Investigation of Latent Fingerprint Detection and Cheiloscopy Development Using Li₂SrSiO₄:Tb³⁺ Phosphor for Forensic-Based Applications

Inorganic phosphors with rare-earth metal doping have recently been created and used in hot topics including phosphor-converted light-emitting diodes (pc-LEDs), counterfeit prevention, cheiloscopy (lip print detection), and fingerprint visualization. Using the Pechini sol–gel process, a silicate-based rare-earth metal-doped Li₂SrSiO₄:Tb³⁺ (LSS:Tb) green-emitting phosphor was synthesized, and its characteristics were determined by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and photoluminescence studies. Through the JCPDS file, the prepared phosphor’s structure was confirmed. Photoluminescence studies displayed the characteristic emission peaks of Tb³⁺ under an excitation wavelength of 254 nm. Implementation of the powder dusting method using LSS:3 mol % Tb phosphor on the latent fingerprint displayed good selectivity and contrast. Along with this, latent fingerprints were also detected on different surfaces to see the practicality of the prepared phosphor. Under UV irradiation, the level 1–3 structural properties of latent fingerprints and the level 1–6 detection of lip prints were distinguished and probed. The obtained results indicated that the synthesized phosphor could be used for fingerprint and lip print detection.