Carbon nanotubes chemical functionalization

Attaching chemical functionalities to CNTs can improve their solubility and allow for their manipulation and processability [24]. The chemical functionalization can tailor the interactions of nanotubes with solvents, polymers and biopolymer matrices. Modified tubes may have physical or mechanical properties different from those of the original nanotubes and thus allow tuning of the chemistry and physics of carbon nanotubes. Chemical functionalization can be performed selectively, the metallic SWCNTs reacting faster than semiconducting tubes [25]. 

Roman, J.A., Niedzielko, T.L., Haddon, R.C., Parpura, V, Floyd, C.L., 2011. Single-waUed carbon nanotubes chemically functionalized with polyethylene glycol promote tissue repair in a rat model of spinal cord injury. J. Neurotrauma 28, 2349-2362. 

Velickovic, Z., et ah, Adsorption of arsenate on iron(lll) oxide coated ethylenediamine functionalized multiwall carbon nanotubes. Chemical Engineering Journal, 2012.181-182(0) p. 174-181. 

Bianco, A., et al.. Biomedical Applications of Functionalized Carbon Nanotubes. Chemical Communications, 2005(5), 571-577. 

TT-Electron materials, which are defined as those having extended Jt-electron clouds in the solid state, have various peculiar properties such as high electron mobility and chemical/biological activities. We have developed a set of techniques for synthesizing carbonaceous K-electron materials, especially crystalline graphite and carbon nanotubes, at temperatures below 1000°C. We have also revealed new types of physical or chemical interactions between Jt-electron materials and various other materials. The unique interactions found in various Jt-electron materials, especially carbon nanotubes, will lay the foundation for developing novel functional, electronic devices in the next generation. 

Heister, E. et al. (2010) Higher dispersion efficacy of functionalized carbon nanotubes in chemical and biological environments. ACS Nano, 4 (5), 2615-2626. 

Kam, N.W.S. and Dai, H.J. (2005) Carbon nanotubes as intracellular protein transporters generality and biological functionality. Journal of the American Chemical Society, 127 (16), 6021-6026. Heller, D.A. et al. (2005) Single-walled carbon nanotube spectroscopy in live cells towards long-term labels and optical sensors. Advanced Materials, 17 (23), 2793-2799. 

An additional and very attractive aspect of molecular qubits is the fact that they are stable in solution, and that the ligand shell can be functionalized with specific chemical groups. In recent years, this has enabled depositing molecular clusters onto different substrates and grafting them to nanostructures or devices, such as carbon nanotube single electron transistors or point contacts [112]. These devices... 

Velasco-Santos C, Marty nez-Hema ndez AL, Fisher FT, Ruotf R, Castano V M (2003b). Improvement of thermal and mechanical properties of carbon nanotube composites through chemical functionalization. Chem. Mater. 15 4470 4475. 

As with fullerenes, carbon nanotubes are also hydrophobic and must be made soluble for suspension in aqueous media. Nanotubes are commonly functionalized to make them water soluble although they can also be non-covalently wrapped with polymers, polysaccharides, surfactants, and DNA to aid in solubilization (Casey et al., 2005 Kam et al., 2005 Sinani et al., 2005 Torti et al., 2007). Functionalization usually begins by formation of carboxylic acid groups on the exterior of the nanotubes by oxidative treatments such as sonication in acids, followed by secondary chemical reactions to attach functional molecules to the carboxyl groups. For example, polyethylene glycol has been attached to SWNT to aid in solubility (Zhao et al., 2005). DNA has also been added onto SWNT for efficient delivery into cells (Kam et al., 2005). 

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. 

Y. Wang, Z. Iqbal, S. Mitra, Rapidly functionalized, water-dispersed carbon nanotubes at high concentration, Journal of American Chemical Society, vol. 128, pp. 95-99, 2006. 

A. Ghosh, K.V. Rao, R. Voggu, S. J. George, Non-covalent functionalization, solubilization of graphene and single-walled carbon nanotubes with aromatic donor and acceptor molecules, Chemical Physics Letters, vol. 488, pp. 198-201, 2010. 

M. Prato, A. Bianco, K. Kostarelos, Binding and condensation of plasmid DNA onto functionalized carbon nanotubes Toward the construction of nanotubes based gene delivery vectors, Journal of American Chemical Society, vol. 127, pp. 4388-4396, 2005. 

Daniel, S., et al., A review ofDNA functionalized/grafted carbon nanotubes and their characterization. Sensors and Actuators B Chemical, 2007.122(2) p. 672-682. 

Palacin, T., et al., Efficient Functionalization of Carbon Nanotubes with Porphyrin Dendrons via Click Chemistry. Journal of the American Chemical Society, 2009.131(42) p. 15394-15402. 

Kong, H., C. Gao, and D. Yan, Controlled functionalization ofmultiwalled carbon nanotubes by in situ atom transfer radical polymerization. Journal of the American Chemical Society, 2003. 126(2) p. 412-413. 

For applications where only mechanical properties are relevant, it is often sufficient to use resins for the filling and we end up with carbon-reinforced polymer structures. Such materials [23] can be soft, like the family of poly-butadiene materials leading to rubber or tires. The transport properties of the carbon fibers lead to some limited improvement of the transport properties of the polymer. If carbon nanotubes with their extensive propensity of percolation are used [24], then a compromise between mechanical reinforcement and improvement of electrical and thermal stability is possible provided one solves the severe challenge of homogeneous mixing of binder and filler phases. For the macroscopic carbon fibers this is less of a problem, in particular when advanced techniques of vacuum infiltration of the fluid resin precursor and suitable chemical functionalization of the carbon fiber are applied. 

Liu S, Shen Q, Cao Y et al (2010) Chemical functionalization of single-walled carbon nanotube field-effect transistors as switches and sensors. Coord Chem Rev 254 1101-1116... 

A different approach can be used to induce nanopartide self-assembly on surfaces or matrixes both by electrostatic interactions and chemical bonding between a functionalized nanoparticle and a surface. This is a vast area of research in which many types of substrates like Si, Si02, Ti02, A1203, MgO, carbon nanotubes, and so... 

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. 

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