Construction Of Nano-gold Modified Electrode And Its Application In Metal Detection In Coastal Water

Coastal zone is a dynamic and complex multi-interface ecosystem with unique land and sea dual attributes.Coastal zone is a dynamic and complex multi-interface ecosystem with unique land and sea dual attributes.The trace metals in seawater（such as Cu,Cd,Pb,Hg,Zn,Se and Ni,etc.）have always attached great importance due to their non-degradability,bioaccumulation,high toxicity and environmental persistence.Reinforcing the accurate detection and analysis of trace metals in coastal waters can not only provide scientific basis for the management and control of heavy metal pollution in marine environment,but also have greatly important significance for the healthy development of marine economy.Therefore,it is an important area in marine environmental science.When the metal elements in seawater are detected by atomic spectroscopy,inductively coupled plasma-mass spectrometry,etc.,in order to eliminate the influence of high salinity in seawater,a complicated pretreatment process are required.The instrument is expensive,and the measurement cost is high.Electrochemical detection methods have certain technical advantages in metal detection of coastal water bodies because of their remarkable advantages such as fast analysis speed,high sensitivity,simple pretreatment process,and small influence by seawater high-salt matrix.Hence,they are widely used in the metal detection of seawater.In this thesis,two new nano-materials with special morphology were used to to improve the electrochemical activity of the electrode.The electrochemical methods were developed to detect trace metal in coastal seawater.The major contents are described as follows:（1）Voltammetric determination of copper in seawater at a glassy carbon disk electrode modified with Au@MnO₂ core-shell microspheresCopper ion in seawater was determined by anodic stripping voltammetry using Au@MnO₂ core-shell modified electrode.The Au@MnO₂ composites were synthesized by the method of electrochemical deposition,in which the electrochemically deposited Au core as active support material promoted the growth of MnO₂,and formed a unique and regular spherical core-shell structure.The diameter of the spherical Au@MnO₂ core-shell microspheres ranged from 200 to 250 nm,and the curled edges of the spheres resembled cactus.Because the structure combined the absorption ability of MnO₂ and the electrocatalytic ability of AuNPs,it had a good anode signal response to copper ions.Under optimized conditions,the linear range of Au@MnO₂ modified electrode for the detection of copper ions in seawater was 20 nmol/L¹μmol/L,and the detection limit was 5 nmol/L.The modified core-shell microsphere electrode possessed good stability and reproducibility,and had been successfully applied to the analysis of copper ions in seawater.（2）Simple synthesis of dendritic nano-gold/porous reduced graphene oxide high performance electrochemical sensor and determination of selenium in seawater by voltammetryIn this chapter,highly stable graphene and gold nanoparticles were used to detect Se in seawater samples.High activity perforated reduced graphene oxide（P-rGO）was synthesized by electrochemical co-deposition of graphene oxide and sacrificial Prussian blue.Subsequently,the AuNDs/P-rGO modified electrodes were composed by electrochemical deposition of AuNDs,and its surface properties of the electrode were characterized by scanning electron microscopy（SEM）and energy dispersive X-ray spectroscopy（EDS）,respectively.The obtained results indicated that GCE/P-rGO have a larger specific surface area than GCE,and a large number of perforated structures formed many conductive channels on the surface of electrodes,which improved the electrocatalytic performance.The results of dopamine detection using P-rGO as a support substrate exhibited that P-rGO nanomaterials have excellent catalytic and conductive properties,which provides an effective theoretical support for the further application of AuNDs/P-rGO modified electrodes.The excellent response signal was obtained by employing AuNDs/P-rGO for detection of Se in seawater samples.Under the optimum conditions,the detection linear range of Se in seawater was 0.5nmol/L¹?mol/L,and the detection limit was 0.15 nmol/L.The proposed method can be used as a general method for electrodeposition of various three-dimensional nanomaterials for electrocatalysis and electrochemistry.