Carbon Fiber Ultramicroelectrodes Research Articles

Determination of nickel accumulation in single biological cells using porphyrinic microsensors

Carbon fiber ultramicroelectrodes modified with a conductive polymeric film of tetrakis(3-methoxy-4-hydroxyphenyl)nickel porphyrin (< 1–3 μm diameter) were used for monitoring the concentration of unbound nickel in individual BC3H-1 myocytes and H4-11-C3 rat hepatoma cells. Detection limits of 8×10 −6 M and 1×10 −6 M, respectively, were obtained. A method is described for fabricating sensors with the length and area of the electroactive surface appropriate for the dimensions of the cells under investigation. The method consists in carefully burning a fiber coated with wax in a controlled temperature gradient obtained with a microburner to sharpen the tip. The length and shape of the electroactive area obtained are controlled by the thickness of the wax coating, which is determined by the temperature of the melted wax. The sharpened tip of the 0.5–1-μm fiber was covered electrochemically with 10–90 monolayers of polymeric porphyrin, demetalated, implanted and used for nickel(II) accumulations and current determinations.

Flow cell based on glucose oxidase‐modified carbon fiber ultramicroelectrode

AbstractGlucose oxidase‐modified carbon fiber electrodes have been prepared by electrochemical deposition of the enzyme in the presence of a platinum complex. The electrode is incorporated as an electrochemical detector in a flow system, exhibiting a very rapid response to dynamic changes in the glucose concentration. The fast response is attributed to the intimate contact of the biocatalytic and sensing sites. Simultaneous lowering of the overvoltage for hydrogen peroxide oxidation is observed. Various response characteristics are evaluated. The relative standard deviation for 40 repetitive injections over a 60‐min period is 3%. The electrodes remain active over a 20‐day period, are inexpensive and easy to prepare, and hold a great promise as in vivo or disposable glucose probes.

An Electrochemical Fabrication Method for Gold and Carbon Ultramicroelectrode

Abstract Au and carbon fiber ultramicroelectrodes have been fabricated by using an anodic electropolishing method. The radii of them were found to be about 450 nm on Au and 240 nm on carbon electrodes from the calculation based on the steady-state limiting currents.

Bevelled carbon-fiber ultramicroelectrodes

A technique for polishing the surface of carbon-fiber ultramicroelectrodes to a bevelled tip is described which simplifies electrode preparation. The bevelled surface has an active area that is more than twice that of a disk electrode fabricated from the same material. This results in larger faradaic currents. It is found that the chronoamperometric current at these electrodes is equal to that calculated for a disk of equivalent area to the elliptical area of the electrode. While the area is increased, the residual current is not, and thus quantitative applications of these electrodes as in vivo probes as facilitated. Furthermore, the bevelled tip results in an electrode that minimizes tissue damage during insertion into brain tissues.