Investigation Of Electrochemical Sensing Based On Carbon Quantum Dots And Its Nanocomposites

The electrochemical sensor has become a hot research issue in the field of analytical chemistry.Because it is economical and practical,easy to operate and portable,rapid response performance and linear output.Thus,it has shown great application prospects in the food industry,biomedicine,and environmental sanitation.The structure and composition of the electrode support membrane directly affect the analytical performance of electrochemical sensors.Therefore,the combination of nanomaterials with unique physical and chemical properties and electrochemical sensors will significantly improve its performance.Carbon quantum dots stand out among various nanomaterials due to its special effects,such as surface effects(high surface energy and activity)and small size effects,which provide a new approach for constructing electrochemical sensors with excellent analytical performance.In this thesis,carbon quantum dots with different electrical activities and their nanocomposites were prepared by calcination method and hydrothermal reaction method.Then the two novel electrochemical sensors were constructed.This thesis enriches the research contents of electrochemical sensing based on carbon quantum dots,and expands their application range of carbon quantum dots and their nanocompounds.The full text is divided into three chapters,the main research contents are as follows:1.The nitrogen doped carbon dots(N-CDs)derived from kiwi seeds,white sesame seeds,and black sesame seeds were prepared by calcination,then coated it on the surface of the working electrode and an enzyme-free nitrite electrochemical sensor was constructed.The effects of micro-morphology and chemical composition of N-CDs on electrochemical performance were studied.The electrocatalytic oxidation performances of nitrite were compared and analyzed.The results showed that the catalytic activities of the three N-CDs modified electrodes on nitrite were significantly improved compared with the bare electrode,and the detection limits for nitrite were 0.23 μM(S/N = 3).These modified electrodes were used for sensitive detection of different components of ham sausage samples,and the satisfactory results were obtained.2.CDs-BP nanocomposites were prepared by hydrothermal reaction and in-situ polymerization.An impedance-based label-free aptamer electrochemical sensor based on CDs-BP was constructed and a new method for detecting ochratoxin A(OTA)was established.The experimental results showed that the electrochemical response of CDs-BP to OTA exhibited a good linear relationship in the range of 0.1 fg/mL~10.0 ng/mL with low detection limit(0.03fg/mL,(S/N = 3)),good selectivity and reproducibility,which provided a new idea for the rapid detection of ochratoxin A in food safety.