Coumarin-based Thiosemicarbazones As Colorimetric and Fluorescent “turn On” Chemosensors for Fluoride Ions and Their Applications in Logic Circuits

Herein, we have reported two novel coumarin based thiosemicarbazones as anionic sensors. The structural elucidation of the synthesized sensors is done by 1HNMR, 13CNMR, CHN analysis, UV-Visible spectroscopy, and fluorescence emission spectroscopy. These sensors displayed naked eye view as color change from colorless to yellow. The chemosensing behavior is attributed to the presence of acidic proton which was abstracted by F? ions triggering spectral changes. Methanol, water, HCl, and trifluoroacetic acid were used to reverse the reaction of F? ions. The limit of detection (LOD) for F- ions was determined as 23.33 and 16.90 & mu;M while the binding constant was assessed as 4.92 x 104 and 4.84 x 104 M-1 for sensor based on UV-Vis titration using Benesi-Hildebrand equation. These sensors can be used in daily life applications (test strip and detection of F? ions in toothpaste sample).