Information encryption gel based on acid-induced and fluorescence resonance energy white-light materials

Abstract

This study develops white light–emitting gel materials based on two mechanisms, namely, acid-induced protonation and fluorescence resonance energy transfer, and applies them to information protection and encryption. The newly synthesized compound Q exhibits fluorescence that transitions from green to yellow to white with increasing protonation owing to mixed multicolor emissions from its protonated states. Q also functions as an energy donor in Förster resonance energy transfer (FRET) systems when paired with dyes such as Nile Red, Rhodamine 6G, and Acridine Red, achieving white-light emission at specifically optimized ratios. Two polyvinyl alcohol (PVA)-based functional gels are developed, namely, a PVA–Q–Nile Red composite and a PVA–Q–150 eq. H⁺ responsive gel; these gels exhibit stable white-light emission for high-resolution information writing and encryption. The PVA–Q–150 eq. H⁺ responsive gel exhibits time-dependent encryption, with OH−-triggered writing traces self-erasing controllably. This study pioneers orthogonal regulation of acid-responsive behavior and FRET in a single compound, creating a dynamic, self-erasing encryption platform, thereby offering a novel approach to the synthesis of smart anticounterfeiting materials.