Ethyl 3-aminobenzo[b]thiophene-2-carboxylate Derived Ratiometric Schiff Base Fluorescent Sensor for the Recognition of In 3+ and Pb 2 .

An ethyl 3-aminobenzo[b]thiophene-2-carboxylate derived ratiometric Schiff base fluorescent sensor R was devised and synthesized. R exhibited a highly sensitive and selective ratiometric response to In 3+ in DMF/H 2 O tris buffer solution. R exhibited a colorimetric/fluorescent dual-channel response to In 3+ . More importantly, R can distinguish In 3+ from Ga 3+ and Al 3+ in less than 5 min. R exhibited a good linear correlation with the concentration of In 3+ in the 5-25 μM range and the limit of detection for In 3+ was found to be 8.36 × 10 -9  M. According to the job`s plot and MS spectra, R formed a complex with In 3+ at 1:2 with a complexation constant of 8.24 × 10 9 M 2 . Based on Gaussian theory calculations, the response mechanism of R to In 3+ can be explained by photo-induced electron transfer (PET) and intramolecular charge transfer (ICT) mechanisms. In addition, R can be used for the detection of indium in tap water with satisfactory recoveries. Meanwhile, R displayed a linear relationship to micromolar concentrations (0-50 μM) of Pb 2+ and recognized Pb 2+ in a ratiometric response with a detection limit of 8.3 × 10 -9  M.