Design of gold nanoparticles-decorated SiO₂@TiO₂ core/shell nanostructures for visible light-activated photocatalysis

In this study, we designed core/shell nanostructures (CSNs) of silicon dioxide (SiO₂)/titanium dioxide (TiO₂), which were decorated with gold (Au) nanoparticles (NPs), to activate the visible light-driven photocatalytic reaction that is not feasible with only the SiO₂@TiO₂ CSN because there is no absorption in the visible wavelengths. The CSNs were simply synthesized by hydrothermal method. In the core/shell structure, TiO₂ covered the SiO₂ core surface, which acts as a template. The attachment of additional Au NPs inside or outside the core/shell led to absorbance in visible wavelengths of light from the Sun, from which most radiation comes with a spectrum peak at yellow wavelength, owing to the localized surface plasmon resonance (LSPR) peak at approximately 550 nm. The SiO₂@Au@TiO₂@Au CSN (0.01 g) decomposed 1% of methyl orange (MO) solution in 15 mL deionized water in 1 h under the visible light. The visible light-driven photocatalytic reaction was ascribed to the LSPR around the Au NPs that were deposited inner or outer the mesoporous TiO₂ shell.