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Nanotubes made of carbon are believed to have important potential electronics and materials applications, but their notorious insolubility in water and most common organic solvents has helped keep such uses tantalizingly out of reach. This year, Maurizio Prato of the University of Trieste, in Italy, and coworkers discovered that attaching organic groups to nanotubes made the nanotubes "remarkably soluble" in most organic solvents and water [J. Am. Chem. Soc., 124, 760 (2002); C&EN, Feb. 4, page 12] and that solubilization can be used to purify nanotubes [J. Am. Chem. Soc., 124, 14318 (2002)]. J. Fraser Stoddart's group at UC Los Angeles (UCLA) found that nanotubes can be dissolved in aqueous solution if they are first encircled with starch (amylose) molecules [Angew. Chem. Int. Ed., 41, 2508 (2002); C&EN, July 15, page 38]. Yoshio Bando and Yihua Gao at the National Institute for Materials Science, Ibaraki, Japan, created carbon nanotubes filled with liquid gallium that could serve as tiny thermometers for measuring temperature in microenvironments [Nature, 415, 599 (2002); C&EN, Feb. 11, page 26]. Hicham Fenniri of Purdue University and colleagues found that rosette (flowerlike) macrocycles self-assemble in water and stack to form intricate and complex rosette nanotubes [Proc. Natl. Acad. Sci. USA, 99, 6487 (2002); J. Am. Chem. Soc., 124, 11064 (2002); C&EN, March 18, page 9]. The structures' self-assembling mechanism of formation should make it possible to design "self-replicating and adaptive nanotubes," Fenniri says. Pulickel M. Ajayan and Ganapathiraman Ramanath of Rensselaer Polytechnic Institute, Troy, N.Y., and coworkers reported a simple technique for growing carbon nanotubes in several different directions at once [Nature, 416, 495 (2002); C&EN, April 8, page 11]. The technique could be useful for fabricating microelectromechanical devices or nanotube-fiber membranes. In another illuminating finding, Ajayan and coworkers discovered that single-wall carbon nanotubes exposed to light at close range burst into flame [Science, 296, 705 (2002); C&EN, April 29, page 9]. The longest and strongest assemblies ever made entirely from carbon nanotubes were created by Dehai H. Wu and coworkers at Tsinghua University, Beijing, China, and were characterized by Ajayan's group [Science, 296, 884 (2002); C&EN, May 6, page 11]. The approximately 20-cm strands look and feel like human hair. A technique for preparing neatly aligned nanotubes from a wide range of polymers, polymer blends, and multicomponent solutions was developed by Martin Steinhart and Joachim H. Wendorff of Philipps University, Marburg, Germany; Ralf B. Wehrspohn and Ulrich M. Gösele of the Max Planck Institute of Microstructure Physics, Halle, Germany; and coworkers [Science, 296, 1997 (2002); C&EN, June 17, page 5]. And Charles R. Martin and coworkers at the University of Florida, Gainesville, used template synthesis to create antibody-laced silica-nanotube membranes and showed they can be used for chiral separations [Science, 296, 2198 (2002); C&EN, June 24, page 13]. Nanotubes are typically made of fullerene carbon, "but for many applications, this is not optimal because carbon is difficult to dissolve and chemically nonreactive," Martin tells C&EN. "The template method gets around this problem by allowing you to make nanotubes composed of any material."
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Chemical & Engineering News |
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SOLUBLE Prato and coworkers made nanotubes more soluble than ever before in both organic solvents and water by decorating them with organic groups (white). COURTESY OF M. PRATO & P. BRAIUCA
