Research On Electrochemical Sensor Based On Hybrid Lnorganic-organic Frameworks

Electrochemical sensors have been widely studied by researchers due to their high sensitivity,fast response,easy miniaturization,and low manufacturing costs.The preparation of new nanomaterials for modified electrodes to improve the performance of sensors is an important research direction in the field of electrochemical sensors.Among them,hybrid inorganic-organic framework materials not only combine the excellent properties of inorganic components and organic components,but also reveal unique morphological structures,numerous derivative materials,and more flexsible,which are expected to improve the performance of electrochemical sensors.In this paper,novel electrochemical sensor electrode nanomaterials based on hybrid inorganic-organic framework materials were successfully prepared and used for the detection of protocatechuic acid（PCA）and ascorbic acid（AA）.Specifically,it includes the following three contents:1.A novel hybrid inorganic-organic framework EDAPb Cl₄@ZIF-67（EDA=ethylenediamine）was prepared by embedding a hybrid organic-inorganic perovskites（HOIPs）into a porous zeolite imidazolate frame material（Zeolitic Imidazolate Frameworks,ZIFs）.Afterwards,it is applied to the detection of PCA.Physical characterization was carried out by means of X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FTIR）,transmission electron microscopy（TEM）,scanning electron microscopy and energy spectroscopy（SEM&EDS）.The results of a series of electrochemical performance tests showed that the EDAPb Cl₄@ZIF-67 modified glassy carbon electrode（GCE）can effectively amplify the signal of the electrochemical response to the oxidation of PCA.The peak current of EDAPb Cl₄@ZIF-67/GCE was linearly increased with the concentration in the range of 22–337μM.The linear regression equation was I_（μA）=0.0031 C_（μM）+1.6968（R²=0.9916）,the detection limit（S/N=3）was 15μM.Meanwhile,EDAPb Cl₄@ZIF-67/GCE was effectively utilized for the detection of PCA in green tea and cough syrup with the recoveries above 96%.2.A novel hybrid inorganic-organic framework-derived metal oxide material,Ni O@La Mn O₃,was prepared by metal-organic framework（MOF）template method.And it combined with multi-walled carbon nanotubes（MWCNTs）as conductive substrate to form Ni O@La Mn O₃/MWCNTs.Meanwhile,the composite material was used as an electrochemical sensor electrode material for the detection of AA.Its physical properties were characterized by XRD,TEM,SEM&EDS and other characterization methods.The results of a series of electrochemical performance tests including electrochemical impedance spectroscopy（EIS）,cyclic voltammetry（CV）and differential pulse voltammetry（DPV）showed that the Ni O@La Mn O₃/MWCNTs modified GCE has high sensitivity and excellent selectivity for the determination of AA.And its current signal response increased linearly with the AA concentration in the range of 2.60～36.44μM.The linear regression equation was I（μA）=0.5902 C（μM）+1.4407（R²=0.9909）,the detection limit（S/N=3）was 2.41μM.In addition,Ni O@La Mn O₃/MWCNTs modified GCE had been applied to analyze the determination of AA in vitamin water and water-soluble C100 beverages and gave the recovery of 93.73～109.93%.3.Co₃O₄-La Mn_0.5Ni_0.5O₃,a novel hybrid inorganic-organic framework derivative,was prepared by calcination which could turn ZIF-67 and La Mn Ni ternary-metal-MOF precursors into metal oxides.Then,Co₃O₄-La Mn_0.5Ni_0.5O₃/MWCNTs was formed after self-assembling with MWCNTs.The nanocomposite was used for the modification of glass carbon electrode（GCE）and simultaneous determination of PCA and AA.Through various physical characterization methods and a series of electrochemical tests,it was proved that the modified GCE can significantly increase the oxidation peak current of PCA and AA.Moreover,the oxidation peaks of PCA and AA could be separated obviously by CV and DPV.Under the optimum conditions,the linear relationship between the currents and PCA and AA concentrations was obtained over the range 9.31～272.28μM and 9.26～210.68μM,respectively.And the detection limits for PCA and AA were 8.83μM and 7.35μM,respectively.The linear regression equations of the current response and concentration were I_pa=0.1450C_PCA-0.1237（R²=0.9968）and I_pa=0.0865C_AA-0.1063（R²=0.9977）,respectively.It was shown that the Co₃O₄-La Mn_0.5Ni_0.5O₃/MWCNTs modified GCE can facilitate their simultaneous and individual determination.Finally,this sensor had been utilized to detect PCA and AA successfully in real samples with relative standard deviations（RSD）which are both less than 4.26%.