Recent advances in making nano-sized TiO ₂ visible-light active through rare-earth metal doping

Doping with metals and non-metals is a popular technique that facilitates visible light activity of titanium dioxide. More recently, rare-earth metals have shown tremendous potential as dopants not only in red-shifting the absorption but also in improving the photocatalysis of TiO2. This feature article discusses recent developments in making TiO2 visible-light active through single and co-doping with rare earth metals. An emphasis is placed on wet chemical techniques and their associated effects on the phase, adsorption, surface area, and photocatalytic activity of TiO2. New techniques, such as electrospinning, magnetron sputtering, co-precipitation, and complexation, as well as the use of nanotubes and physical support are also discussed.