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Abstract: ZnO nanoparticles (NPs) have been successfully synthesized by the chemical precipitation method in different atmospheres at 500°C. The annealing atmospheres were argon, forming gas (50% Ar/50% O2) and air, respectively. The effects of annealing atmosphere on the structure and optical properties of ZnO NPs were investigated in detail by X-ray diffraction, transmission electron microscope, photoluminescence and Raman scattering measurements. The results showed that the as-prepared ZnO NPs had a hexagonal wurtzite structure, and all the samples kept the overall crystal structure of bulk ZnO. From the Raman and photoluminescence spectra, it can be seen that the content of oxygen in different annealing atmospheres strongly influenced the crystallization and light emission of the ZnO NPs. The results revealed that the content of oxygen in air was the optimal condition for growing the ZnO NPs with the best crystalline quality and optical properties. Defect emission was significantly enhanced by annealing in Ar atmosphere, which indicated that the green defect emission was most likely due to oxygen vacancy. Moreover, the effect mechanism of annealing atmospheres on the structure and optical properties of ZnO NPs were also investigated. [Copyright &y& Elsevier]

Abstract: ZnO nanoparticles (NPs) have been successfully prepared by the chemical precipitation method at a low temperature of 200°C. X-ray diffraction (XRD), transmission electron microscope (TEM), photoluminescence (PL) and Raman were used to investigate the effect of annealing temperature on the structure and optical properties of ZnO NPs. The XRD analyses revealed that the average size of the as-prepared samples was about 8nm under 200°C, which had a good agreement with TEM images. Raman spectra showed that the E2 (high) mode became stronger and sharper with the increase of annealing temperature, but the intensity of phonon peak located at 580cm−1 was relatively suppressed. The position of ultraviolet (UV) emission peak in the room-temperature PL spectra showed a red-shift when the annealing temperature was increased. In addition, after annealing under 500°C, the intensity of the UV peak became strongest and the intensity of the green emission almost disappeared, which indicated that ZnO NPs have much better crystallization after annealing. [Copyright &y& Elsevier]