Morphology investigation of hydrothermally prepared ZnO micro-crystals influenced by Cu2+ ions

Micrometer-sized ZnO with various shapes have been synthesized by a hydrothermal route with Zn(Ac)2/NH3·H2O in the presence of copper ions. Powder X-ray diffraction and scanning electron microscopy were utilized to characterize the composition and structure of the samples, respectively. As-synthesized, the ultrasonic pretreatment, pH value, reaction time and hydrothermal temperature played important roles in crystal structure tailoring. Novel nut-like ZnO crystal with improved crystal quality was obtained with initial Zn2+/Cu2+ ratio of 10, at reaction temperature of 100 °C, with initial pH of 7.0 and in a reaction time of 4 h, with ultrasonic pretreatment. Time-dependent experiments show that transfer of the Cu ions plays a crucial role as it causes the difference in crystal growth velocity.