Improving the spectral sensitivity of photocatalysts may significantly enhance photoprocesses by distinctly absorbing more light. The design of more selective photocatalysts that can be activated by visible light and can be applied in medical diagnosis or therapy (in cancer treatment, implantology or as an antibacterial material) or novel photocatalysts for the production of energy resources (from biomass or from water splitting) are among the major goals of application for doped and undoped titania photocatalysts in biological and chemical applications. Here, we discuss surface charge generation and photocatalysis in nano-titania and methods of obtaining a shift to a higher wavelength for this photocatalytic transition. With some examples, we also show how photocatalysis can be probed.