A novel “on-off-on” halogen-substituted bis(salamo)-like fluorogenic chemosensor for sequentially identifying Cu2+ ions and cysteine

Abstract

A novel bis(salamo)-like fluorogenic chemosensor (BDS) was designed for recognition Cu2+ ions through fluorescence “off” in DMSO/H2O (v/v = 9:1) Tris-HCl (pH = 7.26) buffer system to form a 1:2 BDS-Cu2+ complex. Significantly, the product BDS-Cu2+ for recognition Cu2+ could relay identify cysteine (Cys) in the same solvent system. In this process, the Cys captured Cu2+ in BDS-Cu2+ due to competitive coordination and released BDS, accompanied by the fluorescence recovery (“turn on”) of the system. Interestingly, the chemosensor BDS shows orange fluorescence in solid phase but blue fluorescence in liquid phase (DMSO/H2O, v/v = 9:1). The chemosensor BDS presents high sensitivity and selectivity to Cu2+ ions and Cys with the limits of detection (LOD) toward Cu2+ and Cys of 191 nM and 211 nM separately. Furthermore, the chemosensor BDS can be practical applied in detecting Cu2+ ions on medical swab platform via the naked eye and fluorescence dual channel. Finally, the fluorescence “on-off-on” recognition mechanism of the chemosensor BDS to Cu2+ ions and sequentially Cys was rationally explained by performing density functional theory (DFT) calculations.