Luminescent properties of Eu3+-doped silica nanophosphors derived from rice husk

Abstract

Rice husk nanosilica (RH-SiO2) doped with europium (RH-SiO2: Eu3+) was produced by the sol-gel method. X-ray Diffraction patterns show amorphous silica with increased crystallinity as the concentration of Eu increases. Phase transformation occurred with the addition of Eu3+ ion due to the presence of oxygen vacancy as well as strain in the lattice imposed by the larger size of the dopant ion in the lattice. The quartz structure emerged at a relative low concentration (1 mol%) and increased with Eu3+ content and at 3 mol% doping, the cristabolite phase emerged. No Eu3+ phase was observed. Scanning Electron Microscopy review agglomerates of nano-sized particles and Transmission Electron Microscopy show dispersed spherical nanoparticles measuring an average size of 35 nm. Fourier Transform Infra-red spectroscopy confirms the presence of SiO2. The surface area of the nanophosphor measured by Brunauer-Emmett-Teller is 189.64 m2/g. Photoluminescence (PL) analysis shows Eu3+ ion transitions leading to red emission. The asymmetry ratio and Judd-Ofelt intensity parameters indicate a low symmetry environment for the Eu3+ in the RH-SiO2 nanophosphors. The Ω2 values increase with increasing Eu3+ concentration, suggesting an increase in structural deformation or transformation of SiO2. The International Commission on Illumination (CIE) chromaticity coordinates values are close to the national television standard committee (NTSC) standards for red phosphors, which confirms the suitability of these red nanophosphors for display applications.