| "seed-mediated gold nano-particles growth method"was introduced to electrode modification, and gold nano-particles modified glassy carbon electrode (Au/GCE) was prepared in this thesis. Based on Au/GCE, gold nano-particles and self-assembled monolayers were further combined in electrode modification to fabricate three-dimensional monolayer modified electrode. Field emission scanning electron microscope (FE-SEM), ultraviolet-visible (UV-vis) spectroscopy analysis and electroalaylsis were employed to study the morphology, structure of modified electrodes, and their electrochemical performances. Series of environmental-electrochemical sensors were prepared based on Au/GCE. These sensors have been successfully used in electrochemical determination of nitrite, phenolic compounds, uric acid (UA) and ascorbic acid (AA), and Cu2+. The main contents are listed as following:(1) Gold nanoparticles modified glassy carbon electrode was fabricated successfully and the particle size was in the range of 50 to 90 nm. Electron transfer kinetics between the redox couple and the modified electrode interface was improved. The redox reaction of the oxidation product of L-cys assembled monolayer (L-cysoxid) could be observed on gold nano-particles, which has no faradaic current on planar gold. The unique three-dimensional monolayer structure could decrease the ordered and compact property of two-dimensional monolayer. Thus, the electron transfer kinetics of [Fe(CN)6]3-/[Fe(CN)6]4- on the former electrode was 2.5 higher than that on the latter electrode. In addition, the amount of L-cys monolayer was found to increase with the increase of the particle size.(2) Excellent electrocatalytic activity for nitrite oxidation could be observed at Au/GCE. Compared with planar electrode, the response current of Au/GCE was 1.6 times as large as that of planar electrode, accompanied with the decrease of peak potential. The nitrite oxidation was controlled by the diffusion of nitrite to the Au/GCE electrode withα=0.3, and pH has no influence on the oxidation potential. The linear range of determination was 1.0×10-5– 5.0×10-3 mol/L with a regression coefficient of 0.9995. The sensitivity of modified electrode was 22.2μA/mmol·L-1. The accurate determination of nitrite in real wastewater was realized on Au/GCE with good long-term stability, anti-interfere ability and applicability.(3) Au/GCE exhibited different electrocatalytic activity to the oxidations of 15 kinds of phenolic compounds. Their peak currents were all increased as compared with GCE and planar gold electrode. The oxidation potential was determined by the activity of analyte. Trace phenolic compounds determination could be realized on modified electrode. The prepared electrode had a good current response to salicylic acid, with good linear relationship to its concentration. And the response sensitivity was 1.8 fold than that obtained on GCE. Furthermore, the multiple linear regression model was developed for quantitative relationship between the electrochemical oxidation potential at modified electrode and molecular structures of phenolic compounds.(4) The electrocatalytic activity of Au/GCE to the oxidation of AA was proved by the negative shift of oxidation potential with 100 mV. The oxidation peaks of UA and AA were divided on modified electrode with 170 mV separation, which only presented one fold peak on planar gold electrode. The pH presented prominence influence on separation and acidic solution could facilitate the simultaneous determination of UA and AA. And L-cysoxid/Au/GCE presented obviously electrocatalytic effect on AA oxidation. In 6.4 pH solution, 150 mV peak separation was observed on L-cysoxid/Au/GCE, which could not be realized on L-cysoxid/planar gold. Although the separation on L-cysoxid/Au/GCE was also influenced by pH, better separation and broader pH range were gained than that on Au/GCE. Response sensitivities of UA and AA on modified electrode were 10.065 and 18.101μA/mmol·L-1 respectively, in the concentration range of 2.0×10-6– 1.0×10-3 mol/L.(5) Cu2+ exhibited a good electrochemical response on L-cys/Au/GCE and the best current response was obtained at 7.0 pH. And the amount of assembled L-cys had obvious effect on current response. The modified electrode presented good anti-interfere ability, stability and reproducibility with a linear detection range of 1.0μg/L-500.0μg/L. Under potential deposition (UPD) effect could be avoided and better current response could be obtained on three-dimensional 3-mercaptopropionic (3-MPA) monolayer in Cu2+ determination. And pH of supporting electrolyte had influence on response. Good linear relationship was obtained between response current and Cu2+ concentration in the range of 0.1-80.0μg/L. and the response sensitivity was improved by 10 fold than that obtained on L-cys/Au/GCE which was processed at open-circuit pre-concentration. And the concentration of Cu2+ in actual sample was determined at modified electrode with good reproducibility.
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