NEWS OF THE WEEK NANOSCALE
ELECTRONICS
PROBING THE UNSEEN Methods reported for fabricating and characterizing molecular-scale structures O R D E R L Y Styrene chains capped by TEMPO molecules (with blue and red NO moiety in inset) can be positioned precisely on a silicon crystal.
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ANOMETER-SCALE E L E O
tronics moved forward on two fronts recently as a pair of research teams reported advances in fabricating and characterizing molecular devices. In one ofthe studies, researchers demonstrated a new vibrational
spectroscopy technique that can be used to probe molecules hidden in buried interfaces in molecular junctions. In the other investigation, scientists devised a roomtemperature method for fabricating complex molecular structures and positioning them on surfaces with atomic-scale control. With conventional electronics-fabrication methods rapidly SPECIALTY
approaching the limit of miniaturization, scientists are trying to fashion nanoscale electronic components using small numbers of molecules. The goal is to drastically miniaturize today's circuitry to prepare faster and even more densely packed electronic components. At the University of Minnesota, chemistry professor Xiaoyang Zhu and graduate student Yongseok Jun developed a procedure for recording infrared spectra from molecules concealed in molecular junctions. Typically, the junctions are formed by trapping molecules between a pair of very fine metal electrodes. The setup is used to probe current-voltage properties of the trapped molecules but provides little information about their structure and conformation. To sidestep that problem, the Minnesota team sandwiched layers of octadecyltrichlorosilane— and separately, mercaptohexadecanoic acid—between a gold electrode and a silicon crystal designed for attenuated total-reflec-
tion Fourier transform infrared spectroscopy [J. Am. Chem. Soc, published online Sept. 24, http:// dx.doi.org/10.1021/ja046431p]. By using a lightly doped crystal or by coating the crystal with a very thin layer of gold, the group enabled the semiconductor to function as an IR waveguide and an electrode. T h e n the team measured changes in the frequency, intensity, and shape of spectral features caused by bringing gold into contact with the molecules. Now the group is working to record spectra while voltage is applied to the samples. Meanwhile, Mark C Hersam, Rajiv Basu, and their coworkers in the materials science and engineering department at Northwestern University used a scanning tunneling microscope tip to deposit tetramethylpiperidinyloxy (TEMPO) radicals on opposite ends of a row of silicon-atom dimers on a hydrogen-covered silicon crystal. Then they removed a single hydrogen atom from the same row of dimers—thereby exposing a silicon dangling bond (an unsaturated valency) —and exposed the crystal to styrene. The room-temperature sequence resulted in a precisely positioned chain of styrene molecules bound at both ends by a pair of TEMPO molecules [Appl. Phys. Lett, 85, 2619 (2004)}.—MITCH JACOBY
POLYMERS
Materia Buying Cymetech Unit In Bid To Expand Metathesis
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lefin metathesis technology developer Materia, of Pasadena, Calif., is buying the polydicyclopentadiene business of Cymetech, which makes polymeric materials out of compounds such as dicyclopentadiene (DCPD) and norbornene. As part of the transaction, Materia will receive intellectual property for using Grubbs catalyst technology to make poly(DCPD); Cymetech's headquarters and molding technology center in Huntsville, Texas; and Cymetech's Telene and Prometa resin families. Cymetech isn't giving up its Ultrene line of DCPD products.
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Materia was founded in 1997 as Advanced Sports Materials to commercialize the work of California Institute of Technology chemistry professor Robert H. Grubbs in olefin metathesis. The company has licensed poly(DCPD) materials to sporting equipment maker Easton Sports for use in products ranging from baseball bats to archery bows. It is also working on applications for metathesis in fine chemicals. According to Materia, combining the poly(DCPD) operations of Materia and Cymetech in one company will broaden the range of applications in the polymers.
Materia had been limited to pursuing sporting and recreational equipment under its license from Cymetech, whereas Cymetech had applications for agricultural equipment and other products under its license from Caltech. "Materia and Cymetech have a long history of productive cooperation, and unifying the Grubbs olefin metathesis technology in a single organization is an important milestone in achieving its successful commercial implementation," says Michael A. Giardello, Materia's CEO and chief technology officer.—ALEX TULLO
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