Synthesis and application of CDs/diatomaceous earth nanocomposites for selective and sensitive detection of hexavalent chromium

In this study, nanocomposites with signal amplification capability and high fluorescence quantum yield were prepared by compositing carbon dots (CDs) with diatomaceous earth (DE) by hydrothermal method. The resulting CDs/DE nanocomposites were characterized using fluorescence spectroscopy, Fourier-transform infrared spectroscopy, transmission electron microscope (TEM), scanning electron microscopy, X-ray diffraction (XRD), and UV-visible light analysis. The characterization data demonstrate that the fluorescence intensity of CDs can be significantly enhanced, and the fluorescence quantum yield can be increased from 10.1 % to 32.3 % through encapsulation with DE. The CDs/DE nanocomposites have a sensitive and highly selective fluorescence quenching phenomenon on hexavalent chromium ions (Cr(VI)). Under the irradiation of 365 nm ultraviolet light, the fluorescence color of the test paper changed from pink to blue with the increase of the concentration of hexavalent chromium ions on the test paper in the dark environment.