nanoparticles prepared through a conventional citrate-reduction method were directly coated with silica by means of a seeded polymerization technique based on the Stober method. The method required no surface modification. The addition of tetraethylorthosilicate and water prior to ammonia was found to be critical to obtain a proper coating. The silica shell thickness was varied from 30 to 90 nm for TEOS concentrations of 0.0005-0.02 M at 10.9 M of water and 0.4 M of ammonia. The optical spectra of the core-shell gold-silica composite particles agreed with predictions of Mie theory. (C) 2003 Elsevier Inc. All rights reserved., ACADEMIC PRESS INC ELSEVIER SCIENCE
JOURNAL OF COLLOID AND INTERFACE SCIENCE, 2003年08月,
［査読有り］ Preparation and properties of silica-coated cobalt nanoparticlesY Kobayashi; M Horie; M Konno; B Rodriguez-Gonzalez; LM Liz-Marzan, The synthesis of monodispersed, amorphous cobalt nanoparticles coated with silica in aqueous/ethanolic solution is described. Both the core size and the silica shell thickness can be controlled through the synthetic conditions. Furthermore, the transformation of the cobalt cores into crystalline, metallic cobalt upon annealing in air is demonstrated through X-ray diffraction data. Both the initial, amorphous nanoparticles and their crystalline counterpart are magnetic, which promises important applications for ferrofluid preparation and for magnetic recording media., AMER CHEMICAL SOC
JOURNAL OF PHYSICAL CHEMISTRY B, 2003年07月,
［査読有り］ Alumina coating on quartz glass and nickel substrates using aqueous sol derived from AlCl3 center dot 6H(2)OT Ishizaka; Y Kobayashi; Y Kurokawa, The thick alumina films (0.2-0.5 mum) were prepared on quartz glass and nickel substrates by a dipping method using an alumina sol derived from an aqueous AlCl3 solution. The hardness of this coating was compared to those of similarly coated substrates that had been heat-treated at various temperatures. The hardness of the alumina coating increased with increasing heat-treatment temperature. This sol gave crack-free and well-coated substrates that could be heat-treated to temperatures up to 800degreesC. This may have been due to the formation of an amorphous mixed oxide interface layer between the alumina films and the substrates. At temperatures higher than 900degreesC, problems with the coating started to appear because the oxide layer formed into alpha-alumina accompanying evolution of stress in the interface. (C) 2003 Kluwer Academic Publishers., KLUWER ACADEMIC PUBL
JOURNAL OF MATERIALS SCIENCE, 2003年03月,
［査読有り］ Low-temperature synthesis of single-phase lead zirconate titanate thin film with a nm-seeding techniqueT Tanase; A Nishikata; Y Iizuka; Y Kobayashi; M Konno; T Miwa, Ferroelectric lead zirconate titanate (PZT) thin films containing crystalline seeds of barium strontium titanate (BST) nanoparticles were prepared by the complex alkoxide precursor method on indium titanium oxide (ITO) glass electrodes. The PZT films approximately 500 nm thick at BST particle concentrations of 0-34.2 mol% were fabricated with a spin-coating method and annealed at various temperatures. A non-seeded PZT film was crystallized into a perovskite structure by annealing at 500degreesC. The seeding with the BST particles promoted crystalline growth of PZT perovskite around the seeds, and lowered the crystallization temperature of the PZT films to 420degreesC., CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
JOURNAL OF THE CERAMIC SOCIETY OF JAPAN, 2002年10月,
［査読有り］ Sol-gel derived gold nanoclusters in silica glass possessing large optical nonlinearitiesST Selvan; T Hayakawa; M Nogami; Y Kobayashi; LM Liz-Marzan; Y Hamanaka; A Nakamura, Sol-gel derived gold/silica glasses, starting with Au sols prepared by two different methodologies, one without the aid of any external stabilizing agent and the other with silica-coated Au, are described. The optical absorption spectra show the typical surface plasmon resonance for Au at around 520-530 nm. Transmission electron microscopy reveals the existence of spherical Au particles in the silica matrix. The mean diameters of Au nanoclusters in gels and glasses vary from 10 to 20 nm and from 27 to 38 nm, respectively, supported by X-ray diffraction data. The third-order optical nonlinearities \chi((3))\ determined by a degenerate four-wave mixing (DFWM) method exhibit a higher value of 2.2 x 10(-9) esu for a glass with 0.5 wt % Au heated at 600 degreesC indicating that a larger size induces an enhancement effect. This method also offers a greater chi((3))/alpha (alpha: absorption coefficient) value of I x 10(-11) esu cm, which is comparable to those values obtained by a sputtering method. Thus, these novel Au-SiO2 nanocomposites fabricated by facile sol-gel methods render them potential candidates for photonic applications., AMER CHEMICAL SOC
JOURNAL OF PHYSICAL CHEMISTRY B, 2002年10月,
［査読有り］ Template-synthesized nanotubes for chemical separations and analysisM Wirtz; M Parker; Y Kobayashi; CR Martin, We have developed a new class of synthetic membranes that consist of a porous polymeric support that contains an ensemble of gold nanotubes that span the thickness of the support membrane. The support is a commercially-available microporous polycarbonate filter with cylindrical nanoscopic pores. The gold nanotubes are prepared by electroless deposition of Au. onto the pore walls, that is, the pores acts as templates for the nanotubes. We have shown that by controlling the Au deposition time, Au nanotubes that have effective inside diameters of molecular dimensions (< 1 nm) can be prepared. These nanotube membranes can be used to cleanly separate small molecules on the basis of molecular size. Furthermore, use of these membranes as a novel electrochemical sensor is also discussed. This new sensing scheme involves applying a constant potential across the Au nanotube membrane and measuring the drop in the transmembrane current upon the addition of the analyte. This paper reviews our recent progress on size-based based transport selectivity and sensor applications in this new class of membranes., WILEY-V C H VERLAG GMBH
CHEMISTRY-A EUROPEAN JOURNAL, 2002年08月,
［査読有り］ Molecular sieving and sensing with gold nanotube membranesM Wirtz; M Parker; Y Kobayashi; CR Martin, We have developed a new class of synthetic membranes that consist of a porous polymeric support that contains an ensemble of gold nanotubes that span the thickness of the support membrane. The support is a commercially available microporous polycarbonate filter with cylindrical nanoscopic pores. The gold nanotubes are prepared via electroless deposition of An onto the pore walls; i.e., the pores act as templates for the nanotubes. We have shown that by controlling the An deposition time, Au nanotubes that have effective inside diameters of molecular dimensions (<1 nm) can be prepared. These nanotube membranes can be used to cleanly separate small molecules on the basis of molecular size. Furthermore, use of these membranes as a novel electrochemical sensor is also discussed. This new sensing scheme involves applying a constant potential across the An nanotube membrane and measuring the drop in the transmembrane current upon the addition of the analyte. This paper reviews our recent progress on size-based transport selectivity and sensor applications in this new class of membranes. (C) 2002 The Japan Chemical Journal Forum and Wiley Periodicals, Inc., JOHN WILEY & SONS INC
CHEMICAL RECORD, 2002年,
［査読有り］ Sol-gel processing of silica-coated gold nanoparticlesY Kobayashi; MA Correa-Duarte; LM Liz-Marzan, Two procedures are presented which allow the homogeneous incorporation of silica-coated gold nanoparticles within transparent silica gels. Both UV-visible absorption spectra and transmission electron microscopy show that there is no aggregation of the metal particles during sol-gel transition. The optical properties of the gels are compared with those of the starting sols and interpreted on the basis of the porous structure of the gets and standard optical theories. Evidence is also shown of the potential of these methods for the preparation of gels with different particle sizes and shapes as well as with very high nanoparticle concentrations, which can be useful for several applications., AMER CHEMICAL SOC
LANGMUIR, 2001年10月,
［査読有り］ Deposition of sliver nanoparticles on silica spheres by pretreatment steps in electroless platingY Kobayashi; Salgueirino-Maceira, V; LM Liz-Marzan, A new method was developed for the homogeneous deposition of silver nanoparticles on colloid silica spheres. The method does not make use of an external electron source, but of a chemical moiety adsorbed on the surface, which can easily get oxidized. The process is mainly performed in two steps: a first step in which the adsorption of Sn2+ ions occurs on the surface of the silica particles and a second step comprising the addition of Ag+ ions, which are reduced and simultaneously adsorbed on the surface, while Sn2+ oxidizes to Sn4+ The whole process can be repeated to obtain a denser coating on the surface., AMER CHEMICAL SOC
CHEMISTRY OF MATERIALS, 2001年05月,
［査読有り］ Photodegradation of SiO2-coated CdS nanoparticles within silica gelsMA Correa-Duarte; Y Kobayashi; RA Caruso; LM Liz-Marzan, A comparative study of the photodegradation of CdS nanoparticles coated with silica shells dispersed in water and embedded in two silica gels with different pore size is presented. Although encapsulation of the quantum dots in a silica shell previously was proven to provide a basically permanent protection against light-induced surface oxidation (photodegradation), this protection is not always maintained when the coated particles are incorporated within different silica gels, Degradation of the CdS occurs when the coated particles are incorporated within silica gels with an open structure, which suggests that the shells somehow crack due to tension in the gel structure. This behavior is analyzed by absorption and luminescence spectroscopies, electron microscopy, and nitrogen sorption., AMER SCIENTIFIC PUBLISHERS
JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY, 2001年03月,
［査読有り］ Preparation of Silica-Coated Magnetic Nanoparticles
Y. Kobayashi; L. M. Liz-Marzán
Studies in Surface Science and Catalysis, 2001年, ［査読有り］
Preparation of mesoporous carbon from organic polymer/silica nanocompositeD Kawashima; T Aihara; Y Kobayashi; T Kyotani; A Tomita, A mesoporous carbon was prepared from a carbon/silica nanocomposite. The composite was obtained by mean of a sol-gel process using tetraethoxy silane (TEOS) in the presence of furfuryl alcohol (FA) as a carbon precursor and then the silica framework was removed from the composite by HF treatment. It was found that the resultant carbon is porous, and its mesoporosity depends on the sol-gel reaction conditions. For the production of mesoporous carbon, the amounts of both FA and acid catalyst (HCl) in the initial sol solution must be optimized. Under optimized conditions, the present method made it possible to develop uniform mesopores of 4 nm in diameter., AMER CHEMICAL SOC
CHEMISTRY OF MATERIALS, 2000年11月,
［査読有り］ Fabrication of Multilayered Au/Silica/Gadolinium Compound/Silica Core-Shell Particles
Y. Kobayashi; H. Inose; T. Nakagawa; K. Gonda; N. Ohuchi
Abstract Book of New and Advanced Materials International Congress (NAMIC2012), 2000年, ［査読有り］
Highly sensitive methods for electroanalytical chemistry based on nanotubule membranesY Kobayashi; CR Martin, Two new methods of electroanalysis are described. These methods are based on membranes containing monodisperse An nanotubules with inside diameters approaching molecular dimensions. In one method, the analyte species is detected by measuring the change in trans-membrane current when the analyte is added to the nanotubule-based : cell. The second method entails the use of a concentration : cell based on the nanotubule membrane. In this case, the change in membrane potential is used to detect the analyte.: Detection limits as low as 10(-11) M have been achieved. Hence, these methods compete with even the most sensitive of modern analytical methodologies. In addition, excellent molecular-sized-based selectivity is observed., AMER CHEMICAL SOC
ANALYTICAL CHEMISTRY, 1999年09月,
［査読有り］ Preparation of a γ-Alumina Film Doped with Fine γ-Iron (III) Oxide ParticlesY. Kobayashi; D. Kawashima; A. Tomita, A poly(vinyl alcohol)-alumina hydrate composite film prepared by using a sol-gel process was transparent in the visible region. The composite film was insoluble in water after being heated at about 100 degrees C but exhibited hydrophilicity. These characteristics are suitable for the deposition of Fe2O3 . nH(2)O in the film by a counter diffusion method. By heating at 600 degrees C in air, this deposited film was transformed to a gamma-Fe2O3-doped gamma-Al2O3 film NO absorption peaks were observed in the visible region at a wavelength of > 550 nm. The crystallite size could be controlled in the range 3-8 nm by changing the counter diffusion time. Due to the orientation of the alumina hydrate matrix, the gamma-Fe2O3-doped film was more easily magnetized in the direction parallel to the film plane than to the perpendicular., AMER CHEMICAL SOC
Chemistry of Materials, 1997年08月,
［査読有り］ Toward a Molecular Coulter® Counter Type DeviceY. Kobayashi; C. R. Martin, The Coulter(R) counter is a device used to count biological cells and colloidal particles. It consists of a small aperture that separates two electrolyte solutions, one of which contains the particles to be counted. The size or the particle that can be counted is related to the size of the aperture used. We have recently shown that metal nanotubules can be electrolessly plated within the pores of microporous filtration membranes. Tubules with inside diameters that approach molecular dimensions (<2 nm) have been prepared. Because the inside diameter of these nanotubules can be of molecular dimensions, it seemed possible that a Coulter(R)-type device based on the nanotubule membranes might be able to count molecules. If so, this device might provide a new and general approach for determining trace concentrations of molecules in solution. A prototype device was constructed and used to determine the concentrations of the cations Ru(bpy)(3)(2+) (bpy = 2,2-bipyridine) and methylviologen in aqueous solution. Concentrations of Ru(bpy)(3)(2+) as low as 10(-9) M could be detected. (C) 1997 Elsevier Science S.A., ELSEVIER SCIENCE SA LAUSANNE
Journal of Electroanalytical Chemistry, 1997年06月,
［査読有り］ Preparation of aqueous gold colloid by vapor deposition methodY Kobayashi; A Tomita, Gold vapor and water vapor were co-condensed on a cooled surface and then the ice was melted to obtain highly pure aqueous gold colloid. After removing gold aggregate, we obtained a supernatant solution of gold which is transparent and purple in color. A surface plasmon resonance absorption peak appeared at about 550 nm. The gold colloid was stable for more than a year without any additives. (C) 1997 Academic Press, ACADEMIC PRESS INC ELSEVIER SCIENCE
JOURNAL OF COLLOID AND INTERFACE SCIENCE, 1997年01月,
［査読有り］ Preparation of tin oxide monolith by the sol-gel method from inorganic saltY Kobayashi; M Okamoto; A Tomita, Tin oxide monolith was prepared by a sol-gel process using inorganic salt as a starting material. The tin oxide prepared had no aggregations visible to the naked eye and was very transparent in the visible wavelength even after heating in air at 600 degrees C. It was confirmed from X-ray diffraction results that the crystal structure of the tin oxide was of the rutile type. The crystal size changed from 1.4 nm to 23.5 nm as the heating temperature increased from room temperature to 700 degrees C, indicating a possibility to control the crystal size., CHAPMAN HALL LTD
JOURNAL OF MATERIALS SCIENCE, 1996年12月,
［査読有り］ Preparation of tubular alumina membrane with uniform straight channels by anodic oxidation processY Kobayashi; K Iwasaki; T Kyotani; A Tomita, We prepared alumina tubes by an anodic oxidation process. The tube obtained was mechanically tough against a pressure of about 1 MPa from the outside of the tu be. The tu be was characterized by scanning electron microscopy (SEM) and a gas permeability measurement. The SEM observations revealed that this has uniform straight channels penetrating through the tube wall. The channels are vertical to the tube surface and their dia meter is a bo ut 150 nm. The permeability of gas was measured with H-2, He, N-2, O-2 and CO2 in the range of 0-100 kPa. The gas flow was mainly governed by Knudsen flow. This indicates the absence of big cracks in the tube., CHAPMAN HALL LTD
JOURNAL OF MATERIALS SCIENCE, 1996年12月,
［査読有り］ Chemistry of Ca(OH)(2) leaching on mineral matter removal from coalJ Wang; ZG Zhang; Y Kobayashi; A Tomita, An attempt was made to remove mineral matter from Newstan coal by Ca(OH)(2) leaching followed by dilute hydrochloric acid washing. Ash removal of 76% was achieved by using 5% CaO loading at 340 degrees C for 120 min and an autogenous vapor pressure. CaO loading was found to be very important for optimization of ash removal. Above 5% CaO loading, a significant fraction of calcium was retained in treated coal. X-ray diffraction analysis and inductive coupling plasma spectroscopy analysis were used to study the chemistry of demineralization. The major crystalline minerals in the original coal were quartz and kaolinite. Quartz and kaolinite reacted with Ca(OH)2 to form ill-crystalline calcium silicate hydrates and calcium aluminum silicate hydrates, respectively. At lower CaO loadings, these products were effectively removed by acid washing, whereas at higher CaO loadings, calcium silicate hydrates and/or calcium aluminum silicate hydrates formed were less soluble in acid. Hence, treated coal was enriched with the undissolved calcium. Upon high-temperature ashing, the residual Ca-containing species were allowed to react with SO2 released from coal and capture a fraction of sulfur as a form of calcium sulfate., AMER CHEMICAL SOC
ENERGY & FUELS, 1996年03月,
［査読有り］ PREPARATION OF TRANSPARENT ALUMINA FILMS BY THE SOL-GEL PROCESS AND ITS APPLICATION TO PHOTO-FUNCTIONAL FILMSY KUROKAWA; Y KOBAYASHI; S NAKATA, We have examined the presentation of transparent alumina film and semiconductor microcrystalline- or organic dye-doped alumina film prepared by the sol-gel process using aqueous sol starting from AlCl3 . 6H2O. The resulting non-doped alumina film obtained by sol-gel transformation is transparent in the visible and near infrared, even heated up to 1000-degrees-C. From XRD and Al-27 MAS NMR results, it appears that the transitions of the alumina are as follows: 25-300-degrees-C, amorphous; 400-1000-degrees-C, a kind of gamma(gamma, delta, etc.); above 1000-degrees-C, alpha. Alumina films doped with laser dyes (rhodamine 6G (R6G), rhodamine B (RB), sulforhodamine 101 (SR 101), coumarin 1 (Cl) and 2-(1-naphthyl)-5-phenyl oxazole (alpha-NPO)) and laser dye pairs (R6G-RB, Cl-uranin and diphenyl oxazole-alpha-NPO) have exhibited laser emission and energy-transfer-type emission by nitrogen laser pumping, respectively. The maximum conversion efficiency is 2.1% (for R6G).
Absorption spectra of films doped with hole-burning dyes (5,8-dihydroxy-1,4-naphthoquinone, resorufin and alpha,beta,gamma,delta-tetrakis (4-sulfophenyl) porphine (TPPS)) have been burned on irradiation by laser. The hole spectrum of TPPS-doped film was observed even at 60 K. Film doped with nonlinear optical dye (2-methyl-4-nitroaniline) has exhibited the second harmonic wave laser by irradiation with an Nd:glass laser (lambda = 1064 nm) as a fundamental. CdS-doped film showed relatively sharp blue-shifted absorption attributed to the size quantization effect compared with bulk CdS. Large non-linear absorption and refractive index have been observed, because high concentration of CdS particles can be achieved by using this method., JOHN WILEY & SONS LTD
HETEROGENEOUS CHEMISTRY REVIEWS, 1994年12月
PHOTOLUMINESCENCE OF FINE SEMICONDUCTOR (CDS, CDSE, GE) PARTICLE-DOPED FILMS PREPARED BY A MUTUAL COUNTER DIFFUSION METHOD AND A SOL-GEL PROCESSY KOBAYASHI; Y KAKEGAWA; Y KUROKAWA; K SUZUKI; Y OKA, CdS or CdSe-doped polymer films (acetyl cellulose and polyvinyl alcohol) were prepared by a mutual counter diffusion method. CdS or Ge-doped alumina films were produced by a sol-gel process. Each CdS- or CdSe-doped film exhibited photoluminescence by excitation with an Ar+ laser. In particular, the CdS-doped alumina film did not emit photoluminescence derived from a deep trap level, but only one derived from the absorption edge. Moreover, photoluminescence of the Ge-doped alumina film was first observed., CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI
NIPPON SERAMIKKUSU KYOKAI GAKUJUTSU RONBUNSHI-JOURNAL OF THE CERAMIC SOCIETY OF JAPAN, 1993年01月
2ND HARMONIC-GENERATION IN 2-METHYL-4-NITROANILINE-DOPED ALUMINA FILMS PREPARED BY A SOL-GEL PROCESSY KOBAYASHI; S MUTO; A MATSUZAKI; Y KUROKAWA, 2-methyl-4-nitroaniline (MNA) was doped into a transparent alumina film by a sol-gel process starting from AlCl3 . 6H2O. A surface-active reagent, cetyl trimethyl ammonium bromide, was utilized in solubilizing MNA into the sol. Poling or co-doping of p-nitroaniline enhanced the intensities of second harmonic waves radiated from the doped films., ELSEVIER SCIENCE SA LAUSANNE
THIN SOLID FILMS, 1992年05月,
［査読有り］ PREPARATION OF A TRANSPARENT ALUMINA FILM DOPED WITH CDS AND ITS NONLINEAR OPTICAL-PROPERTIESY KOBAYASHI; S YAMAZAKI; Y KUROKAWA; T MIYAKAWA; H KAWAGUCHI, We have examined the preparation of transparent alumina film and CdS-doped alumina film prepared by the sol-gel process using aqueous sol starting from AlCl3. The resulting alumina films obtained by sol-gel transformation are transparent in the visible and near infrared up to 1000-degrees-C. Homogeneous solution of alumina sol and Cd(CH3COO)2 was converted into gel film by dehydration. Then, on exposure to H2S stream at 250-600-degrees-C, a CdS-doped film was obtained. It shows relatively sharp blue-shifted visible absorption that is attributed to size quantization effect. Large nonlinear absorption and refractive index have been obtained, because high concentration of CdS particles can be achieved by using this method., CHAPMAN HALL LTD
JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 1992年03月,
［査読有り］ レーザー色素ドープアルミナ膜の発振特性掛川進秀、小林芳男、武藤真三、黒川洋一, Laser dye doped alumina film was prepared by sol-gel process starting with AlCl
36 H
2O. Dyes used were Sulforhodamine 101(SR 101), Coumarin 1(C 1), 2-(1-Naphthyl)-5-phenyloxazole (a-NPO) and 2, 5-Diphenyloxazole (PPO). When the films doped with SR 101, C 1or α-NPO were irradiated wifh a N
2laser, lasers were acted. The film doped with both PPO and α-NPO exhibited energy-transfer-type laser emission. These results indicated that these doped alumina films have ability to operate as a compact dye laser., 公益社団法人 日本化学会
日本化学会誌, 1992年
PREPARATION OF A TRANSPARENT ALUMINA FILM DOPED WITH FLUORESCENCE DYE AND ITS ENERGY-TRANSFER LASER-EMISSIONY KOBAYASHI; H SASAKI; S MUTO; S YAMAZAKI; Y KUROKAWA, A transparent alumina film was prepared from an aqueous sol by the sol-gel process. Changes in the fluorescence of 7-azaindole were monitored during the processing from the aqueous sol to the dried gel by dehydration. Coumarin 1, which is insoluble in water, and an anionic dye, uranin, were doped into the film by utilization of surface-active reagents, Triton X-100 and cetyltrimethylammonium bromide respectively. This doped film exhibited energy-transfer-type laser emission by nitrogen laser pumping., ELSEVIER SCIENCE SA LAUSANNE
THIN SOLID FILMS, 1991年05月,
［査読有り］ OPTICAL NONLINEARITIES OF AL2O3 GLASSES WITH CDS MICROCRYSTALLITESH KAWAGUCHI; T MIYAKAWA; N TANNO; Y KOBAYASHI; Y KUROKAWA, Fabrication of Al2O3 glasses with CdS microcrystallites by means of the sol-gel method, as well as their linear and nonlinear optical characteristics, is reported for the first time. The shift in the wavelength of the absorption edge through a quantum size effect was clearly observed for the Cds-doped Al2O3 prepared by changing the annealing temperature. A large nonlinear absorption and refractive index were obtained because a high CdS microcrystallite concentration was achieved through the sol-gel method., JAPAN J APPLIED PHYSICS
JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS, 1991年02月,
［査読有り］ 分散剤添加によるローダミン6G分散アルミナ膜の光特性の改善小林芳男、武藤真三、佐々木秀明、黒川洋一, Rhodamine 6 G doped alumina film was prepared by sol-gel process. Triton X-100 or β-cyclodextrin was added to the doped film to improve its photo-properties. For the laser action by pumping with a N
2 laser, Triton X-100 improved the emissibility and β-cyclodextrin prevented the photo-bleaching., The Surface Science Society of Japan
表面科学, 1991年,
［査読有り］ 対向拡散法によるCdS微粒子分散高分子膜の調製佐々木秀明、小林芳男、黒川洋一, 多孔性酢酸セルロース及びポリビニルアルコールゲル膜中にCdS超微粒子を対向拡散法により分散させた. ゲル膜を介してNaOH水溶液とCd (CH
3COO)
2またはCdCl
2水溶液を接触させて, 膜中にカドミウム水酸化物の沈殿を形成させ, 次に, Na
2S水溶液を作用させてCdS分散膜とした. この方法により, 2～10nmのCdS粒子が均一に分散した高分子複合膜を得ることができた. 分散膜は量子サイズ効果を示し, Nd-YAGレーザー照射により3倍高調波を発生した., The Society of Polymer Science, Japan
高分子論文集, 1990年,
［査読有り］
