Continuous facile synthesis of nano-sized zinc oxide and its optical properties

Zinc oxide (ZnO) was synthesized by using continuous microwave (Mw) flow synthesis. The synthesized nanoparticles were characterized by x-ray diffraction and transmission electron microscopy techniques to study the phase composition, particle size and morphology. Transmission electron microscopy studies revealed an increase in the particle size from 6-12 nm upon increasing the reaction time. Photoluminescence (PL) studies were utilized to explore the surface defects and oxygen vacancies present in the ZnO. PL results confirmed a gradual decrease in the intensity of surface oxygen vacancies and defects of ZnO nanoparticles on increasing the dwell time inside the Mw. Similarly, energy bandgap studies showed a red shift in the energy bandgap from 3.19 eV to 2.91 eV with change in the reaction time. A red shift in energy bandgap is a good sign as it can enhance the utilization of ZnO nanoparticles in many of visible range applications such as optoelectronics and solar cells industry