Spherical Silica Particles with Double-layer Structures Containing Silver Halides in the Core

Minahiro OKABAYASHI*, Zhi-Ping BAI, Hiroshi KATO††, Shigeki OKAZAKI, Aiko HATTORI and Yuya SENTO

Department of Materials Science and Engineering, Kochi National College of Technology; 200-1 Monobe, Nankoku-shi 783-8508 Japan
†Coordination Chemistry Institute and The State Key Laboratory of Coordination Chemistry, Nanjing University; Nanjing, 210093, P. R. China
††Tokuyama Research Center, Tokuyama Corporation; Mikage-cho, Tokuyama-shi 745-8648 Japan

Silver halides were deposited in the core of the double-layer by the decomposition of silver complex and trialkoxy(haloalkyl)silanes. The complex, bis[3-(2-aminoethyl)aminopropyl(trimethoxy)silane]silver(I) nitrate, was prepared from silver nitrate and [3-(2-aminoethyl)aminopropyl]trimethoxysilane in a glove box filled with nitrogen gas and co-hydrolyzed with tetraethoxysilane. The core particles were prepared by titration of copolymer from tetraethoxysilane, the silver complex, 3-bromopropyl(triethoxy)silane and chloromethyl(trimethoxy)silane into the mixture of methanol and ammonia water. Subsequently, the core was coated with the shell formed via titration of tetraethyoxysilane. The resulting particles were larger in diameter than the core particles. The scanning electron micrograph observation has proved that those particles are spherical and that the particle size distribution is narrow. Silver chloride was only deposited in particles when the silver complex and chloromethyl(trimethoxy)silane were used as the precursor. On the other hand, silver bromide was generated when 3-bromopropyl(triethoxy)silane or its mixture with chloromethyl(trimethoxy)silane was employed for the formation of silver halide. Deposited silver halides in particles were detected on the samples heated up to 700 °C by the X-ray diffraction measurement.

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