Influence of Li+ doping on the luminescence performance of green nano-phosphor CaWO4:Tb3+ as a sweat pores fingerprint and cheiloscopy sensor

Abstract We have developed green phosphors nanoparticles CaWO4:Tb3+ co-doped Li+ using facial co-precipitation process, which can accurately control the composition, nanostructure, and surface condition of luminescent NPs. The structures and morphology of the developed nanophosphores were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscope (TEM), and energy dispersive X-ray (EDX) methods. Their optical properties were performed by UV-visible, fluorescence, and FTIR methods. The phosphors exhibit green emission peak at 540 nm upon excitation at 255 nm corresponding to 5D0→ 7F2 transitions characteristic of Tb3+ with excellent CIE coordinates (x = 0.282 and y = 0.600), which are in close agreement with the regular NTSC values (xd = 0.290, yd = 0.600). This phosphor powder exhibited a flexible fluorescent mark for the detection of level 1- 3 details with high contrast of latent fingerprint (LFP) and I-type V of Cheiloscopy for individual identification in forensic science. Our results reveal that the developed nanophosphors (CaWO4: Tb3+, Li+) has potential practical application for latent fingerprint identifications on different types of non-pores and pores surfaces common to forensic cases to solve crimes and as a valuable tool for law enforcement. Also, the novel nano-phosphor has significant ability to minimise the background fluorescence interference irrespective of the surface type used.