Application Of Tetrazole-bonded Silica And Polyaniline Modified Electrodes In Electroanalytical Chemistry

This thesis involves two parts:Part one Documents reviewChemically modified electrodes(CMEs)are currently under intense investigation,owing to that it represents a new concept in electrode/electrolyte interface,with important significance in theoretics and application studies of electrochemistry.In this part of thesis,the definiens, origin and development of CMEs are mentioned,and the preparations,types and characterization techniques of CMEs are introduced subsequently.In addition,the preparation methods and applications in electrochemical analysis of functional silica and polymer modified electrodes are detailedly reviewed.Part two Research reportThe second part of thesis is experiment part,including two aspects mainly.On the one hand, tetrazole-bonded silica modified carbon paste electrode(TSiE)was characterized by electrochemical manners,and its electrostatic accumulation for electroactive anions was studied.Furthermore,a catalytic voltammetric method for the determination of Cu(â…¡)ion was proposed at TSiE.On the other hand,a novel electrochemical method,zero current potentiometry,was proposed taking pH response of conductiving polyaniline(PAN)film as an example,and the process of anodic Pt oxide film growth was further characterized by above novel method.Specific research results are described as follows:1.Voltammetric behaviors of Fe(CN)₆^3-,Fe(CN)₆^4-and ferrocene at TSiE and silica modified carbon paste electrode(SiE)were examined,and the accumulation capacity and dynamics of TSiE and SiE for Fe(CN)₆^3-and Fe(CN)₆^4-were studied by chronocoulometry.The accumulation capability of TSiE and SiE for Fe(CN)₆^3-were 1.00×10^-11mol and 2.98×10^-12 mol respectively,and their average adsorption rate were 1.68×10^-12mol·min^-1and 4.97×10^-13mol·min^-1respectively.The results demonstrated that the electroactive anions such as Fe(CN)₆^3-,Fe(CN)₆^4-were attracted at TSiE,and the accumulation was enhanced with the increase of negative charge numbers of anions.Contrarily,the accumulation of ferrocene with positive charge decreased.2.Voltammetric behaviors of Cu(â…¡)ion at TSiE were investigated in the absence and the presence of K₂S₂O₈.The reduction and oxidation peak potential of Cu(â…¡)ion at TSiE appeared -0.05 V and 0.05 V(vs.SCE)respectively in pH 9.1 NH₃·H₂O-NH₄Cl buffer solution.Comparing with the voltammetric response of Cu(â…¡)ion at SiE,the enhancement action was characterized by the increase of peak current,which resulted from the chemical chelation between tetrazole and Cu(â…¡)ion.Catalytic reduction peak current generated in the presence of K₂S₂O₈ was enhanced significantly three times compared with that in the absence of K₂S₂O₈.A catalytic voltammetric method for the determination of Cu(â…¡)ion was proposed, a linear range of 1.0×10^-7～1.0×10^-5mol·L^-1was obtained along with a detection limit of 5×10^-8mol·L^-1.3.A novel potential-induced zero current potentiometry was established,taking pH response of PAN film as an example.PAN film modified platinum was in series between the terminal joints of working electrode and counter electrode,I-E curves were obtained when linear sweep potential was applied.Owing to effect of interface potential between PAN film and the solution,I-E curves shifted along E-axis with variations of pH.Zero current potential E_zcpof I-E curves at the resulting zero current was measured,a Nernstian response was obtained between zero current potential E_zcpand pH of solution with a slope of -56 mV/pH in range of pH 1.81～6.80.Comparing to classical potentiometry(measured open circuit potential E_opc), the proposed method exhibited a vast improvement over stability and precision of potential response.4.Zero current potentiometry was used to characterize the growth of anodic Pt oxide films. The theoretical and experimental points of zero current potentiometry characterizing the growth of anodic Pt oxide films were studied simply.The experimental results illustrated that the logarithm of Pt anodic oxide film coverage logθwas linearly proportional to zero current potential E_zcpin three different extensions,indicating there were three layers Pt anodic oxide films in different forms extended on Pt surface.Moreover,Pt anodic oxide film coverage was characterized by the linearity relationship.