Development Of Benzothiazole-based Ratiometric Fluorescent Probes And Their Performance Studies

2-(2’-hydroxyphenyl)benzothiazole (HBT) is a fluorophore with good photostability and reasonable fluorescent quantum yield. Moreover, HBT can undergo excited state intramolecular proton transfer (ESIPT) process upon photoexcitation, which produces a large Stokes shift. Therefore, HBT is an ideal candidate for the design of fluorescent probes. In this dissertation, two fluorescent probes based HBT were developed for the detection of sulfite and fluoride.Based on ESIPT and intramolecular charge transfer (ICT) mechanisms,2-(2’-hydroxy-4-carbaldehydephenyl)benzothiazole (HB-I) was designed and synthesized as a ratiometric fluorescent probe for the detection of sulfite. With the addition of sulfite, the fluorescence spectra displayed a79nm blue-shift from539nm to460nm. This novel ratiometric probe show good selectivity and high sensitivity for sulfite. The detection limit of probe HB-Ⅰ for sulfite is determined as1.1×10-7M in aqueous acetonitrile solution.Based on ESIPT and ICT mechanisms, HB-Ⅱ has been developed as a bifunctional fluorescent probe for ratiometric detection of fluoride and sulfite using tert-butyldimethylsilyl ether and acrylonitrile units as sensing groups. Upon addition of fluoride, the solution of HB-Ⅱ displays a large red-shift from498nm to634nm in its fluorescence spectra. On the other hand, with the addition of sulfite, the solution of HB-Ⅱ exhibits a large blue-shift from498nm to371nm in fluorescence spectra. This bifunctional probe shows high sensitivity and excellent selectivity for both of fluoride and sulfite.