(E)-N'-(quinolin-2-ylmethylene)-3-[(E)-quinolin-2-ylmethyleneamino]-benzohydrazide(QQB)

as a chelating fluorophore

can detect Zn

2+

selectively by shifting emission peak from 405 nm to 510 nm upon Zn

2+

addition.Zinc binding not only makes the emission band red-shifts

but also enhances the fluorescence intensity.The probe is highly selective for Zn

2+

over biologically relevant alkali metals

alkaline earth metals and the first row transition metals such as Mn

2+

Co

2+

and Ni

2+

.Spectrophotometric titration and ESI-MS spectra indicate the formation of a 1:1 complex of Zn

2+

with QQB.