Coating of CNTs

Abrasive Adhesion (or Drop-Coating) of CNTs Preceding MPc Coating... 

Carbon nanotubes have been successfully used as removable templates for the synthesis of a variety of oxide nanotubes. Ajayan et al.9 reported the preparation of V205 nanotubes by using partially oxidized carbon nanotubes as templates. Apart from coating of CNTs by the oxide phase, metal oxide fillings in the internal cavities and thin oxide layers between the concentric shells of the tubes were also obtained (Fig. 30). A mix-... 

Finally, an approach which is based on plasma polymerisation treatment enables the coating of CNTs with a very thin ( 3 nm) polymer layer. Polymer... 

Many polymers have been successfully used for the coating of CNTs via these approaches and in general, presynthesized polymers react with the surface of pristine or oxidized CNTs [7-8]. Modification of CNTs with polymers not only improves dispersion properties of CNTs but also provide the combination... 

Recently, Kevlar-functionalized nanotubes were prepared by heating Kevlar with MWNTs in the presence of sulfuric and nitric acids under reflux. This resulted in the partial oxidation and functionalization of CNTs with carboxylic acid groups, which formed hydrogen bonds with amido-groups, as well as terminal carboxylic acid and amino groups in Kevlar. This process produced Kevlar-coated CNTs, which have been utilized for the fabrication of MWNT-polyvinylchloride (PVC) composites. Plasma polymerization treatment enables the coating of CNTs with a very thin (3 nm) polymer layer. Polymer composites based on these coated nanotubes enhanced interfacial bonding in a PS polymer matrix [22, 91]. 

CNT-coated electrodes can be constructed easily as long as stable CNT suspensions are obtained. However, one needs to choose a suitable surfactant dispersant for the fabrication of CNT/surfactant-modihed electrodes with high catalytic and good selectivity toward the analytes. 

It has been demonstrated that the presence of CNTs greatly increases the oxidation peak current of 6-benzylaminopurine. The CNT-modified electrode is suitable for the determination of trace amounts of benzylaminopurine and has the advantages of high sensitivity, quick response, and good stability [86], Wang et al. have studied the electro-catalytic oxidation of thymine at a a-cyclodextrin incorporated CNT coated electrode in an alkaline media. A sensitive detection scheme for thymine has been further developed by using differential pulse voltammetry [87], The electrochemical determination... 

An alternative efficient approach to disperse CNTs relies on the use of synthetic peptides. Peptides were designed to coat and solubilise the CNTs by exploiting a noncovalent interaction between the hydrophobic face of amphiphilic helical peptides and the graphitic surface of CNTs (Dieckmann et al., 2003 Zoibas et al., 2004 Dalton et al., 2004 Arnold et al., 2005). Peptides showed also selective affinity for CNTs and therefore may provide them with specifically labelled chemical handles (Wang et al., 2003). Other biomolecules, such as Gum Arabic (GA) (Bandyopadhyaya et al., 2002), salmon sperm DNA, chondroitin sulphate sodium salt and chitosan (Zhang et al., 2004 Moulton et al., 2005), were selected as surfactants to disperse CNTs (Scheme 2.1). 

The effects of size surface area, shape, purity method of synthesis, charge, surface coating, functionalized groups, and aggregation need to be carefully considered when assessing potential risks of CNT toxicity. Toxicology studies on CNTs should be accompanied by improved control in manufacturing and improved analysis before CNTs can be successfully used for pharmaceutical applications. 

Fig. 3.20 (a) Schematic representation of noncovalent attachment (i.e., n-stacking) of benzyl alcohol molecules for subsequent coordination with Titanium resulting in the coating of the tube, (b) SEM image of pristine CNTs prior to derivatization. (c) SEM image of CNTs after derivatization with benzyl alcohol and subsequent coordination with Titanium resulting in the coating of the tubes. Adapted with permission from [102], 2008 Wiiey-VCH. 

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