Gold Nanomaterials Based Chemically Modified Electrodes For Detection Of Copper In Seawater Samples

Copper plays an important role in the marine ecosystem.But copper has heavy metal toxicity to marine organisms,which results in seawater pollution at higher concentration.It is gradually recognized that the impact of trace copper on the environment depends on both of the total amount and the speciation.Sensitive,rapid and accurate analysis of trace copper and its speciation is helpful in environmental analysis.Among various analytical techniques,electrochemical methods offer the advantages of high sensitivity,simple experiments operation,and portability.In this thesis,we developed two chemically modified electrodes for speciation analysis of copper in seawater samples.The main contents are listed as follows:(1)In-situ synthesis of reduced graphene oxide/gold nanoparticles modified electrode for speciation analysis of copper in seawaterA modified electrode of reduced graphene oxide/gold nanoparticle/Nafion(rGO/AuNP/Nafion)was fabricated through in-situ synthesis,which was used for determination of copper ions in seawater samples by differential pulse anodic stripping voltammetry.This in-situ synthesis procedure was based on the ion-exchange and electrochemical reduction.The rGO provides a larger surface and more active sites while electron transfer was accelerated by incorporating AuNPs.Nafion was utilized as a cation exchange polymer in which rGO and AuNPs could be tightly attached to the electrode surface.The physical and electrochemical characterizations of the as-prepared modified electrode were studied by transmission electron microscopy,scanning electron microscopy,energy dispersive X-ray spectroscopy and cyclic voltammetry.AuNPs with diameter of 5–10 nm on rGO decorated in the gold electrode surface were observed.Under the optimal conditions,the proposed electrode had a linear response to copper ions in the concentrations range from 20 nmol/L to 1?mol/L(R~2=0.998),with the detection limit of 4 nmol/L.Combined with pre-treatment,this method was successfully applied to the speciation analysis of free,dissolved and total copper in seawater samples.(2)Synthesis of three-dimensional gold nanostructure modified glassy carbon electrode by glycol as a growth directing agent for determination of copper in seawaterUsing ethylene glycol as a growth directing agent,three-dimensional gold nanostructure was prepared on glassy carbon electrode by one-step electrochemical deposition.The concentration of copper ion in seawater samples was detected in by square wave anodic stripping voltammetry.Gold nanostructure could accelerate the rate of electron transfer.The three-dimensional electrode structure provides a larger specific surface area and more active binding sites.Under the optimal experimental conditions,this proposed modified electrode had a wide linear response to Cu(II)ranged from 0.02~1?mol/L(R~2=0.999)and the detection limit of 3 nmol/L.This electrode is easier to preparation with had good selectivity and reproducibility.The relative standard deviation of 100 measurements for the same modified electrode in the same copper standard solution was 3.7%.The proposed method has been successfully applied to the detection of copper in seawater samples,implying good applicability.