(70ba) Synthesis of Au/Tio2 Core-Shell Nanoparticles by Sol-Gel Method

Au/TiO2 core-shell particles have been expected to appear a different optical and photocatalytic property with Au/SiO2 core-shell nanoparticles. In this study, in order to identify the optical property, the TiO2 shell on the surface of Au nanoparticles is prepared from hydrolysis reaction of the mixed solution of titanium(¥³) isopropoxide (TIPO) and triethanolamine (TEOA). This TIPO/TEOA mixed solution was fabricated under nitrogen atmosphere at a molar ratio of TIPO:TEOA 1:2 to form a stable complex of Ti4+ for preventing the excessively rapid hydrolysis of Ti4+ ion. Au colloid was prepared by using a HAuCl4¤ý4H2O and C6H5Na3¤ý2H2O. The size of synthesized Au nanoparticles was 15nm. Mercaptoundecanoic acid (MUA) was used as a coupling agent to improve affinity between Au and TiO2. For optimizing synthesis conditions of Au/TiO2 nanoparticles, the concentration of Ti4+ in stock solution and temperature of synthesis were altered. The morphology of obtained Au/TiO2 core-shell nanoparticles was observed by using transmission electro microscope (TEM) and the optical property and the stability of the nanopaticles in solution was observed by using UV/VIS spectrometer. The Au/TiO2 core-shell structure nanoparticles could be obtained when the concentration of TIPO in the stock solution was from 25mM to 50mM and the temperature of hydrolysis reaction was 80°C, and the thickness of TiO2 shell on the surface of Au nanoparticles showed about 10nm. The position of UV/VIS absorption peak for the Au/TiO2 core-shell nanoparticles was blue-shifted as about 3nm as compare with that of pure Au particles. This blue shift was caused by the TiO2 shell formed on Au nanoparticles. The synthesized TiO2 shell has amorphous structure similar to anatase.