Nanotube noncovalent attachments

Magnetism is yet another successful method for the alignment of individual peptide fibers. Magnetite (Fe304) particles approximately lOnm in size were noncovalently attached to diphenylanalanine nanotubes during fiber... 

Sun, J., Gao, L., and Iwasa, M., Noncovalent attachment of oxide nanoparticles onto carbon nanotubes using water-in-oil microemulsions, Chem. Commun., 832-833, 2004. 

The noncovalent attachment of solubUity-enhancing groups is another alternative to obtain stable suspensions or solutions of carbon nanotubes. The wrapping with various polymeric substances serves especially well to this purpose. The... 

Zhou HJ, Zhang ZP, Yu P, Su L, Ohsaka T, Mao LQ. Noncovalent attachment of NAD" " cofactor onto carbon nanotubes for preparation of integrated dehydrogenase-based electrochemical biosensors. Langmuir 2010 26 6028-6032. 

Landi, B. J. Evans, C. M. Worman, J. J. Castro, S. L. Bailey, S. G. RaffaeUe, R. R. Noncovalent attachment of CdSe quantum dots to single wall carbon nanotubes. Mater. Lett. 2006,60,3502-3506. 

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. 

Unlike the covalent functionalization approach, noncovalent functionalization provides an alternative method to modify and tailor the surface properties of CNTs in order to increase their solubility in solvents or compatibility with polymer matrix. In this method, the tubular surface of a CNT is noncovalently wrapped with polymer chains due to van der Waals attractive forces or through tt-tt interactions. This noncovalent wrapping approach has also been widely used and is particularly attractive because it offers the possibility of attaching chemical handles without affecting the electronic network of the nanotubes [42-45]. Coleman et al [46-49] illustrated an example of noncovalent wrapping by tt-tt interaction between CNTs and poly(m-phenylenevinylene-co-2,5-dioctoxy-p-phenylene vinylene) (PmPV), a conjugated luminescent polymer, to obtain a CNT-PmPV composite. 

Figure 1 Chemical functionalization of carbon nanotubes (CNTs) involves the covalent bonding of a variety of chemical groups (R) to the graphitic lattice of CNTs. Supramolecular approaches can, in principle, enable the attachment of the same functionality (R) throngh nondestructive noncovalent interactions to CNTs in both an exohedral and endohedral fashion.

Most supramolecular nanotube modifications involve noncovalent interactions on the external surface of the CNT (i.e., exohedral. Figure 1). For example, n-n stacking is employed to attach pyrene " and porphyrin " molecules to the surface of CNTs. Hydrophobic and van der Waals interactions are necessary for micelle-forming compounds (i.e., surfactants and lipids ) and polymer (both syn-thetic " and natural ) to functionalize CNTs. The so-called r-cation interactions represent an additional exohedral approach for functionalizing CNTs. Finally, organometallic bonding is required for the decoration of CNT with metal nanoparticles (NP) at defect sites. ... 

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