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.