FOR MoS, CLUSTER SIZE RULES - C&EN Global Enterprise (ACS

Jan 15, 2007 - FOR MoS, CLUSTER SIZE RULES. NANOSTRUCTURES: Numbers of edge atoms dictate physical and chemical properties of nanoparticles...
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to a $3.8 billion sale of its silicones and quartz business, GE Advanced Materials, to Apollo Management last September. During a conference call last October, Immelt reminded analysts that "there is no business that's off SPIN-OFF: A sale would follow limits." And hinting that the industry has become more divestment of silicones business last year mature than it once was, he added, "Clearly, plastics has changed dramatically in the last 10 years." GE Plastics had sales of $6.6 billion in 2005. ENERAL ELECTRIC has contacted private-eqG. Stephen Tusa Jr., a stock analyst with JPMorgan uity companies and competing plastics firms Securities, is receptive to GE's apparent decision. "The regarding the possible sale of GE Plastics for fact that GE is seeking strategic alternatives for its plasas much as $10 billion, according to reports in the New tics unit is not a surprise, but the move is positive nonetheless," he wrote in a recent report to clients. York Times and Wall Street Journal To manage the sale, GE is said to have retained GoldAustin Peppin, a plastics consultant with Chesterman Sachs, which the reports say has already contacted field, Mo.-based BRG Peppin, figures that a private-eqtwo plastics companies and four private-equity firms. uity purchase of GE Plastics is more likely than a mergGE told C&EN that it has "no comment on rumors er with an industry player. "If I was to put my money on or speculation" about the business, which makes engiit, I would favor a private-equity firm," he says. neering polymers such as polycarbonate, polyphenylGE has a roughly 30% global market share in polyene oxide, and acrylonitrile-butadiene-styrene (ABS). carbonate, Peppin says, which would likely rule out But GEO Jeffrey Immelt has been dancing around the polycarbonate competitors Bayer and Dow Chemical as issue of a sale of the plastics business since GE agreed prospective buyers.—ALEX TULLO

GE EXPLORES PLASTICS SALE

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"There are potentially some industry buyers that aren't in polycarbonate or ABS, but then the question is who has the cash to buy such a large business." -AUSTIN PEPPIN

triangular in shape, contain highly active catalytic sites, which are especially active when the clusters are very small. The high activity is often attributed to the unique coordination of edge atoms and the presence of reactive edge defect NANOSTRUCTURES: Numbers of sites. But those features have not r edge atoms dictate physical and been explored in atomic-resolution chemical properties of nanoparticles detail until now. On the basis of scanning tunneling microscopy (STM) measurements, Aarhus HAT A DIFFERENCE a few atoms can make. University physics professors Jeppe V. Lauritsen and Flemming Besenbacher and their Tiny variations in the numbers of atoms coworkers at Aarhus and at catalyst manufacturalong the edges of molybdenum disulfide er Haldor Tops0e have shown that nanoclusters nanoparticles can profoundly influence the crystal's with six or more molybdenum atoms along an edge atomic-scale structure and coordination, electronic coordinate sulfur differently than do nanoclusters properties, and other characteristics, researchers in containing fewer than six edge molybdenum atoms. Denmark have shown. The findings may lead to improvements in MoS2-based desulfurization catalysts Specifically, the team finds that along the edges for fuel cleanup and to advanced lubricants and other of the larger crystallites, each Mo atom bonds with applications. two outermost S atoms (S "dimers"), which tend to line up with neighboring atoms to form pairs of S "diWith legislation in the U.S., Europe, Japan, and elsewhere calling for ever lower levels of sulfur in transpormers." In contrast, the edges of smaller clusters exhibit tation fuels, scientists are redoubling their efforts to sort Mo-S-Mo bridge structures (Nat. Nanotechnol. 2007,2, out the reaction mechanism that drives hydrodesulfur21). The team also reports that the smaller clusters are ization, a process in which sulfur is stripped from hydro- less stable (more reactive) and more prone to vacancy In a large MoS2 cluster, S "dimers"pair (as carbons and converted to volatile hydrogen sulfide in defects than the larger clusters. And they note sizeshown by arrows); in the presence of MoS2-based catalysts. dependent differences in the clusters' STM signatures, a small one, S atoms Previous studies indicate that the edges of thin, sup- which indicate the clusters' differing electronic struc(yellow) bridge Mo atoms (blue). ported MoS2 nanoclusters, which are often equilateral- tures.— MITCH JACOBY

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JANUARY 15. 2007