Preparation Of Novel Carbon Nanocomposites For Electrochemical Sensing Application

With the development of science and technology,more and more new carbon materials are gradually discovered and cognized.Among these new carbon materials,carbon nanotubes,graphene and carbon quantum dots（CDs）,are undoubtedly the best.In this study,these three types of carbon materials were taken as the main research objects.Through the different synthesis and modification methods,single or multiple carbon compounds were be applied to the detection of heavy metal ion,and phytohormone in plants in vivo/vitro and in water environment.The main contents are as follows:1.The extract from green tea was used as carbon source to prepare a kind of carbon quantum dots with red emission by solvothermal method.The CDs were characterized by FT-IR spectra,Uv-vis spectra,fluorescence spectra and transmission electron microscopy.The results showed that the carbon quantum dots had good fluorescence stability at different p H and salt concentrations.2.The residue of sunflower seeds after oil extraction was used as carbon source to prepare CDs by hydrothermal,and then modified CDs on the surface of glassy carbon electrode.The simultaneous electrochemical detections of cadmium and lead ions were realized by differential pulse voltammetry（DPV）.The results showed that the linear range of Cd²⁺and Pb²⁺were 30～4500μg/L,with the detection limit for Cd²⁺of 2.7μg/L,and 0.35μg/L for Pb²⁺.3.The residue of dark tea were used as carbon source to prepare carbon quantum dots by pyrolysis under nitrogen atmosphere at 300 ℃,then,modified the carbon quantum dots on the electrode surface.Further,the electrochemical method was used for the reduction of CDs,to build Nafion/Er CDs/GCE electrochemical sensor for lead ion detection.The results showed that the linear range of Pb²⁺was 1～1000μg/L,R²=0.937,with the detection limit of 0.49μg/L.4.The extract from green tea as carbon source,which contains antioxidant substances such as tea polyphenols,was used to achieve the reduction of graphene oxide（GO）.The mixture was conducted by hydrothermal reaction,and then the CDs/reduction GO composite materials were obtained.We constructed an electrochemical sensor with this compositefor simultaneous detection of cadmium and lead ions.The linear range of Cd²⁺was from 2to1350μg/L,R²=0.999,with the detection limit was 0.81μg/L,and the linear range of Pb²⁺was from 3.5 to 1100μg/L,R²=0.998,with the detection limit was 0.90μg/L.5.The thiolated polyaniline modified with high dispersion of gold nanoparticles（Au NPs/TPANI-MWCNTs）composite materials were prepared by microwave assisted method.The covalent cross-linking reaction was used to further combine with the HRP-Ig G/gold nanoparticles,and the gold nanoparticles/IAA antibody,to construct the electrochemical immunosensor.It has a specific response to IAA in the range of 1.0 pg/m L to 10 ng/m L,the R² is 0.999,and the the detection limit is 0.97 pg/m L.