Development of photochromic carboxymethyl cellulose-based hydrogel toward dual-mode authentication stamp with self-healing properties

Abstract

Ultraviolet-induced photochromism has proven to be an appealing encoding strategy to improve the anti-counterfeiting of commercial items. However, recent reports have highlighted significant disadvantages with photochromic inks such as high cost, low efficiency and poor durability. Herein, we present a self-healable ink for anti-counterfeiting applications from a hydrogel of carboxymethyl cellulose (CMC) combined with rare-earth activated aluminate (REA) nanoparticles (NPs). Self-healing security inks provide high durability. The REA@CMC hydrogel has the ability to efficiently self-heal under ambient conditions. Using UV light to promote photochromism, the REA@CMC ink showed excellent photostability. To create a composite ink with a wide range of emission characteristics, different quantities of REA NPs were used. CIE (Commission Internationale de L'éclairage) Lab established that stamping a homogeneous film onto a paper surface gives them a transparent layer that transformed into green upon exposure to ultraviolet spectrum. The morphological features of REA NPs were investigated to show a particle diameter of 3–7 nm. The morphology of the photochromic films were studied using different analytical methods. Both ink solution rheological properties and stamped paper sheet mechanical characteristics were examined. The luminous films peaked in green emission at 518 nm, whereas their excitation wavelength was at 370 nm.