Sm3+-activated Sr2MgMoO6 red phosphors for high-contrast latent fingerprint visualization and white light-emitting diodes

Abstract

A novel series of Sm³⁺-doped Sr₂MgMoO₆ (SMMO:Sm³⁺) phosphors were successfully synthesized via a precision-controlled high-temperature solid-state reaction methodology. Systematic investigations into the crystalline architecture, surface topography, and photoluminescence dynamics were conducted to evaluate their potential for advanced forensic applications. Upon near-ultraviolet excitation at 397 nm, the SMMO: Sm³⁺ materials exhibit an intense, narrowband red-emitting peak at 644 nm, resulting from the intra-4f electronic transition of Sm³⁺ activators from the ⁴G_5/2 to the ⁶H_9/2 level. The emission intensity reached its optimized at a critical doping concentration of 15 mol%. Based on Dexter’s theoretical framework, the dominant quenching mechanism was identified as nearest-neighbor ion interaction. These phosphors demonstrate exceptional color purity exceeding 98.5%, with chromaticity coordinates strategically located in the orange-red spectral region. Furthermore, SMMO:Sm³⁺ exhibited good stability in 300–480 K, with luminescent intensity remaining 55.7% at 420 K compared to room temperature (300 K). Practical application in forensic science demonstrated that the Sr₂MgMoO₆:15 mol%Sm³⁺ phosphor enables high-resolution visualization of latent fingerprints across diverse substrates, facilitating the identification of Level I through Level III ridge features. The internal quantum efficiency (IQE) of SMMO:Sm³⁺ is 23.7%. Both red and white light-emitting diodes (LEDs) were prepared using SMMO:Sm³⁺. The chromaticity coordinates of w-LED were measured as (0.3433, 0.3329), correlating to a correlated color temperature (CCT) of 5006 K and exhibiting a good color rendering index (CRI, R_a = 94).