Emission Properties of Individual AIE‐Luminogens in Solution at Room Temperature†.

Comprehensive Summary: Here, we combined the photon antibunching analysis, fluorescence correlation spectroscopy, and time‐domain fluorescence lifetime imaging microscopy (TD‐FLIM) to study the emission properties of a representative AIE‐luminogen—4,4'‐(benzo[c][1,2,5] thiadiazole‐4,7‐diyl)bis(N,N‐diphenylaniline) (TPA‐BT) at the single emitter level in a tetrahydrofuran (THF)/water solution where water is a non‐solvent for TPA‐BT. Our findings suggest that, at a constant water fraction in the solution, the size of TPA‐BT aggregates increases with the TPA‐BT concentration; TPA‐BT aggregates are not a quantum emitter at room temperature in the solution. Moreover, utilizing TD‐FLIM and a gel trapping technique allowed us to study the fluorescence lifetime of individual TPA‐BT aggregates. Adding a polar solvent like water does not result in an overall decrease in fluorescence lifetime. Rather, it causes the fluorescence lifetime distribution to become wider, and only some molecules experience a decrease in their fluorescence lifetime. These results could represent a step forward in further understanding the photophysics of AIE‐luminogens. [ABSTRACT FROM AUTHOR]