A new insight into the sensing mechanism of thiazole-substituted pyrazoline fluorescent sensor for the detection of picric acid

Abstract

With safety requirements raised, the study of sensing mechanisms has become very important in the development of new chemical sensors with highly sensitivity and selectivity in detecting chemical explosives. In this paper, the sensing mechanism of a novel thiazole-substituted pyrazoline sensor 1 for the detection of picric acid (PA) was theoretically explored in detail. The results of geometry, density gradient function, binding energy, and Gibbs free energy indicated that the optimal interaction mode between sensor 1 and PA was the synergistic interaction of intermolecular hydrogen bonding and π-π stacking. Electronic transition and frontier molecular orbitals revealed that the strong luminescent properties of sensor 1 depends on the intramolecular charges transfer. However, through a photo-induced electron transfer process, the fluorescence of the sensors quenches upon exposure to PA.