Amplification of intense red emission through integrating Li+ ions to V2O5:Eu3+ phosphors: Optical thermometry, cheiloscopy and extraction of level III features for individual identification

Abstract

This study presents the synthesis of V2O5:Eu3+ phosphors in concentrations ranging from 1 to 9 mol %, using a solution combustion method with Areca Nut (A.N) as a bio-fuel. The samples exhibit an orthorhombic crystal structure, confirmed by powder X-ray diffraction (PXRD), and rod-like morphology as shown by field emission scanning electron microscopy (FE-SEM). Photoluminescence (PL) studies reveal that the emission intensity of the 5D0→7F2 transition at 619 nm increases with the Eu3+ concentration up to 5 mol %, where it peaks before quenching due to quadruple-quadruple interactions, according to the Van Uitert relation. To improve luminescence, Li+ ions are added, with the V2O5:5Eu3+ co-doped with 4Li+ (V2O5:5Eu3+, 4Li+) ions showing the highest PL intensity, about 5.03 times higher than that of Eu3+ alone. This optimized phosphor has Commission Internationale de l’Eclairage (CIE) chromaticity coordinates of (0.6022, 0.3963), closely matching commercial red-emitting phosphors and demonstrating a colour purity (CP) of 88.69 %. Thermal stability assessments indicate that these phosphors have a high activation energy (Ea) of about 0.224 eV, signifying robust thermal properties. The optimized V2O5:5Eu3+, 4Li+ phosphors efficiently reveal level I–III features in latent fingerprints (LFPs) and accurately identify lip prints (LPs) groove patterns of type I–VI under 365 nm UV light, providing high resolution and contrast. These characteristics make the optimized phosphor an excellent candidate for use in photonic devices, advanced forensic and data security applications.