engleski

Application of Carbon Fiber Microelectrodes in Electrochemical Investigations

In electroanalysis, the performance of the electrode with respect to speed and spatial resolution scales is inversely proportional to the electrode radius. During the past few decades, intensive research has resulted in electrodes of radii down to 1 mikro m and 1 nm. With a decrease in radius, elemental detection level has been brought down to parts per billion (ppb) levels. At the present time the diameter of carbon nanotubes is about 100 nm. With these nanoelectrodes, the smallest of sensors can be made, for example, for in situ monitoring of chemical reactions inside tissue as well as potential on cell membranes. In this work, electrocrystallization of nickel from Ni^2+ - acidic bath was investigated using an assembly of carbon microelectrodes, which consisted of single and multi microdiscs randomly distributed inside the matrix of a non-conducting polymer. The microdiscs were so far apart that the crystals could not interact in any way. This limited the total observed current density to a linear superposition of the current densities from each crystal considered independently. The number of crystals as a function of time, N(t) from the total current density as a function of time, I_N(t) during electrochemical nucleation and growth have been determined. By combining random assemblies of microelectrodes and the Bootstrap algorithm (based on mathematical methods of harmonic and numerical analyses), it was possible to avoid diffusional interaction and obtain plots of the number of crystals versus time as direct output from the current-time transients (chronoamperometric measurements). In addition, a high rate of nucleation after a rapid increase in the overpotential was discussed on the basis of the physical model for three-dimensional (3D) nucleation with diffusion controlled growth. An excellent agreement between the simulated results and the theoretical curve for the 3D progressive nucleation was obtained.

carbon nanotubes; microelectrodes; nucleation (crystallization); nickel;

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