Boron-doped diamond electrodes electrical conductivity

Boron-doped diamond is electrically conducting and has found applications as electrode material in waste-water treatment, ozone generation, electroanalysis, and trace metal detection [ii]. Due to their exceptional chemical inertness and mechanical strength, diamond electrodes have been proposed for applications in extremely aggressive media such as strong acids or plasmas. See also -> carbon electrodes. 

A composite biomaterial formed by Pd metal, carbon-ceramic mixture and oxidoreductase enz3ones constitutes a new t3rpe of renewable smface biosensor with a controllable size reaction layer [198]. The carbon provides the electrical conductivity, the enzymes are used for biocatalyst process, metallic palladimn is used for electrocatalysis of biochemical reaction product and the porous silica provides a rigid skeleton. The hydrophobicity of this composite material allows only a limited section of the electrode to be wetted by the aqueous analyte, thus providing a controlled thickness reactive layer. Another biocomposite material containing enzyme-modifled boron-doped diamond was used in the development of biosensors for the determination of phenol derivatives [199], alcohol [200] and glucose [201]. 

Boron incorporated during a chemical vapor deposition (CVD) process is now proving to be the most popular means of imparting electrical conductivity on the diamond lattice for use in electrochemistry, both from a research perspective and commercially, for reasons that will be discussed later. There have been many reviews since 1983, both in journals [2-9] and books [10] on the use of diamonds in electrochemistry. This chapter aims to review the field and provide a comprehensive discussion on the current understanding of the fundamental factors controlling the response of boron-doped diamond (BDD) electrodes. Latest developments (as of 2014) are also highlighted. 

Conductive sp -bonded diamond is being developed as an advanced catalyst support material. Boron-doped diamond thin-film electrodes possess excellent properties for this application, such as electrical conductivity, chemical inertness, extreme corrosion resistance, and dimensional stability. Compared with more commonly used sp -bonded carbon materials, diamond is highly resistant to electrochemical corrosion. For exam-... 

Batch experiments were conducted in a stirred, 20 mL, sealed, glass cell containing ei er ethanol or aqueous solutions. Sodium chloride was added to each solvent to provide electrical conductivity, and sodium hydroxide was added to die aqueous solutions in order to increase the solubility of triclosan. The pK, value for triclosan is 7.9 (10), and all experiments in aqueous solutions were conducted at a constant pH value of 12. The working electrode was a boron doped diamond (BDD) film on a silicon substrate (CSEM, Neuchitel, Switzerland) with a nominal sur ce area of 1 cm. A stainless steel wire encased in a Nafion (DuPont) sheath was used as the coimter electrode, and die reference electrode was Hg/Hg2S04 (EG G, Oak Ridge, TN). 

To solve the problem, we considered that a boron-doped diamond, BDD, is the most ideal anode for electrochemical fluorination and so we focused on a BDD electrode. The BDD film is prepared on a carbon substrate by hot-filament chemical vapor deposition with doping boron into the diamond lattice, adding trimethylboran gas to a mixed gas of methane and hydrogen. Since a BDD film has a high electric conductivity and stability of structure such as diamond, it is expected that a BDD electrode can be used as a new anode material in this... 

Still the electrochemical behavior of diamond electrodes is influenced by more parameters than the surface termination alone. Most of all it is a doping of the diamond phase that provides the required electric conductivity. Usually boron-doped electrodes are employed. In this case, the electric conductivity increases with the content of boron-the resulting properties range from an isolator at low... 

There are several challenges associated with the synthesis of BDD suitable for electrochemistry. Since diamond is a semiconductor with exceptional properties, precise control of dopant impurities and extended defects is required to dope the diamond lattice with sufficient boron to make the material conduct. However, as the boron levels increase, it can be harder to maintain crystallinity and control the amount of nondiamond carbon (NDC) both within crystal defects and at grain boundaries. While NDC can increase material conductivity, it is be detrimental to a diamond electrochemist, as the widely recognized electrochemical properties of BDD (wide solvent window, low background currents, reduced susceptibility to electrode fouling, corrosion resistance) are impaired and the electrochemical response becomes more akin to glassy carbon. If the presence of NDC is unaccounted for, electrical resistivity measurements will mislead the user into believing that there is more boron than actually present in the matrix. 

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