Titanium dioxide (TiO2), an example of metal-oxide type
semiconductors, has been studied and widely used as a photocatalytic
material for self-cleaning coatings, environmental purifiers,
antifogging mirrors and many other applications [1]. TiO2 has a
bandgap of 3.0 eV for the rutile phase and 3.2 eV for the anatase
phase. These values require ultraviolet (UV) radiation to activate