Fluorescence quenching of novel pyrazoline derivative with aniline in different solvents

The fluorescence quenching process of a new pyrazoline derivative (4-[5-(2,3,4-trimethoxypheny1)-3-(4-trifluoromethylphenyl)-4,5-dihydro-1H-pyrazole-1-yl] benzensulfonamide, fluorophore T) and aniline was investigated in four different solvents (tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), acetonitrile (ACN) and Ethanol (EtOH)) by using UV-vis. absorption, steady-state and time-resolved fluorescence techniques. According to the data obtained, it was determined that fluorescence intensity of fluorophore T decreased as the concentration of aniline increased in all solvents used due to the fluorescence quenching process between fluorophore T and aniline. The mechanism of the quenching process between the fluorophore T and the aniline was explained by Stern-Volmer plots. The fluorescence quenching parameters such as Stern-Volmer constants (K-S and K-D), bimolecular quenching constants (kq), the probability of quenching per encounter (p) and activation energy of quenching (E-a) were determined from both steady-state and time-resolved measurements. The results obtained with the modified Stern-Volmer equation presented that the fluorescence quenching process quenching is dominated by static interactions between the fluorophore T and the aniline with a minor dynamic component. In addition, the calculated activation energy of quenching (E-a) values confirmed that the quenching process did not occur with material diffusion only. It is thought that fluorophore T can be used for aniline detection via fluorescence quenching in future.