Structural And Optical Properties Of Small-sized ZnO Nanostructures Synthesized Via Solvothermal Method

ZnO, as a direct wide-band-gap semiconductor with a large exciton binding energy (60 meV) which makes it an attractive candidate for room-temperature ultra-violate emission material, has been extensively investigated for applications to UV-LED and–LD, solar cell window and electrode, piezoelectric transducers, surface acoustic coatings, varistors, photo-catalysts and so on. For those applications that make use of the unique optical, chemical and electrical properties of ZnO powders, which strongly depend on its morphology, size and size distribution, the development of easy and cheap routes to synthesize mono-dispersed ZnO nano-particles is of great importance. So far, there are mainly two ways to prepare zinc oxide: one is physical approach, the other is chemical approach. The later approach is highly effective, very simple, and fit for mass production requirements. Therefore we use the chemical process to prepare small-sized zinc oxide nanostructures, and investigate its structural and optical characteristics. Although there have been many reports on solvothermal synthesis of zinc oxide, the size of the obtained zinc oxide nanostructures is usually quite large. In this work we have successfully reduced the size of the nanosturctures through controlling the reaction condition, and the optical and structural properties of the nanostructures were investigated.We expatiate two approaches to prepare ZnO nanostructures via solvothermal: First, using 1,6-Hexylenediamime as an auxiliary agent, methanol as reaction solution, we successfully synthesized smaller zinc oxide nanospheres; We observe that the big sphere have complex structure. The nanospheres are consisted of smaller spheres (20nm-30nm) which can be seen in high resolution FESEM. Experimental results indicate that 1,6-Hexylenediamime play the key role in the procedure of nanospheres formation. Through the obtained sample's XRD spectrum analysis, the as-prepared samples are all wurtzite zinc oxide. Second, the reaction condition is similar with that applied in the preparation of zinc oxide nanospheres, but the reaction solution was changed from methanol to ethanol, ZnO nanorods of diameter 5 nm were obtained. Scanning electron microscope, Photoluminescence spectroscopy, UV–vis absorption spectroscopy were employed to study the structure and optical properties.