Gold Nanoparticles Yield Better Catalysts
In the search for new catalysts to help break down air pollutants, scientists at the DOE's Brookhaven Lab may have discovered the mystery behind a new "gold standard" -- gold nanoparticles layered on titanium dioxide.
Using a technique called high-resolution photoemission at the National Synchrotron Light Source, the Brookhaven team has shown that the addition of gold, a notoriously unreactive element, to titanium dioxide, a widely used industrial catalyst, changes the electronic properties of both materials. The result is a catalyst that is five to ten times more reactive than ordinary titanium dioxide when it comes to adsorbing and destroying sulfur dioxide (SO2), a common cause of acid rain. "The two materials work cooperatively to dissociate the SO2 molecule," said Brookhaven chemist Jose Rodriguez, who leads the team.
The scientists are now investigating whether this gold-titania catalyst might also be effective at breaking down the deadly components of chemical weapons.
Gang Liu, a postdoctoral fellow in Rodriguez's group, presented this work, which was funded by DOE's Office of Science, Division of Chemical Sciences, during the "Nanoscience and Nanotechnology" session on Thursday, August 22, at 9:45 a.m. in the Hynes Convention Center, Room 107.
New Class of Solvents May Clean up Radioactive Waste
Scientists at the DOE's Brookhaven Lab are investigating whether ionic liquids might be useful as solvents for cleaning up radioactive waste. These new solvents are made of positive and negative ions, just like sodium chloride and other common salts that form ordered crystalline solids, but they are liquid at room temperature because the ions are chosen so that they pack very poorly to form weak crystals.
Ionic liquids offer many benefits over traditional solvents, says Brookhaven chemist James Wishart, because they don't evaporate or burn and can probably be used over and over again. Another reason they might be useful in breaking down nuclear waste is that they often contain boron and/or chlorine, two elements that block neutrons from starting unwanted nuclear chain reactions.
But before ionic liquids are put to the test cleaning up spent fuel and other nuclear waste, the scientists need to know if these liquids can withstand the radiation. To find out, Wishart and his colleagues are bombarding samples of various ionic liquids with a beam of high-energy electrons generated by Brookhaven's Laser Electron Accelerator Facility (LEAF).
The pulses and resolution at LEAF allow the scientists to follow chemical changes over trillionths of a second, and observe the reactions of the short-lived primary radicals produced by the radiation. "Accumulation of radiation damage depends on the yields and reactivity of the primary species," Wishart said. "Looking at these fast reactions will allow us to determine which ionic liquids can tolerate radiation and how they can be made even more stable."
Wishart presented a talk on this work, which was funded by DOE's Office of Science, Division of Chemical Sciences, during the "Ionic Liquids as Green Solvents: Progress and Prospects" session on Thursday, August 22, at 4:20 p.m. in the Hynes Convention Center, Room 200.
Tweaking Charges and Spins in Oxides
When complex metal oxides are cooled down to low temperatures, the charges and spins of the metal ions can arrange themselves in an orderly fashion. This ordering depends on the subtle details of the composition and may be useful for electronic devices and sensor applications.
In systematic studies over the last three years, a collaboration of scientists from the DOE's Brookhaven Lab, Oslo University, and Ohio State University has characterized a particular family of oxides. The team has shown that minute variations in the oxygen stoichiometry (variations in the relative amount of oxygen) result in dramatically different ordering of charges and spins, or even the suppression of ordering.
Using high-resolution x-ray and neutron powder diffraction in combination with thermal, electrical, and magnetic transport measurements at the National Synchrotron Light Source, the team identified and characterized "transient phases." These phases exist only in a very narrow temperature range and when the material has a particular oxygen content. In particular, the high-resolution x-ray powder diffraction studies allowed the scientists to correlate minute lattice expansions with changes in magnetic and electronic properties.
"The fundamental understanding of these processes may help scientists exploit the ability to tweak these properties for application in devices such as sensors, catalysts, and electronic devices," said Brookhaven physicist Thomas Vogt.
Vogt presented a talk on this research, which is funded by DOE's Office of Science, Division of Materials Science, during the "Metal Oxides" session on Tuesday, August 20, at 11:55 a.m. in the Hynes Convention Center, Room 313.
Also of Interest:
* Steven Dierker, Chairman of Brookhaven's National Synchrotron Light Source Department (http://nslsweb.nsls.bnl.gov/nsls/Default.htm), gave an overview of synchrotron radiation, the facilities that produce it, and its most significant applications for research in the chemical sciences on Wednesday, August 21, at 8:40 a.m. at the Sheraton Boston, Back Bay Ballroom D.
* Richard Hahn of Brookhaven's Chemistry Department presented the latest results from the Sudbury Neutrino Observatory, which show evidence of neutrino oscillations (http://www.bnl.gov/bnlweb/pubaf/pr/2002/bnlpr042002.htm) on Sunday, August 20, at 9:25 a.m. at the Back Bay Hilton, Washington Room.
Complete information about the 224th ACS meeting can be found at: http://www.chemistry.org/meetings/boston2002
The U.S. Department of Energy's Brookhaven National Laboratory (http://www.bnl.gov) conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies. Brookhaven also builds and operates major facilities available to university, industrial, and government scientists. The Laboratory is managed by Brookhaven Science Associates, a limited liability company founded by Stony Brook University and Battelle, a nonprofit applied science and technology organization.