Green emanating BiOCl:Tb3+ phosphors for strategic development of dermatoglyphics and anti-counterfeiting applications

Abstract

• Green emitting BiOCl:xTb 3+ (x = 1–9 mol%) nanophosphors are prepared by propellant solution combustion route. • A new fluorescence based platform has been setup for in-situ visualization of latent fingerprints and lip prints by powder dusting method. • Well defined fluorescence fingerprint images on variety of surfaces by revealing type 1–3 ridge characteristics. • Developed latent fingerprints shows superior contrast, sensitivity, efficiency, selectivity and negligible background hindrance. • Fabricated unclonable invisible security ink and make it highly suitable for brush mode. In this work, we reported green emitting Tb 3+ ions (1–9 mol%) doped BiOCl nanophophors (NPs) synthesized by solution combustion route using Mimosa pudica ( M. p. ) plant extract as a bio-fuel. Powder X-ray diffraction (PXRD) patterns exhibit tetragonal structure of matlockite-type P4/nmm space group. Scanning electron microscopy (SEM) reveals that the prepared NPs were shown flake-like morphology. The energy bandgap of BiOCl:Tb 3+ (1–9 mol%) NPs were estimated and found to be in the range ∼3.50–3.53 eV. The photoluminescence (PL) spectra show characteristic emission peaks at ∼489, 545, 591 and 622 nm, which were corresponding to 5 D 4 → 7 F 6, 5 D 4 → 7 F 5 , 5 D 4 → 7 F 4 and 5 D 4 → 7 F 3 transitions of Tb 3+ ions, respectively. The maximum PL intensity was found to be for 5 mol% doped NPs and later diminishes. The diminished PL intensity was mainly ascribed to concentration quenching. The estimated CIE (Commission International de I’Eclairage) co-ordinates were close to the green emission standard values set by the National Television System Committee. The optimized NPs was used for development and visualization of latent fingerprints (LFPs) and lip prints. The developed fingerprints and lips prints revealed level I-III ridge details with high sensitivity, selectivity and without any background hindrance. The developed anti-counterfeiting labels were encrypted only under UV light illumination, but were completely invisible under normal light. These results clearly demonstrated that the optimized NPs can help to narrow the search gap in criminal investigations and forensic purposes.