In 2001 Asahi et al. [1] introduced a co-sputtering process to produce N-doped TiO2. This led to a modification of the band structure, which activated a visible light photo response in TiO2. The modified material immediately stimulated broad interest and was explored widely for photocatalytic applications. Usually nanoscale powders or nanotubes [2] are used to achieve a high surface area and thus to increase the reaction rate.

Recently, researchers in Germany have shown that porous WO3 – a material that in many respects has an even higher potential for wide bandgap applications than TiO2 – can be modified by a comparably simple heat treatment in NH3 gas to drastically increase (18 times) its visible light photo response. The combination of ordered nanoscale morphology obtained by the self-ordering anodization of W-sheet and the now introduced visible light activity makes the material a promising candidate for enhanced solar cells, electrochromic materials and specific photocatalytic applications.

[1] R Asahi, T Morikawa, T Ohwaki, K Aoki and Y Taga 2001 Science 293 269
[2] A Ghicov, J M Macak, H Tsuchiya, J Kunze, V Haeublein, L Frey and P Schmuki 2006 Nanolett. 1080.

The researchers presented their work in the journal Nanotechnology.