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Chemie der Kohlenstoffnanoröhren

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Carbon nanotube chemistry involves chemical reactions, which are used to modify the properties of carbon nanotubes (CNTs). CNTs can be functionalized to attain desired properties that can be used in a wide variety of applications. The two main methods of CNT functionalization are covalent and non-covalent modifications.[1]

Because of their hydrophobic nature, CNTs tend to agglomerate hindering their dispersion in solvents or viscous polymer melts. The resulting nanotube bundles or aggregates reduce the mechanical performance of the final composite. The surface of CNTs can be modified to reduce the hydrophobicity and improve interfacial adhesion to a bulk polymer through chemical attachment.

Chart summarizing options for the chemical modification of carbon nanotubes.

Covalent modification

Covalent modification of carbon nanotubes.

Covalent modification attaches a functional group onto the carbon nanotube. The functional groups can be attached onto the side wall or ends of the carbon nanotube.[1] The end caps of the carbon nanotubes have the highest reactivity due to its higher pyrimidization angle and the walls of the carbon nanotubes have lower pyrimidization angles which has lower reactivity. Although covalent modifications are very stable, the bonding process disrupts the sp2 hybridization of the carbon atoms because a σ-bond is formed.[1] The disruption of the extended sp2 hybridization typically decreases the conductance of the carbon nanotubes.

Oxidation

The purification and oxidation of carbon nanotubes (CNTs) has been well represented in literature.[2][3][4][5] These processes were essential for low yield production of carbon nanotubes where carbon particles, amorphous carbon particles and coatings comprised a significant percentage of the overall material and are still important for the introduction of surface functional groups.[6] During acid oxidation, the carbon-carbon bonded network of the graphitic layers is broken allowing the introduction of oxygen units in the form of carboxyl, phenolic and lactone groups,[7] which have been extensively exploited for further chemical functionalisation.[8]

First studies on oxidation of carbon nanotubes involved a gas-phase reactions with nitric acid vapor in air, which indiscriminately functionalized the carbon nanotubes with carboxylic, carbonyl or hydroxyl groups.[9] In liquid-phase reactions, carbon nanotubes were treated with oxidizing solutions of nitric acid or a combination of nitric and sulfuric acid to the same effect.[10] However, overoxidation may occur causing the carbon nanotube to break up into fragments, which are known as carbonaceous fragments.[11] Xing et al. revealed sonication assisted oxidation, with sulfuric and nitric acid, of carbon nanotubes and produced carbonyl and carboxyl groups.[12] After the oxidation reaction in acidic solution, treatment with hydrogen peroxide limited the damage on the carbon nanotube network.[13] Single-walled carbon nanotubes can be shortened in a scalable manner using oleum (100% H2SO4 with 3% SO3) and nitric acid. The nitric acid cuts carbon nanotubes while the oleum creates a channel.[1]

Esterification/Amidation

Carboxylic groups are used as the precursor for most esterification and amidation reactions. The carboxylic group is converted into an acyl chloride with the use of thionyl or oxalyl chloride which is then reacted with the desired amide, amine, or alcohol.[1] Carbon nanotubes have been deposited on with silver nanoparticles with the aid of amination reactions. Amide functionalized carbon nanotubes have been shown to chelate silver nanoparticles. Carbon nanotubes modified with acyl chloride react readily with highly branched molecules such as poly(amindoamine), which acts as a template for silver ion and later being reduced by formaldehyde.[14] Amino-modified carbon nanotubes can be prepared by reacting ethylenediamine with an acyl chloride functionalized carbon nanotubes.[15]

Halogenation reactions

Carbon nanotubes can be treated with peroxytrifluroacetic acid to give mainly carboxylic acid and trifluroacetic functional groups.[1] The fluorinated carbon nanotubes, through substitution, can be further functionalized with urea, guanidine, thiourea and aminosilane.[16] Using the Hunsdiecker reaction, carbon nanotubes treated with nitric acid can react with iodosobenzenediacetate to iodate carbon nanotubes.[17]

Cycloaddition

The most well-known 1,3 cycloaddition reaction involves azomethine ylides reacting with carbon nanotubes, which are of great interest. The addition of a pyrrolidine ring can lead to a variety of functional groups such as second-generation poly(amidoamine) dendrimers,[18] phthalocyanineaddends,[19] perfluoroalkylsilane groups,[20] and amino ethyleneglycol groups.[21] The Diels-cycloaddition reaction can occur, especially on fluorinated carbon nanotubes. They are known to undergo Diels–Alder reaction s with dienes such as 2,3-dimethyl-1,3-butadiene, anthracene, and 2-trimethylsiloxyl-1,3-butadiene.[15]

Radical addition

Top: electron micrographs showing interaction of CNTs with 4-(1-pyrenyl)phenyl radical (a) and its boronic ester (b). Bottom: corresponding models.[22]

The modification of carbon nanotubes with aryl diazonium salts was studied first by Tour et al.[23] Due to the harsh conditions needed for the in situ generated diazonium compound, other methods have been explored. Stephenson et al. reported using aniline derivatives with sodium nitrite in 96% sulfuric acid and ammonium persulfate.[24] Price et al. demonstrated that stirring carbon nanotubes in water and treating with anilines and oxidizing agents proved to be a milder reaction.[1] The diazonium chemistry functionalized carbon nanotubes which was used as a precursor to further modifications. Suzuki and Heck coupling reactions were performed on iodophenyl-functionalized carbon nanotubes.[25] Wong et al. demonstrated mild photochemical reactions to silylate the carbon nanotubes with trimethoxysilane and hexaphenyldisilane.[26]

Nucleophilic addition

Hirsch et al. conducted nucleophilic additions with organolithium and organomagnesium compounds onto carbon nanotubes. With further oxidation in air, they were able to create alkyl-modified carbon nanotubes.[27] Hirsch was also able to show the nucleophilic addition of amines by generating lithium amides, leading to amino-modified carbon nanotubes.[28]

Electrophilic addition

The alkyl and hydroxyl modification of carbon nanotubes was demonstrated with the electrophilic addition of alkylhalides by microwave irradiation.[1] Tessonnier et al. modified carbon nanotubes with amino groups by deprotonating with butyl lithium and reacting with amino substitution.[28] Balaban et al. applied Friedel-Crafts acylation to carbon nanotubes with nitrobenzene at 180 °C along with aluminum chloride.[29]

Non-covalent modifications

Non-covalent modification of carbon nanotubes.

Non-covalent modifications utilize van der Waals forces and π-π interactions by adsorption of polynuclear aromatic compounds, surfactants, polymers or biomolecules. Non-covalent modifications do not disrupt the natural configuration of carbon nanotubes with the cost of chemical stability, and is prone to phase separation, dissociation in between two phases, in the solid state.[1]

Polynuclear aromatic compounds

Some common polynuclear aromatic compounds that are functionalized with hydrophilic or hydrophobic moieties are used to solubilize carbon nanotubes into organic or aqueous solvents. Some of these amphiphiles are phenyl, naphthalene, phenanthrene, pyrene and porphyrin systems.[30] The greater π-π stacking of aromatic amphiphiles such as pyrene amphiphiles had the best solubility compared to phenyl amphiphiles with the worse π-π stacking, lead to more solubility in water.[30] These aromatic systems can be modified with amino and carboxylic acid groups prior to functionalizing the carbon nanotubes.[31]

Biomolecules

The interaction between carbon nanotubes and biomolecules has been widely studied because of their potential to be used in biological applications.[32] The modification of the carbon nanotubes with proteins, carbohydrates, and nucleic acids are built with the bottom-up technique.[1] Proteins have high affinity to carbon nanotubes due to their diversity of amino acids being hydrophobic or hydrophilic.[1] Polysaccharides have been successfully been used to modify carbon nanotubes forming stable hybrids.[33] To make carbon nanotubes soluble in water, phospholipids such as lysoglycerophospholipids have been used.[34] The single phospholipid tail wraps around the carbon nanotube, but the double tailed phospholipids did not have the same ability.

π-π stacking and electrostatic interactions

Molecules that have bifunctionality are used to modify the carbon nanotube. One end of the molecule are polyaromatic compounds that interact with the carbon nanotube through π-π stacking. The other end of the same molecule has a functional group such as amino, carboxyl, or thiol.[1] For example, pyrene derivatives and aryl thiols were used as the linkers for various metal nanobeads such as gold, silver and platinum.[35]

See also

References

Vorlage:Reflist Vorlage:Commons category

  1. ↑ a b c d e f g h i j k l Nikolaos Karousis, Nikos Tagmatarchis, Dimitrios Tasis: Current Progress on the Chemical Modification of Carbon Nanotubes. In: Chemical Reviews. 110. Jahrgang, Nr. 9, 14. Juni 2010, S. 5366–5397, doi:10.1021/cr100018g.
  2. ↑ S. C. Tsang, P. J. F. Harris, M. L. H. Green: Thinning and opening of carbon nanotubes by oxidation using carbon dioxide. In: Nature. 362. Jahrgang, Nr. 6420, 1993, S. 520, doi:10.1038/362520a0.
  3. ↑ P. M. Ajayan, T. W. Ebbesen, T. Ichihashi, S. Iijima, K. Tanigaki, H. Hiura: Opening carbon nanotubes with oxygen and implications for filling. In: Nature. 362. Jahrgang, Nr. 6420, 1993, S. 522, doi:10.1038/362522a0.
  4. ↑ S. C. Tsang, Y. K. Chen, P. J. F. Harris, M. L. H. Green: A simple chemical method of opening and filling carbon nanotubes. In: Nature. 372. Jahrgang, Nr. 6502, 1994, S. 159, doi:10.1038/372159a0.
  5. ↑ Hidefumi Hiura, Thomas W. Ebbesen, Katsumi Tanigaki: Opening and purification of carbon nanotubes in high yields. In: Advanced Materials. 7. Jahrgang, Nr. 3, 1995, S. 275, doi:10.1002/adma.19950070304.
  6. ↑ K Esumi, M. Ishigami, A. Nakajima, K. Sawada, H. Honda: Chemical treatment of carbon nanotubes. In: Carbon. 34. Jahrgang, Nr. 2, 1996, S. 279, doi:10.1016/0008-6223(96)83349-5.
  7. ↑ M Shaffer, X. Fan, A.H. Windle: Dispersion and packing of carbon nanotubes. In: Carbon. 36. Jahrgang, Nr. 11, 1998, S. 1603, doi:10.1016/S0008-6223(98)00130-4.
  8. ↑ Ya-Ping Sun, Kefu Fu, Yi Lin, Weijie Huang: Functionalized Carbon Nanotubes: Properties and Applications. In: Accounts of Chemical Research. 35. Jahrgang, Nr. 12, 2002, S. 1096–104, doi:10.1021/ar010160v, PMID 12484798.
  9. ↑ Wei Xia, Chen Jin, Shankhamala Kundu, Martin Muhler: A highly efficient gas-phase route for the oxygen functionalization of carbon nanotubes based on nitric acid vapor. In: Carbon. 47. Jahrgang, Nr. 3, 1. März 2009, S. 919–922, doi:10.1016/j.carbon.2008.12.026.
  10. ↑ V. Datsyuk, M. Kalyva, K. Papagelis, J. Parthenios, D. Tasis, A. Siokou, I. Kallitsis, C. Galiotis: Chemical oxidation of multiwalled carbon nanotubes. In: Carbon. 46. Jahrgang, Nr. 6, 1. Mai 2008, S. 833–840, doi:10.1016/j.carbon.2008.02.012.
  11. ↑ Céline Bergeret, Jack Cousseau, Vincent Fernandez, Jean-Yves Mevellec, Serge Lefrant: Spectroscopic Evidence of Carbon Nanotubes’ Metallic Character Loss Induced by Covalent Functionalization via Nitric Acid Purification. In: The Journal of Physical Chemistry C. 112. Jahrgang, Nr. 42, 23. Oktober 2008, S. 16411–16416, doi:10.1021/jp806602t.
  12. ↑ Yangchuan Xing, Liang Li, Charles C. Chusuei, Robert V. Hull: Sonochemical Oxidation of Multiwalled Carbon Nanotubes. In: Langmuir. 21. Jahrgang, Nr. 9, 1. April 2005, S. 4185–4190, doi:10.1021/la047268e.
  13. ↑ F. Avilés, J. V. Cauich-Rodríguez, L. Moo-Tah, A. May-Pat, R. Vargas-Coronado: Evaluation of mild acid oxidation treatments for MWCNT functionalization. In: Carbon. 47. Jahrgang, Nr. 13, 1. November 2009, S. 2970–2975, doi:10.1016/j.carbon.2009.06.044.
  14. ↑ Lei Tao, Gaojian Chen, Giuseppe Mantovani, Steve York, David M. Haddleton: Modification of multi-wall carbon nanotube surfaces with poly(amidoamine) dendrons: Synthesis and metal templating. doi:10.1039/B609065F.
  15. ↑ a b J. S. Jeong, S. Y. Jeon, T. Y. Lee, J. H. Park, J. H. Shin, P. S. Alegaonkar, A. S. Berdinsky, J. B. Yoo: Fabrication of MWNTs/nylon conductive composite nanofibers by electrospinning. In: Diamond and Related Materials (= Proceedings of the joint 11th International Conference on New Diamond Science and Technology and the 9th Applied Diamond Conference 2006ICNDST-ADC 2006). 15. Jahrgang, Nr. 11–12, 1. November 2006, S. 1839–1843, doi:10.1016/j.diamond.2006.08.026.
  16. ↑ Luca Valentini, Jelena Macan, Ilaria Armentano, Francesco Mengoni, Josè M. Kenny: Modification of fluorinated single-walled carbon nanotubes with aminosilane molecules. In: Carbon. 44. Jahrgang, Nr. 11, 1. September 2006, S. 2196–2201, doi:10.1016/j.carbon.2006.03.007.
  17. ↑ Karl S. Coleman, Amit K. Chakraborty, Sam R. Bailey, Jeremy Sloan, Morgan Alexander: Iodination of Single-Walled Carbon Nanotubes. In: Chemistry of Materials. 19. Jahrgang, Nr. 5, 1. März 2007, S. 1076–1081, doi:10.1021/cm062730x.
  18. ↑ Stéphane Campidelli, Chloé Sooambar, Enrique Lozano Diz, Christian Ehli, Dirk M. Guldi, Maurizio Prato: Dendrimer-Functionalized Single-Wall Carbon Nanotubes: Synthesis, Characterization, and Photoinduced Electron Transfer. In: Journal of the American Chemical Society. 128. Jahrgang, Nr. 38, 1. September 2006, S. 12544–12552, doi:10.1021/ja063697i.
  19. ↑ Beatriz Ballesteros, Gema de la Torre, Christian Ehli, G. M. Aminur Rahman, F. Agulló-Rueda, Dirk M. Guldi, Tomás Torres: Single-Wall Carbon Nanotubes Bearing Covalently Linked Phthalocyanines − Photoinduced Electron Transfer. In: Journal of the American Chemical Society. 129. Jahrgang, Nr. 16, 1. April 2007, S. 5061–5068, doi:10.1021/ja068240n.
  20. ↑ Vasilios Georgakilas, Athanasios B. Bourlinos, Radek Zboril, Christos Trapalis: Synthesis, Characterization and Aspects of Superhydrophobic Functionalized Carbon Nanotubes. In: Chemistry of Materials. 20. Jahrgang, Nr. 9, 1. Mai 2008, S. 2884–2886, doi:10.1021/cm7034079.
  21. ↑ Bruno Fabre, Fanny Hauquier, Cyril Herrier, Giorgia Pastorin, Wei Wu, Alberto Bianco, Maurizio Prato, Philippe Hapiot, Dodzi Zigah: Covalent Assembly and Micropatterning of Functionalized Multiwalled Carbon Nanotubes to Monolayer-Modified Si(111) Surfaces. In: Langmuir. 24. Jahrgang, Nr. 13, 1. Juli 2008, S. 6595–6602, doi:10.1021/la800358w.
  22. ↑ Molecular interactions on single-walled carbon nanotubes revealed by high-resolution transmission microscopy. In: Nature Communications. 6. Jahrgang, 2015, S. 7732, doi:10.1038/ncomms8732.
  23. ↑ Hugh Hayden, Yurii K. Gun’ko, Tatiana S. Perova: Chemical modification of multi-walled carbon nanotubes using a tetrazine derivative. In: Chemical Physics Letters. 435. Jahrgang, Nr. 1–3, 12. Februar 2007, S. 84–89, doi:10.1016/j.cplett.2006.12.035.
  24. ↑ Jason J. Stephenson, Jared L. Hudson, Samina Azad, James M. Tour: Individualized Single Walled Carbon Nanotubes from Bulk Material Using 96% Sulfuric Acid as Solvent. In: Chemistry of Materials. 18. Jahrgang, Nr. 2, 1. Januar 2006, S. 374–377, doi:10.1021/cm052204q.
  25. ↑ Fuyong Cheng, Patigul Imin, Christian Maunders, Gianluigi Botton, Alex Adronov: Soluble, Discrete Supramolecular Complexes of Single-Walled Carbon Nanotubes with Fluorene-Based Conjugated Polymers. In: Macromolecules. 41. Jahrgang, Nr. 7, 4. März 2008, S. 2304–2308, doi:10.1021/ma702567y.
  26. ↑ Roberto Martín, Liliana Jiménez, Mercedes Alvaro, Juan C. Scaiano, Hermenegildo Garcia: Two-Photon Chemistry in Ruthenium 2,2′-Bipyridyl-Functionalized Single-Wall Carbon Nanotubes. In: Chemistry – A European Journal. 16. Jahrgang, Nr. 24, 25. Juni 2010, S. 7282–7292, doi:10.1002/chem.200903506.
  27. ↑ Ralf Graupner, Jürgen Abraham, David Wunderlich, Andrea Vencelová, Peter Lauffer, Jonas Röhrl, Martin Hundhausen, Lothar Ley, Andreas Hirsch: Nucleophilic−Alkylation−Reoxidation: A Functionalization Sequence for Single-Wall Carbon Nanotubes. In: Journal of the American Chemical Society. 128. Jahrgang, Nr. 20, 1. Mai 2006, S. 6683–6689, doi:10.1021/ja0607281.
  28. ↑ a b Zois Syrgiannis, Frank Hauke, Jonas Röhrl, Martin Hundhausen, Ralf Graupner, Yiannis Elemes, Andreas Hirsch: Covalent Sidewall Functionalization of SWNTs by Nucleophilic Addition of Lithium Amides. In: European Journal of Organic Chemistry. 2008. Jahrgang, Nr. 15, 1. Mai 2008, S. 2544–2550, doi:10.1002/ejoc.200800005.
  29. ↑ T. S. Balaban, M. C. Balaban, S. Malik, F. Hennrich, R. Fischer, H. Rösner, M. M. Kappes: Polyacylation of Single-Walled Nanotubes under Friedel–Crafts Conditions: An Efficient Method for Functionalizing, Purifying, Decorating, and Linking Carbon Allotropes. In: Advanced Materials. 18. Jahrgang, Nr. 20, 17. Oktober 2006, S. 2763–2767, doi:10.1002/adma.200600138.
  30. ↑ a b Yasuhiko Tomonari, Hiroto Murakami, Naotoshi Nakashima: Solubilization of Single-Walled Carbon Nanotubes by using Polycyclic Aromatic Ammonium Amphiphiles in Water—Strategy for the Design of High-Performance Solubilizers. In: Chemistry – A European Journal. 12. Jahrgang, Nr. 15, 15. Mai 2006, S. 4027–4034, doi:10.1002/chem.200501176.
  31. ↑ Trevor J. Simmons, Justin Bult, Daniel P. Hashim, Robert J. Linhardt, Pulickel M. Ajayan: Noncovalent Functionalization as an Alternative to Oxidative Acid Treatment of Single Wall Carbon Nanotubes with Applications for Polymer Composites. In: ACS Nano. 3. Jahrgang, Nr. 4, 28. April 2009, S. 865–870, doi:10.1021/nn800860m.
  32. ↑ Wenrong Yang, Pall Thordarson, J Justin Gooding, Simon P Ringer, Filip Braet: Carbon nanotubes for biological and biomedical applications. 17. Oktober 2007, doi:10.1088/0957-4484/18/41/412001.
  33. ↑ Hui Yang, Shiunchin C. Wang, Philippe Mercier, Daniel L. Akins: Diameter-selective dispersion of single-walled carbon nanotubes using a water-soluble, biocompatible polymer. doi:10.1039/B515896F.
  34. ↑ Ran Chen, Slaven Radic, Poonam Choudhary, Kimberley G. Ledwell, George Huang, Jared M. Brown, Pu Chun Ke: Formation and cell translocation of carbon nanotube-fibrinogen protein corona. In: Applied Physics Letters. 101. Jahrgang, Nr. 13, 24. September 2012, doi:10.1063/1.4756794, PMID 23093808, PMC 3470598 (freier Volltext).
  35. ↑ Zhijuan Wang, Meiye Li, Yuanjian Zhang, Junhua Yuan, Yanfei Shen, Li Niu, Ari Ivaska: Thionine-interlinked multi-walled carbon nanotube/gold nanoparticle composites. In: Carbon. 45. Jahrgang, Nr. 10, 1. September 2007, S. 2111–2115, doi:10.1016/j.carbon.2007.05.018.
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