Electrochemical Sensors Based On Composite Materials Prepared By Citric Acid Coordination Combustion Method

In this paper,we have synthesized the copper manganese oxide(Cu_1.0Mn_3.2O_7.0)nanosheets,the molybdenum zirconium oxide-reduced graphene oxide(Zr_1.00Mo_2.37O_9.11-GO)cystic composites and the hollow hexagonal-structured lanthanum zinc oxide(Zn_1.00La_0.86O_3.58)composites.On the basis of the obtained materials,three kinds of non-enzymatic electrochemical sensors were constructed to detect hydrogen peroxide?H₂O₂?,nitrite?NO₂^-?and chlorogenic acid,respectively.The main research contents are as follows:?1?Cu_1.0Mn_3.2O_7.0 nanosheets were synthesized by the modified citric acid coordination combustion method.The morphology,composition and structure of the nanosheets were characterized by scanning electron microscopy?SEM?,transmission electron microscopy?TEM?and X-ray photoelectron spectroscopy?XPS?.A modified electrode was prepared by modifying Cu_1.0Mn_3.2O_7.0 on the surface of glassy carbon electrode with chitosan as dispersant and film former.Electrochemical characterization experiments show that Cu_1.0Mn_3.2O_7.0 significantly improves the conductivity of the electrode.The modified electrodes based on the nanosheets show the good catalytic ability for hydrogen peroxide?H2O2?.According to the optimum condition,the current signals display the good linear relationship with the concentration of H₂O₂ in the range of 1.0 nM to 10.0 mM with the sensitivity of 0.689?A/??mol/L?and the detection limit of 0.77 nmol/L?S/N=3?.With the benefit of good stability and anti-interference ability,the built sensors were applied to the detection of H₂O₂ from the metabolism of melanoma cells and in serum with high recovery rate of 99.4%-102.5%.?2?The Zr_1.00Mo_2.37O_9.11-GO cystic composites were synthesized by hydrothermal method and modified citric acid coordination combustion method.The characteristics of the composites in the morphology,composition and structure were measured by SEM,energy dispersive spectroscopy?EDS?and X-ray diffraction?XRD?.The modified electrodes were prepared by dropping the dispersion liquid of Zr_1.00Mo_2.37O_9.11-GO on the surface of glassy carbon electrodes with chitosan as the dispersant and the film-forming agent.The electrochemical characterizations demonstrate that the conductivity of the modified electrodes(CS/Zr_1.00Mo_2.37O_9.11-rGO/GCE)was significantly improved after electroreduction.The modified electrodes were applied to the determination of NO₂^-with the obvious electrocatalytic effect on the oxidation of NO₂^-.With the benefit of optimization,the differential pulse voltammetry?DPV?oxidation signals present the good linear relationship with the concentration of NO₂^-in the range of 0.010?M to 0.10?M with the sensitivity of 0.381?A/??mol/L?,as well as the range of 0.10??to 10.0 mM with the sensitivity of 0.007?A/??mol/L?.The detection limit for NO₂^-is 1.87 nmol/L?S/N=3?with the advantage of high anti-interference ability to common interfering substances even in 50 times concentration.The constructed sensors were applied to the detection of NO₂^-from the actual samples of pickled food,and the high recovery rate between 98.1%and 102.1%indicates the good reliability.?3?According to the citric acid coordination combustion method,a series of morphological composites were obtained by the regulation of the concentration of poly?acrylamide?.SEM and XPS were used to characterize the morphology,composition and structure of the composites.The conductivity and detection ability of modified electrodes with chitosan as the film-forming agents were investigated for the various morphological composites,and the optimal was originated from the hollow hexagonal-structured one.Based on the composites,the modified electrodes possess the good catalytic ability for the chlorogenic acid.According to the optimum condition,the DPV signals exhibited the good linear relationship with the concentration of chlorogenic acid in the range of 0.020?M to 0.10?M with the sensitivity of 0.778?A/??mol/L?,as well as the range of 0.10??to 0.80 mM with the sensitivity of 0.0096?A/??mol/L?.The detection limit is 9.96 nmol/L?S/N=3?,and the sensors could accurately determine the content of chlorogenic acid in honeysuckle with the good anti-interference ability.