Study On Novel Chemically Modified Electrode And Its Applications For Life Science And Environmental Science

The chemically modified electrodes(CMEs) have been a most burgeoning and one of the most flourish research realms in the electrochemistry and electroanalytical chemistry since it was developed in the middle of 70's.It was for the moment widely applied in many cases such as life sciences,environmental science,analytical science and material science.The distinguishing feature of CMEs are that a generally thin film of a selected chemical is bonded or coated onto the electrode surface to endow the electrode with the chemical,electrochemical,optical,electrical,transport and other desirable properties of the film in a rational,chemically designed manner.For analytical applications,CMEs should possess certain properties;good mechanical and chemical stability of electrode surface,good short-term reproducibility and long-term stability of the modifiers activity towards the analyte,wide dynamic range of responds,low and stable background currents over the potential range required, simple and reliable fabrication that results in consistency of the response from one electrode to another.The main work of this paper is focus on the novel modified electrode,increasing the electron transfer rate between the electroactive molecules and the electrode.We have developed chemically modified electrodes with improved sensitivity that exhibited good resistance to surface fouling,resulting in long-term stability of the electrode.We have also showed great improvements in sensitivity and reproducibility of these modified electrodes for determination of glutathione,glucose and nitroaromatic compounds.One of the principal researches is about the preparation of the CEMs and their application in Environmental Science or Life Science.The primary research work is as follows:1 Electrochemistry and Electrocatalysis of MultiWalled Carbon Nanotubes/mv RuO-RuCN Films Modified Electrode for GSH and GSSG(Chapter 2)A glassy carbon electrode doped multiwalled carbon nanotube was deposited from a solution containing micromolar concentrations of RuCl₃ and K₄Ru(CN)₆ to fabricate the GC/MWCNTs/mv RuO-RuCN.The MWCNTs/mv RuO-RuCN film was characterized with scanning electron microscope(SEM) and its electrocatalytical behavior was studied by electrochemical methods.It also showed that the GC/MWCNTs/mv RuO-RuCN modified electrode had excellent electrocatalytical effect to glutathione.The responses were in good linear with the concentrations of glutathione from 1.0×10^-6mol/L to 2.0×10^-3mol/L with the detection limit of 5.0×10^-7 mol/L.The electrocatalytical mechanism to glutathione with GC/MWCNTs/mv RuO-RuCN modified electrode was also developed in this paper.Finally,The MWCNTs/mv RuO-RuCN modified electrode was used to separate the glutathione by capillary electrophoresis/electrochemistry.The electrode showed many advantages as a glutathione sensor such as simple preparation,high sensitivity,excellent electrocatclytical activity and long-term stability.It suggested that the modified film also could enhance the sensitivity of glutathione when it was applied in the capillary electrophoresis.It is promising for these fields such as life science,clinic medicine and medication kinetics.2 Novel Electrochemical Assay for Glucose Biosensor Based Amplex UltraRed and Horseradish Peroxidase(Chapter 3)A novel method for low-level,low-potential electrochemical detection of glucose using a chemically activated redox mediator has been developed.This method is unique in that it utilizes a fluorogenic peroxide substrate,Amplex UltraRed (N-acetyl-3,7-dihydroxyphenoxazine),Upon peroxidase catalyzed turnover of H₂O₂ with Amplex UltraRed,the fluorescent and electroactive product resorufin (7-hydroxy-3H-phenoxazin-3-one)was detected amperometrically in a thin-layer flow cell with high selectivity.And its electrocatalytical behavior were also studied by electrochemical methods.It showed that the modified electrode had excellent electrocatalytical effect to glucose.A linear detection range from 0.8μmol L^-1 through 324μmol L^-1 was obtained and the detection limit of 0.4μmol L^-1.The apparent Michaeli-Menten constant was 21.78μmol L^-1.Moreover,the interferents influencing the proposed biosensor were researched in detail,and the biosensor possessed excellent selectivity and good stability.The method demonstrated here is facile but reliable and durable and may fine some interesting physiological and pathological applications.3 {MSU/PDDA}n LBL assembled modified sensor for electrochemical detection of ultratrace explosive nitroaromatic compounds(Chapter 4)In this paper,layer-by-layer{MSU/PDDA}n films assembled by alternate adsorption of mesoporous SiO₂(MSU) and Poly(diallyldimethylammonium chloride) (PDDA)onto a glassy carbon electrode were reported.MSU that we used in this work was synthesized by the precursor of zeolite Y and ionic liquid of 1-hexadecane-3-methylimidazolium bromide(CMIMB),which was used as a template in basic medium.It exhibited larger pore diameter,pore volume and surface area.The electrochemical characteristics of the {MSU/PDDA}n films have been studied by electrochemical impedance spectroscopy in 0.1 M KC1 solution containing 5.0 mM Fe(CN)₆^3-/Fe(CN)₆^4-.By differential pulse voltammetry(DPV) measurement, the ultratrace nitroaromatic compounds(NACs) such as TNT,TNB,DNT and DNB can be detected with nM level.The sensitivity for NACs determination in {MSU/PDDA}n films was dependent on the number of layers,pH and ionic strength of electrolyte,based on which a set of optimized conditions for film fabrication was inferred.The current responses were linear with NACs ranging from 10^-9mol/L to 10^-7mol/L with low detection limits.It is a sensitive,rapid and easy-to-use method for the fast determination of NACs.