A Ratiometric Green Fluorescent Carbazole-Bis(hydrazinobenzothiazole) Probe for the Selective Detection of Toxic Hg²⁺...

A dyad Carbazolyl-bis(hydrazinobenzothiazole) was designed to form a symmetrical structure that containing two-arm active binding sites facilitates coordination with Hg²⁺ ion. This sensor has imparted a colorimetric and fluorometric changes in presence of Hg²⁺ ions. The ligand showed a selective blue shift in presence of Hg²⁺even in co-existence with heavy metal ions with luminescence change from colorless to blue and colorless to green under day light. Enhanced Intramolecular charge transfer process is responsible for fluorescence transformation when ligand interacts with Hg²⁺ ion. The emission spectra showed a ratiometric response to increasing addition of Hg²⁺ ions. The sensor is capable of detecting above the lower concentration of 6.8025×10^-8 M. The fluorescence efficiency of CBT-2 with Hg²⁺ ion is quite stable under different co-metal ions and wide range of pH 6 to 9. The sensor CBT-2 forms a 1 : 1 stoichiometric complex with Hg²⁺ ions and the binding nature is confirmed from the 1H-NMR, FTIR, and mass spectroscopic studies. The sensor CBT-2 and its Hg²⁺ complex possess good binding nature to protein in Bovine Serum Albumin which could be good in biological applications. Additionally, wedevelop a practical application in real water sample analysis and electrochemical detection via oxidation potential discrimination.