Application Of Electrochemical Sensors Based On Hollow Carbon Spheres And Their Composites In Food Detection

The development of rapid,sensitive and accurate food safety testing methods is an important technical support for the implementation of China's food safety programme and is of great importance for safeguarding people's health.The use of various food additives and dietary supplements in different food products has a strict range of use and addition levels(such as sunset yellow(SY),hydrogen peroxide(H2O2)and L-tyrosine(L-Tyr),etc.),and it is important to detect their addition levels quickly in food.Electrochemical methods are increasingly being used as a rapid,simple and sensitive analytical method for food analysis and detection.Hollow mesoporous carbon nanospheres and their derivatives are characterised by large specific surface area,high electrical conductivity and good biocompatibility,and they are beneficial for improving the analytical performance such as sensitivity and detection limits of the modified electrodes.In this paper,a series of mesoporous carbon nanospheres and carbon sphere composites were synthesized and different electrochemical sensors were constructed using hollow mesoporous carbon nanospheres as carbon substrates to achieve rapid and sensitive detection of sunset yellow,hydrogen peroxide and L-tyrosine.The main research includes three parts as follows:(1)Hollow mesoporous carbon spheres(HMCS)of different diameters were prepared using the hard template method and characterised using SEM,TEM,XRD,XPS and BET.The properties of the material were tested by cyclic voltammetry,differential pulse voltammetry and impedance methods using the properties of the hollow carbon spheres with high electrical conductivity,and the best performance was obtained for the smallest diameter hollow carbon spheres.A new electrochemical sensor for sunset yellow was constructed by modifying the smallest diameter hollow mesoporous carbon spheres on a glassy carbon electrode(GCE).A standard working curve was established at the optimum enrichment potential(0.3 V),enrichment time(8 min),pH of the supporting electrolyte(pH=7.0)and modification volume of the material suspension(3 ?L).The response current values in the concentration range of 0.0015 ?M-0.057 ?M and 0.057 ?M-4 ?M of sunset yellow showed a good linear relationship with a limit of detection(LOD)of 0.12 nM.The repeatability and reproducibility RSD of the sensor are all less than 5%,and the current value drops to 95.03%of the initial current value within four weeks,showing good stability.In the detection of actual samples of Fanta carbonated beverage,the recoveries ranged from 96.03-104.49%,indicating that the sensor has the potential for practical application.(2)Hollow mesoporous carbon spheres with different iron loadings were synthesized by the one-pot method,and a new hydrogen peroxide electrochemical sensor was constructed by modifying the iron-loaded hollow mesoporous carbon spheres on a glassy carbon electrode.The Fe/mesoporous carbon spheres were characterized by SEM,TEM,XRD and XPS,and cyclic voltammetry was performed for each material,with the highest response current for hydrogen peroxide at the electrode modified with 150 mg of iron phthalocyanine.Under the optimal test potential,the response current values in the concentration range of 0.08 ?M-100 ?M and 100?M-230 ?M of hydrogen peroxide showed a good linear relationship with a limit of detection(LOD)of 0.098 ?M.The repeatability and reproducibility RSD of the sensor are all less than 5%,and the current value drops to 95.08%of the initial current value within four weeks,showing good stability.In the detection of actual samples of pure milk and chicken feet with pickled peppers,the recoveries ranged from 94.2%to 102.1%,indicating that the sensor has the potential for practical application.(3)Different silver-loaded hollow mesoporous carbon spheres were synthesized by chemical reduction,and a novel tyrosine electrochemical sensor was constructed by modifying the silver-loaded hollow mesoporous carbon spheres on a glassy carbon electrode.The silver/mesoporous carbon spheres were characterized by SEM,TEM,XRD and XPS,and each material was tested by cyclic voltammetry,with the hollow mesoporous carbon spheres with moderate silver loading showing the highest response current to tyrosine.At the optimum support electrolyte pH(pH=7.0)and optimum test potential(0.45 V),the response current values in the concentration range of 0.08 ?M-100 ?M and 100 ?M-230 ?M of tyrosine showed a good linear relationship with a limit of detection(LOD)of 20 nM.The repeatability and reproducibility RSD of the sensor are all less than 5%,and the current value drops to 95.33%of the initial current value within four weeks,showing good stability.In the detection of actual samples of pure milk,the recoveries ranged from 98.03%to 100.14%,indicating that the sensor has the potential for practical application.