Oxygen-Independent Photoactivation of Kinetically Trapped Persistent Room-Temperature Phosphorescence State for Smart Cold-Chain Monitoring
Stimuli-responsive room-temperature phosphorescence (RTP) materials face challenges in environmental robustness and spatiotemporal controllability, particularly for oxygen- and temperature-sensitive applications. Here, by taking advantage of the high oxygen-permeability barrier of polyvinyl alcohol (PVA) and its photochemical reaction toward certain polyaromatic hydrocarbons, we present phenanthrene- and triphenylene-doped PVA films that exhibit photoactivatable and persistent RTP, with an observable afterglow time >70 s by the naked eye, likely via a kinetically trapped radical pathway. Specifically, such UV-enhanced persistent RTP occurs under both aerobic and anaerobic conditions, contrasting with a regular RTP turn-on mechanism via photo-induced molecular oxygen depletion. The activated RTP state shows temperature-dependent kinetic persistence, i.e., lasting ~5 h at 25°C vs. ~72 h at 4°C, creating irreversible RTP switching from “on” to “off” ideal for cumulative temperature monitoring. The PVA-based ink patterns printed on perishables (e.g., fresh milk bottles) can be used to quantify ambient exposure via RTP decay kinetics (relative intensity loss >84.2% after 3 h at 25°C vs. at 4°C). The current study establishes a kinetic-control strategy for designing programmable RTP materials, addressing unmet needs in smart sensing and quality assurance.