Turn-off detection of Cr(III) with chelation enhanced fluorescence quenching effect by a naphthyl hydrazone Shiff base chemosensor.

A thiophene substituted naphthyl hydrazone derivative NHT was synthesized using a one-step route for the detection of trivalent chromium (Cr). UV-visible absorption and emission spectra, density functional theory calculations as well as H NMR titration confirmed that the probe underwent a turn-off response via the chelation enhanced fluorescence quenching effect upon exposure to Cr and the NHT-Cr complex was formed at a 1:1 binding stoichiometry. NHT exhibited a fast response rate of 2.3 min in buffer solution and a relatively low limit of detection of 41 nM. In addition, the Schiff base chemosensor exhibited excellent selectivity with high affinity towards Cr in the presence of other competing cations. Bioimaging of the probe in PC3 cells further demonstrated the potential real life application of the probe in detecting Cr.