Photophysical properties of 1-pyrene-based derivatives for nitroaromatic explosives detection: Experimental and theoretical studies

Novel pyrene-based derivatives, 4-(p-tolylethynyl)pyrene (Py-ET) and 9-(pyren-3-yl)-9H-carbazole (Py-CZ), were synthesized for application of nitroaromatic explosives detections. Introduction of groups into pyrene moieties resulted in a bathochromic shift in absorption and emission spectra. The fluorescence quantum yield varied between 0.26 and 0.44. Fluorescence quenching behavior of 1-pyrene-based derivatives for sensing of nitroaromatic explosives, which are 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT), in dichloromethane solution was studied. It was found that the Py-ET had a higher sensitivity and quenching efficiency than Py-H and Py-CZ with detection limits of 2.32 and 3.09 ppm for DNT and TNT, respectively. This was explained by using theoretical studies with density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. It revealed that Py-ET was quenched by nitroaromatic explosives via intermolecular π-π interaction with highest binding energy and lowest energy gap. Most of electrons (>90%) were transferred from HOMO of the pyrene derivatives to the LUMO of quencher molecules during the quenching process.