Mg doping induced high structural quality of sol-gel ZnO nanocrystals: Application in photocatalysis

摘要

Undoped and Mg doped ZnO nanocrystals (NCs) ZnO:x%Mg (x = 1, 2, 3, and 5) were synthesized using sol-gel method. The structural and optical properties were investigated by X-ray diffraction (XRD), Raman spectroscopy, diffuse reflectivity, and photoluminescence (PL). XRD analysis demonstrates that all prepared samples present pure hexagonal wurtzite structure without any Mg related phases. The NCs size varies from 26.82 nm to 42.96 nm with Mg concentrations; it presents an optimal value for 2% of Mg. The Raman spectra are dominated by the E-2high mode. For highly Mg doping (5%), the occurrence of silent B-1(low) mode suggested that the Mg ions do substitute at Zn sites in the ZnO lattice The band gap energy was estimated from both Tauc and Urbach methods and found to be 3.39 eV for ZnO:2%Mg. The PL spectra exhibit two emission bands in the UV and visible range. Their evolution with Mg doping reveals the reduction of defect density in ZnO at low Mg doping by filling Zn vacancies.