deadline twice. In late August, which was the original deadline, it appeared that only BSA would bid. The DOE contract solicitation reflects the difficulties facing bidders. It emphasizes that the eventual operator must have strong experience in conducting worldclass research and in addressing environmental, safety, and health problems. Although the lab is renowned for its science, it is also a designated Superfund waste cleanup site with a recent history of environmental and safety problems, particularly tritium leaks from a holding tank containing spent reactor fuel rods, a situation that led to termination of AlU's contract in May (C&EN, May 19, page 30). However, that termination is now being challenged by AUI in a breach of contract claim filed Sept. 10. AUI is charging that DOE intentionally misled the association on the eve of its termination to assume that corrective actions concerning the tritium leak were sufficient and its contract would be continued. AUI quotes DOE as saying remediation of tritium contamination was "aggressive and appropriate," although some weaknesses remained. Charging that the termination was an abuse of discretion, AUI is seeking damages to recover the loss of income for the canceled contract. DOE officials refuse comment but say a response will be issued within 60 days. Lyle Schwartz, AUI president, says the organization will await DOE's decision before considering alternatives, which include legal action. AUI officials chose not to bid, Schwartz adds, because they believed AUI was viewed so negatively by
DOE that it would have been a "hopeless quest" to bid alone and it was unable to find partners, although it had directly or indirectly contacted all of the eventual bidders. Jeff Johnson
Putting the squeeze on quantum dots An array of silver quantum dots that when squeezed shifts from being an insulator to a metal may prove to be the forerunner of an entirely new class of solids whose electronic and optical properties can be controlled at will. Quantum dots, or nanocrystals, are tiny isolated bits of matter tens of angstroms in diameter. In some respects, they act as individual atoms: Electrons are confined to each dot, and the dots behave as insulators. Much current research is devoted to finding ways to harness the unusual properties of nanocrystals. One goal is to try to assemble them into new types of solids—ordered structures that use the dots as building blocks. Researchers at the University of California, Los Angeles, and at UC Berkeley have demonstrated that an ordered monolayer of quantum dots, which starts off as an insulator, can be compressed into a conducting metal film. What's more, the process is entirely reversible [Science, 277, 1978 (1997)]. "They've learned how to control the transition between metal and insulator in a very simple way," says George C.
Schatz, a chemistry professor involved in theoretical studies of quantum dot systems at Northwestern University in Evanston, 111. "That's exciting." Graduate student C. Patrick Collier and chemistry professor Richard J. Saykally at Berkeley and chemistry professor James R. Heath and colleagues at UCLA prepared monolayers of quantum dots, controlling the size of the particles by "capping" each one with an alkylthiol group. The dots float in a monolayer on water, their cores spaced about 12 À apart. The researchers then gradually compressed the film at ambient conditions until the separation between the dot cores was about 5 À. They discovered that, as the distance between the cores decreased, reflectivity and absorbance measurements took on the characteristics of a metal. What's going on, Heath and Collier explain, is that the wavefunctions of the individual dots are overlapping. The electrons become delocalized, linking the dots together classically and quantum mechanically. "The individual dot identity is gone," Heath says. Heath likens the thiol caps to springs that can be compressed—when the pressure is released, the quantum dots spring back. Without the thiol groups, he says, the dots would simply merge and become a traditional solid. The synthetic advances that enabled them to create quantum dot monolayers of very narrow size distributions were "really critical," Heath says. The group would like to explore the properties of magnetic particles in a similar setup, says Collier. Elizabeth Wilson
Louisiana chemist wins presidential mentoring award Isiah M. Warner, Philip W. West Professor of Analytical & Environmental Chemistry at Louisiana State University, Baton Rouge, is one of two chemists who received the 1997 Presidential Award for Excellence in Science, Mathematics & Engineering Mentoring. Géraldine L. Richmond, a professor of chemistry at the University of Oregon, Eugene, is the other (C&EN, Sept. 22, page 10). Another eight individuals and nine institutions also received the award. Given for thefirsttime last year and administered by the National Science Foundation, the award recognizes outstanding efforts by individuals and organizations "to increase the participation of underrepresented groups in science, mathematics, and engineering." Recipi-
ents receive a $10,000 grant and a certificate. A letter nominating Warner for the award describes him as "an excellent mentor to students of all backgrounds. . . . However, his own experiences have increased his sensitivity to and awareness of the issues facing minority students in science, and he has made a special effort to encourage and support those students." Nevertheless, Warner says, "it doesn't require an African-American to mentor African-Americans. It takes someone who cares. There's always a way, if a mentor cares." One of his goals is to host a conference at Louisiana State on all aspects of mentoring, using mentoring programs in chemistry as the model. Mairin Brennan
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