Neutron Sciences Highlights

Targeted Drug Delivery Systems

Neutron scattering studies reveal how molecules function within solutions at different pH levels (above). Simulating levels present in the human body helps determine how drugs will act when administered.

A young researcher in the Neutron Scattering Sciences Division (NSSD) is using a broad suite of elastic and inelastic SANS to study the structure and dynamics of polyamidoamine (PAMAM) starburst dendrimers in the hope that these repeatedly branched molecules will become an effective, targeted drug delivery system for the treatment of cancers.

Wei-Ren Chen, who received his doctorate in nuclear science and engineering at MIT in 2004, is a Clifford G. Shull fellow at ORNL. Chen studies "dendritic molecules," synthetic macromolecules that can be envisioned as polymeric colloidal particles, which are globular in shape. Read More...

Energy Solutions from Catalysis Research

Catalysis research revealed the dynamics of surface water on catalytically active nanomaterials. Such studies are playing a key role in developing solutions for energy needs, environmental protection, and the problem of global warming.

How water molecules move at the interface with solids is one of the more urgent questions in current research into catalytic materials. Using a combination of neutron scattering and molecular dynamics simulations, researchers at SNS were able to probe interfacial water dynamics on a time scale from a nanosecond (1 billionth of a second) to a picosecond (1 trillionth of a second). In the process, they gained a fundamentally new understanding of how water engages a surface at varying temperatures. Water is a key element in many catalytic reactions, and the ultimate goal is to develop new catalytic and catalyst-support nanomaterials. Those nanomaterials can then be used as catalysts for chemical production processed in various industries. Read More...

New Methods for Solar Energy Conversion

Neutron research on biomolecules, such as this rendering of a light-harvesting complex, is helping scientists develop synthetic, bio-inspired systems for solar energy conversion.

Natural photosynthetic systems have developed a complex machinery for efficient conversion of sunlight to chemical energy, which to the present day has not been matched by human-made technologies. ORNL researchers are investigating ways to mimic these exquisite molecular architectures to develop synthetic, bio-inspired systems for the conversion of solar energy to electricity and fuel.

The ultimate goal, says principal investigator Hugh O'Neill of the Chemical Sciences Division (CSD), is to convert solar energy into electricity or fuel, thereby developing a competitive energy source. Read More...

Biomass Studies: Growing Energy

The physical structure of lignin (a component of biomass) in aqueous solution was modeled using computer simulation and neutron scattering data. Biomass research can help lower energy costs, reduced dependence on oil, and decrease pollution.

Biomass from plants offers a potentially abundant source of ethanol from the fermentation of component sugars. But its complex laminate structure, consisting of the biopolymers cellulose, xylan, pectin, and lignin often collectively termed lignocellulose is difficult to disrupt and break down into fermentable sugars. Pretreatment is required to separate the components, detach lignin, and discompose the cellulose fibers for efficient conversion to fermentable sugars.

To learn why lignocellulose is so diffucult to break down, a team of ORNL researchers is using the Bio-SANS instrument at HFIR and the unique resources of the Cray XT4 supercomputer at the National Leadership Computing Facility (NLCF) at ORNL to investigate biomass samples from the BioEnergy Science Center (BESC), also at ORNL. Read More...

Advances in Unconventional Iron-Based Superconductors

Landmark research about a newly discovered superconducting material will lead to more efficient, less-expensive products in fields such as energy, transportation, and medicine.

In mid-March 2008 Pengcheng Dai, researcher in the Neutron Scattering Science Division (NSSD) and joint professor of condensed matter science at the University of Tennessee, attended a conference in his native China. He asked a fellow scientist familiar with a paper in the February 23, 2008, issue of the Journal of American Chemical Society why he and his colleagues were so excited. The scientist called the paper "fantastic" and said that the paper reports the discovery in Japan of a new iron-based superconducting material. Read More...

Self-Healing Polymers

Neutron research with polymers is opening up a new field of biologically dynamic materials that can be used for improved antimicrobial agents and medical devices, such as hip implants.

Imagine a hip replacement made of materials so tallored that only a thin layer on the outer surface the part in contact with the body is biocompatible, while the rest of it is designed to be strong and stable to cope with any stress the body might put on it. Or imagine a material designed to coat a doorknob, in which the outer layer is designed to be microbially resistant, while the rest of it, that which holds it to the doorknob, is tallored for adhesive properties. When someone with a cold touches the doorknob, the antimicrobial agents immediately kill the bacteria, while the adhessive properties in the matrix material keep the coatling in place. A collaboration of polymer scientists at ORNL is using the SNS Liquids Reflectometer to study the dynamics of polymer mixtures that hold promise for applications from biocompatible films for human implants to semiconductors, substrates for electronic displays, toys for children, and durable, self repairing aircraft body materials. Read More...

ORNL Research Reveals Nanoscale Structure of New Metallic Alloys

	Structure of nanocrystalline particles in BMG Zr52.5Cu17.9Ni14.6Al10Ti5. Click image for a larger view.

Because structure determines the properties of materials, a fundamental understanding of composition variations and morphology at the nanoscale is essential in the design of advanced materials. Led by ORNL’s Neutron Sciences researcher Xun-Li Wang, a recent study combining state-of-the-art microscopy, in situ scattering at Argonne National Laboratory’s Advanced Photon Source, and neutron data from the Paul Scherrer Institute revealed the structure of the nanocrystalline particles in Zr52.5Cu17.9Ni14.6Al10Ti5, a rather complex multicomponent bulk metallic glass (BMG) alloy. Potential applications range from biomedical devices to sporting goods to automotive and aerospace structures.

Experimental challenges have kept the structure of nanocrystalline particles in metallic glasses a mystery for more than a decade. However, the findings from this research promise new possibilities for developing materials with the ideal properties for specific applications. Such “designer” materials could lead to less expensive, more efficient, and better performing materials in a variety of fields.

This image to the right was selected for the cover of the March 2009 issue of Advanced Materials (published by Wiley-VCH), one of the top publications in the field of materials science.

Cover picture info: Adv. Mater. 101, Vol. 21, Issue 3 (March 2009).

Phonon Density of States of LaFeAsO_1-xF_x

A. D. Christianson, M. D. Lumsden, O. Delaire, M. B. Stone, D. L. Abernathy, M. A. McGuire, A. S. Sefat, R. Jin, B. C. Sales, D. Mandrus, E. D. Mun, P. C. Canfield, J. Y. Y. Lin, M. Lucas, M. Kresch, J. B. Keith, B. Fultz, E. A. Goremychkin, R. J. McQueeney

We have studied the phonon density of states (PDOS) in LaFeAsO_1-xF_x with inelastic neutron scattering methods. The PDOS of the parent compound (x = 0) is very similar to the PDOS of samples optimally doped with fluorine to achieve the maximum Tc (x~0.1). Good agreement is found between the experimental PDOS and first-principle calculations with the exception of a small difference in iron mode frequencies. The PDOS reported here is not consistent with conventional electron-phonon mediated superconductivity.

Read the full article: Phys. Rev. Lett. 101, 157004 (2008).

This research was conducted at SNS on the Wide Angular-Range Chopper Spectrometer (ARCS) and at HFIR on the HB-3 Triple-Axis Spectrometer.