Aggregation-induced delayed fluorescence for time-resolved luminescence sensing of carboxylesterase in living cells

An aggregation-induced delayed fluorescence emitter is demonstrated for time-resolved luminescence turn-on sensing of carboxylesterase in living cells. • The strategy of AIDF-based TRLS was first proposed and realized. • A multiply twisted luminophore revealed typical AIDF behavior. • The turn-on TRLS of carboxylesterase was achieved in buffer and HeLa cells. Thermally activated delayed fluorescence (TADF) materials with long-lived fluorescent emission, have been considered to be promising candidates for time-resolved luminescence imaging (TRLI) and sensing (TRLS). Though the development of the TADF luminophores for TRLI has received considerable attention, the oxygen-caused delayed fluorescence quenching has greatly stagnated the progress of TADF-based TRLS. In this work, we firstly proposed the strategy of in situ generated aggregation-induced delayed fluorescence (AIDF) for TRLS. A new luminophore FAc-Py with multiply twisted geometry and AIDF behavior was designed to offer the long-lived emission for meeting the time-resolved requirement. The carboxylester-capped FAc-Py , namely FAc-Py-Ester , which is non-emissive but shows good liposolubility, was then rationally synthesized for the delayed fluorescence turn-on sensing of carboxylesterase. Carboxylesterase easily promoted the in situ release of hydrophobic FAc-Py from FAc-Py-Ester , accompanying with the activation of air-insensitive AIDF emission and finally paving a way for the functional TRLS of carboxylesterase in living cells.