Highly sensitive TNT photoluminescent sensing by a phosphorescent complex

Photoluminescent (PL) sensing is a common method for the detection of trace nitroaromatic explosive 2,4,6-trinitrotoluene (TNT). In this work, a red emissive phosphorescent iridium(III) complex was synthesized and used for TNT sensing. The obtained iridium(III) complex is highly emissive, and the PL response of the complex in solution toward TNT was researched by examining the steady state emission intensity to the concentration of TNT. Efficient PL quenching was obtained when TNT was added to the detection solution. The long excited-state lifetime of obtained phosphorescent complex is beneficial for interaction with TNT molecules. In addition, suitable matching of the lowest unoccupied molecular orbital (LUMO) levels of the iridium(III) complex with TNT also benefits the electron transfer from the complex to TNT molecules and enhances the PL quenching. As a small molecular material, the obtained phosphorescent complex shows comparable PL quenching efficiency to TNT with reported conjugated polymers.