Photoluminescent dual-mode anticounterfeiting stamp using self-healable tricarboxy cellulose and polyvinyl alcohol hybrid hydrogel

Abstract

Novel ultraviolet-induced photochromic nanocomposite hydrogel ink with self-healing properties was prepared to establish a photochromic stamp with dual-mode encoding emission for secure authentication. Organic-inorganic hybrid ink was prepared from a mixture of rare-earth activated aluminate (RESA) nanoparticles suspended in tricarboxy cellulose (TCC) and polyvinyl alcohol (PVA) hybrid hydrogel. The TCC/PVA composite hydrogel was prepared by the freezing/thawing method. The TCC comprising three carboxyl groups on each anhydroglucose unit was prepared via the one-shot oxidation method, followed by aqueous solutions of TCC with PVA. Homogeneous photochromic film was stamped directly onto paper surface to provide transparency with the ability to switch color to green under ultraviolet as demonstrated by photoluminescence spectra and CIE Lab parameters. When excited at 365 nm, the luminescent paper sheets demonstrated an emission peak at 518 nm. Transmission electron microscopy (TEM) revealed the size of synthesized lanthanide-doped aluminate particles in the range of 12–18 nm. The morphological features of the stamped papers were examined by different analytical methods. The printed papers showed reversible photochromic emission without fatigue. The rheological features of the luminescent hydrogel ink, and the mechanical activity of the printed papers were conducted. Different industrial sectors can profit from the present TCC-PVA hydrogel ink as a competent approach for authentications.