Core-shell spherical cerium oxide, N-doped carbon dots and copper oxide nanocomposites with oxidase-like activity for colorimetric detection of hexavalent chromiums

Hexavalent chromium (Cr(VI)) is a particular toxic chemical not only hazardous to human health but also causes environmental pollution. It can diffuse in the environment and has a tendency to accumulate in living organisms, so chromium detection is important for environmental protection. In this work, a colorimetric method for the determination of Cr(VI) in water based on the solvothermal synthesis of cerium oxide doped carbon quantum dot composite copper oxides (CeO2/N-CQDs@CuO NPs) with oxidase-like activity. The particles were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and Electron paramagnetic resonance (EPR). The 3,3′,5,5′-tetramethylbenzidine (TMB) was used as a chromogenic substrate, and CeO2/N-CQDs@CuO NPs exhibited significant oxidase-like activity in the presence of Cr(VI). The method was able to successfully perform colorimetric detection of Cr(VI). The method is independent of potential interfering ions and has excellent selectivity for the detection of Cr(VI). Tap water testing verified the feasibility of the method for the analysis of real samples. Hence, we anticipate that the method can successfully create a unique portable high-throughput visual sensing platform for Cr(VI) detection, opening up a new approach for testing real water samples in the field.