Triluminescent Functional Composite Pigment for Non-Replicable Security Codes to Combat Counterfeiting

Abstract

Herein, a novel strategy to design of unclonable triluminescent pigment derived security ink is formulated to protect valuable merchandise, bank notes, pharmaceuticals, confidential documents etc. against counterfeiting, by embedding luminescent security codes/images. This triluminescent security ink is designed with combinatory chemistry that involves the strategically admixing of the triluminescent functional composite pigments in commercially available polyvinyl chloride gold medium. The triluminescent functional composite pigment is composed of NaYF4: Yb3+, Er3+(Sodium Yttrium Fluoride doped with Ytterbium and Erbium ions), NaYF4: Eu3+ (Sodium Yttrium Fluoride doped with Europium ion) and ZnO (Zinc Oxide) materials which have multifunctional features as it looks white in ambient light and shows strong green (NaYF4: Yb3+, Er3+), red (NaYF4: Eu3+) and green (ZnO) colors at three different excitations of 980 nm, 254 nm and 379 nm wavelengths, respectively. The structural/microstructural and photoluminescence properties of triluminescent functional composite are confirmed by XRD (X-ray diffraction), SEM (Scanning electron microscope), TEM (Transmission electron microscope) and photoluminescence spectroscopic techniques, respectively. The quality and spatially distributed PL intensity of printed images/code from triluminescent ink was investigated by photoluminescence confocal mapping microscopy technique. Hence, the obtained results suggest that the security code/images printed by using ink formulated from triluminescent functional composite pigment provides one step ahead novel security features which could be easy to detect but extremely difficult to replicate.