Enhancement of luminescence intensity and spectroscopic analysis of Eu3+ activated and Li+ charge-compensated Bi2O3 nanophosphors for solid-state lighting

The present work reports the synthesis, characterization, photoluminescence and photocatalytic activity of Eu3+ (1 mol% -11 mol%) doped and Li+ (0.5 mol% -5 mol%) co-doped Bi2O3 nanophosphors (NPs) by sonochemical method. The average particle size was estimated using powder X-ray diffraction (PXRD) and transmission electron microscopy (TEM) and is found to be in the range of 30-35 nm. The scanning electron microscopy (SEM) images were highly dependent on sonication time and concentration of epigallocatechin gallate (EGCG) bio-surfactant. The energy gap of doped and co-doped Bi2O3 nanophosphors was estimated using Kubelka-Munk (K-M) function and is found to be in the range of 2.9-3.08 eV. The effect of Li+ co-doping on luminescence of optimized Bi2O3:Eu3+ was studied and is found about more than 3 fold enhancement of emission intensity. Judd-Ofelt parameters (Omega(2), Omega(4) and Omega(6)), transition probabilities (A(T)), quantum efficiency (eta), luminescence lifetime (tau(rad)), color chromaticity co-ordinates (CIE) and correlated color temperature (CCT) values were estimated from the emission spectra and are discussed in detail. The estimated CIE chromaticity co-ordinates are very close to the NTSC (National Television Standard Committee) standard value of red emission. The synthesized NPs show excellent photocatalytic activity of acid red-88 under UV-light irradiation, which can degrade 98.1% in 60 min. The decreasing electron-hole pair recombination rate with quick electron transfer ability is predominantly ascribed to the balance between crystallite size, morphology, band gap, defects, surface area, etc. These results show a light for the use of sonochemical route of Bi2O3:Eu3+:Li+ in solid state display and photocatalytic applications. (C) 2019 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.