A Highly Selective and Sensitive Fluorescent Chemosensor for Aluminum Ions Based on Schiff Base.

An efficient "off-on" type fluorescent chemosensor, (E)-N'-(4-(diethylamino)-2-hydroxybenzylidene)-2-hydroxybenzohydrazide (H 2 L), based on Schiff base for the determination of Al3+ has been designed, synthesized, and evaluated. Upon treated with Al3+, the fluorescence of H 2 L was enhanced 45-fold due to the chelation-enhanced fluorescence (CHEF) effect based on the formation of a 1:1 complex between the chemosensor and Al3+. Other metal ions, such as Na+, K+, Mg2+, Ca2+, Cu2+, Ga3+, Zn2+, Cr3+, Cd2+, Ag+, Fe3+, In3+, Mn2+, Pb2+, Co2+, and Ni2+ had little effect on the fluorescence. The results demonstrate that the chemosensor H 2 L has stronger affinity with Al3+ than other metal ions. The detection limit of H 2 L for sensing Al3+ is 3.60 × 10-6 M in EtOH-H2O (3:7, v/v) solution. And the recognizing behavior has been investigated both experimentally and computationally.