Cu2+-selective NIR fluorescence sensor based on heptamethine cyanine in aqueous media and its application

A near-infrared (NIR) colorimetric fluorescence sensor, Cy7C3, based on heptamethine cyanine dye was synthesized for determining the presence of Cu2+ ions. The sensor showed highly sensitive fluorescence quenching toward Cu2+ ions in acetonitrile/buffer solution at physiological pH with long emission wavelength of 718 nm. Cy7C3 also provided an excellent selectivity to Cu2+ ions over other competing metal ions, with a low detection limit of 9 ppb, which was lower than the maximum concentration of Cu2+ ions in drinking water of U.S. EPA. Cy7C3 could achieve naked-eye detection of Cu2+ ions via the color change from blue to colorless, which allowed determination of Cu2+ ions in hydroponic fertilizers. Additionally, the sensor was developed to detect Cu2+ ions in HepG2 cancer cells via fluorescence imaging.