Exploring the luminescent and thermal properties of Sm3+ doped BaYAlZn3O7 for latent fingerprint detection and optoelectronic applications

Abstract

Current luminescent nanophosphors face challenges in latent fingerprints (LFPs) detection, such as poor adhesion, low contrast on complex surfaces, and limited photostability. In white light emitting diodes (w-LEDs), issues like low thermal stability, poor color purity, and efficiency loss hinder performance. This study addresses these gaps by preparing Sm³⁺ doped BaYAlZn₃O₇ (BYAZO: Sm³⁺) phosphors prepared using solution combustion method with enhanced luminescence, strong adhesion, and high thermal stability, making them promising for both forensic and LED applications. X-ray powder diffraction analysis coupled with Rietveld refinement confirmed the formation of a single-phase hexagonal structure (space group: P6₃mc (186)) in the BYAZO: Sm³⁺ samples. These phosphors exhibited a prominent orange-red photoluminescence (PL) peak at 644 nm, attributed to the electric dipole transition ⁴G_5/2 → ⁶H_9/2 of Sm³⁺ ions. The optimal doping concentration for maximum luminescence intensity is determined to be 5 mol %. Temperature dependent photoluminescence (TDPL) studies revealed exceptional luminous thermal stability (LTS), with the emission intensity retaining 92.70 % of its original value at 420 K. The activation energy (E_a) is calculated as 0.305 eV, further underscoring the high thermal robustness of the phosphor. Fluorescence intensity and lifetime analyses indicated maximum relative temperature sensitivity (S_R) and absolute temperature sensitivity (S_A) values of 4.21 % K⁻¹ and 0.120 K⁻¹ at 300 K, respectively. The chromaticity coordinates of BYAZO:5Sm³⁺ are consistently situated in the orange-red region of the 1931 Commission Internationale de l'Éclairage (CIE) diagram, demonstrating high color purity (CP: 95.7 %). Furthermore, the potential application of BYAZO:5Sm³⁺ phosphors in LFPs detection is evaluated across various surface types. The phosphor displayed excellent adhesion to ridge patterns, enabling clear distinction between ridges and furrows, while providing detailed information necessary for fingerprint (FP) individualization. These findings highlight the superior luminescent properties and multifunctional applicability of BYAZO:5Sm³⁺ phosphors, positioning them as promising candidates for advanced LFPs detection and optical thermometry applications.