A new fluorescence probe L based on carbazole Schiff-base for Cu 2＋ was synthesized. The recognition ability of probe L to metal ions was investigated by UV-Vis and fluorescence spectra. The experimental results showed that the probe L in CH 3 CN displayed a distinct color change from yellow to colorless upon the addition of Cu 2＋ , which can be directly detected by the naked eye for Cu 2＋ . The fluorescence spectra showed that the probe L had high selective and sensitive recognition toward Cu 2＋ in CH 3 CN, the fluorescence intensity was increased with the increase of Cu 2＋ concentration, and it was not affected by other metal ions. The association constant between the probe L and Cu 2＋ was detected to be 1.38×10 4 L/mol and the corresponding detection limit was calculated to be 2.34×10 -7 mol/L. The detection limit of L for Cu 2＋ was far lower than the maximum allowable level of the WHO limit (20 mol/L) for drinking water. The results indicate that the probe L should be applicable to the research on the environmental applications associated with Cu 2＋ .

Three novel carbazole-thiosemicarbazides based Schiff-base were synthesized. The recognition ability of representive 2-((N-heptane-carbazol-3-yl)methylidene)hydrazine carbothioamide (L 2 ) to metal ions was investigated by naked-eye, UV-Vis, fluorescence and mass spectra. The experimental results showed that this compound had a good water solubility and can be investigated in DMSO-H 2 O (V∶V＝6∶4, Tris-HCl buffer, pH＝7.0). The compound L 2 in the DMSO-H 2 O displayed a distinct color change from colorless to yellow upon the addition of Cu 2＋ , other metal ions did not induce significant colour changes, which indicated that Schiff base L 2 can be used as a probe with naked eye detection for Cu 2＋ . The fluorescence spectra showed that the probe L 2 was a high selective and sensitive "turn-off" fluorescence probe for Cu 2＋ in DMSO-H 2 O (V∶ V＝6∶4, Tris-HCl buffer, pH＝7.0). The association constant between the probe L 2 and Cu 2＋ was detected to be 3.42×10 4 L•mol -1 , and the detection limit was calculated to be 8.96×10 -6 mol•L -1 . MS analysis showed a 1∶1 binding stoichiometry between Cu 2＋ and L 2 . The detection limit of L 2 for Cu 2＋ was far lower than the maximum allowable level of World Health Organization (WHO) limit (20 mol•L -1 ) for drinking water.