A novel turn-on fluorogenic probe based on 4-(bis(2-((2-hydroxyethyl)thio)ethyl) amino)benzaldehyde the detection of Hg2+ ions has been designed and developed. The probe BMA showed high selectivity for Hg2+ ions over the series of other tested cations in an aqueous acetonitrile medium. Only the addition of Hg2+ ions to probe BMA in aqueous acetonitrile solution (CH3CN/H2O (7:3, v/v) could induce a remarkable red shift of about 20 nm in UV-vis absorbance spectra and a dramatic fluorescent enhancement with a blue shift of 10 nm in the emission spectra. With the help of a fluorescence spectrometer, the detection limit was calculated to be 73 nM. The binding stoichiometric ratio between BMA and Hg2+ ions was found to be 1:1 by Jobs plot, which was further confirmed by 1H NMR titration, FT-IR, HR-MS, and density functional theory calculations. The probe BMA can selectively detect Hg2+ ions, with several advantages, including ultra-fast response, low detection limit, conspicuous fluorescent changes, robust anti-interference capability, and exciting reversibility. The probe BMA can also serve as a portable extractant for removing Hg2+ ions in aqueous solution and act as an efficient and practical solid-state fluorescent sensor for mercury in on-field measurements. In addition, the in situ formed BMA-Hg2+ ensemble may be used for fluorescent recognition of histidine over other common amino acids via an indicator displacement assay mechanism. The low detection limits of BMA-Hg2+ for histidine were calculated to be 0.91 µM.
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