We report a new method to fabricate self-organized nanoporous titania films (pore diameter approximate to 30 nm; approximate to 1100 nm thick) and ordered titania nanorod arrays (rod diameter approximate to 30-60 nm; 70-260 nm high) by combined anodizing of superimposed Al/Ti layers sputter-deposited on glass substrates. The titania nanostructures mimic the ordered nanoporous anodic alumina films via a through-mask anodization. We propose a new anodizing electrolyte, i.e., a diluted nitric acid solution, for fabricating uniform, self-organized, ordered nanoporous titania films with parallel cylindrical pores and without any thickness limit. More significantly, the nanoporous titania films contain a small amount of titanium nitride and dissociated nitrogen, and exhibit a moderate transparency and an enhanced absorption throughout the UV and visible light regions of the electromagnetic spectrum. After heating at 600 degrees C for 2 h, the nanoporous titania films develop a small absorption red-shift and exhibit high photocatalytic activity under UV illumination.
