Carbon dots–quinoline derivative nanocomposite: facile synthesis and application as a “turn-off” fluorescent chemosensor for detection of Cu2+ ions in tap water

In this paper, a novel quinoline derivative: 8-(pyridin-2-ylmethoxy)quinoline-2-carboxylic acid (Q) has been successfully synthesized, then it was coupled with carbon dots (CDs) to synthesize a CDs–Q nanocomposite by a simple and green method. The CDs–Q nanocomposite can act as a “turn-off” fluorescent chemosensor for detection of Cu2+ ions. It's a good candidate for Cu2+ sensing on account of its excellent properties such as its high sensitivity and selectivity, easy synthesis, excellent fluorescence stability towards temperature and pH, direct detection in aqueous solution and tap water and distinct fluorescence quenching towards Cu2+. We have also discussed the fluorescence quenching mechanism of CDs–Q and the possible coordination mode of CDs–Q with Cu2+. CDs–Q have a wide linear range (0.01–1.2 μM) and high sensitivity towards Cu2+ ions with a detection limit of 0.56 nM. In addition, this fluorescent chemosensor was also applied to determine Cu2+ in tap water with satisfying results.