Oxygen group preparation

Among the surface-modified CNTs materials, a bulk-modified CNT paste (CNTP) has also been reported [126]. The new composite electrode combined the ability of CNTs to promote adsorption and electron-transfer reactions with the attractive properties of the composite materials. The CNTP was prepared by mixing MWCNTs powder (diameter 20-50 nm, length 1-5 jim) and mineral oil in a 60 30 ratio. The oxidation pretreatment [performed in ABS (pH 5.0) for 20 s at 1.30 V, vs Ag/AgCl] proved to be critical in the state of the CNTP surface. Pretreatments improved the adsorption and electrooxidation of both DNA and DNA bases, probably due to the increase in the density of oxygenated groups. 

Amorphous carbons, carbon black, soot, charcoals, and so on, are forms of graphite or fullerenes. The physical properties depend on the nature and magnitude of the surface area. They show electrical conductivity, have high chemical reactivity due to oxygenated groups on the surface, and readily intercalate other molecules (see later). Graphite and amorphous carbons as supports for Pd, Pt, and other metals are widely used in catalysis and for the preparation of diamond films.18... 

However, it has to be taken into account that some oxygen groups may not be stable under the heat-treatment conditions (i.e., reduction) to which the catalysts are subjected during the preparation stage to obtain the active phase. If they are acting as anchoring centers for the active phase or for the precursor, their decomposition could lead to sintering of the metal species and a loss of dispersion [20]. 

Several other methods have been employed for the preparation of carbon-supported catalysts, although to a lesser extent that impregnation methods. Nakamura et al. [38] prepared molybdenum catalysts for ethene homologation by physical deposition of gaseous [Mo(CO)6]. Their supports were commercial activated carbons that were subjected to different treatments to modify then-surface. The authors compared these supports with oxidic supports and concluded that the interaction between the metal carbonyl and the carbon supports were weaker. Furthermore, they observed that oxidation of the carbon surface was effective in enhancing the catalytic activity of Mo/C, and they ascribed this effect to the contribution of the surface oxygen groups to the partial oxidation of decomposed [Mo(CO)6]. 

Since it is symmetrical, having identical alkyl groups, preparation by dehydration of an alcohol is efficient. Also, since the compound contains two oxygens, a compound with two hydroxyl groups as the main functional groups, a diol, must have been used. The dihydroxy compound having two carbons is called ethylene glycol, HO-CHaCHa-OH. The reaction is shown below. 

The adsorption of molecular probes, followed by infrared or NMR spectroscopy and thermal desorption studies, is the most commonly adopted way to study basic sites. Carbon dioxide is frequently used in infrared studies, particularly of cationic zeolites with added alkali metals.Chloroform is also suitable, since the interaction with the chlorine atom and subsequently the C-Cl stretching frequency is a measure of the basic strength. NMR studies of basic zeolites have concentrated on the use of C containing probes such as methyl iodide and chloroform. Addition of methyl iodide results in its decomposition and the formation of methoxy groups at framework oxygens. The shift of the methyl carbon is expected to be related to the basicity of the framework, that is the tendency of the framework oxygens to donate electrons - C MAS NMR of methoxy groups prepared in this way shows a clear distinction between basic zeolites, such as Cs-X, and acidic zeolites, such as H-ZSM-5. 

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