Significant improved selectivity of a fluorescent sensor for Al3+ made from a fluorinated rhodamine B Schiff base

摘要： Two rhodamine B-based Schiff bases (RBF, RBC) with different substituent groups (–F and –COOH) have been synthesized. In order to study the sensing properties of two Schiff bases for metal ions, the interaction of Schiff bases with different metal ions was studied over UV–Vis absorption spectra and photofluorescent spectra. The results show that the RBF is a turn-on fluorescent chemosensor for Al3+ ions with being highly selective and sensitive in ethanol. The value of the fluorescence increase factor shows a good linear relationship with the concentration of Al3+ in the range of 1–9 μM with a detection limit of 0.8 μM. Meanwhile, upon addition of Al3+ or Fe3+ ions, the fluorescence intensity of RBC increased significantly (FAl3+/FFe3+ = 0.77). These studies show that, compared with the carboxyl group (–COOH), the introduction of fluorine atoms (–F) to a rhodamine B-based Schiff base can significantly improve selectivity to Al3+.