Quantification of 2-chlorohydroquinone based on interaction between N-doped carbon quantum dots probe and photolysis products in fluorescence system.

As a member of chlorophenolic compounds, 2-chlorohydroquinone (HQCl) has been widely used as intermediates in various chemical industries and leaded to serious threat on the environment. It is urgent to develop simple and robust analytical method for sensitive and selective determination of HQCl. Carbon quantum dots (CQDs), a promising photoluminescence nanomaterial, have gained sufficient concern as optical sensors owing to their outstanding photochemical properties. In this work, nitrogen doped carbon quantum dots (N-CQDs) were successfully synthesized by a simple secondary hydrothermal method and applied as a fluorescent probe for the quantitation of HQCl. A new fluorescence region centered at excitation wavelength of 310 nm and emission wavelength of 390 nm appeared after nitrogen doping. It was found that the N-CQDs exhibited a high selectivity towards HQCl with sensitive fluorescence response and the fluorescence quenching of N-CQDs was linear with the concentration of HQCl in the range of 30-90 μM (Y = 0.0049X + 0.1255, R = 0.996). This is the first time that the dual role of excitation light was observed in the fluorescence detection system. The ultraviolet light acted as not only the excitation energy source for N-CQDs photoluminescence, but also the light source for photolysis of HQCl. In the detection process, HQCl was degraded to p-benzoquinone by light, and then the CQDs combined with p-benzoquinone through Michael addition reaction under the action of doped nitrogen. The electron transfer from N-CQDs to the linked p-benzoquinone caused the quenching of fluorescence originated from the edge state of N-CQDs. Furthermore, this established method can be applied for the quantitative determination of HQCl in environmental water samples with satisfactory recoveries between 94.31 and 105.51%.