Development Of Novel Chemically Modified Electrodes And Its’ Applications In The Environmental Analysis

Graphene （GR）, a new class of material with two–dimensional nanostructure, hasattracted enormous attentions because of its large specific surface area, superiormechanical strength, excellent electronic conductivities, high stability and strongadsorption. Owing to these unique properties, GR has been found improtantapplications in electromechanical sensors. In order to further improve the selectivityand sensitivity of sensors, GR-based composite materials have attracted more and moreinteresting in electrochemical analysis. In this thesis, GR-based composite materialhave been used to construct electromechanical sensors, and their applications in thefield of environmental analysis were also discussed in detail. The creative works ofthis thesis are summarized as follows:（1） The graphene–Au nanoparticles–chitosan hybrid film modified glassy carbonelectrode （GR–AuNPs–CS/GCE） was fabricated by one-step electrodeposition, andshowed enhanced electron transfer properties and excellent performance for theanalysis of lead （Ⅱ）. With differential pulse anodic stripping voltammetry, afteroptimization, the resulting calibration plots are linear over the range from0.5μg L^-1to100μg L^-1for lead （Ⅱ）. The calibration curve is y=0.12x+0.17and the linearcorrelation coefficient is0.998. The limit of detection was0.01μg L^-1（S/N=3）.Combining the advantages of GR （high surface area and conductivity）, AuNPs（excellent electronic conductivities） and CS （excellent film-forming ability and goodwater permeability）, the proposed GR–AuNPs–CS sensor presented a number ofother attractive features for the detection of lead （Ⅱ）, such as high selectivity, lowdetection limit, fast current response and wide linear range. Furthermore, the sensingsystem was applied for the determination of lead （Ⅱ） in river water samples and theresult was consistent with the results obtained by ICP-MS.（2） In this work, graphene-Cu nanoparticles hybrid film modified glassy carbonelectrode （GR-CuNPs/GCE） was prepared by one-step electrodeposition method.Through controlling electrodeposition time, the film thickness was uniform andcontrollable, which also contributed to improving the reproducibility and sensitivity ofthe sensor. Because CuNPs have special electrocatalytic activity for the oxidation ofnitrite, the GR-CuNPs/GCE showed great detection result, with an obvious oxidationpeak at round0.8V. Under the optimal experimental conditions, the results of the experiments indicated that the currents of its oxidation peak were linear functions ofits concentrations over the range from2μM to450μM and the limit of detection （LOD,S/N=3） was0.5μM. All above results suggest that GR-CuNPs/GCE shows goodsensitivity and high efficiency to NO2-.（3） Taking advantages of the larger specific surface area and excellent electronicconductivities of graphene and the special chelation between polypyrrole and heavymetal mercury, the graphene-polypyrrole modified glassy carbon electrode（GR-PPy/GCE） was constructed and applied to detect Hg²⁺. The structure andproperties of the modified electrode was characterized by scanning electronmicroscopy and electrochemical techniques. The effects of concentration of GR,amount of pyrrole, deposition time and applied potential on the sensitivity of thesensor have been systemically investigated. Results indicated that, GR-PPy hybrid filmindeed could be modified on the surface of the electrode through one-stepelectrodeposition and showed good adsorbing effect to Hg²⁺. Under the optimalexperimental conditions, the stripping peak current of Hg²⁺was found to be linear withthe Hg²⁺concentration in the range of6to50ng L^-1, with a correlation coefficient of0.9956. The limit of detection （LOD, S/N=3） was0.8ng L^-1. The excellent propertiesowed to the enrichment of Hg²⁺by polypyrrole, because it could not only simplifyadsorbing process, but also enhance special chelation between N atom in polypyrroleand Hg²⁺in a ratio of4:1. The sensor also displays very high selectivity and stabilityto Hg²⁺.