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

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

A Versatile Approach to Organic Photovoltaics Evaluation Using White Light Pulse and Microwave Conductivity

State-of-the-art low band gap conjugated polymers have been investigated for application in organic photovoltaic cells (OPVs) to achieve efficient conversion of the wide spectrum of sunlight into electricity. A remarkable improvement in power conversion efficiency (PCE) has been achieved through the use of innovative materials and device structures. However, a reliable technique for the rapid screening of the materials and processes is a prerequisite toward faster development in this area. Here we report the realization of such a versatile evaluation technique for bulk heterojunction OPVs by the combination of time-resolved microwave conductivity (TRMC) and submicrosecond white light pulse from a Xe-flash lamp. Xe-flash TRMC allows examination of the OPV active layer without requiring fabrication of the actual device. The transient photoconductivity maxima, involving information on generation efficiency, mobility, and lifetime of charge carriers in four well-known low band gap polymers blended with phenyl-C₆₁-butyric acid methyl ester (PCBM), were confirmed to universally correlate with the PCE divided by the open circuit voltage (PCE/<i>V</i>_oc), offering a facile way to predict photovoltaic performance without device fabrication