Comparison of the Performance of Fluorescent, Phosphorescent and TADF Luminophores for Explosives Sensing

This study investigates how the emission mechanism (fluorescence, phosphorescence, or thermally activated delayed fluorescence, TADF) of a luminescence-quenching chemical sensor influences the sensitivity of explosives detection. Steady-state and time-resolved photoluminescence measurements were used to evaluate the quenching kinetics of representative emitters in the presence of 2,4-dinitrotoluene (DNT), a model nitroaromatic explosive. Linear Stern-Volmer behavior was observed for the fluorescent and phosphorescent emitters, whereas the TADF compound exhibited a pronounced downward deviation in steady-state measurements, arising from the simultaneous but distinct quenching of singlet and triplet exciton populations. To describe this behaviour, we derived a modified Stern–Volmer formalism comprising separate relationships for the prompt and delayed fluorescence. The quenching dynamics of the TADF system was found to be strongly dependent on the intrinsic parameters Ф_ISC^0 Ф_RISC^0, k_Stot and k_Ttot, with the singlet and triplet populations being quenched with different efficiencies. These insights highlight the potential of TADF luminophores to act as sensitive photoinduced electron transfer-based explosives sensors.