A cost-effective intense blue colour cobalt doped gahnite pigment for latent finger print, cheiloscopy and anti-counterfeiting applications

Abstract

Alanine is used as a novel fuel in the solution combustion method (SCS) to produce nanocrystalline Co2+ (0.25–5 mol%) doped gahnite (ZnAl2O4: ZAO) nano pigments (NPs). A thorough investigation was conducted to comprehend the interaction of dopant (Co2+) and ZAO host matrix, as well as the influence of doping on their structural, optical, and luminescence properties. The powder samples were thoroughly characterized using XRD, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Photoluminescence (PL) spectroscopic techniques. SEM micrographs of clearly exhibit the formation of dense particles, voids, and pores in the sample. In addition, tiny aggregates were detected on the surface of more prominent clusters. The nominal composition of Zn, Al, Co and O was assessed using Energy Dispersive X-Ray Analysis (EDS). The optimized ZAO:5Co2+ phosphor powder demonstrated levels 1–3 fingerprint (FP) features and groove patterns (types 1–5) of lip print that can be clearly recognised, with excellent resolution and contrast, under 320 nm UV light. The appropriate thickening agent and defoamer were added to blue pigment during fabrication to generate anti-counterfeiting (AC) inks that mark on multiple surfaces with high resolution without spreading or tracing. The preceding results suggest that the ZAO:Co2+ NPs can serve as a significant candidate for the detection and individualization of latent fingerprints (LFP), lip prints (LP) and anti-counterfeiting applications.