Detection and Distinction of DNT and TNT with a Fluorescent Conjugated Polymer Using the Microwave Conductivity Technique

Abstract

We report the detection and distinction of dinitrotoluene (DNT) and trinitrotoluene (TNT) by the microwave conductivity technique using a cyclopentadithiophene-bithiazole-based polymer (CPDT-BT) as sensor. Although the conventional fluorescence quenching experiments showed just "turn OFF" of the polymer fluorescence for both DNT and TNT, time-resolved microwave conductivity (TRMC) revealed that the photoconductivity of the polymer, which is "turned OFF" in the pristine state became "ON" in the presence of DNT but remained "OFF" with TNT, allowing easy distinction between them. Moreover, the decay rate of the transient kinetics was found to be sensitive to the DNT concentration, implementing a unique method for the determination of unknown DNT concentration. The observations are discussed in viewpoint of charge separation (CS) and formation of charge transfer (CT) complex by considering deeper LUMO of TNT than DNT calculated from the DFT method. This study brings out a novel technique of speedy detection and distinction of environmentally important analytes, an alternative to the fluorescence quenching.