An unusual AIE fluorescent sensor for sequentially detecting Co2+-Hg2+-Cu2+ based on diphenylacrylonitrile Schiff-base derivative

Aggregation-induced emission (AIE) molecules with strong fluorescence in aggregated states are favourable for preparing the organic fluorescence sensor in aqueous phase. In this work, a red fluorescent sensor 5 based on AIE diphenylacrylonitrile Schiff-base derivative was prepared in yield of 83.7%. Sample 5 exhibited strong AIE property in water with red fluorescence at lambda(ex) = 620 nm and the Stokes shift was as large as 260 nm. The experiments of sensing series of metallic ions suggested that sample 5 possessed the sequentially detecting abilities for Co2+-Hg2+-Cu2+, which was observed firstly for organic fluorescence sensor. The fluorescence of sample 5 was quenched rapidly in presence of Co2+, then recovered by adding Hg2+ and quenched once more by further adding Cu2+. The detection limits for Co2+, Hg2+ and Cu2+ were 0.0937, 0.0221, and 0.0988 mu M, respectively. The sensor mechanism was confirmed by fluorescence titration, H-1 NMR and MS spectra, indicating the 2:1 stoichiometric ratios of sample 5 with ions. The sensor for ions was successfully applied in test paper, exhibiting good practical application potential for detecting Co2+-Hg2+-Cu2+ sequentially. Sample 5 showed good bioimaging performance on living cell. The fluorescence of living cells with sample 5 also displayed the similar change of quenching-recovering-quenching by adding Co2+-Hg2+-Cu2+ orderly, implying the good ions-detecting prospect in living body environment.