Synthesis and characterization of ZnO micro-tubes

ZnO microtubes were synthesized by two step process, (i) synthesis of ZnO microrods and (ii) etching the microrods to form microtubes. The ZnO microrods are synthesized by the simple solution growth method using the zinc chloride and hexamine as a precursors at around 95 °C. Using the KOH as the etchant the ZnO microrods have etched into ZnO microtubes. ZnO micro-tube formation was studied as a function of KOH concentration and etching time. At low KOH concentration the tubes were not completely etched whereas at higher concentration the tube walls were damaged. ZnO tubes were characterized by X-ray diffraction, scanning electron microscopy, UV-vis spectrophotometer and room temperature photoluminescence (PL) measurement. From the UV absorption spectra and PL spectra reveals the presence (Oxygen vacancies related) of defect states due to KOH etching. The as-synthesized Zinc Oxide micro tubes have a diameter of ~600 nm, wall thickness of 30-40 nm, and length of ~7 μm. ZnO microtubes were tested as the catalyst for the photo degradation of the methylene blue (MB) dye. The result shows the photo degradation efficiency of the tubes are twice faster compared to that of rods, this is due to high surface area associated with the tubes.