Photoluminescence and Raman scattering study in ZnO:Mg nanocrystals

In this work, Zn_1−xMg_xO nanoparticles (NPs) were fabricated for x ranging from 0 to 0.05. The structural, morphological, photoluminescence and Raman properties of the Zn_1−xMg_xO NPs were investigated and well-studied by XRD, XPS, UV–Vis, PL and Raman spectroscopy. The XRD results showed that the obtained NPs of all the samples are single wurtzite structure and no secondary phases were detected which indicated that Mg ions substituted for Zn ions. The UV–Vis measurement of the Zn_1−xMg_xO NPs showed that the bandgap increased gradually with increasing the Mg doping concentration. The PL spectra showed the blue shift of the ultraviolet emission peak which indicated that the concentration of the surface defects increased when the Mg doping concentration increased. Also an interesting phenomenon was that strong surface-enhanced Raman scattering (SERS) signals were obtained when 4-mercaptobenzoic acid as the probing molecule adsorbed on the surface of Zn_1−xMg_xO NPs. The electron and energy transfer between the semiconductor’s and the molecule’s interfaces play an important role in the charge-transfer mechanism of the SERS performances.