Electrochemical study and characterization of novel microelectrode materials.

摘要

Microelectrodes have received much attention over the past decade. This dissertation addresses the fabrication, behavior and analytical utility of new novel microelectrode materials. Microelectrodes and micro-composite electrodes were constructed from various carbonaceous substrates. The dimensions of the active carbon segments are determined using both physical means and by comparing the response to established theory. The electrochemical response was also studied to see if the advantages of microelectrodes are obtained. These advantages are a result of enhanced mass transport and a decrease in the potential losses and the double-layer capacitance. Once the behavior of the electrode is determined, the ability to apply the new sensor is addressed.; Chapter 2 reports on the preparation and electroanalytical utility of microelectrodes constructed using a new, unique form of carbon based on carbonized poly(acrylonitrile) (PAN). A composite electrode produced by impregnating a micro-porous foam is shown to possess the behavior of a microelectrode ensemble. PAN has also been used as a precursor for the production of micro-thin films. The PAN film is sandwiched between two insulating supports and results in a band configuration. These PAN electrodes exhibit electrochemical behavior characteristic of microelectrodes. Cyclic voltammetry, chronoamperometry and/or flow-amperometry are utilized to determine the electrode behavior. Due to the negligible ohmic losses, undistorted voltammograms are obtained in non-aqueous and highly resistive solutions. The use of the PAN composite electrode as a substrate for a mercury film in the anodic stripping analysis of trace metals (Cd, Pb and Cu) is demonstrated.; The modification of microelectrodes is addressed in chapter 3. The ease of fabrication of the carbon paste electrode is exploited in the construction of a micro-band and a micro-disk electrode. The behavior of the band electrode is observed using an unmodified matrix, as well as with a paste modified with cobalt phthalocyanine (CoPC: redox mediator) and poly(vinyl pyridine) (PVP: ion-exchange polymer). The micro-disk electrode is modified with tissue containing polyphenol oxidase to produce a bioelectrode that is selective for dopamine. The electrode is shown to give a response for dopamine, even in the presence of other neurologically important compounds.; In chapter 4, the effect of surface characteristics on the electrode response is studied. The effect on the electrode surface from the application of a short electrochemical pretreatment are examined, as well as changes in the behavior of electrode substrates obtained from different sources. The surface morphology is responsible for the catalysis of electron transfer and the protection from surface fouling.