Size-controlled electrochemical synthesis and properties of SnO2 nanotubes

SnO2 nanotubes with controlled diameter and length were synthesized using an electrochemical method at room temperature. The length and wall thickness of the nanotubes increased monotonically with the deposition time and the diameter of the nanotubes was altered by varying the pore size of the scaffolds. Post-annealing at 400 degrees C in dry air significantly improved the crystallinity while maintaining the nanotube structure. The temperature-dependent photoluminescence spectra indicated an activation energy of 58 meV for emission centered at 410 nm. The temperature-dependent electrical resistance revealed that the dominant electrical conduction mechanism alters from the ionization of the main donor centers to impurity scattering as the temperature decreases. The electrical conductance of 200 nm diameter nanotubes increased to 33 times the original value upon UV illumination at 254 nm.