A novel molecular probe of N-(2-hydroxy-5-chlorophenyl) based rhodamine B hydrazide(HCPRH) was synthesized through a simple two-step reaction.Then its structure and fluorescence response were studied.Addition of Zn2+ into N

N-dimethylformamide(DMF) solution containing HCPRH resulted in increasement of fluorescence

while a fluorescent color change from colorless to yellow could be observed promptly with naked eyes under 365 nm ultraviolet lamp

indicating that the probe HCPRH could be used for rapid

sensitive and naked eye recognition of Zn2+.Moreover

the fluorescence emission of this probe toward Zn2+ was hardly affected by other metal ions.The binding constant between HCPRH and Zn2+ was calculated by Benesi-Hildebrand equation

and the 1∶1 binding mode was proposed based on the Job's method.In addition

according to the experimental results of fluorescence titration

the difference value of fluorescent intensity was proportional to Zn2+ concentration in the range of 10-250 μmol/L with a detection limit of 3.6 μmol/L.Results showed that HCPRH could be used in detection of trace amount of Zn2+.Subsequent experimental studies also showed that this molecular probe could be successfully applied in the continuous fluorescence response toward Zn2+ and S2-.