Modification of graphite

Fig. 1. The hexagonal modification of graphite. Typically, o = 2.46 and co = 6.7 A, so that the spacing between adjacent, carbon planes is 3.35 A.

Modification of Graphite-type materials by the Co-Ni complex pyrolyzed at 500°C improves significantly the performance of these material in the anode of Li battery. The inner mechanism of this effect is still unclear. We suggest the formation of nanosized spinel structures which facilitate the charge transfer across SEI. 

Yoon, S., Kim, H., and Oh S. M., Surface modification of graphite by coke coating for reduction of initial irreversible capacity in lithium secondary batteries, J. Power Sources (2001), 94, 68-73. 

A new class of conjugated hydrocarbons is that of the fullerenes [11], which represent an allotropic modification of graphite. Their electrochemistry has been studied in great detail during the last decade [126]. The basic entity within this series is the Ceo molecule (23). Because of its high electron affinity, it can be reduced up to its hexaanion (Fig. 4) [14,127]. Solid-state measurements indicate that the radical anion of Ceo reversibly dimerizes. NMR measurements confirm a u-bond formation between two radical anion moieties [128,129]. 

Stability of Prussian blue modified screen-printed electrodes The operational stability of all the PB-modified sensors is a critical point, especially at neutral and alkaline pH. A possible explanation for reduced stability could be the presence of hydroxyl ions at the electrode surface as a product of the H202 reduction. Hydroxyl ions are known to be able to break the Fe-CN-Fe bond, hence solubilising the PB [21]. An increased stability of PB at alkaline pH was first observed by our group after adopting a chemical deposition method for the modification of graphite particles with PB for the assembling of carbon paste electrodes [48]. 

Carbon exists in two allotropic forms graphite and diamond. Under norma conditions graphite is the thermodynamically more stable form. Two modifications of graphite are known a hexagonal and a rhombohedral form. 

For carbide modification of graphite tubes (for a recent review see Refs. [183, 184], use is made of physical and chemical vapor deposition with metals such as Ta, W, Zr, etc., which leads to the formation of MC-coated graphite tubes or platforms. A solid layer of tantalum or niobium carbide can also be obtained as a result of treatment of the graphite furnace with large quantities of pure salts or a suspension of the element or its oxide in water however, this can lead to tubes with shorter lifetimes. Alternatively, the surface may be treated with aqueous [e.g. of Na2WC>4, (NH CriCb or ZrOCh] or alcoholic solutions of the salts of the elements mentioned. 

Barriere, R, and Downard, A.J. 2008. Covalent modification of graphitic carbon substrates by non-electrochemical methods. Journal of Solid State Electrochemistry 12, 1231-1244. 

Diamond has a higher density than graphite (Pgraphite = 2.25 diamond = 3.51 gcm ), and this allows artificial diamonds to be made from graphite at high pressures (see Box 14.5). There are two structural modifications of graphite. 

Graphite shows a sharp diffraction peak at 26°, and the corresponding interlayer distance is 3.36 A, which reveals the crystalline nature of graphite. Modification of graphite to graphite oxide occurs mainly due to intercalation of some oxide functional groups. The XRD peak of graphite oxide appears at... 

Most assays for thallium in blood require hemolysis by detergent, followed by chelation with a dithiocarbamate, and extraction into MIBK [34]. The organic extract is then also assayed by either flameless AAS or DPASV. Typically, 5 mL of heparinized blood is mixed with 1 mL of 2% DDC and Triton X-100, followed by extraction with 2-5 mL of MIBK [16,21,95]. Recent modification of graphite furnace AAS methods allows for detection limits in whole blood or plasma as low as 1.0 and 0.7 p,g/liter, respectively [44], Determination of thallium in tissue requires digestion by acid before treatment. Typically 5 g of wet tissue is digested with 10 mL of a 3 1 1 mixture of nitric/perchloric/sulfuric acids [21]. 

To increase lateral resolution in CFM, Lieber and coworkers [78-80] have utilized carbon nanotubes (CNs) as an AFM tip for CFM. The tip end of CNs can be functionahzed by using a chemical modification of graphite [21]. 

Sun B, SkyUas-Kazacos M. Modification of graphite electrode materials for vanadium redox flow battery apphcation i. Thermal treatment. Electrochim Acta 1992 37 1253-60. 

R.G.M. Moreno, E. de Oliveira, J.J. Pedrotti, and P.V. Oliveira. An electrochemical flow-cell for permanent modification of graphite tube with palladium for mercury determination by electrothermal atomic absorption spectrometry. Spectrochimica Acta Part B 57 769-778, 2002. 

The formation of highly reactive intermediates from the photolysis of aromatic azides favor their use for surface modification and the preparation of substrates for solid phase reactions. Thus, azide photochemistry has been exploited for facile modification of graphitic surfaces and N-5-azidonitrobenzoyloysuccinimide undergoes photoaddition in a solid state reaction. A review on the covalent functionalization of graphene includes examples via photogenerated nitrenes. ... 

For carbide modification of graphite tubes (for a recent review see Refs. [216, 217]), use is made of physical and chemical vapor deposition with metals such as... 

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