Organic room-temperature phosphorescence of imidazole-based films by self-assembly enhancement strategies

Organic room-temperature phosphorescence (RTP) shows high potential in optical fields, and self-assembly method via various non-covalent interactions is one facile and efficient way to enhance RTP performance. Herein, we investigated the RTP behaviors of three imidazole-based polymer films containing imidazole, methyl imidazolium, and benzyl imidazolium moieties, respectively. Their RTP behaviors and chemical structures were compared and discussed to explore the underlying structure-properties relationships. Owing to plenty of hydrogen bonds of polyacrylamide matrix to lock phosphors, imidazolium-based films gave an obvious green RTP due to cations and iodine anions-enhanced intersystem crossing. The blue RTP signals of imidazole-containing film was aroused by coordination with Zn 2+ ions due to crosslinking and heavy atom effects. Moreover, the RTP performance of benzyl imidazolium-based film was remarkably improved by host-guest complexation with cucurbit[7]uril, showing a long lifetime up to 230.6 ms. By utilizing the difference in their RTP lifetimes, information encryption application was successfully achieved as a proof of concept.