Rational Design of Low-Molecular-Weight Organogels with Ultralong Room-Temperature Phosphorescence for Security

Abstract

Supramolecular organogels have emerged as a promising matrix for achieving dynamic room-temperature phosphorescence (RTP) due to their rigid three-dimensional network structure, sensitive responsive behavior to external stimuli, and perfect reversibility. However, the efficient construction of single-component, ultralong organic RTP materials remains a significant challenge. In this study, we utilized all-atom molecular dynamics simulations to predict the self-assembly process of three low-molecular-weight carbazole derivatives with rigid chemical structures (Cz-P, Cz-PF, and Cz-PCl), ultimately identifying Cz-P as a potential RTP organogelator. Cz-P could form a stable gel in the mixture of DMSO/H₂O (1:1 v/v), and introducing a halogen atom to build halogen bonding was destructive to achieve balanced intermolecular interactions, which is essential for gelation. Notably, the Cz-P gel emitted ultralong RTP (τ_p = 581.8 ms) in the gel state. Moreover, the triplet-to-singlet Förster resonance energy transfer (TS-FRET) between the Cz-P donor and the fluorescent dye Sulforhodamine 101 (acceptor) provided a long-lived red fluorescence. Due to the gel’s sensitive responsive to thermal stimuli, the afterglow could be conveniently switched “on” and “off”, demonstrating excellent fatigue resistance and multilevel anticounterfeiting capabilities.