Growth of flower-like ZnO via surfactant-free hydrothermal synthesis on ITO substrate at low temperature

Without any surfactant, rod-like and three kinds of flower-like ZnO microstructures were synthesized on indium-doped tin oxide (ITO) glass substrates through a simple and environmentally-benign hydrothermal process at 70 degrees C. The result indicated that rod-like ZnO would be transformed into flower-like ZnO microstructures with decreasing the concentration of sodium hydroxide. The ends, numbers and diameters of the petals of flower-like ZnO varied greatly by modulating the concentration of sodium hydroxide. The secondary nucleation and growth phenomena of ZnO were observed. Time-dependent experiments results indicate that the flower-like ZnO formed in a short period of time. The evolution of morphology and size of ZnO microstructures depended on the reaction time. The amounts and diameters of the petals of flower-like ZnO changed with increasing reaction time. On the basis of our observations and the mechanism proposed previously, the possible growth mechanism for flower-like ZnO was proposed.