Boron doping reaction

W. Han, Y. Bando, K. Kurashima, T. Sato, Boron-doped carbon nanotubes prepared through a substitution reaction, Chem. Phys. Lett., vol. 299, pp. 368-373,1999. 

In this case, the above process is called EC mechanism. Examples of this reaction scheme are the reduction of Ti(IV) in the presence of Hydroxylamine, the reduction of Fe3+ in the presence of H2O2 (Fenton reaction) [2, 4, 6], or the mediated reduction of oxygen via the reduced form of methyl viologen at a boron doped diamond electrode [54]. 

This basic system was designed to deposit Si02 from the SiH4 + 02 reaction at about 400°C and atmospheric pressure. It can also deposit doped oxides by introducing PH3 for phosphorus doping or B2H6 for boron doping. In order to protect personnel from these toxic dopants, the reactor is housed in a vented enclosure. 

Recently, Colley et al. [104] studied the distribution of electrochemical activity in microarray electrodes. The array contained 50-pm diameter boron-doped regions spaced 250 pm apart in an intrinsic diamond disk. Reaction rate imaging was done in the substrate generation/tip collection mode. The electroactive boron doped regions were biased at a suitable potential to reduce the mediator, [Ru(NH3)6]3+, and the product of the reduction reaction was collected at the tip. Two-dimensional scans over different regions (Fig. 21) revealed wide variations in local electroactivity. 

Abstract Boron-doped diamond (BDD) electrodes provide an unusually wide electrochemical window in protic media, since there exist large offset potentials for the evolution of molecular hydrogen and oxygen, respectively. At the anode, alcohols are specifically converted to alkoxyl radicals. These can be used for chemical synthesis. When the enormous reactivity of such intermediate spin centers is not controlled, mineralization or electrochemical incineration dominates. Efficient strategies include either high substrate concentrations or fluorinated alcohols which seem to stabilize the spin centers in the course of reaction. 

Kirste A, Nieger M, Malkowsky IM, Stecker F, Fischer A, Waldvogel SR (2009) ortho-Selective phenol-coupling reaction by anodic treatment on boron-doped diamond electrode using fluorinated alcohols. Chem-Eur J 15 2273-2277... 

Flonda K, Yamaguchi Y, Yamanaka Y, Yoshimatsu M, Fukuda Y, Fujishima A (2005) Flydroxyl radical-related electrogenerated chemiluminescence reaction for a ruthenium tris (2, 2 )bipyridyl/co-reactants system at boron-doped diamond electrodes. Electrochim Acta 51 588-597... 

Malkowsky IM, Griesbach U, Putter H, Waldvogel SR (2006) Unexpected highly chemse-lective anodic ortho-coupling reaction of 2,4-dimethylphenol on boron-doped diamond electrodes. Eur J Org Chem 4569 1572... 

Marselli B. Electrochemical oxygen transfer reaction on synthetic boron-doped-diamond thin film electrode, PhD thesis no. 3057, EPFL (Ecole Polytechnique Federale de Lausanne) (2004). 

In principle, oxidation could occur simultaneously during a HDH (reduction) reaction. For example any de-halogenated compounds could be oxidised to C02 in the anode compartment. Thus in the case of pentachlorophenol the phenol produced by the HDH could be oxidised at a suitable anode (e.g. boron-doped diamond) to C02 ... 

Diamond doped with boron is conductive, and hence can serve as a highly inert and robust electrode material. Indeed, there are many reports on the study of electrochemical reactions with -> boron-doped diamond 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]. 

Figure 4. FT-ICR mass spectra showing evidence for the production of boron and boron/potassium doped 60-ati n fuiloenes. The bottom panel shows the result of reaction with ammonia. Note that the boron-doped clusters have been titrated with ammonia, demonstrating that the boron is substituting for a carbon as part of the fullerene cage. Note also that the clusters in the top panel marked K(K C4o) and K2(K C o) are missing after reaction with ammonia in the bottom panel, demonstrating that the extra potassium atoms were on the outside, unprotected by the fullerene cage.

Boron-doped diamond (BDD) thin films were synthesized at CSEM (Neuchatel, Switzerland) by the hot filament chemical vapor deposition technique (HF CVD) on p-type, low-resistivity (l-3mQcm), single-crystal, silicon wafers (Siltronix). The temperature of the filament was between 2440 and 2560 °C and that of the substrate was monitored at 830 °C. The reactive gas was a mixture of 1% methane in hydrogen, containing trimethylboron as a boron source (1-3 ppm, with respect to H2). The reaction chamber was supplied with the gas mixture at a flow rate of 51 min giving a growth rate of 0.24 pm h for the diamond layer. The obtained diamond film has a thickness of about 1 pm ( 10%) and a resistivity of 15mQcm ( 30%). This HF CVD process produces columnar, random textured, polycrystalline films [9]. 

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