The mechanisms of fluorescence quenching of carbon dots upon interaction with heavy metal cations

The paper presents the results of a study of the interaction of heavy metal cations Fe3+, Cr3+, Cu2+, Pb2+, Zn2+, Ni2+, Ag+ with carbon dots synthesized by the hydrothermal method in water. It was found that all the studied cations quench the fluorescence of nanoparticles to one degree or another. The series of cations were determined according to the degree of their influence on the fluorescence of carbon dots. The mechanisms of quenching the fluorescence of carbon dots upon interaction with cations have been investigated. It is shown that the quenching of the luminescence of nanoparticles in the presence of the investigated cations of heavy metals has a complex character. The observed changes in the intensity of fluorescence of carbon dots are the result of a superposition of several factors—electrostatic interactions of metal cations with surface fluorophores of carbon dots, aggregation of nanoparticles, and the effect of an inner filter for iron ions.