A highly sensitive and selective turn-on fluorescent probe for Pb(ii) ions based on a coumarin–quinoline platform

Abstract

A new fluorescent probe T1, which contained a coumarin fluorophore with a triazole substituted 8-hydroxyquinoline (8-HQ) receptor and a Schiff base spacer, was rationally designed and synthesized. It displayed a high affinity towards Pb²⁺ ions with a dissociation constant (K_d) of 0.1 μM and possessed a high selectivity for Pb²⁺ ions. A visually detectable colour change from colourless to yellow and a 30-fold fluorescence enhancement were observed upon addition of Pb²⁺. Experiments also indicated that a 1 : 1 stoichiometry of T1 with Pb²⁺ inhibited the photo-induced electron transfer (PET) process, resulting in the increase of fluorescence intensity.