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ABSTRACT: Boron-doped polycrystalline diamond electrodes have been used extensively in the field of electroanalysis. The development of knowledge about the mechanism of diamond film deposition, boron doping, and charge transfer reactions rendered the quality of analytical information. New aspects regarding the design of diamond-based electrodes, and mechanisms of redox reactions at their surface are briefly discussed. Recent applications of the diamond-based sensor in inorganic and organic analysis are presented.
Key Words: diamond, polycrystalline, boron, electrochemical sensors.
1. INTRODUCTION
Almost all electrochemical studies to date are performed with diamond films prepared by chemical vapor deposition (CVD). Synthetic films often posses a polycrystalline and textured microstructure, with a small volume fraction of non-diamond impurity.1 The applications for synthetic diamonds, primarily in the area of active electronic components, did not realize to a great extent because of the poor structural quality (i.e., the polycrystalline nature) of most CVD grown films.
Some of the inherent "electrochemically" desirable properties of diamond are hardness, high thermal conductivity, corrosion resistance, chemical inertness, variable conductivity via doping, and electrode geometry patterning using selective growth methods. The resistivity of polycrystalline diamond thin films made by chemical vapor deposition (CVD) can be decreased by doping with boron.2 The resulting films can posses either p-type semiconducting or semimetal electronic properties, depending on the doping level. Resistivity as low as 0.01Omega-- cm has been reported for boron-doped films, rendering them conductive enough for electrochemical studies.
The electrochemical behavior of diamond electrodes in H^sub 2^O^sub 2^solution was reported.3 The accuracy of the analytical information assured by using boron-doped polycrystalline diamond film electrodes rendered the technique to be used successfully in electroanalysis and electrochemical sensors. The response current is proportional to the square root of the scan rate, reflecting the mass transport controlled by planar diffusion. Excellent stability and reproducibility are attractive properties of the diamond electrode even for the later application.
Boron-doped diamond exhibits (BDD) several superior electrochemical properties that are significantly different from those of other carbon allotropes, for example, glassy carbon (GC), pyrolytic graphite (PG), and highly oriented pyrolytic graphite (HOPG), which have been widely used as electrode materials for many years. Its attractive features include a wide electrochemical potential window in aqueous media, very low capacitance, and extreme electrochemical stability. BDD electrodes appear...