Experimental And Theoretical Study On Polymer-Modified Nickel Foam Electrodes For Non-Enzyme Glucose Sensing

In recent years,the detection of glucose has become extremely important in many fields,such as biological monitoring,medical diagnosis and food industry.Non-enzyme glucose sensors have caused more and more attention because of good stability,low cost,simple structure and easy storage,etc.,and therefore,researchers focus on developing simple,fast and accurate enzyme-free glucose sensors.Nickel Foam(NF)is a special(3D)material with high specific surface area and many active sites.NF-based sensor has been widely used.However,NF is easy to be oxidized in aqueous solution on account of its unsatisfactory chemical stability,and cannot be directly used for non-enzymatic glucose sensing accordingly.Polyaniline(PANI)is a famous conjugated polymer with high conductivity,chemical stability and biocompatibility,therefore can be used for adsorption and enrichment of biomolecules,such as glucose.As a result,PANI-modified NF is supposed to be used as an electrocatalyst with high electrochemical stability and reversibility for non-enzymatic glucose sensing.Experimental research relative:NF was used as a base material for preparing PANI-modified non-enzymatic glucose sensing electrodes(PANI/NF)through an in-situ chemical polymerization.SEM,EDS,TEM,XRD,FT-IR,TGA and other experimental methods were employed to characterize the PANI/NF composite.Cyclic voltammetry(CV)was utilized to study the electrochemical behavior of PANI/NF electrode in lithium hydroxide(LiOH),as well as the electrocatalysis for glucose oxidation.Chronoamperometry was utilized to measure the current-time(i-t)curve of PANI/NF in LiOH solution with successive addition of glucose.In addition,the stability and reproducibility of the PANI/NF electrode in glucose detection were also investigated in this thesis.The results show that PANI fibers are deposited on NF surface successfuly.The PANI/NF electrode exhibits excellent glucose sensing ability,such as high stability and reproducibility,along with a high response sensitivity of 237μA/(mmol/L cm2)and a fast response time of approximately 3 s.Here we also prepared other two electrodes,conductive poly(3-methyl thiophene)-modified NF(P3MT/NF)and PANI-hydroxyapatite composite-modified NF(PANI/HAP/NF).CV experiments indicate both the electrodes can catalyze the glucose electrooxidation in LiOH solution obviously.And the electrocatalytic glucose oxidation on P3MT/NF,as well as PANI/HAP/NF,belongs to a diffusion-controlled process,which is the same as PANI/NF.The results of i-t curves indicate the two electrodes also exhibit excellent glucose sensing ability,respectively.Theoretical research relative:According to a large number of literatures,researchers usually segmented the linear relationship between response current and glucose content into two or more lines by reason of a real nonlinearity of the relationship in a much wide concentration range.We consider the reason is the diffusion coefficient of glucose in a solution changes with the type of electrolyte and glucose concentration.In thesis,we try to fit the change of response current(i)of PANI/NF electrode with glucose concentration(c)in solution into a semi-empirical equation,in order to express the relationship in theory.The overall mean square error between the experimental and fitted values is almost zero.For verifing the applicability of the theoretical model,we apply it to fit i-t curves of the other two synthesized electrodes,PANI/HAP/NF and P3MT/NF.The results show the fitted values accord with the experimental data measured under the relative conditions in this study.The semi-empirical fitting formula solves a problem,since a non-linear current-content relationship is approximatively divided into two or more linear segments,that the glucose content in the range of two linear segments can not be measured accruately.