Acylhydrazone as a novel "Off-On-Off" fluorescence probe for the sequential detection of Al3+ and F-

A new acylhydrazone fluorescence probe, SPBH, was synthesized from salicylaldehyde and 4-(pyridin-4-yl)benzohydrazide (PBH). SPBH exhibited high selectivity and a sensitive fluorescence response towards Al3+, even in the presence of other competing metal ions in DMF/H2O (1:1, v/v) medium. And, the chemosensor can even detect Al3+ in the intracellular region of human non-small cell lung cancer H460 cells. The binding phenomenon of SPBH was investigated by H-1 NMR spectroscopy and HR-MS. Mass spectrometry analysis showed a 1:1 complex formation of SPBH with Al3+. The Job plot also confirmed its 1:1 interaction. This SPBH/Al3+ complex exhibited excellent fluorescence turn-off properties towards the F- anion. Thus, SPBH acts as a sequential fluorescence Off-On-Off probe. The limits of detection for Al3+ and F- were calculated from the titration curve and found to be 1.1 x 10(-7) M and 1.47 x 10(-6) M, respectively.