Preparation of Platinum Nanoparticles Using Linear Polyethyleneimine as a Stabilizer by Liquid-phase Reduction Method
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1217-Y08-17
Preparation of Platinum Nanoparticles Using Linear Polyethyleneimine as a Stabilizer by the Liquid-phase Reduction Method Takanori Imai1, Yoshimoto Abe1,2, Keishi Nishio3; Ryuji Tamura3, Hirobumi Shibata3, Tohru Kineri4, and Takahiro Gunji1. 1 Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba, 278-8510 Japan 2 Department of Food Science, Faculty of Health and Nutrition, Tokyo Seiei College, 1-4-6 NishiShinkoiwa, Katsushika, Tokyo 124-8530 Japan 3 Department of Materials Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba, 278-8510 Japan 4 Department of Applied Chemistry, Tokyo University of Science, Yamaguchi, 1-1-1 Daigaku-Dori, SanyoOnoda, Yamaguchi, 756-0884 Japan
ABSTRACT Platinum nanoparticles stabilized by linear polyethyleneimine were prepared by the liquid-phase reduction of chloroplatinic(IV) acid with sodium borohydride. The particle sizes were 3.26 nm and 1.76 nm when the molecular weights of linear polyethyleneimine were 25000 and 2150, respectively. These nanoparticles were well-dispersed in water in the range of pH 1-6. Branched polyethyleneimine also provided nanoparticles that dispersed in water in the range of pH 0-8. Linear poly(ethyleneimine-co-Nmethylethyleneimine) gave nanoparticles that dispersed in water in the range of pH 0-10. The dispersibility of the nanoparticles decreased with increasing content of the N-methyl group. INTRODUCTION Platinum is known as a good catalyst in both organic synthesis and environmental science and is widely used in these scientific fields. Platinum nanoparticles are also used as a magnetic material for iron/platinum alloy 1, a quantum dot 2, a catalyst with high durability, high activity, and high chemical stability 3-6. To date, platinum nanoparticles have been used in the air-cleaning catalyst of the exhaust gases from automobiles and various industries 7,8. In the application of platinum nanoparticles as a catalyst, the nanoparticles must be supported on a stable supports such as silica gels and alumina gels. The mesoporous silicas are one of the best supports because they are constructed in the form of a honeycomb structure by the accumulation of long silica channels 8. Platinum nanoparticles are often introduced in the silica channels and are fixed onto the surfaces of these silica channels. The introduction of platinum nanoparticles into the silica channels is achieved by the immersion of mesoporous silica in a solution of platinum nanoparticles. Therefore, the platinum nanoparticles should have the following properties: easy dispersion in aqueous solution: dispersion in acidic or basic aqueous solution: supportable particle size in a mesopores with a diameter of approximately 2.5-50 nm. To date, there have been many reports and reviews regarding the preparation of platinum nanoparticles. The preparation methods can be classified as follows: (1) reduction of chloroplatinic(IV) acid in the presence of poly(methacrylic acid) 9: (2) redu
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