A Carbon-Dot-Based Fluorescent Probe for the Sensitive and Selective Detection of Copper(II) Ions

Fluorescent carbon dots (CDs) are widely applied for the detection of heavy metal ions due to their nontoxicity, high sensitivity and stability. In this work, CDs were synthesized by a simple and green pyrolysis method without complicated post-processing procedures and characterized by transmission electron microscope, X-ray diffraction, fourier transform infrared spectroscopy, UV-visible spectrophotometer and fluorescence spectroscopy. The CDs exhibited a relatively narrow size distribution of 3.5-8.6 nm with an average size of 6.1 nm and their surface was decorated with abundant functional groups such as hydroxy and amino groups. They exhibited a strong fluorescent peak at 468 nm with a quantum yield of 25% under 365 nm UV irradiation. The CDs exhibited a strong fluorescence response to 70 μM Cu ²⁺ with the sensitivity up to 77% due to the complexation between the amino groups decorated on the CD surface and the adsorbed copper ions. They also exhibited short response times of less than 1 min, high response selectivity and good stability.