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

Abstract

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 (Ω2, Ω4 and Ω6), transition probabilities (AT), quantum efficiency (η), luminescence lifetime (τrad), color chromaticity coordinates (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.