Tunable bandgap and optical properties of (Eu, Sm) codoped ZnO nanoparticles

The (Eu, Sm) codoped ZnO nanoparticles were prepared by chemical precipitation route and characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscope, X-ray photoelectron spectroscopy, photoluminescence and UV–Vis spectroscopy. The results revealed that these prepared ZnO were indeed composed of Eu3+, Sm3+ codoped ZnO nanoparticles. The combination between doping and chemical precipitation treatment significantly controlled the optical properties of ZnO and tuned their bandgap. The bandgap of doped samples decreased and the rare-earth doping concentration played the main role in tunable bandgap. The Eu3+-related red emissions from 5D0 → 7F0, 5D0 → 7F1 and 5D0 → 7F2 transition followed a similar trend as whole deep level emission, and these red emissions further enhanced by Sm3+ doping which may be due to the assistance of VO∗\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{V}}_{\text{O}}^{*}$$\end{document} as the luminescent centers in the energy transfer from ZnO host to Eu3+ ions.