A reversible fluorescent chemosensor for Fe3+ and H2PO4 - with on-off-on switching in aqueous media

To realize highly selective relay recognition of Fe3+ and H2PO4 (-) ions, a simple benzimidazole-based fluorescent chemosensor (L) was designed and synthesized. Sensor L displays rapid, highly selective, and sensitive recognition to Fe3+ in H2O/DMSO (1:1, v/v) solutions. The in situ-generated L-Fe3+ complex solution exhibits a fast response and high selectivity toward dihydrogen phosphate anion via the Fe3+ displacement approach. The detection limits of sensor L to Fe3+ and L-Fe(3+)complex to H2PO4 (-) anion were estimated to be 1.0 x 10(-9) mol/L. Notably, the sensor was retrievable to indicate dihydrogen phosphate anions with Fe3+, and H2PO4 (-), in turn, increased. This successive recognition feature of sensor L makes it a potential utility for Fe3+ and H2PO4 (-) anion detection in aqueous media.