Imaging sweat pore structures in latent fingerprints and unclonable anti-counterfeiting patterns by sensitizers blended LaOF:Pr3+ nanophosphors

Abstract

Ultra-bright luminescent nanomaterials can be controlled by blended with suitable dopant ions offers a significant strategy to combat the counterfeiters and the reveal latent fingerprints. Herein, we report Pr3+ activated LaOF nanophosphors blended with monovalent alkali metal ions (Na+, K+, Li+) prepared via eco-friendly sonochemical route. The X-ray diffraction profiles confirm the tetragonal crystal system. The photoluminescence emission showed characteristic peaks at ~497, 531, 555, 612, 641, 685, 702 and 734 nm, which corresponds to 3P0→3H4, 3P1→3H5, 3P0→3H5, 3P0→3H6, 3P0→3F2, 3P1→3F3,3P1→3F4 and 3P0→3F4 transitions Pr3+ ions, respectively. A significant luminescent enhancement was achieved in Li+ co-dopant when compared to Na+ and K+. Upon co-doping, color coordinates shifted from orange to pure red region. The latent fingerprint results on various surfaces clearly showed the high resolution images of active or inactive sweat pores with superior sensitivity and selectivity and low background hindrance. A greater possible stochastic process to make unclonable anti-counterfeiting patterns using optimized nanophosphor was designed to reduce counterfeit products. Therefore, we believe that this optimized nanophosphor for visualization of latent fingerprints as well as unclonable anti-counterfeiting tags find widespread use in advanced forensic investigations and product safety applications.