Low-temperature synthesis of Fe-Doped ZnO nanotubes

We report on the synthesis Zn_1-x Fe _x O nanotubes with average tube diameter of 60 nm to 100 nm and wall thickness of about 20 nm. The nanotubes were synthesized by a low-temperature electrochemical process, and their morphology was found to be sensitive to the electrolyte concentration and growth time. The maximum Fe doping achieved by this process was estimated to be approximately 4 wt.%. High-resolution transmission electron microscopy and x-ray diffraction showed good crystalline quality of the doped and undoped nanotubes with preferential growth along the wurtzite c-axis. The Fe-doped nanotubes exhibit wurtzite crystal structure with an increase in the c-axis lattice constant when compared with the undoped nanotubes, indicative of the fact that Fe ions substitute for Zn as 2+ ions in the ZnO crystal lattice. Further evidence of Fe as a substitutional dopant is provided by Raman and photoluminescence spectroscopy. A comparison of the effective magnetic moment in the undoped and doped nanotubes reveals the presence of four unpaired electrons in the Fe-doped sample and zero unpaired electrons for the undoped sample.