Carbon nanotubes noncovalent

Keywords Single-wall carbon nanotube, noncovalent nanotube functionalization, Raman... 

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Noncontact printing, in microarray fabrication, 16 386 Noncoordinating anions, 16 95 Noncovalent carbon nanotube functionalization, 17 53 Noncovalent fluorescence labeling, 20 519... 

Scheme 2.1 Examples of noncovalent functionalisation of carbon nanotubes (CNTs) with different biomolecules...

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The vast majority of functionalization methods of carbon nanotubes belong to two broad categories (a) covalent and (b) noncovalent functionalization of the external CNT surface. The former is achieved by covalent attachment of functional groups to the C-C double bond of the n-conjugated framework. The latter is based on the adsorption through van der Waals type bonds of various functional entities. 

Functionalization of carbon nanotubes with metals can be achieved by different techniques exploiting either the covalent or the noncovalent approach. This topic, which is important for many applications, will be briefly discussed in a separate section after the description of the two methods. 

The second type of functionalization of carbon nanotubes is based on noncovalent interactions, such as CH-n, n-n stacking, van der Waals and electrostatic forces. 

Encapsulation of different entities inside the CNT channel stands alone as an alternative noncovalent functionalization approach. Many studies on the filling of carbon nanotubes with ions or molecules focus on how the presence of these fillers affects the physical properties of the tubes. From a different point of view, confinement of materials inside the cylindrical structure could be regarded as a way to protect such materials from the external environment, with the tubes acting as a nanoreactor or a nanotransporter. It is fascinating to envision specific reactions between molecules occurring inside the aromatic cylindrical framework, tailored by CNT characteristic parameters such as diameter, affinity towards specific molecules, etc. 

H. Dai, Noncovalent functionalization of carbon nanotubes for highly specific electronic biosensors, Proceeding of the National Academic of Science of the United States of America, vol. 48, pp. 4984-4989, 2003. 

Yang, W., et al., Carbon nanotubes decorated with PtnNanocubes by a noncovalent functionalization method and their role in oxygen reduction. Advanced Materials, 2008. 20(13) p. 2579-2587. 

NONCOVALENT FUNCTIONALIZATION OF SINGLE-WALLED CARBON NANOTUBES FOR BIOLOGICAL APPLICATION RAMAN AND NIR ABSORPTION SPECTROSCOPY... 

Noncovalent approaches can usually preserve the structures and properties of carbon nanotubes after functionalization17 (though not necessarily the near-infrared absorption characteristics due to well-established doping effects), thus are equally important to the biocompatibilization and bioapplications of nanotubes.15 Among commonly employed noncovalent schemes are surfactant dispersion,18 tt-tt stacking with aromatic compounds,19 and polymer wrapping.20... 

Besides synthetic polymers and small molecules, biological or bioactive species are used in the functionalization of carbon nanotubes not only for water solubility but also enhanced biocompatibilities and biorecognition capabilities. Various proteins, DNAs, and carbohydrates have been covalently or noncovalently functionalized with carbon nanotubes, producing highly aqueous stable and biocompatible... 

Scheme 6.3 Noncovalent biofunctionalized carbon nanotubes. (From References 21, 41, and 53. Reprinted with permission.)...

Although the noncovalent binding is a versatile way to functionalize carbon nanotubes with proteins, the interaction is rather weak in comparison to covalent binding. For example, it has been reported that the nanotube-adsorbed proteins were largely... 

Noncovalent functional strategies to modify the outer surface of CNTs in order to preserve the sp2 network of carbon nanotubes are attractive and represent an effective alternative for sidewall functionalization. Some molecules, including small gas molecules [195], anthracene derivatives [196-198] and polymer molecules [118, 199], have been found liable to absorb to or wrap around CNTs. Nanotubes can be transferred to the aqueous phase through noncovalent functionalization of surface-active molecules such as SDS or benzylalkonium chloride for purification [200-202]. With the surfactant Triton X-100 [203], the surfaces of the CNTs were changed from hydrophobic to hydrophilic, thus allowing the hydrophilic surface of the conjugate to interact with the hydrophilic surface of biliverdin reductase to create a water-soluble complex of the immobilized enzyme [203]. 

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