Rare-Earth Ion-Activated Nanostructured Fluorescent Marker for Easy Naked Eye Detection and Swift Imaging of Latent Fingerprints

Abstract

Latent fingerprint (LFP) imaging is critical for crime scene detection and personal data recognition. In law enforcement applications, there is a great need for new materials that are affordable, environmentally friendly, and extremely sensitive. Here, a dual excitable and intense red-emitting oxide-based nanophosphor, Y 2 SrZnO 5: x Eu 3+ ( x = 0–0.4 mol), was successfully synthesized by a self-igniting combustion technique. The phase purity, crystal structure, and lattice parameters were characterized by powder X-ray diffraction (XRD) using WIN-INDEX (ver. 3.08) software. Scanning electron microscopy (SEM) confirms the surface morphology with a uniform size distribution of ∼250 nm. Upon excitation at 393 and 465 nm, the synthesized nanophosphor exhibited intense red emissions with peaks at 595 and 612 nm and color purity of 99.8% due to the characteristic transitions of Eu 3+ ions from 5 D 0 → 7 F J ( J = 0–3). It has a higher external quantum yield (EQY) of 41 and 56% at 393 and 465 nm, respectively, compared to commercial Y 2 O 3:Eu 3+, which has an EQY of <1% for these wavelengths. With this result, it became clear that the problem of low absorption in the blue region (450–470 nm) of the commercial red phosphors (Y 2 O 3:Eu 3+ ) for producing efficient white light-emitting diodes has been solved. The LFPs exhibit specific discrimination features including levels I, II, and III, with high sensitivity and no background hindrance. The results obtained with the synthesized Y 2 SrZnO 5:0.2Eu 3+ nanophosphor indicate its potential use in detecting and imaging latent fingerprints at crime scenes.