A significant challenge in solar energy utilization is to identify and develop materials that can efficiently trap and store solar energy and allow tunable and controllable transfer of that energy. Central to the material design is enhancing photoinduced charge separation and storage, and controlling the use of stored charge to carry out selective catalytic reactions. We present photocatalytic activities of metal oxide nanoparticles such as TiO2 and ZnO modified with structurally and energetically well-defined monolayer-protected gold clusters (MPCs) passivated with tiopronin or glutathione in the photocatalytic degradation of industrial dye molecules. The photocatalytic activities are found to be greatly enhanced with MPC modification. The photocatalytic reactions were performed with various dye molecules to understand the enhancing mechanism of the catalytic activities. In addition, the effects of MPC core size on the dynamics of photoinduced charge transfer and the photocatalytic activity will be presented.