Research On Electrochemical Sensing Based On Polyaniline Derivative/Transition Metal Oxide Nanocomposites

Electrochemical sensors have been extensively applyed in many research areas because of their high sensitivity,good selectivity,easy miniaturization and fast analysis.In recent years,many functional materials have been prepared to improve electrocatalytic performance,and developed in fabrication of highly sensitive and highly selective electrochemical sensors.Conducting polymer based composite catalysts usually have electro-catalytic performances superior to their individual components because of synergetic effects.The nanocomposites of polyaniline derivative/transition metal oxide are frequently applied as the cocatalysts.However,the precise controls in their compositions,microstructures,and interactions between different components are big challenges.In this paper,three kinds of polyaniline derivative based nanocomposites were synthesized by electrochemical method,and used in constraction of electrochemical sensors for sensitive detection of chloramphenicol and dopamine.In chapter 1,an overview of electrochemical sensors and a development of conducting polymer based nanocomposite in electrochemical sensors have been introduced.The use of electrochemical methods to prepare nanocomposites of transition metal oxide has been highlighted.In chapter 2,the sulfonate polyaniline nanowires based nanocomposite Cu_xO/SPAN was synthesized by underpotential deposition and electrochemical oxidation.The oxygen atom of sulfonic group（-SO₃H）can form high coordination bond with copper ions in solution.Therefore,copper can be electrodeposited on the surface of SPAN nanowires at-0.1 V（vs.Ag/Ag Cl）that is positive to its thermodynamically reversible potential.Due to it is easy to form metal-support bond between copper atom and-SO₃H group,the copper nano-particles with a diameter of 40 nm were obtained,and then could be changed to copper oxide nano-particles through electrochemical oxidation.The SEM,XRD and XPS were used to characterize the morphology and compositions of this nanocomposite.The study of synergistic effect of the nanocomposite to electrocatalytic performance of chloramphenicol was performed by cyclic voltammetry.The linear range of the electrochemical sensor was0.02μM-50.0μM,and the detection limit was 0.006μM（S/N=3）.The obtained sensor was avaiable for determination of chloramphenicol in honey specimens.In chapter 3,the Zr O₂/SPAN nanocomposite was prepared by electrochemical cathodic hydrolysis.The Zirconium ions can coordinate with hydroxyl group under neutral conditions,and then electrochemical cathodic hydrolysis（the formation of OH^-from H₂O and O₂）results in the formation of zirconium hydroxide[Zr（OH）₄].Finally,Zr O₂ nano-particles can be obtained through dehydration of[Zr（OH）₄].The XRD and XPS were used to characterize the morphology and compositions of the nanocomposite.The research on synergistic effect of this nanocomposite to electrocatalytic performance of chloramphenicol is performed by cyclic voltammetry.The linear range of the constructed electrochemical sensor was 0.05-100.0μM,and the detection limit was 0.015μM（S/N=3）.The electrochemical sensor exhibited good selectivity and had the ability to detect chloramphenicol in honey samples.In chapter 4,the composite Zr O₂/PABA was synthesized by electropolymerization and electrochemical cathodic hydrolysis.PABA/GCE was prepared through electropolymerization,and then Zr O₂ nano-particles were modified on the PABA/GCE by electrochemical cyclic voltammetry（-1.0-0.7 V）.The boric acid group in PABA combined with Cis-dihydroxyl to form cyclic esters,which could effectively improve the enrichment of dopamine on the polymer surface.Based on the boronate affinity of PABA and the electrocatalytic performance of Zr O₂ nano-particles,the linear range of the electrochemical sensor was 0.02-600.0μM,and the detection limit was 0.008μM.