A highly selective and sensitive polymer-based OFF-ON fluorescent sensor for Hg2+ detection incorporating salen and perylenyl moieties

Abstract

A chiral conjugated polymer sensor with incorporated (R,R)-salen and perylenyl moieties in the main chain backbone could be obtained by the polymerization of 1,7-bis((3-formyl-4-hydroxyphenyl)ethynyl)perylene-3,4:9,10-tetracarboxylic tetrabutylate (M-1) with (R,R)-1,2-diaminocyclohexane (M-2) via a nucleophilic addition–elimination reaction. The polymer sensor can emit the fluorescence situated at 635 nm due to the introduction of a strong fluorophore perylenyl group. Compared with the other cations (including Na⁺, K⁺, Ca²⁺, Ag⁺, Ni²⁺, Cd²⁺, Pb²⁺, Cr³⁺ Al³⁺, Fe³⁺, Co²⁺, Zn²⁺), only Hg²⁺ can lead to the most pronounced response of the polymer sensor, which is as high as a 26-fold fluorescence enhancement without interference from other metal ions. More importantly, the fluorescent color of the polymer sensor displays an obvious change from red to bright yellow upon addition of Hg²⁺, which could be easily detected by the naked eye. The results indicate that the polymer sensor with incorporated (R,R)-salen and perylenyl moieties can be favorably utilized for the development of a potential sensor for Hg²⁺ detection.