Oct 4 2010
This month in Albuquerque, New Mexico, scientists and engineers from around the world will convene to discuss some of the latest breakthroughs in nanotechnology, alternative energy, materials research, and medicine at the AVS 57th International Symposium & Exhibition, from October 17-22, 2010 in the Albuquerque Convention Center.
Reporters are invited to attend the conference free of charge.
1) "ARPES" TECHNIQUE EXPANDS KNOWLEDGE OF PLUTONIUM PROPERTIES
Scientists have long pursued a deeper understanding of the elusive properties of plutonium (Pu), because of its potential application to defense, threat reduction, and energy policy. Plutonium materials exhibit enhanced mass, magnetism, multiple solid-state allotropes, superconductivity, and other properties, according to physicist John Joyce at Los Alamos National Laboratory in NM.
"This wide range of complex properties is both scientifically interesting and also very challenging to understand," says Joyce, "largely because of the complexity of the Plutonium electronic structure."
Central to the understanding of these electronic properties is an accurate picture of the plutonium 5f electrons. Photoemission provides a direct window into the electronic structure, including the 5f electrons, because photoemission measurements can be directly compared to electronic structure calculations. A technique called angle-resolved photoemission (ARPES) adds a component called "crystal momentum" to the measurements, providing a two-dimensional landscape for comparison to theory. The ARPES technique has enabled Joyce and colleagues to investigate how 4f and 5f electronic structure drives the chemistry, physics, and materials science of lanthanide and actinide materials.
"LANL currently has the world's only ARPES capability for transuranic materials including plutonium," says Joyce. "This unique capability provides an opportunity for a deeper understanding of plutonium electronic structure and places our plutonium research on a level comparable to other types of materials research."
The presentation, "Angle-Resolved Photoemission and the 5f Electronic Structure of Pu Materials" is at 9:40 a.m. on Monday, October 18, 2010.
2) PINNING MOLECULES TO A SURFACE
Using techniques common in semiconductor production, a group of researchers at Columbia University has developed ways to control the position of biological molecules, such as DNA, on surfaces with resolution on the order of the size a single molecule. The research could have applications in the study of DNA-protein interactions, for diagnostic investigations, and as a tool for driving self-organization of functional nanostructures on surfaces.
"We are developing a platform for nanoscale biological applications as the material science necessary to place and organize structures as small as one molecule," says Matteo Palma.
The researchers used high-resolution lithographic techniques to fabricate arrays of metal dots with diameters less than 10 nanometers on glass or silicon. By using the dots as anchors for molecules with specific chemical properties, they were able to bind DNA molecules and DNA nanostructures to the surface in a way that retains their shape and function. This provides a platform to study biomolecular interactions. The high resolution of the placement allows precise control of the position and interaction of individual molecules, such as DNA and proteins, and opens the possibility of building electronic devices on the scale of a single molecule.
The presentation, "Bio-functionalization of Nanopatterned Surfaces and their Integration with DNA Nanostructures" is at 2:40 p.m. on Monday, October 18, 2010.
3) WATER AND ITS AMBIGUOUS ROLE IN NUCLEAR WASTE STORAGE
Scientists at the Institute for Transuranium Elements in Germany are studying the effects of oxidation and reduction that water may have on spent nuclear fuel. The solution is challenging because waste fuel is mainly comprised of the so-called group of actinide elements, which includes uranium (U) and plutonium (Pu), and which have peculiar and unpredictable properties.
While most studies indicate water causes actinides to oxidize (lose electrons), recent findings have shown that under certain circumstances exactly the opposite may happen -- water can indeed cause "reduction" of the actinides (gaining of electrons).
Thomas Gouder and colleagues are using X-ray photoemission spectroscopy and other techniques to investigate the adsorption of water ice on the surface of plutonium-dioxide (PuO2) thin-films. Looking at thin-films is akin to understanding the surface of a material, where oxidation and reduction take place first. To isolate the effect, the actinide films are confined to a few atomic layers, where the transformation is best observed.
Previous studies found that water may oxidize PuO2, which may have serious safety implications. In a surprising twist, the group found that under appropriate conditions, the reverse may be true -- that the actinides are actually adding electrons upon their exposure to water ice -- in other words, PuO2 is reducing to Pu2O3, not oxidizing. The process is attributed to a photochemical surface-reaction involving the 5f states of the electrons.
"Understanding the extent of this effect may be of great importance for the prediction of the long-term storage properties of nuclear waste and thus is an intimate part of handling the nuclear legacy," says Gouder.
The paper, "Electronic Structure and Surface Reactivity of Actinide Systems" is at 2:40 p.m. on Monday, October 18, 2010.
Source: http://www.aip.org/