Fluorescence quenching study of new coumarin-derived fluorescent imidazole-based chemosensor

Abstract

In this study, we report a new coumarin-based fluorescent sensor (CUM-P10) for sensitive detection of different inorganic quenchers (halide ions, aromatic amines or transition metal ions). The CUM-P10 copolymer was obtained through a post-synthesis modification reaction with coumarin fluorophore (e.g. 3-(bromoacetyl) coumarin) of an imidazole-based copolymer. CUM-P10 derivative exhibited strong fluorescence in the visible region (around 460 nm) and its interaction with different quenchers was studied in detail via fluorescence technique. For the halide ions series, its sensitivity is higher for KI (Climit = 4 × 10−4 M) than for KBr (Climit = 6 × 10−4 M) and KCl (Climit = 16 × 10−4 M) correspondingly, while the fluorescence quenching occurred mainly through a dynamic process. Similar considerations were observed for Aniline quencher too, when static and dynamic quenching take place simultaneously. Regarding transition metal ions, at a fixed ion concentration (45 × 10−3 M), best performance was achieved for Cu2+ (fluorescence intensity was reduced by 83.5%), while for Co2+ and Ni2+, the sensor performance was evaluated to be rather equivalent (72.15% and 72.44%, respectively). In the presence of Pb2+ ions, the sensor response was weak; its fluorescence was quenched with only 40.6%, respectively. Thus, minimum detection limits (10−5–10−4 M range) recommended the use of such derivatives as highly sensitive sensors capable to monitor delicate changes in varied environments.