Carbon nanotubes chemical modification

N. Karousis, N. Tagmatarchis, Current progress on the chemical modification of carbon nanotubes, Chemical Reviews, vol. 110, pp. 5366-5397, 2010. 

Nano tubes, in particular SWNTs, are typically held together as bundles, resulting in poor NT dispersion in polymer matrices. Since, due to the relatively smooth graphene Hke surface of NTs, there is a lack of interfacial bonding between polymer matrix and carbon nanotubes, surface modification by chemical means of NTs has been envisaged as a very important factor to overcome this problem and to fadhtate NTs processing and applications [30]. 

The covalent methods previously discussed for fullerene modification using cycloaddition reactions also can be applied to carbon nanotubes. This strategy results in chemically linking molecules to the graphene rings on the outer surface of the cylinder, resulting in stable... 

M. Liu, Y. Yang, T. Zhu, and Z. Liu, Chemical modification of single-walled carbon nanotubes with peroxytrifluoroacetic acid. Carbon 43, 1470-1478 (2005). 

In recent years, CNTs have been receiving considerable attention because of their potential use in biomedical applications. Solubility of CNTs in aqueous media is a fundamental prerequisite to increase their biocompatibility. For this purpose several methods of dispersion and solubilisation have been developed leading to chemically modified CNTs (see Paragraph 2). The modification of carbon nanotubes also provides multiple sites for the attachment of several kinds of molecules, making functionalised CNTs a promising alternative for the delivery of therapeutic compounds. 

Functionalization of carbon nanotubes becomes essential for multiple reasons. Firstly, chemical modification can allow debundling and therefore solubilization of the tubes, which is an important feature for their processability. Secondly, insertion of functional groups enables attachment of more complex moieties that find applications in several fields. 

Encapsulation of other material into carbon nanotubes would also open up a possibility for the applications to electrodevices. By applying the template method, perfect encapsulation of other material into carbon nanotubes became possible. No foreign material was observed on the outer surface of carbon nanotubes. The metal-filled uniform carbon nanotubes thus prepared can be regarded as a novel onedimensional composite, which could have a variety of potential applications (e.g novel catalyst for Pt metal-filled nanotubes, and magnetic nanodevice for Fe304-filled nanotubes). Furthermore, the template method enables selective chemical modification of the inner surface of carbon nanotubes. With this technique, carbon... 

This is mainly due to their laborious purification procedures and their required chemical modification for solubilization. Only recently, Prato et al. reported the electrochemistry of carbon nanotubes functionalized using the 1,3-dipolar cycloaddition reaction.120 The cyclic voltammogram obtained is shown in Fig. 8.9. 

An other interesting strategy is the modification of the surface of the electrodes with multiwalled carbon nanotubes (MWNTs) or single-walled carbon nanotubes (SWNTs) [13,32]. The MWNTs are grown on the electrodes covered with a nickel catalyst film by plasma-enhanced chemical vapour deposition and encapsulated in Si02 dielectrics with only the end exposed at the surface to form an inlaid nanoelectrode array [13]. In the other case, commercial SWNTs are deposited on SPE surface by evaporation [32], The carbon nanotubes are functionalised with ssDNA probes by covalent attachment. This kind of modification shows a very efficient hybridisation and, moreover, the carbon nanotubes improve the analytical signal. 

In this chapter, we review the recent advances in the chemical modification of carbon nanotubes related specifically to their bioapplications, discuss various approaches and developments in the use of carbon nanotubes in biology and medicine, and provide some perspectives on further investigations and emerging opportunities. 

In general, on chemical modification carbon nanotubes exhibit much less toxicity or nontoxicity to living cell lines that have been investigated so far.117,118 For instance, Dumortier et al. conducted an in vitro cell uptake study of the functionalized SWNTs with B and T lymphocytes and macrophages.117 Two types of functionalized SWNTs were used, one prepared via 1,3-dipolar cycloaddition reaction and the other obtained through oxidation/amidation treatment. Both types of the functionalized nanotubes were rapidly taken up by lymphocytes and macrophages without affecting the overall... 

Yokoi, T., Iwamatsu, S., Komai, S., Hattori, T., and Murata, S. Chemical modification of carbon nanotubes with organic hydrazines. Carbon (2005), 43, 2869-2874. 

The different flame-retardant (FR) mechanisms of action of current nanoparticles, such as layered silicates, carbon nanotubes (CNTs), and nano-oxides or -hydroxides, according to their nature and interfacial modifications, are relatively well known and detailed in numerous works.5 13 These mechanisms are rather different from those exhibited by usual FRs and correspond mainly to the following physical, physicochemical, or chemical actions ... 

Another approach to covalently attach carbon nanotubes is based on the chemical modification of a PEEK matrix which allows further covalent interaction with functionalized carbon nanotubes. In 2007 Babaa et al. (40) proposed a route to covalently graft commercial MWCNTs by using this approach. The process initiates by dissolution of PEEK in concentrated H2S04, leading to functionalization yields of 70%. MWCNTs covalently functionalized with... 

Figure 34 Surface modification of carbon nanotubes through chemical reactions with sp network. For clarity, one substitution with n multiples is illustrated...

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