Construction Of Graphene Modified Electrode And Its Application In Metal Detection In Coastal Water

Coastal zone is the interaction area between land and sea,which is an important place for human activities.Iron and zinc are the necessary metal elements for organisms,and they are also the important nutrient elements for aquatic organisms.Their concentrations and forms in coastal waters not only have a significant impact on coastal water ecology,but also further affect marine ecology.Therefore,the accurate and sensitive methods for the detection of trace elements is conducive to the effective monitoring of coastal waters.In this thesis,two electrochemical methods are developed based on the nanocomposites related to grapheme,which are used in the detection of Fe²⁺and Zn²⁺in coastal waters.The main research work is outlined as follows:1)Voltammetric determination of trace Fe²⁺in seawater samples by reducedgraphene oxide/leucomethylene blue/platinum nanoparticles modifiedelectrodeIn this work,the modified electrode based on nanocomposites of reduced graphene oxide/leucomethylene blue/platinum nanoparticles/glassy carbon electrode?rGO/LMB/Pt NPs/GCE?was fabricated via an electron relay effect.Cationic dye of methylene blue?MB?was absorbed on the surface of graphene oxide?GO?with through?-?bond interactions.Then PtCl₆^2-was self-assembled on the surface of the composites of GO/MB through Coulomb interactions.Using NaBH₄ as the reducing agent,Pt NPs were formed and GO was reduced to rGO.With the aid of Pt NPs,MB was catalytically degraded to LMB,a nanocomposites of rGO/LMB/Pt NPs were successfully prepared.To increase the selectivity and sensitivity for Fe²⁺determination,Bp was used as the complexing agent to form the complex of Fe²⁺-Bp.During the process of electrochemical deposition,Fe²⁺-Bp might be adsorbed onto the surface of rGO/LMB/PtNPs/GCE.The complex follows a simple one-electron transfer process in aqueous solution.Due to the excellent electrochemical properties of rGO and the well-established assistant reductant of MB,as well as the catalytic amplifying effect of Pt NPs,the as prepared rGO/LMB/Pt NPs modified electrode showed excellent properties for the voltammetric determination of Fe²⁺with the linear range of 0.01 to 2mM and a detection limit of 3 nM.This proposed electrochemical method was successfully applied to determine the content of Fe²⁺in seawater samples.2)Voltammetric determination of trace Zn²⁺in seawater sample using apoly?sodium 4-styrenesulfonate?/wrinkled reduced graphene oxide compositemodified electrodeIn this study,the nanocomposites of poly?sodium 4-styrenesulfonate?/wrinkled reduced graphene oxide composite were modified on the surface of glassy carbon electrode via electrochemical deposition method.This modified electrode was used for the determination of trace Zn²⁺in seawaters by differential pulse voltammetry.It was shown that the three-dimensional graphene layer formed on the electrode surface can significantly promote the electron transfer and increase the specific surface area of the electrode.Meanwhile,the poly?sodium 4-styrenesulfonate?film might effectively improve the stability of modified electrode,absorb cations and repel anions on the electrode surface.Zn²⁺was enriched and dissolved on the electrode,and then the current signal was obtained.Under the optimal conditions,the response of the modified electrode to Zn²⁺was obtained at in the linear range from 5 to 720 nM,with a detection limit of 1.7 nM?S/N=3?.Additionally,this modified electrode was successfully applied to the determination of Zn²⁺in real seawater samples.