Photoreduction altered work function of Au-TiO2 nanoparticles measured by scanning Kelvin probe microscopy.

The present study investigates the systematic changes observed in work function (WF) of Au-nanoparticles supported on TiO2 as a result of variation in surface plasmon resonance induced absorption intensity. Synthesis of hybrid Au-TiO2 nanoparticles was carried out by sol-gel process followed by photoreduction of gold (III) chloride trihydrate in presence of UV light. Surface Plasmon resonance appearing at 540 nm in the UV/Vis absorption spectra, confirms the formation of Au nanoparticles. The composition of these hybrid Au-TiO2 nanoparticles was determined from Rutherford back scattering studies. Transmission electron microscopy measurements reveal the size of synthesized Au nanoparticles to be 15 +/- 2 nm with well defined lattice fringes. With increase in photoreduction time, the concentration of Au nanoparticles increases, size remaining the same. To observe the efficiency of these hybrid nanoparticles towards photo-assisted applications, their work function was measured using scanning Kelvin probe microscope. The detail analysis of variation of their WF values with photoreduction time reveals that a plateau or saturation behavior of Au-TiO2 nanoparticles close to that of pure Au is achieved after a photoreduction time of 6 hours due to occurrence of maximum Au loading on TiO2 surface.