Copper Ion Detection Using Green Precursor-Derived Carbon Dots in Aqueous Media

Highly accurate quantitative detection of heavy metals is crucial for preventing environmental pollution and safeguarding public health. To address the demand for sensitive and specific detection of Cu2+ ions, we have developed carbon dots using a simple hydrothermal process. The synthesized carbon dots are highly stable in aqueous media, environmentally friendly, and exhibit strong blue photoluminescence at 440 nm when excited at 352 nm, with a quantum yield of 5.73%. Additionally, the size distribution of the carbon dots ranges from 2.0 to 20 nm, and they feature excitation-dependent emission. They retain consistent optical properties across a wide pH range and under high ionic strength. The photoluminescent probes are selectively quenched by Cu2+ ions, with no interference observed from other metal cations such as Ag+, Ca2+, Cr3+, Fe2+, Fe3+, Hg2+, K+, Mg2+, Sn2+, Pb2+, Sr2+, and Zn2+. The emission of carbon dots exhibits a strong linear correlation with Cu2+ concentration in the range of 0–14 μM via a static quenching mechanism, with a detection limit (LOD) of 4.77 μM in water. The proposed carbon dot sensor is low cost and has been successfully tested for detecting Cu2+ ions in general water samples collected from rivers in Taiwan.