Humidity Sensing Studies of Ag Doped TiO2

Practical applications of TiO2 are limited due to its wide band gap and fast recombination of electron-hole pairs within nanoseconds. So far numerous researches have been focused on defeating these disadvantages by introducing the noble metals into titania lattice. Noble metals deposited or doped in TiO2 have the high Schottky barriers among the metals and act as the electron traps, facilitating electron-hole separation and promotes interfacial electron transfer process. These additives capture electrons resulting in lower recombination rate of electron-hole pairs. However, some noble metals such as Pt, Pd, Rh, Au are too expensive to be used for the industrial scale. Therefore, the research on Ag-doped TiO2 has significant practical value. Silver is suitable for industrial applications due to its comparable cost and easy preparation. It is a suitable element, which improves the TiO2 photo-catalytic performance, it is also believed that the silver ions interact with sulfur, oxygen and nitrogen in the molecules of microorganisms and inactivate the cellular proteins resulting in titania as better bioactivite material. Ag-doped titania layers with different morphologies have been grown by Sol-gel method. As the Fermi levels of these noble metals are lower than that of TiO2, photoexcited electrons can be transferred from the conduction band to the metal particles deposited on the surface of TiO2, while photogenerated valence holes remain in the TiO2. These activities greatly reduce the possibility of electron-hole recombination, resulting in efficient separation and stronger photo-catalytic reactions.