Oxidation diamond film

Figure 6.36 Reflection IR-spectra of adamantanone (bottom) and of an oxidized diamond film (top) ( ACS 2003).

After having achieved the basic functionalization of a diamond film it is possible to attach much more complex structures. Hydrogenated, halogenated, aminated and oxidized diamond films are aU suitable for these reactions that will be illustrated by some typical examples in the following. 

Bouvrette P, Hrapovic S, Male KB et al (2006) Analysis of the 16 Environmental Protection Agency priority polycyclic aromatic hydrocarbons by high performance liquid chromatography-oxidized diamond film electrodes. J Chromatogr A 1103 248-256... 

Set the diamond film in a single-compartment electrochemical cell, and carry out the anodic oxidation treatment by passing a charge of ca. 720mC cm-2 at an applied potential of+2.64V vs. SCE for 4 min, in pH 2 Britton-Robinson buffer. 

In Section 2 we showed that the properties of amorphous carbon vary over a wide range. Graphite-like thin films are similar to thoroughly studied carbonaceous materials (glassy carbon and alike) in their electrode behavior. Redox reactions proceed in a quasi-reversible mode on these films [75], On the contrary, no oxidation or reduction current peaks were observed on diamondlike carbon electrodes in Ce3+/ 41, Fe(CN)63 4. and quinone/hydroquinone redox systems the measured current did not exceed the background current (see below, Section 6.5). We conventionally took the rather wide-gap DLC as a model material of the intercrystallite boundaries in the polycrystalline diamond. Note that the intercrystallite boundaries cannot consist of the conducting graphite-like carbon because undoped polycrystalline diamond films possess excellent dielectric characteristics. 

Lead and mercury are deposited as micron-sized clusters, predominantly at intercrystallite boundaries [105] so does lithium from the polyethylene oxide solid electrolyte. What is more, Li intercalates into the sp2-carbon [22, 138], Thus, observations on the Li intercalation and deintercalation enable one to detect non-diamond carbon on the diamond film surface. Copper is difficult to plate on diamond [139], There is indirect evidence that Cu electrodeposition, whose early stages proceed as underpotential deposition, also involves the intercrystallite boundaries [140], We note that diamond electrodes seem to be an appropriate tool for use in the well-known electroanalytical method of detection of traces of metal ions in solutions by their cathodic accumulation followed by anodic stripping. The same holds for anodic deposition, e.g. of, Pb as PbCh with subsequent cathodic reduction [141, 142], Figure 30 shows the voltammograms of anodic dissolution of Cd and Pb cathodically predeposited from their salt mixtures on diamond and glassy carbon electrodes. We see that the dissolution peaks are clearly resolved. The detection limit for Zn, Cd, and Pb is as low as a few ppb [143]. 

Diamond film electrode has an inert character with weak adsorption properties (Martin et al. 1996 Swain et al. 1998 Pleskov 1999). Weak interactions of D ( OH) lead to low anode activity toward oxygen gas evolution [Reaction (3.3)] and high oxidation reactivity to the organic pollutants incineration [Reaction (3.2)]. Due to the high oxidizing power of the radicals, highly persistent pollutants, which cannot be decomposed with bioremediation method, advanced oxidation process, or even electrooxidation process with other kinds of electrodes, can be successfully degraded with the diamond film electrode. 

Furthermore, it has been proved that direct oxidation can happen on the diamond film electrode before the oxygen gas evolution potential (Zhi et al. 2003). Direct oxidation takes place, accompanying with the adsorption of chemical molecules on the diamond electrode surface. An as-grown diamond film with high hydrogen coverage is inert to adsorption of polar molecules (Vinokur, Miller et al. 1996 Yano... 

Ti, Ta, Zr, and Nb are preferred, because of their ability of forming stable compact oxides film during anodic polarization. Compared with other metals, titanium has the lowest density, easy machinability, high anticorrosion and quick repassivation electrochemical performance, and relatively low cost (Leyens and Peters 2003). It becomes a preferred choice as the substrate material of diamond film electrode (Drory and Hutchinson 1994 Chen andLin 1995 Chen et al. 2003 Hian et al. 2003 Gerger et al. 2004 Chen et al. 2005 Guo and Chen 2007a). 

Single pulse, shock tube decomposition of acetic acid in argon inv olves the same pair of homogeneous, molecular first-order reactions as thermolysis (19). Platinum on grapliite catalyzes the decomposition at 500—800 K at low pressures (20). Ketene, methane, carbon oxides, and a variety of minor products are obtained. Photochemical decomposition yields methane and carbon dioxide and a number of free radicals, wliich have complicated pathways (21). Electron impact and gamma rays appear to generate these same products (22). Electron cyclotron resonance plasma made from acetic acid deposits a diamond [7782-40-3] film on suitable surfaces (23). The film, having a polycrystalline stmcture, is a useful electrical insulator (24) and widespread industrial exploitation of diamond films appears to be on the horizon (25). 

Bormett RW, Asher SA, Witowski RE, Partlow WD, Lizewski R, Pettit F (1995) Ultraviolet Raman spectroscopy characterizes chemical vapor deposition diamond film growth and oxidation. J Appl Phys 77 5916... 

The attrition of a diamond film is promoted by a high portion of sp -material. The grain boundaries in UNCD represent predetermined breaking points and facilitate fracture of the film. The comparatively low elasticity of diamond contributes to its friability as well. Furthermore, sp -carbon atoms are more easily oxidized at contact with air, leading to material losses of the film which thus might become porous upon strong wear. 

In addition to the statistical nature of the interface instabilities active in diamond CVD, the orientation effect and anisotropic growth of crystals (i.e., evolutionary selection) play an important role in the observed instability phenomenon. Surface chemical reactions that occur preferentially between the growing diamond surface and oxidizing species in the combustion synthesis ambient also influence the development of the microstructure and morphology of crystals in diamond films. For example, in combustion CVD,... 

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