The Application Of The Pre-anodized Carbon Paste Electrode And Bismuth Film/Nichrome Electrode

Modification on the suface of electrodes had an enormous effect on the electrochemical reactions,becauses the traditional bare electrodes were already far from satisfying the needs of the researchers.Electrode modified materials had been developed since1970s. Ion, molecular and polymer modificationswere found to change the structure of substrate electrode surface, which allowed the modified electrodesfunction as rationally designed or accelerate the electrode reaction to improve the sensitivity.In this thesis, carbon paste electrode was adopted as a substrate to fabricate pre-anodized carbon pasteelectrode, nichrome was adopted to construct bismuth film electrode, and the applications of the abovedtwo modifed electrodes were presented.PartⅠ: Pre-anodized carbon paste electrodeA pre-anodized carbon paste electrode （PACPE） was prepared by running successive cyclicvoltammetry.The scanning electron microscope images of PACPE and carbon paste electrode revealed thatthe apparent electroactive surface area of the electrode was effectively increased. Variousoxygen-containing functional groups （-COOH,-OH,-O-） were generated on the surface of the electrode inthe pre-anodization, which can form strong hydrogen-bonding interaction with different substances. Hence,the PACPE exhibited an excellent electrocatalytic activity.1. The simultaneous determination of acetaminophen and dopamine at pre-anodized carbon paste electrodeThe functional PACPE exhibited a high electrocatalytic activity toward for the electrochemicalbehaviors of acetaminophen （APA） and dopamine （DA）. The peak difference of196mV allowedsimultaneous detecting of APA and DA in their mixture solution. The peak current of APA gave linearresponse in the range of2.0×10-6-5.0×10^-4mol/L in the presence of20μmol/L DA, and the detection limitwas0.42μmol/L. The peak current of DA gave linear response over the ranges2.0×10-6-5.0×10^-4mol/Lwhile the concentration of APA was kept constant as15μmol/L, and the detection limit was0.21μmol/L.The proposed method was successfully applied to the determination of APA and DA in commercialpharmaceutical samples.2. The electrochemical determination and the diffusion mechanism of aminophenol isomers at a pre-anodized carbon paste electrodeA PACPE has been fabricated and was used to investigate the electrochemical behaviors ofaminophenol isomers. The oxidation peak currents of aminophenols not only related to the concentration ofthe diffusion to the working electrode surface, but also depended on the reaction of oxygen dissolved in thesolution that happened on the auxiliary electrode.Compared with the bare carbon paste electrode （CPE）, theoxidation peak currents of of p-, o-, m-aminophenol at PACPE increased remarkably in pH=8.44BR buffersolution. The semi-derivative oxidation peak current was proportional to the concentration of p-, o-, m-aminophenol over the ranges of2.5×10^-7-1.0×10^-4mol/L,2.5×10^-7-2.5×10^-5mol/L, and2.5×10^-7-1.25×10^-4mol/L, and the detection limits were3.5×10^-7mol/L,5.8×10^-8mol/L,3.1×10^-7mol/L, respectively.3. The simultaneous determination of5-hydroxytryptophan and tryptophan at pre-anodized carbon pasteelectrodeA PACPE was fabricated and used to investigate the electrochemical behaviors of5-hydroxytryptophan（5-Htp） and tryptophan （Trp） by cyclic vohammetry. The results indicated that the voltammetric responsesof5-Htp and Trp were considerably enhanced at PACPE compared to the bare CPE in pH=4.0Na2HPO4-citric acid buffer solution. Under the optimized conditions in linear scan voltammetry technique,5-Htpand Trp gave linear response over a certain concentration range, the detection limits were found to be1.16×10^-8mol/L for5-Htp and1.54×10^-8mol/L for Trp.Part Ⅱ: Bismuth film/nichrome electrode1. Application of bismuth film/nichrome electrode for electrocatalytic reduction of4-nitrophenolIn this paper, the nichrome was adopted as a substrate to fabricate the bismuth film/nichrome electrode（BNCE）, the BNCE was used as the working electrode to investigate the reduction behavior of4-nitrophenol. The results revealed that the reduction peak currents of4-nitrophenol not only related to theconcentration of the diffusion to the working electrode surface, but also depended on the oxidation reactionof H2O that happened on the auxiliary electrode.The BNCE exhibited a sensitive electrochemical responseto4-nitrophenol, the peak current was proportional to the concentration of4-nitrophenol in the ranges of5.0×10^-8-7.0×10^-7mol/L and1.0×10^-6-3.0×10^-5mol/L. The detection limit of this method was5.97×10^-9 mol/L（S/N=11）. It was successfully applied to determine4-nitrophenol in lake water sample, withrecoveries ranging from97.5%to102.1%.