A highly selective and sensitive fluorescent turn-on Al3+ chemosensor in aqueous media and living cells: experimental and theoretical studies

A highly selective and sensitive fluorescent chemosensor (1) based on a 2-aminobenzoic acid Schiff base has been synthesized in one step. The binding properties of 1 with metal ions were investigated by fluorescence, UV-vis, H-1 NMR and electrospray ionization mass spectra. This sensor exhibited enhanced fluorescence in the presence of Al3+ in aqueous solution and aka in living cells. The sensing mechanism of 1 toward Al3+ was explained by DFT/TDDFT calculations. The binding constant was determined to be 3.1 x 10(8) M-1 which is one of the highest binding affinities among such simple Schiff bases for Al3+ in buffer solution. The calibration curve for the analytical performance of Al3+ was found to be linear over a concentration range with a very low detection limit of 290 nM (3 sigma).