ZnO micro and nanostructures were synthesized on a quartz substrate by the carbothermal evaporation method. The thin layers of gold were used as
catalyst and synthesis were carried out at different persistence time. Characterization of the layer was conducted in order to study the effect of
persistence time on morphology and crystal structure and optical properties of the fabricated ZnO nanostructures. The samples were characterized
by scanning electron microscopy, x-ray diffraction (XRD) and UV-visible spectrophotometry which were performed to investigate the optical
properties of fabricated ZnO layer. The XRD spectrum clearly shows that the structure is in a hexagonal wurtzite phase. Optical properties of ZnO
micro and nanostructures were evaluated from transmittance data using the method proposed by Swanepoel (In the regions ?=200-900 nm). Our
results indicate that increasing the persistence time as well as decreasing the size of ZnO nanostructures enhances the optical band gap to about 3.46
eV. To the best of our knowledge, this is the first report on the study of the correlation of optical properties obtained by Swanepoel method and
morphology of ZnO nanostructures.