Structural and photovoltaic properties of highly ordered ZnFe2O4 nanotube arrays fabricated by a facile sol–gel template method

Highly ordered ZnFe2O4 nanotube arrays were successfully prepared using porous anodic aluminum oxide (AAO) template from sol–gel solution. The ZnFe2O4 nanotubes are orderly arranged in parallel and each nanotube is composed of many agglutinating nanoparticles. The UV–vis absorption and surface photovoltage spectra of the ZnFe2O4 nanotubes and gel powders have been compared. The photovoltaic response threshold of the ZnFe2O4 nanotubes exhibited a blue-shift of about 150 nm with respect to that of the ZnFe2O4 gel powder, which implies that the photogenerated charges in the nanotubes have a higher redox activity than that of the gel powder. Both materials behave like a p-type semiconductor with photogenerated electrons accumulated at their surface.