Investigation On Electrochemical Sensors For Dopamine And Saccharide Based On Boronate Affinity

Phenylboronic acid and its derivatives can combine with cis-diol compounds to generate cyclic ester via reversible covalent bonds in an aqueous or non-aqueous media.An electrochemical method based on boronate affinity for the detection of saccharide,catechols,glycohemoglobin and cells.This thesis is based on boronic acid and its derivatives as molecular recognition unit.Molecularly imprinted electrochemical sensor was constructed to detect dopamine by sol-gel method;Poly?aniline-co-3-aminobenzeneboronic acid?nanowires were prepared by chemical oxidation polymerization to build a non-enzyme current electrochemical sensor for the detection of glucose with high sensitivity and selectivity;A potentiometric electrochemical sensor was constructed to detect monosaccharide using situ electrochemical polymerization based on poly?anilineboronic acid?/graphene composite.The main contributions of this thesis included four sections in following:1.The first chapter was mainly introduced catechol,saccharide,glycoprotein and cell types of electrochemical sensor based on boronate affinity;Molecular imprinting electrochemical sensor and molecularly imprinted sol-gel technique was applied in electrochemical sensor based on boronate affinity.Finally,a brief introduction of this paper was also investigated.2.Poly?aniline boronic acid?was prepared on Au electrode through electrochemical method which provided amounts of covalent binding sites for the affinity to dopamine?DA?.A precursory sol solution containing DA and ammonium fluorosilicate was spin-coated on the modified electrode to form film.The hydroxyl ions were generated in solution and catalyzed the hydrolysis of fluorosilicate to form silica matrix when the modified electrode was placed in NH3 atmosphere.When DA was remove from the imprinted hybrid,the imprinted cavities with specific recognition sites were generated.The imprinted hybrid demonstrated higher affinity to DA than that to epinephrine,ascorbic acid and uric acid due to the combined effects of covalent interaction,cavities matching and electrostatic repulsion.The imprinted hybrid sensor exhibited a quick response,sensitive and selective identification to DA in the concentration range from 0.05 to 500?M with a detection limit of 0.018 ?M and the response time for 5 minutes.3.The cationic surfactant hexadecyl trimethyl ammonium bromide as a soft template to synthesis poly?aniline-co-3-aminobenzeneboronic acid?[SP?AN-co-AB?]nanowires by chemical oxidation polymerization process.The morphology and structure of SP?AN-co-AB?nanofibers have been characterized by FTIR,UV-Vis and SEM.The self-doped copolymer of sulfonated polymer has good solubility in water and still has electrocatalytic activity in neutral and alkaline environments.Through ?-? interaction between the sulfonated polymer and the graphene to construct the modified electrode based on SP?AN-co-AB?nanowire/graphene composite.Based on the covalent interaction of boronic acid and diol,the negatively charged sulfonic acid groups was adsorbed the release of protons which resulting in sulfonated polymer oxidation peak current was increased.By regulating the comonomer molar ratios of o-aminobenzenesulfonic acid?ASA?,aniline?ANI?,3-aminophenylboronic acid?APBA?can be achieved the detection of glucose with highly sensitive.The electrochemical response mechanism of the modified electrode to detect glucose was also studied when the interferents such as ascorbic acid,uric acid and dopamine were existed in vivo.The linear range was 0.5?25 mM?n = 7,R= 0.9979?and a detection limit of 0.16 mM?S/N = 3?.4.A novel potentiometric electrochemical sensor was constructed to detect D-glucose and D-fructose using situ electrochemical polymerization based on poly?anilineboronic acid?/graphene composite.The modified electrode utilizes open circuit potential via boronic acid-diol and combine with the high specific surface area and conductivity of graphene.The 3?/S based detection limits of D-glucose and D-fructose were estimated to be 0.4 mM?R =0.9968?and 0.1 mM?R = 0.9977?,with the sensitivity of 0.7 mV·mM^-1 and 1.3 mV·mM^-1,respectively.