"In recent years... use of semiconductor materials as photocatalysts for the removal of... organic and inorganic species from aqueous or gas phase systems in environmental clean-up, drinking water treatment, industrial and health applications... is because of the ability of TiO2 to oxidize organic and inorganic substrates in air and water through redox processes. ...TiO2 has ...emerged as one of the most fascinating materials in... ... engaging... physical chemists, physicists, material scientists and engineers in exploring distinctive semiconducting and catalytic properties."