Highly efficient nitrate ester explosive vapor probe based on multiple triphenylaminopyrenyl-substituted POSS

Compared with nitroaromatic explosive detection, nitrate ester explosive detection has not received considerable attention possibly due to the absence of an aromatic ring and their difficulty in being detected. An eight triphenylamino-pyrenyl substituted POSS (P8PT) was designed as a sensory material. POSS was chosen as the skeleton due to its nano structure, multiple reactive sites, structural similarity with nitrate esters and high thermal stability, which will contribute to large surface area induced high sensitivity, tunable sensory units number, stronger interaction force with nitrate esters and high stability. For comparison, triphenylamino-pyrene (Py-TPA) (without POSS), one and three Py-TPA substituted POSS were also synthesized and characterized. Their chemical structures, photophysical and electrochemical properties show that P8PT has a 3-D symmetrical spatial conformation, higher molar extinction coefficient, higher area-to-volume ratio, multiple exciton transfer path, and matched energy level with nitrate ester explosives, which will all contribute to highly efficient sensing performance and efficient selectivity for the detection of nitrate ester explosives such as nitroglycerin (NG). The fluorescence of the P8PT film is 63% quenched upon exposure to a saturated vapor of NG for 50 s and 92% quenched for 300 s at room temperature due to photoinduced electron transfer between the probe and NG. These results reveal that P8PT is suitable for preparing a highly sensitive and efficient thin-film device for detecting nitrate esters.