Near infrared and colorimetric fluorescence sensor for ultra-selective detection of Cu2+ level with applications in diverse water samples, brain tumor cell and flow injection analysis

A new colorimetric NIR fluorescence sensor based on heptamethine cyanine connected to 2-(4-(2-amino-ethylsulfanyl)butylsulfanyl)ethanamine (Cy7C4) was successfully synthesized and characterized in this work. The sensor possessed high sensitivity to discriminate Cu2+ from other interfering ions with colorimetric change and NIR-fluorescence quenching. Cy7C4 formed a complex with Cu2+ in 1:1 ratio (Cy7C4:Cu2+) derived by Job's plot analysis and the possible structure of Cy7C4:Cu2+ complex was predicted using molecular modeling. The detection limit was calculated to be 1.56 ppb, which was lower than the highest of Cu2+ level in safe drinking water defined by the U.S. EPA. In addition, Cy7C4 was capable to detect Cu2+ in diverse real water samples and brain tumor cells. Moreover, this sensor was adopted in flow injection analysis (FIA) for automated monitoring Cu2+ in dual channels of UV-Vis absorption and fluorescence signaling.