Application Of Conductive Polymer Composites Modified Electrodes In The Electrocatalytic Reduction Of Nitrate

Coastal zone is the core of the marine economic zone and the base of marine development activities.The concentrations and distribution of nitrate in coastal waters are closely related to aquaculture and ecological health.Exploring the content and distribution of nitrate in coastal waters are helpful for obtaining the data of water quality and effectively monitoring and controlling the water environment.Electrochemical methods have a series of merits,such as simplicity,low-cost,fast,sensitive,easy to miniaturization and integration,being used in speciation analysis and suitable for on-line and in-situ determination.The core is the electrochemical reduction of nitrate on the working electrode as for the electrochemical detection of nitrateIn this thesis,micro-needle electrode which selected different functional nano modification materials to enhance the electrochemical performance of the electrode was used as the determination of nitrate(NO3-)in real coastal river water.Characters of modified electrodes were investigated by using SEM,EDX,and electrochemical methods The main contents of this research are as follows:1.In this work,a new micro-needle electrode(MNE)based on copper microspheres(CuMSs)and polyaniline(PANI)was fabricated through two steps of electrodeposition method,and explored its electrocatalytic reduction performance of NO3-.The experiment results showed that,the PANI functions as the conductive polymer and adhesion agent not only increased the stability and improved the electrochemical performance of the modified electrode,but also made the CuMSs more easily deposited on the MNE surface.CuMSs with diameter of about 0.5 to 1 ?m were decorated on the PANI/MNE.The PANI/CuMSs/MNE had shown a linear response to NO3-in the concentrations ranging from 0.02 to 6 mM(R2=0.995)with the detection limit of 8 ?M.In the meantime,the determination of NO3-in coastal river water samples was achieved with the micro-needle electrode with satisfactory results2.Herein,Chitosan(CTS)and Polyvinylpyrrolidone(PVP)were modified on the micro-needle electrode by electrodeposition method.Silver nanoparticles(AgNPs)were self-assembled on the electrode surface,because of the reduction property of CTS and PVP to silver ions.CTS/PVP/AgNPs/MNE was established though above process,and its electrochemical catalytic reduction ability to NO3-was investigated.CTS and PVP increased the specific surface area of MNE.What's more,AgNPs with diameter of about 20 nm were modified on the needle electrode steadily.CTS/PVP/AgNPs/MNE reflected superior electrochemical catalytic reduction ability to NO3-,which showed a linear response to NO3-in the concentrations ranging from 0.05 to 2 mM(R2=0.996)with the detection limit of 0.2 ?M.Additionally,the CTS/PVP/AgNPs/MNE was successfully applied to the rapid determination of NO3-in real coastal river water samples3.Preparation of silver nanoparticles(AgNPs)and polyethyleneimine(PEI)film modified MNE,using the reduction action of ultraviolet light to silver ions and the adhesion effect of PEI.The results indicated the electrochemical catalytic reduction ability of PEI/AgNPs/MNE to NO3-.PEI being the modification material of electrode,enlarged the specific surface,enhanced the electrochemical performance,and provided more binding sites for the deposition of AgNPs.The average diameter of the AgNPs which attributed to the reduction action of ultraviolet light were 100?200 nm.The PEI/AgNPs/MNE had shown excellent electrochemical properties for determination of NO3-.Under the optimal conditions,a good linear of 0.2 to 7 mM(R2=0.999),and a detection limit of 60 ?M can be obtained,which responsed good practical application prospect in electrochemical sensor.