Synthesis Of Coal-based Carbon Quantum Dots Through Green Method And The Application For Fe³⁺ Detection

As a kind of novel fluorescent carbon nanomaterials,carbon quantum dots(CQDs)have great attention owing to their unique structure and excellent property,of which the green preparation is one of the frontiers and hotspots in the preparation of carbon nanomaterials.Now,several approaches have been developed to fabricate CQDs,such as chemical oxidation,electrochemical method,hydrothermal method,laser ablation method,among them chemical oxidation methods is the most common method,because of its simple operation,mild reaction conditions and cheap equipment.However strong oxidizing agents(e.g.HNO3,H2SO4)has been widely employed to exfoliate CQDs from carbon material.This approach has been the inherent difficulty in thoroughly removing both the excess oxidizing agents and the inorganic salts.Therefore,it is essential that green and facile CQDs production strategies are developed to synthesis CQDs at low-cost and larger-scale of production.The research of which the majority results are briefly summarized as follows:Firstly,CQDs can be synthesized by ozonation exfoliation of lignite coal for its abundant and inexpensive.Transmission electron microscopy(TEM)image,Dynamic light scattering(DLS),Fourier transform infrared(FT-IR)spectroscopy and X-ray photoelectron spectroscopy(XPS)were used to characterize the high quality CQDs,the result showed CQDs had good dispersibility,the size distribution of the obtained CQDs centralized from 2 to 4 nm with average diameter was 2.8 nm.In addition,the as-prepared CQDs containing rich oxygen functional groups exhibited good water-solubility.UV-vis absorption spectrum and photoluminescence(PL)were used to further characterize optical property of the CQDs,The CQDs showed excellent fluorescent photostability,pH stability and excitation-dependent PL behavior.The resultant CQDs showed a highly sensitive and selective quenching effect to Fe3+ with desirable anti-interference performance,the detection limit was 0.26 ?M.Secondly,CQDs can be synthesized by H2O2 oxidation exfoliation of lignite coal for its abundant and inexpensive.transmission electron microscopy(TEM)image,Dynamic light scattering(DLS),Fourier transform infrared(FT-IR)spectroscopy and X-ray photoelectron spectroscopy(XPS)were used to characterize the high quality CQDs,the result showed CQDs have good dispersibility,the size distribution of the obtained CQDs centralized from 2 to 4 nm with average diameter was 2.8 nm.In addition,the as-prepared CQDs containing rich oxygen functional groups exhibited good water-solubility.UV-vis absorption spectrum and photoluminescence(PL)were used to further characterize optical property of the CQDs,The CQDs showed excellent fluorescent photostability,pH stability and excitation-dependent PL behavior.The resultant CQDs showed a highly sensitive and selective quenching effect to Fe3+ with desirable anti-interference performance,the detection limit was 0.54 ?M.Thirdly,the optical properties of CQDs were briefly studied,through the comparison of two kinds of carbon quantum dots by ozone and hydrogen peroxide oxidation methods,although their average diameters were 2.8 nm,but the fluorescence emission color were not the same.Through the comparison of the surface content of C,N and O,their content were different.Therefore,surface defects play a key role in the luminescence properties of carbon quantum dots.Moreover,the size of the quantum dots prepared under different reaction time was different,and the colors were also different.