December 22, 2003
Volume 81, Number 51
CENEAR 81 51 pp. 39-50

ISSN 0009-2347


MATERIALS

STU BORMAN, C&EN WASHINGTON

Materials science advances can also sometimes be used to help solve environmental problems. An example is the class of "green" zeolites developed this year. Ralph T. Yang and coworkers at the University of Michigan, Ann Arbor, discovered zeolites that adsorb aromatic sulfur compounds from commercial fuels at ambient temperature and pressure [Science, 301, 79 (2003)]. The zeolites--whose selectivity and capacity for sulfur are at least 40 times higher than those reported previously--could help refineries meet strict air-quality regulations.

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LAYERED LOOK Takada and coworkers found that this cobalt oxide-based layered complex exhibits superconductivity, just like the layered copper oxides that created a sensation when they were discovered in 1986. REPRINTED WITH PERMISSION FROM NATURE © 2003

Mark E. Davis and colleagues at Caltech and Chevron recently created zeolite-templating structure-directing agents (SDAs) that can be disassembled after zeolite synthesis at relatively low temperatures, allowing the molecular fragments to be removed, recovered, and reused [Nature, 425, 385 (2003)]. The work advances green chemistry because SDAs usually have had to be burned off at high temperatures, which is wasteful, expensive, and sometimes detrimental to the zeolites themselves.

In another materials chemistry advance with potential environmental applications, Omar M. Yaghi of the University of Michigan, Ann Arbor, and coworkers designed and constructed metal-organic framework crystals with an extended porous structure that can adsorb up to 2% by weight of hydrogen at room temperature and 10 atm of pressure and up to 4.5% at lower temperatures [Science, 300, 1127 (2003)]. It's a step toward the practical use of hydrogen as a fuel.

Among other materials breakthroughs in 2003, a procedure for spinning composite carbon nanotube fibers that are tougher than spider silk and any other natural or synthetic organic fiber reported previously was devised by Ray H. Baughman of the University of Texas, Dallas, and coworkers [Nature, 423, 703 (2003)]. The new fibers may be useful for advanced supercapacitors and textiles.

Since the first report in 1986 of high-temperature superconductivity in layered copper oxides, researchers have searched without success for similar behavior in other layered transition-metal oxides. In 2003, Kazunori Takada of National Institute for Materials Science, Tsukuba, Japan, and coworkers found a cobalt oxide that becomes superconducting at about 5 K [Nature, 422, 53 (2003)].

Takuzo Aida of the University of Tokyo, Takanori Fukushima of Japan Science & Technology Agency, and coworkers discovered that carbon nanotubes and room-temperature ionic liquids can be blended to form gels that may be used to make novel electronic devices, coating materials, and antistatic materials [Science, 300, 2072 (2003)]. Aida's group also helped integrate biomolecular motion into materials science by demonstrating that large barrel-shaped chaperonin proteins can entrap and stabilize a quantum dot (semiconductor nanoparticle) as a guest and release it in response to adenosine triphosphate binding--the usual trigger for chaperonins to release a refolded protein [Nature, 423, 628 (2003)].

Liquid-crystal compounds that are Janus-like (with two chemically different halves) and self-organize into materials with desirable chemical functionality and physical properties at nano- and mesoscopic length scales were designed, synthesized, and characterized by Isabel M. Saez and John W. Goodby of the University of Hull, in England [Chem. Commun., 2003, 1726].

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JANUS Goodby and Saez designed the "two-faced" dendritic compounds at left, which have chemically different components (yellow and blue) that form liquid crystals.
A beautiful purple glass, in which nanoscale-size magnetic particles of a Co(II)/Fe(III) Prussian blue complex form spontaneously in a single-pot sol-gel reaction, was developed by Albert E. Stiegman of Florida State University and coworkers [Angew. Chem. Int. Ed., 42, 2741 (2003)]. The material is transparent and superparamagnetic--each nanoparticle behaves like an independent magnetic domain--and it exhibits tunable photomagnetism, suggesting magnetic switch applications.

Gerard C. L. Wong and coworkers at the University of Illinois, Urbana-Champaign, developed a biomineralization procedure in which molecular details of biological molecules are replicated on inorganic crystals by electrostatically guiding crystallization at the nanoscale [J. Am. Chem. Soc., 125, 11786 (2003)]. Such custom-designed crystals could have useful electronic, magnetic, and optical properties.

A new way to create solid chiral surfaces having catalytic properties may make it easier to synthesize or sense chiral molecules. A team led by Jay A. Switzer of the University of Missouri, Rolla, discovered how to electrochemically deposit a copper oxide film with either right- or left-handed chirality onto an achiral gold surface [Nature, 425, 490 (2003)].

YbGaGe, the first electrically conductive compound that maintains its room-temperature volume when heated, was prepared and characterized by Mercouri G. Kanatzidis and coworkers at Michigan State University, East Lansing [Nature, 425, 702 (2003)]. Potential applications of such electrically conducting zero-thermal-expansion materials include multilayered printed circuits.

Highlights2003--Switzer_ch
HANDED X-ray diffraction "pole figures" of two copper oxide films electrodeposited on a gold substrate by Switzer and coworkers are nonsuperimposable mirror images, showing that the films are chiral.COURTESY OF J. SWITZER, E. BOHANNAN, & NSF



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