Chad Talley (right) and Thomas Huser
National Security, Health and Nanoscience
February / March 2005
Volume 3 Number 1
Can the study of nanoparticles, tens of thousands of times thinner than a human hair, contribute to the nation's security and improve human health? For scientists at Lawrence Livermore National Laboratory, the answer is a resounding "yes." Using the tools of nanotechnology, LLNL scientists are conducting research that supports the laboratory's national security missions. While Livermore's primary goals are ensuring the effectiveness of the nation's nuclear weapons stockpile and protecting the nation against chemical and biological threats, its basic and applied research could soon evolve into technology that can bolster human health, contribute to energy independence, and help protect the environment.
LLNL has developed a three-pronged strategy towards nanoscience in support of national security, built around three centers that work collaboratively. The Nanoscale Synthesis and Characterization Laboratory (NSCL) focuses on hard materials for stockpile stewardship. The BioSecurity and Nanosciences Laboratory (BSNL) develops soft materials solutions to bio-security challenges. And the Quantum Simulations Group (QSG) uses high-performing computing to help understand and design materials for both missions.
"Working at the intersection of biology, chemistry and materials science, we seek new ways to characterize and detect harmful pathogens such as viruses, spores and bacteria," says Jim De Yoreo, director of the BSNL "We believe our science can help fight such threats as anthrax, plague and botulinum toxin."
To efficiently detect, diagnose and find treatments for these pathogens—€”whether their source is a bioterror attack or natural exposure—€”researchers need to understand both how the organisms function at the most basic, molecular level and how the properties of nanomaterials change when they encounter those organisms. BSNL researchers are using special microscopes to investigate the behavior of structures, such as individual virus particles, that are no bigger than ten nanometers (a nanometer is one-billionth of a meter). At the same time, scientists are using materials of comparable size to build miniature detectors capable of seeing a single virus.
In one project, BSNL researchers have developed unique optical microscopes that use lasers, fluorescent dyes, and gold nanoparticles to quickly detect the presence of single toxin molecules. "With this approach," says De Yoreo, "we may one day be able to detect ultra-low concentrations of many substances, including DNA, viruses, bacteria, and even chemical agents."
LLNL's internal-reflection fluorescence microscope, for example, can positively identify a single target molecule tagged with a fluorescent dye floating in a sea of other molecules in two hours or less, compared with up to four days for traditional assays. Another Livermore approach uses a technique called "surface-enhanced Raman spectroscopy" to identify cells and track their activity without introducing antibodies, which can disturb the cells' normal functioning.
When a molecule is exposed to a laser, it vibrates and scatters the light at a distinct frequency, a phenomenon known as Raman scattering. BSNL physicist Thomas Huser and his colleagues have developed optical probes that can detect the Raman scattering of a single molecule, and use spectroscopy to look for differences between individual cells.
Huser and his colleagues are using nanoprobes to study how microbes are able to digest toxic materials as part of the Department of Energy's Genomics: GTL Program, the successor to DOE's involvement in the Human Genome Project. And they are part of a new effort to study prions, the mysterious misfolding proteins that cause mad cow disease and Creutzfeldt-Jacob disease in humans.
It's Not Just Size that Matters
What makes nanotechnology such a scientifically interesting and promising field isn't just the small size of the materials—€”it's the special properties that materials take on at the nanoscale. At that size the laws of quantum mechanics take over, and atoms rearrange themselves in unexpected ways. A material's shape and crystalline structure change, as do its melting and boiling temperatures. Its magnetic properties may also be different at the nanoscale.
Take quantum dots, for example. These nanometer-sized specks of silicon and germanium, containing between 100 and 1,000 atoms, have different electrical and optical properties than larger aggregates of the same material. LLNL scientists have been able to make silicon and germanium quantum dots that emit light throughout the visible spectrum, from the infrared to the ultraviolet, just by changing the size of the dots.
There are many possible uses of the rainbow of colors emitted by quantum dots, including ultrafast, all-optical switches and logic gates, tunable lasers, and nanocrystal solar cells. A single quantum dot can function as a microelectronic unit such as a transistor—€”forming the basis of nanoelectronics. An array of billions of dots would have incredibly fast operating speeds—€”one picosecond or less—€”and extremely low power requirements.
Taking advantage of Livermore's capability in high-performance computing, the Quantum Simulations Group has developed cutting-edge algorithms that accurately simulate the structure and properties of these nanoparticles.
Recently, researchers in the QSG led by the group's director, Giulia Galli, computationally modeled nanodiamonds—€”diamond particles consisting of just a few hundred atoms—€”and found to their surprise that their outer surface is shaped like a fullerene, or "buckyball," similar to other pure carbon clusters. Collaborating with Tony van Buuren, an experimental physicist in the Nanoscale Synthesis and Characterization Laboratory, the team was the first to predict the exotic properties of "bucky diamonds," which could constitute a new family of carbon clusters.
The Livermore simulation team is now working with NSCL experimentalists to establish a basic knowledge of the structure and optical properties of bucky diamonds and other semiconductor nanoparticles, with an eye toward producing silicon nanoparticles that are useful for chemical and biological detection and other biological and electronics applications.
While QSG researchers are working to understand the properties of materials at the nanoscale, scientists in the NSCL are pursing the development of designer materials that can be synthesized and assembled from the "bottom up," one atom at a time. The bucky diamonds are just one example; NSCL researchers are also focused on ways to fabricate nanostructured alloys that can be used as targets in the Laboratory's National Ignition Facility (NIF), which will be the world's most powerful laser facility when completed later this decade.
Alex Hamza, the NSCL's director, notes that by starting with nanostructures, scientists will be able to control the target materials' precise properties, enhancing the target's performance and NIF experiments.
Nanotech Enters the Marketplace
Nanotechnology is a new field of research, dating back only to the late 1970s, but applications are already beginning to find their way into the commercial marketplace. One of the earliest and most promising is NanoFoil—„, a low-temperature joining technique developed at Livermore that is now being commercialized for use in applications ranging from computer chips and circuit boards to attaching ceramic armor on military vehicles.
Licensed by Reactive NanoTechnologies (RNT) of Hunt Valley, Md., the reactive joining process can form strong, electrically and thermally conductive bonds between different materials and components without damaging temperature-sensitive materials. Nanostructured foils, which consist of thousands of alternating layers of aluminum and nickel 10 to 20 nanometers thick, release heat through an atomic-scale chemical reaction when activated by a small pulse of energy. When placed between two layers of solder or braze and the two components to be joined, the activated foil generates enough localized heat to quickly melt the solder or braze and form a bond—€”while the materials being joined remain at or near room temperature. The new approach enables precision, lead-free soldering and brazing, eliminates the need for conventional heat sources such as furnaces, torches and lasers, and can be used to join dissimilar metals, form strong ceramic-to-metal bonds and mount and seal such temperature-sensitive components as microprocessor chips and optical devices.
NSCL senior scientist Troy Barbee developed the technology along with Tim Weihs, a postdoctoral fellow in Barbee's laboratory who subsequently left Livermore to continue his research in reactive foils as a professor at Johns Hopkins University. There he teamed up with fellow professor and modeling expert Omar Knio, along with many students and postdocs. After five more years of additional development, they founded RNT in 2001.
In its strategic plan published in December, the federal government's National Nanotechnology Initiative (NNI) praised the RNT-LLNL-Johns Hopkins partnership that produced NanoFoil: "The Reactive NanoTechnologies story shows how entrepreneurs can transfer technology developed through federally funded research to the private sector. A broad array of customers, from computer chip and circuit board makers to aerospace manufacturers, are enthusiastic about this new bonding method," according to the NNI.
Like the science itself, many of the researchers pursuing the promise of nanoscience are relatively young. More than half of the scientists in LLNL's three nanoscience centers, for example, are less than 35 years old.
"From the start," says De Yoreo, "we adopted a strategy of investing in young talent, both from around the laboratory and around the nation, who are just starting their careers."
De Yoreo says the many young people create an environment where scientists are willing to try new approaches and seek breakthroughs: "They have youthful enthusiasm, and a willingness to risk failure as they explore the frontiers of science."
Charles Osolin is a public information officer at Lawrence Livermore National Laboratory.
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