Big results on a small scale: The Center for Nanoscale Materials

In the research and development world, many disciplines are merging in the revolutionary field of nanotechnology. Argonne is at the forefront of this revolution with the opening of its Center for Nanoscale Materials.

The Center for Nanoscale Materials(CNM) at Argonne will integrate nanoscale research with Argonne's existing capabilities in synchrotron X-ray studies, neutron-based materials research and electron microscopy with new capabilities in nanosynthesis, nanofabrication, nanomaterials characterization, and theory and simulation. The center is one of five being built at national laboratories across the country as part of the U.S. Department of Energy's Nanoscale Science Research Center program under the Office of Basic Energy Sciences.

Nanotechnology is the understanding and control of matter at dimensions of roughly 1 to 100 nanometers, where unique phenomena enable novel applications. A nanometer is one-billionth of a meter, or about 70,000 times smaller than the width of a human hair.

At the nanoscale, the physical, chemical and biological properties of materials differ in fundamental and valuable ways from the properties of individual atoms and molecules or bulk matter. "It's hard to imagine a technology that won't be impacted by nanoscience, including biotechnology, computation, materials development and energy technology. The list is endless," says Eric Isaacs, director of the CNM.

In fact, nanoscience is already at work in our daily lives. Take, for example, titanium dioxide or TiO 2. The material is normally white and is used as a common ingredient in paint. TiO 2 nanparticles, however, are so small that they are transparent at optical wavelengths, but still block ultraviolet (UV) light. These nanoparticles are now used as a UV blocker in a wide range of sunscreens and cosmetics. Former Argonne scientist Richard W. Siegel was one of the founders of Nanophase Technologies a primary company selling nanoparticles for use in markets from personal care products to a variety of ultra-fine polishing applications, including semiconductor wafers, hard disk drives and optics.

Argonne researchers have also developed a special form of diamond with extremely fine grain sizes. Because the grains are so small, the films can be made extremely smooth, while still maintaining the hardness associated with diamond, making ultrananocrystalline diamond an excellent wear-resistant coating. These films are also biologically inert, so they can be used as a protective coating for medical implants such as artificial retinas. Argonne has spun out a company called Advanced Diamond Technologies to commercialize these materials.

Small is different

"Electrical, optical and thermal properties of materials are drastically altered at the nanoscale," says Isaacs. "For example, any given bulk semiconductor will emit light, or ‘glow,' in only one color. In contrast, almost any color in the rainbow can be obtained using nanoscale particles of that same semiconductor by controlling the size of the nanoparticle. This is due to a fundamental physical law of quantum mechanics, namely quantum confinement."

Nanoparticles are dominated by surfaces and interfaces with other materials, therefore it's important to understand how they relate to a material's atomic structure and surface chemistry. This is where a number of disciplines come into play, including materials physics, surface chemistry and organic chemistry. For example, it has been recently demonstrated that the color of the emission from a semiconductor nanoparticle can be controlled not only by size, but by binding a single or a few organic molecules to the surface.

Creating new materials

The fundamental research conducted at the center will lead to a better understanding of the behavior of nanomaterials, which researchers hope will lead to the creation of new materials that transcend the performance constraints limiting present-day materials and processes. These materials could be incorporated into new devices and applications, such as ultra strong permanent magnet nanocomposites, magnetic electronics and sensors, solar energy conversion and storage systems, and molecular conductors – with specific functionality for diverse energy-related applications.

For example, by manipulating their size and chemical composition, nanoparticles can be tuned to very efficiently absorb light from the sun and turn the absorbed photons into electrical charge carriers. It may also be possible to link them into an inexpensive polymer matrix while still retaining these properties. "This holds forth the promise of making solar cell materials that can be'painted' on — just like house paint — that are inexpensive and efficient. Argonne researchers are exploring the ways in which nanoparticles interact with light and how these interactions can be controlled," says Stephen Streiffer, associate director for science at the CNM.

There are several approaches to designing new nanomaterials. "There are many processes in nature that occur at the nanoscale, even many of the processes in the human body," Isaacs said. "Nature has done a great job, but we can do better. We want to look at how nature does it and then reverse engineer to create new, faster, more efficient processes and better materials.

"We also want to look at natural self assembly. The complexity required for most functional materials, devices or systems, such as laptop computers, is such that creating them at the nanoscale using established top-down methods is extremely challenging. Instead, we want to learn how to do it from the bottom up, taking a lead from what nature has done for billions of years. This is called hierarchical assembly of functional nano-materials," said Isaacs. "We ultimately hope to learn what, if any, are the design rules for self-assembly.”

Work at the CNM will also look at integrating novel materials, specifically combining bio-organic and inorganic materials. This research will lead to the creation of entirely new classes of materials with tailored functionalities unattainable with individual components. "For example, we're looking at designing organic scaffolds that mimic proteins for the catalytic production of hydrogen. This would aid in the development of a hydrogen economy," Isaacs said.

The center will also have the multidisciplinary ability to mix and combine materials with patterning. "We want to go beyond making materials and create novel devices," Isaacs said. "We will have that capability in house. Ultimately, the five nanoscale science research centers bring new capabilities to the Department of Energy's family of user facilities, namely the ability to synthesize and fabricate novel materials and devices at the nanoscale."

For example, information storage currently depends on very tiny spots of magnetic information being written into a layer. However, as magnetic materials in traditional form become very small, they lose their ability to be magnetized in a particular direction, and thus information cannot be stored. This limits the prospects for developing even tinier hard drives.

"By creating unique nanoscale devices and materials that make use of quantum effects that become apparent at length scales below 100 nanometers, it's possible to control the magnetic properties of an electron in these materials and devices such that the state can be set and probed in new ways. This opens up the possibility of magnetic random access memory, that behaves just like the RAM in your computer but consumes little energy and does not lose information when power is shut off," Streiffer said.

Unique tools, facilities

The center's mission also includes the development of state-of-the-art tools, which includes a joint project with Argonne's Advanced Photon Source to develop the world's best X-ray microscope to study these novel materials. "If you're making little things," Isaacs notes, "you need a tool to look at them.

"The resolving power of this instrument will be 1,000 times better than an optical microscope," said Isaacs. "Since X-rays can penetrate materials non-destructively, researchers will be able to determine the three-dimensional structure of nanoparticles embedded in host materials or under growth conditions. Using this tool to characterize extremely small structures will help us build, atom by atom, new materials with desired properties."

Another part of the facility unique to the Midwest and crucial to the development of nanomaterials is an 11,000-square-foot clean room with state-of-the-art nanofabrication capabilities. "When you're trying to make small materials, the smallest speck of dust is huge and can easily spoil the material," said Isaacs.

The center is now in the early phase of accepting users. Over the next year and a half it will fill with people and tools until it is fully operational in October 2008. The center was built as a joint partnership between the Department of Energy and the State of Illinois. The State of Illinois provided $36 million for the 85,000-square-foot building. The Department of Energy is providing $36 million to develop and build the facility's advanced instrumentation and will provide the necessary funds for its operation as a user facility.

"We expect the CNM to attract hundreds of researchers to Argonne each year," said Isaacs. "What they accomplish here will forever change how we view materials and how we put them to work to improve our world."