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

Abstract

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.

Keywords: Copper sensor; Cyanine; Heptamethine cyanine; NIR; Near infrared fluorescence sensor.