Band gap narrowing of TiO2 by nitrogen doping in atmospheric microwave plasma

Nitrogen (N)-doped titanium dioxide (TiO2) particles of nanometric size are directly synthesized in an atmospheric microwave plasma-torch using gas-phase titanium tetrachloride (TiCl4). The absorption edge of the TiO2 − xNx powders shifts from 365 to 500 nm in UV–visible spectrum, as the content x of nitrogen in titanium dioxide powders increases from x = zero. From the results of the XRD, XPS, and UV–visible data, incorporation of N into the O site of TiO2 was enhanced in a mixture of N2 and O2 by an atmospheric microwave plasma torch, contributing to the band gap narrowing.