A facile approach to TiO_2 colloidal spheres decorated with Au nanoparticles displaying well-defined sizes and uniform dispersion

摘要

This paper describes a straightforward approach for the synthesis of hybrid materials composed of titanium dioxide (TiO_2) colloidal spheres decorated with gold nanoparticles (Au NPs). In the reported method, monodisperse TiO_2 colloidal spheres (～220 nm in diameter) could be directly employed as templates for the nucleation and growth of Au NPs over their surface using AuCl_4 ~- _((aq)) as the Au precursor, ascorbic acid as the reducing agent, PVP as the stabilizer, and water as the solvent. The Au NPs presented a uniform distribution over the TiO_2 surface. Interestingly, the size of the Au NPs could be controlled by performing sequential reduction steps with AuCl_4 ~- _((aq)). This method could also be adapted for the production of TiO_2 colloidal spheres decorated with other metal NPs including silver (Ag), palladium (Pd), and platinum (Pt). The catalytic activities of the TiO _2-Au materials as a function of composition and NPs size were investigated toward the reduction of 4-nitrophenol to 4-Aminophenol under ambient conditions. An increase of up to 10.3-fold was observed for TiO _2-Au relative to TiO_2. A surface-enhanced Raman scattering application for TiO_2-Au was also demonstrated employing 4-mercaptopyridine as the probe molecule. The results presented herein indicate that our approach may serve as a platform for the synthesis of hybrid materials containing TiO_2 and metal NPs displaying well-defined morphologies, compositions, and sizes. This can have important implications for the design of TiO2-based materials with improved performances for photocatalysis and photovoltaic applications.