A novel turn-on colorimetric and fluorescent sensor for Fe3+ and Al3+ with solvent-dependent binding properties and its sequential response to carbonate

Abstract

A novel bis-rhodamine derivative BRU was designed and synthesized in a simple way. In aqueous media, BRU could efficiently recognize Fe3+ and Al3+ among other metal ions with different color appearances through a turn-on colorimetric response. In the presence of Fe3+ or Al3+, BRU solution also displayed enhanced fluorescent emission. According to the detection limit, BRU had high recognition sensitivity towards Fe3+ and Al3+ based on either colorimetric absorbance or fluorescent emission. Interestingly, BRU bound to Fe3+ or Al3+ with a simple 1:1 mode in CH3OH and a 1:2 mode in CH3OH/H2O, displaying solvent-dependent binding property. In addition, the in situ generated BRU-Fe3+ and BRU-Al3+ complex exhibited fluorescence turn-off and color disappearance towards carbonate among other anions. These provide a potential application in sequential detection of Fe3+, Al3+ and carbonate with naked-eyes.