Investigating the use of Er3+ doped β-Ca2SiO4 phosphors derived from agricultural waste for thermal sensing and forensic applications

Abstract

Leveraging agricultural waste, Erbium (Er3+) doped β-Ca2SiO4 phosphors (β-CS:Er3+) with concentrations ranging from 1 to 9 mol % were developed using the solid-state reaction method. These β-CS:Er3+ samples underwent extensive characterization to examine their crystalline structure, surface morphology, photoluminescence (PL) properties, and thermal sensing capabilities. The PL emission, excited at 378 nm, prominently displayed a peak at 549 nm, indicative of the green emission primarily due to the 4S3/2 → 4I15/2 transition. An optimal concentration of Er3+ at 5 mol% (β-CS:5Er3+) is identified, showing peak luminescence intensity, whereas, higher concentrations led to a decrease in intensity because of concentration quenching (CQ) effects. Temperature-dependent photoluminescence (TDPL) analysis revealed an increase in emission intensity at 523 nm, while the peak at 549 nm exhibited a decrease in intensity within the temperature range of 303–463 K. Nevertheless, the emission peak at 549 nm demonstrates remarkable thermal stability at elevated temperatures, maintaining 79.32% of its emission intensity at 423 K. The optimized β-CS:5Er3+ phosphor exhibited its chromaticity coordinates (0.3152, 0.6631) in the green region under 378 nm excitation, alongside promising temperature sensing capabilities with a relative sensitivity of 2.80 % K−1. The application of these phosphors in a powder dusting technique for revealing latent fingerprints (LFPs) and latent lip prints (LLPs) under 365 nm UV light uncovered detailed ridge and groove patterns on various substrates. This approach, highlighting the phosphor's exceptional fluorescence, dual adherence, and non-interfering background, showcased its potential for enhanced forensic analysis. The thorough examination of LFPs and LPs under various conditions, including aging, heat, and UV exposure, confirms the β-CS:Er3+ NPs' suitability for cutting-edge display technologies and forensic methodologies.