A colorimetric and fluorescence "turn-off" chemosensor for the detection of silver ion based on a conjugated polymer containing 2,3-di(pyridin-2-yl)quinoxaline

Two novel conjugated polymers containing 2,3-di(pyridin-2-yl)quinoxaline (DPQ) unit (P1) and 2,3-di(thiophen-2-yl)quinoxaline (DTQ) unit (P2) were designed and synthesized through Sonogashira coupling reaction. P1 provided high sensitivity and selectivity to silver ions: color change from green to brown red and fluorescent emission quenching, which can be observed by naked eye, even in the presence of interference cations. However, P2 with the similar polymer backbone to P1 showed no absorption and fluorescence changes toward any cations. Therefore, the DPQ units in P1 exhibited a key role for the selective recognition of Ag+, which was further confirmed by the H-1 NMR titration, density functional theory (DFT) calculations and electrochemical studies. These results not only imply that DPQ based conjugated polymer is a promising probe of Ag+ ions but also afford a good guidance to design effective polymer sensors in future. (C) 2014 Elsevier B.V. All rights reserved.