Synthesis of Au/TiO₂ Core–Shell Nanoparticles from Titanium Isopropoxide and Thermal Resistance Effect of TiO₂ Shell

Abstract

On the synthesis of Au/TiO2 core–shell structure nanoparticles, the effect of the concentration of Ti4+ on the morphology and optical property of Au/TiO2 core–shell nanoparticles was examined. A gold colloid was prepared by mixing HAuCl4·4H2O and C6H5Na3·2H2O. Titanium stock solution was prepared by mixing solutions of titanium(IV) isopropoxide (TTIP) and triethanolamine (TEOA). The concentration of the Ti4+ stock solution was adjusted to 0.01–0.3 mM, and then the gold colloid was added to the Ti4+ stock solution. Au/TiO2 core–shell structure nanoparticles could be prepared by the hydrolysis of the Ti4+ stock solution at 80 °C. The size of the as-prepared Au nanoparticles was 15 nm. The thickness of the TiO2 shell on the surface of gold particles was about 10 nm. The absorption peak of the Au/TiO2 core–shell nanoparticles shifted towards the red end of the spectrum by about 3 nm because of the formation of the TiO2 shell on the surface of the gold particles. The crystal structure of the TiO2 shell showed an anatase phase. The increase in the Au crystallite size of the Au/TiO2 nanoparticles with increasing heat treatment temperature is smaller than that in the pure Au nanoparticles. This may be due to the encapsulation of Au particles with the TiO2 shell that prevents the growth of the nanoparticle nucleation.