A Highly Selective Colorimetric and “Turn-Off” Fluorimetric Probe Based on Unsymmetrical Naphthalene Formaldehyde Derivatives for the Detection of CN− in Aqueous Media

A novel hydrazone-based CN− fluorescent probe, HNT, was synthesized by 1-hydrazine methyl-2-naphthol and 2,3,4-trihydroxybenzaldehyde. CN− has stronger basicity and a superior hydrogen-bonding ability than other anions. Therefore, CN− can deprotonate naphthalene hydroxyl in fluorescent probe HNT, which induced the bright yellow fluorescence that was quenched before changing the color of the solution from yellow to orange. This color change indicates that fluorescent probe HNT showed selective recognition of CN− and was not interfered with by other anions. HNT can quantitatively detect CN−, and the detection limit is 6.93 × 10-7 M. The manufactured HNT test strip could also quickly detect CN−, which indicates that HNT has certain application value.