Preparation Of Poly(Amino Acid)/Ho(Ⅲ)-Containing Cyano-bridged Heterometallic Coordination Polymer Modified Electrode And Its Electroanalytical Application

In this thesis,a novel poly(amino acid)/Ho(Ⅲ)-containing cyano-bridged heterometallic coordination polymer modified glassy carbon electrode,poly(amino acid)/(Ho(Ⅲ)-Fe(Ⅲ)-WO42-CyHMCP/GCE,was prepared as a sensing platform using the two-step electrodeposition method.Using the modified electrode as working electrode,the voltammetric response characteristics of several test objects were studied The results showed that there was a good synergistic electrocatalytic performance between the two modified components on the surface of the electrode,and the stability,selectivity,signal response and anti-fouling performance of the composite modified electrode were significantly improved compared with the single modified electrode.In particular,the electrocatalytic behaviors of oxalic acid,folic acid and 3-nitropropionic acid(3-NPA)were studied.In addition,based on the excellent electrocatalytic activity of the modified electrode for folic acid and 3-nitropropionic acid,a new electroanalytical method for the rapid and direct determination of folic acid and 3-nitropropionic acid in real samples by voltammetry with modified electrode was established.This paper consists of four chapters.Chapter one:The literature review of this thesisThis section was consisted by the following four parts:(1)The concept and development trend of chemically modified electrode;(2)Application of polymer film modified electrodes in electrocatalysis;(3)Electroanalytical application of chemically modified electrode;(4)The significance and innovation of my studies.Chapter two:Preparation of poly(L-glutamine)/Ho(Ⅲ)-containing cyano-bridged heterometallic coordination polymer modified electrode and investigation of electrocatalytic oxidation behavior of oxalic acidIn this section,a novel poly(L-glutamine)/Ho(Ⅲ)-containing cyano-bridged heterometallic coordination polymer modified glassy carbon electrode,poly(L-glutamine)/(Ho(Ⅲ)-Fe(Ⅲ)-WO42-CyHMCP/GCE,was prepared as a sensing platform using the two-step electrodeposition method.The surface morphology of the modified electrode was characterized by scanning electron microscopy(SEM),and the modified material of CyHMCP was characterized by both high-resolution transmission electron microscope(HR-TEM)and infrared spectrum(FT-IR).An in-depth experimental study of the electrocatalytic oxidation behavior of oxalic acid(H2C2O4)was performed on this composite electrode.The results showed that the two co-modified materials exhibited excellent synergistic catalytic performance for the direct electrooxidation of oxalic acid.Therefore,by using H2C2O4 as the probe molecules,the experimental conditions for preparing this novel composite modified electrode were carefully optimized.Additionally,using differential pulse voltammetry(DPV),there were the good linear relationship between the oxidation peak current and H2C2O4 concentrations in range from 0.50 mmol/L to 40 mmol/L,and the linear regression equations was Ip(μA)=4.011+5.428COA(mmol/L),R2=0.9994.The lower detection limits(LOD)of H2C2O4 was at 0.09 mmol/L(S/N=3).Chapter three:Rapid determination of folic acid by differential pulse voltammetry at the composite modified electrodeIn this section,the direct electrocatalytic oxidation behavior of folic acid was studied at the poly(L-glutamine)/Ho(Ⅲ)-Fe(Ⅲ)-WO42-CyHMCP/GCE as working electrode by differential pulse voltammetry(DPV).The experimental results showed that the composite modified electrode has excellent synergistic electrocatalytic activity for the direct electrooxidation of folic acid.There was good the linear relationship between the oxidation peak current of folic acid and its concentrations in range from 5.00 to 600 μmol/L-1,and the linear regression equation was Ip(μA)=-0.04017+0.01 159CFA(μmol·L-1),R2=0.9994.The lower detection limit(LOD)of folic acid was 2.00 μmol·L-1(S/N=3).Based on the above experimental results,a new method for the direct and rapid determination of folic acid in real samples could be established.The standard addition method had been applied to the determination of folic acid in several folic acid tablets.The recovery for the real samples is 95.g%～109%,the experimental results were satisfactory.Chapter four:Rapid determination of 3-nitropropionic acid in raw sugarcane juice by differential pulse voltammetry with composite modified electrodeIn this section,using poly(L-citrulline)/Ho(Ⅲ)-Fe(Ⅲ)-WO42-CyHMCP/GCE as the working electrode,the direct electrochemical reduction behavior of 3-nitropropionic acid(3-NPA)was studied by differential pulse voltammetry(DPV)-and the electrocatalytic reduction pathway of 3-NPA was preliminarily elucidated based on the experimental results of water-phase infrared spectra technique.In addition,we found fact that adding a small amount of imidazole and acetone solution to the sample’s electrolyte could not only excludes the deoxygenating operation steps in the voltammetric measurement process,but also avoids the fouling and inactivate phenomenon of the working electrode for an actual assay.Actually,a good linear relationship was obtained between the reduction peak current of 3-NPA and testing concentration in the range of 40.0～4.00×103 μmol/L,with a regression equation of Ip(μA)=3.126+0.08804C3-NPA(μmol/L),R2=0.9997.The lower detection limit(LOD)of 3-NPA was estimated to be 16.0 μmol/L(S/N=3).Therefore,the standard addition method could be employed to analyze raw sugarcane samples from different areas in China.The experimental results about the average recovery of 96.8%-104%were also satisfactory.