S. Daneshvar E Asl, S. Kh. Sadrnezhaad,
Volume 37, Issue 2 (Journal of Advanced Materials-Summer 2018)
Rutile-phase titanium dioxide nanorod arrays were prepared by the hydrothermal method. Then, anatase-phase nanoleaves were successfully synthesized on the nanorod arrays via mild aqueous chemistry. Nanorod arrays scanning electron microscopy revealed that the thin film is uniform and crack free and the average diameter and height of the nanorods are 90 nm and 2 µm, respectively. Furthermore, nanorods are vertical to the substrate surface and have desired coverage density due to the predeposition of TiO2 seed layer which leaded to decrease the surface roughness of the substrate. Nanoleafed nanorods scanning electron microscopy indicated that the nanoleaves were grown uniformly on the entire surface of nanorods and the specific surface area and roughness factor of those are significantly improved. Energy dispersive spectrums suggested that F- and Cl- ions are partially doped into TiO2 crystals. Raman and X-ray spectra confirmed the formation of anatase-phase nanoleaves on the rutile-phase nanorods. X-ray diffraction also indicated that the nanorod arrays are highly oriented with respect to the substrate surface. The diffused reflectancetransmittance data revealed the incident light was more efficiently harvested by the nanoleafed nanorod thin film and the values of energy gap are 2.78 and 2.82 eV for rutile TiO2 nanorod and rutile+anatase TiO2 nanoleafed nanorod thin films, respectively. Synthesized nanostructure, having improved charge separation and transfer (due to the presence of the surface anatase/rutile junctions), high specific surface area and light harvesting (due to the presence of the nanoleaves) and low band gap energy (due to the nonmetallic elements doping), is viable alternative to traditional single crystalline TiO2 nanorods for highly efficient photoelectrochemical applications.
