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

Abstract

Comprehensive SummaryHere, 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.