NEWS
Dal Nogare Award Nominations The Chromatography Forum of the Delaware Valley is requesting nominations for the 1993 Stephen Dal Nogare Award for excellence in and significant contributions to the field of chromatography. All nominations should consist of one or more letters of nomination and a biographical sketch describing the nominee's experience and contributions to the field. Nominations submitted in previous years can be renewed and appended with an updated letter. Send nominations by March 31 to Mary Ellen McNally, E. I. du Pont de Nemours & Co., Agricultural Products Department, Experimental Station, Wilmington, DE 19880-0402.
The Count Is In The results of a recent Soviet-American effort to count the neutrinos coming from the Sun (see Anal. Chem. 1990, 62, 1147 A) have been published. The count is, within the limits of the detector, almost 0. Neutrinos are nearly massless, subatomic particles produced by the Sun's fusion reaction. Billions of solar neutrinos bombard the Earth every second, passing right through to the other side, as if the planet did not exist. However, should a neutrino encounter a gallium atom, an isotope of germanium is formed. Measuring the amount of germanium tells how many neutrinos were caught. The number of neutrinos produced by the Sun can be predicted from the rate of fusion. The detector in the Soviet—American Gallium Experiment (SAGE) consists of 30 tons of liquid gallium in four containers. Using standard models of the Sun, the researchers expected to find the remnants of —17 collisions. In the first half of 1990, the scientists looked five times for the germanium. The SAGE detector only revealed three events. There are two possible explanations for the results. The internal operation of the Sun may not be as well understood as originally thought, or neutrinos may change their character after leaving the Sun. If neutrinos change, particle physics will have to undergo revolutionary changes. To help answer their questions, researchers have placed a source of neutrinos next to the detector to calibrate the experiment. They have also added another 30 tons of gallium to the containers. Another gallium experiment in Europe is expected to confirm SAGE's results this summer.
Quantum Dots Scientists at the Lawrence Berkeley Laboratory (LBL) and the University of California at Berkeley (UCB) have synthesized large quantities of gallium arsenide clusters. According to the researchers, the synthesis represents an important step toward using such clusters to
make quantum dots—nanometer-sized crystals that could be used as optical memory chips for computers. Clusters are aggregates of atoms packed together into spherical clumps that are too large to be a molecule but too small to be a liquid or a solid. Because of their size, they often exhibit unusual physical and chemical properties. In the past, studying cluster phenomena was a function of sample availability. Laser-based production methods can provide the appropriate size cluster for structural studies, but not in large enough quantities to study its physical properties. Paul Alivisatos, a chemist in the Materials Science Division at LBL, and his group have developed a method for producing powders that may contain millions of the clusters. It begins with nucleation, or forming crystal nuclei in solution that will react to form a desired type of cluster. The clusters combine and grow in size as individual clusters come together. Growth continues until the desired size is reached; then it is chemically terminated, and the clusters are precipitated out of solution. To produce the gallium arsenide clusters, gallium trichloride was reacted with trimethylsilyl arsine in the solvent quinoline at 240 °C for three days. When the solvent was removed, a red powder remained. UCB chemist Avery Goldstein analyzed this material by electron microscopy and found football-shaped clusters with a major axis of 45 Â and a minor axis of 35Â. The researchers, who have also experimented with making cadmium sulfide clusters, have found one drawback to producing clusters through chemical rather than laser-based methods: The selection of a specific size of cluster is not as precise. Says Alivisatos, "We typically see a variation of about 5% in the size of clusters we produce, which is not as good as it could be. However, because we make so much material we can do more experiments with our samples."
For Your Information The fourth edition of the Eight Peak Index of Mass Spectra is available from the Royal Society of Chemistry. This edition contains more than 80,000 spectra covering 65,600 compounds. Each entry contains the mass-tocharge ratios of the eight most abundant ions and their corresponding intensities, molecular formulas, molecular weights, compound names, and collection identification numbers. The parent peak intensity is provided when it is outside the eight most abundant ions, and the CAS Registry Number is also listed, if available. Data are sorted in three ways in three volumes: by molecular weight and formula, by molecular weight and m/z value, and by the m/z values of the two most abundant ions. To order in North America, contact CRC Press, 2000 Corporate Blvd., N.W., Boca Raton, FL 33431 (407-9940555). Outside this area, contact Royal Society of Chemistry, Turpin Transactions Ltd., Blackhorse Road, Letchworth, Herts SG6 1HN, U.K. (44-0-462-672555; fax 44-0-462-480947).
ANALYTICAL CHEMISTRY, VOL. 64, NO. 4, FEBRUARY 15, 1992 · 261 A
