A novel 1,8-naphthalimide-based Cu2+ ion fluorescent probe and its bioimaging application.

A new 1,8-naphthalimide-based Schiff base compound, named as (Z)-2-butyl-6-(((2-hydroxyphenyl)imino)methyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (BHBD), has been simply synthesized with high yields. BHBD can be employed as a "turn-on" fluorescent probe for Cu2+ ion with high sensitivity, high selectivity and relatively low detection limit (0.48 × 10-6 M). The fluorescence emission of BHBD is very weak in H2O/THF (v/v: 7/3) mixture, which is significantly enhanced after addition of Cu2+ ion. The proposed mechanism is verified by 1H NMR, Job's plot and TOF-MS experiments. Anti-interference experiment, cytotoxicity assay and pH influence results indicated that BHBD meets the requirements of bioimaging. Therefore, BHBD has been successfully applied in detecting Cu2+ ion in HeLa cells.