Rational design of pyrrole derivatives with aggregation-induced phosphorescence characteristics for time-resolved and two-photon luminescence imaging.

Pure organic room-temperature phosphorescent (RTP) materials have been suggested to be promising bioimaging materials due to their good biocompatibility and long emission lifetime. Herein, we report a class of RTP materials. These materials are developed through the simple introduction of an aromatic carbonyl to a tetraphenylpyrrole molecule and also exhibit aggregation-induced emission (AIE) properties. These molecules show non-emission in solution and purely phosphorescent emission in the aggregated state, which are desirable properties for biological imaging. Highly crystalline nanoparticles can be easily fabricated with a long emission lifetime (20 μs), which eliminate background fluorescence interference from cells and tissues. The prepared nanoparticles demonstrate two-photon absorption characteristics and can be excited by near infrared (NIR) light, making them promising materials for deep-tissue optical imaging. This integrated aggregation-induced phosphorescence (AIP) strategy diversifies the existing pool of bioimaging agents to inspire the development of bioprobes in the future. Aggregation-induced emission (AIE) fluorescence probes are indispensable for biomedical imaging, however, interference with tissue autofluorescence results in low signal-to-noise ratio limiting the development of bioimaging with AIE materials. Here the authors develop AIEgen room-temperature phosphors with long emission lifetimes efficiently eliminating intereference with the background signal in imaging.