Microwave assisted hydrothermal synthesis and characterization of ZnO-TNT composites

TiO2 nanotubes with different contents of ZnO (3-40 wt.% ZnO) have been successfully synthesized by microwave assisted hydrothermal process by using commercial TiO2-P25 as a precursor. The phase and crystallinity of the obtained ZnO-TNT were analyzed by X-ray Diffraction (XRD). The surface area of the ZnO-TNT was determined by BET method. The effect of the different contents of ZnO on morphology of TiO2 nanotubes was investigated by SEM and TEM. Optical properties and band gap energy of ZnO-TNT were calculated by using UV-vis DRS spectroscopy and modified Kubelka-Munk equation. Photocatalytic performance of ZnO-TNT was investigated by degradation of rhodamine B (RhB) dye under UV and visible light irradiation. Increasing ZnO content in TNT gradually decreased the diameter and length of nanotubes. Furthermore, addition of 40 wt.% ZnO into the TNT exceeded the saturation limit of ion exchangeability of Zn2+ and Na+ ions and aggregation of finely dispersed ZnO particles on the surface of TNT were observed. The ZnO-TNT has shown relatively larger band gap energies than that of TiO2-P25. However, ZnO-TNT has shown considerable increase in photo-activity for degradation of RhB dye in visible light as compared to UV light irradiation.