Study On Cerium-based Composite Oxide Quantum Dots And Its Application In Electrochemical Sensing

Electrochemical sensing technology plays an important role in the field of biological and environmental measurement and analysis.Comparing to other electrochemical detection and analysis methods,chemically modified electrodes are the most popular tools in electrochemical laboratory research.In electrochemical analysis,the target analytes can be quickly adsorbed.The accumulation efficiency of the target analytes on the electrode surface is greatly improved due to the high surface caused by the defects of quantum dots.However,the quantum dot materials are easily agglomerated into blocks,which affect their catalytic performance.Therefore,we solve this problem by using carbon film to support the quantum dots and the agglomeration of the quantum dots will be restricted.Besides,the glassy carbon electrode（GCE）decorated with quantum dots uniformly can ensure good stability and repeatability of the electrode surface.In this experiment,a composite quantum dot material was prepared by using thin layer carbon of cherry blossom as a biological template and gains the advantages of high specific surface area,uniform particle distribution,fast electron transport,high structural stability and good electrochemical catalytic performance.The synthesized sample materials were characterized by X-ray diffractometry（XRD）,scanning electron microscopy（FESEM）,high-resolution transmission electron microscopy（HRTEM）,nitrogen adsorption desorption instrument,electrochemical workstation,etc.When the thermal condition temperature is 120°C and the holding time is 6 h,the synthesized CeO₂@C,CeO₂@ZnO@C,CeO₂@Mn₃O₄@C,CeO₂@CuO@C composite quantum dot materials have uniform morphology and no agglomeration.The average particle size is rather small and the electrochemical sensing performance is superior to other hydrothermal conditions and its bulk composites.CeO₂@C quantum dot and oxide-based composite metal oxide（ZnO,Mn₃O₄,CuO）quantum dots are explored in experiments to detect various analytes（methylene blue,hydrogen peroxide,dopamine,glucose,melamine,heavy metals）.The electrochemical performance of the samples was characterized by cyclic voltammetry and differential pulse voltammetry.The results showed that CeO₂@C,CeO₂@ZnO@C,CeO₂@Mn₃O₄@C,CeO₂@CuO@C quantum dots have good electrochemical response signals in methylene blue,hydrogen peroxide,dopamine,glucose,melamine and heavy metal ions,and the peak shape,peak potential and peak current value of these analytes were dissimilar,indicating that these quantum dot materials have excellent selectivity.In addition,compared with the bare electrode,the quantum dot modified electrode exhibits a large electrochemical response signal to the analytes,indicating that the presence of the quantum dot material greatly improve the sensitivity of the electrode.Early exploration of CeO₂@C produced better electrochemical signals in methylene blue,hydrogen peroxide and dopamine,but the linear R² value of its concentration and current was not high,and the linear R² value of its concentration and current of later experiments was higher.For example,the R²of the CeO₂@ZnO@C nanocomposite in the glucose solution is 0.99944,and the R²of the CeO₂@CuO@C quantum dot composite in the heavy metal lead ion is 0.9995.