Stoddart Mechanostereochemistry Group

 

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nanomaterials

 

Nanotechnology is an emerging field dealing with the fabrication and engineering of materials, architectures, and systems at the nano-scale. Together with the development of advanced imaging techniques, the development of nanomaterials for various applications has become prevalent in recent years. Their distinguishing physical properties arise from structural features that are less than one hundred nanometers. These distinct properties can be useful for the development of nanoelectronics, smart surfaces, medical implants, sensors, high-powered magnets, improved insulating materials, and batteries. Part of our research is devoted to the development of functional nanomaterials which can acts as molecular muscles,1 light driven molecular machines,2 molecular electronic devices,3 supramolecular polymers, nanovalves,4 molecular elevators,5 carbon nanotube based sensors, and organic field effect transistors.13

Carbon nanotubes, especially single wall carbon nanotubes (SWNTs), are among the most attractive of all nanomaterials due to their unique mechanical and electrical properties. One of the most challenging task about working with SWNTs is that they are insoluble in any common organic solvents and aqueous media. The insolubility of SWNTs results from noncovalent forces between individual tubes which results in spontaneous self-organization. This characteristic of SWNTs limits their application for use in devices. As a result there is a tremendous effort to solubilize them. Although the solubilization of the SWNTs can be achieved by covalent modification of the surface in various solvents, this modification drastically alters their physical properties.



For this reason great attention should be paid to non-covalent solubilization of SWNTs. Noncovalent modification not only improves the solubility of the SWNTs in organic and aqueous media, but it also preserves their unique mechanical and electrical features of SWNTs. Among the approaches for noncovalent modification that have met with some measure of success in solubilizing the SWNTs are the use of surfactants\] synthetic polymers (both helical and rigid),7 and biopolymers.8 We, along with others, have reported the solubilization of carbon nanotubes in water and organic media through the use of conjugated polymer (poly(meta-phenylenevinylene), PmPV) derivatives (Figure 1) 7c and polysaccharides (starch (Figure 2),9 gum arabic,10 and the _-1,3-glucans, curdlan and schizophyllan 11).

The helical structures of conjugated polymers and polysaccharides form a hydrophobic cavity that becomes a suitable host for the nanotube bundles. However, this approach still does not achieve the isolation of an individual nanotube. It is important to note that the supramolecular chemistry which operates between SWNTs and the starch (amylose-iodine complex) can be conducted under physical, chemical, or biological control. It constitutes an im-portant scientific development with implications for both carbon nanotube and starch research.9a At the simplest practical level, it is now easy to purify SWNTs cheaply, under ambient conditions, using readily available starch complexes.



Recently our group has developed a new method for solubilizing carbon nanotubes by using dynamic coordination and supramolecular chemistry (Figure 3). In this study we utilized a porphyrin molecule because of its strong interaction with the nanotube surface. A zinc-porphyrin derivative carrying two pyridine ligands enters into a self-assembly process with a Pd(II) complex and forms acyclic and cyclic complexes in aqueous media.12 This dynamic complex interacts with the nanotubes and facilitates their solubilization. This research introduces the idea of using dynamic coordination chemistry together with supramolecular chemistry to carry out the non-covalent functionalization.

We also are able to show that nanotubes which are functionalized noncovalently with this zinc porphyrin derivative can be used for the detection of light in SWNT field effect transistors. This process may form the basis for applications in artifical photosynthesis and alternative energy sources such as solar cells.13


References:


  1. Y. Liu, A.H. Flood, P.A. Bonvallet, S.A. Vignon, B. Northrop, H-R. Tseng, J. Jeppesen, T.J. Huang, B. Brough, M. Baller, S. Magonov, S. Solares, W.A. Goddard III, C-M. Ho, J.F. Stoddart , J. Am. Chem. Soc. 2005, 127, 9745-9759.

  2. V. Balzani, M. Clemente-León, A. Credi, B. Ferrer, M. Venturi, A.H. Flood, J.F. Stoddart , Proc. Natl. Acad. Sci. USA 2006, 103, 1178-1183.

  3. C.P. Collier, E.W. Wong, M. Belohradsky, F.M. Raymo, J.F. Stoddart, P.J. Kuekes, R.S. Williams, and J.R. Heath, Science 1999, 285, 391-394.

  4. R. Hernandez, H.-R. Tseng, J.W. Wong, J.F. Stoddart, J.I. Zink, J. Am. Chem. Soc. 2004, 126, 3370-3371.

  5. J.D. Badjic, V. Balzani, A. Credi, J.F. Stoddart, Science 2004, 303, 1845-1849.

  6. a) M. J. O'Connell, S. M. Bachilo, C. B. Huffman, V. C. Moore, M. S. Strano, E. H. Haroz, K. L. Rialou, P. J. Boul, W. H. Noon, C. Kittrell, J. Ma, R. H. Hauge, R. B. Weisman, R. E. Smalley, Science 2002, 297, 593-596.

  7. A. Star, J. F. Stoddart, D. Steuerman, M. Diehl, A Boukai, E.W. Wong, X. Yang, S.W. Chung, H. Choi, J. R. Heath, Angew. Chem. 2001, 113, 1771-1775; Angew. Chem. Int. Ed. 2001, 40, 1721-1725; b) D.W. Steuerman, A. Star, R. Narizzano, H. Choi, R. S. Ries, C. Nicolini, J. F. Stoddart, J. R. Heath, J. Phys. Chem. B 2002, 106, 3124-3130; c) A. Star, Y. Liu, K. Grant, L. Ridvan, J. F. Stoddart, D.W. Steuerman, M. R. Diehl, A. Boukai, J. R. Heath, Macromolecules 2003, 36, 553-560. d) A. Star, J. F. Stoddart, Macromolecules 2002, 35, 7516-7520.

  8. V. Zorbas, A. Ortiz-Acevedo, A. B. Dalton, M. M. Yoshida, G. R. Dieckmann, R. K. Draper, R. H. Baughman, M. Jose-Yacaman, I. H. Musselman, J. Am. Chem. Soc. 2004, 126, 7222-7227.

  9. a) A. Star, D.W. Steuerman, J. R. Heath, J. F. Stoddart, Angew. Chem. 2002, 114, 2618-2622; Angew. Chem. Int. Ed. 2002, 41, 2508-2512; b) O.-K. Kim, J. Je, J.W. Baldwin, S. Kooi, P. E. Pehrsson, L. Buckley, J. Am. Chem. Soc. 2003, 125, 4426-4427.

  10. R. Bandyopadhyaya, E. Nativ-Roth, O. Regev, R. Yerushalmi-Rozen, Nano Lett. 2002, 2, 25-28.

  11. M. Numata, M. Asai, K. Kaneko, T. Hasegawa, N. Fujita, Y. Kitada, K. Sakurai, S. Shinkai, Chem. Lett. 2004, 33, 232-233.

  12. K.S. Chichak, A. Star, M.V. Altoé, J.F. Stoddart, Small 2005, 1, 452-461.

  13. D.S. Hecht, R.J.A. Ramirez, M. Briman, E. Artukovic, K.S. Chichak, J.F. Stoddart , G. Gruner, Nano Lett. 2006, 6, 2031-2036.

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