Surface modification of Mg2InSbO6:Eu3+ phosphors and applications for white light-emitting diodes and visualization of latent fingerprint

Abstract

Due to outstanding optical characteristics of phosphors, they have recently been applied to various fields, such as solid-state lighting, forensic science, and laser technology. Herein, a series of Mg2InSbO6:xEu3+ (x = 0.005–0.25) phosphors with pure red emission were prepared via high-temperature solid-state reaction. Under near-ultraviolet 395 nm excitation, photoluminescence spectra of Mg2InSbO6:Eu3+ (MISO:Eu3+) phosphors exhibited a bright red luminescence peak at 612 nm, which is attributed to 5D0→7F2 transition of Eu3+. The thermal quenching temperature of the optimum sample exceeded 480 K, which is much higher than the working temperature of light-emitting diode (423 K). The packaged white light-emitting diode (WLED) had CIE coordinates of (0.336, 0.340) with correlated color temperature of 5322 K and color rendering index value of 90. Furthermore, the latent fingerprints (LFPs) stained with MISO:Eu3+ phosphors were visualized with level 1–3 features, but their accuracy was relatively low. Therefore, oleic acid (OA) was utilized to form a hydrophobic coating on MISO:Eu3+ powders to improve fingerprint development, and the higher accuracy of level 1–3 features was achieved, especially level 3 features. The LFPs on smooth and rough surfaces stained with MISO:Eu3+@OA phosphors were easily collected at high contrast under 395 nm light. The obtained results prove that MISO:Eu3+ and MISO:Eu3+@OA can be considered as promising red phosphors for WLED and LFP identification and provide insight into the improvement of LFP development.