Figure 11.

Photo-luminescence spectra of titanium oxide a nanoparticles (sample 2) and b microtubes (sample 4), the latter having an order-of-magnitude higher emission band from 400 to 700 nm. There are more distinct peaks at specified eVs for the microtubes in (b) in comparison with the nanoparticles in (a). This is due to a larger amount of microtubes with predominant amorphous lamellar wall rather than crystalline TiO, Ti2O3, and TiO2(cf. text)

Huang et al. Nanoscale Research Letters 2010 5:972-985   doi:10.1007/s11671-010-9591-4