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K-State chemists pursue the potential of nanoparticles

By Andy Badeker


Predictions and promises run wild in the wide-open field of nanotechnology, from microscopic computers that will build themselves to spacecraft that can define their missions in a galaxy far, far away. But Kansas State University chemists are applying these new-millennium building blocks to solve earthier problems like hazardous waste, toxic bacteria or life-saving pills that deteriorate in tropical climates.

However big the idea is, "nano" anything starts small: a nanometer is a billionth of a meter. Kenneth J. Klabunde, a K-State university distinguished professor of chemistry, defines "nanomaterials" as ranging in size from one to 100 nanometers. Smaller than your average virus, bigger than an atom.

At that size, elements can, sometimes, be coaxed into new and useful combinations, which is what all the buzz is about, says Christer B. Aakeroy, a K-State professor of chemistry who studies crystal engineering at the "supramolecular" level, a new phase of synthesis, he said.

"We already rival nature in our ability to make complicated molecules," Aakeroy said. "But how we get from the molecular level to physical properties is still shrouded in mystery."

If chemists can map that no-man's land between single molecules and "condensed matter" like the gold ring on your finger, they'll be able to manipulate such properties as density, melting point, stability and solubility.

"That's when everybody gets excited about applications," Klabunde said.

Klabunde has pioneered research on microscopic nanoparticles. The tiny particles have the ability to absorb and destroy toxic materials, and are capable of counteracting chemical and biological weapons. They also can be used to filter water and purify air. His current work uses porous, absorptive nanoparticles that "glom on to bacteria," he said, and injure their membranes by drying them, changing their pH and quite simply cutting them up.

sporesKilling spores, the dormant form of some bacteria, requires more oomph. Johanna Haggstrom, one of Klabunde's doctoral students, has been adding chlorine and other corrosive halogens to nano-sized metal oxides like titanium dioxide. "That makes these halogens a lot more efficient," she said, in destroying otherwise impervious spores of anthrax, for example. She has been experimenting on a benign strain of that high-profile threat.

"It's a smart way, and a slightly safer way, to deliver halogens," Haggstrom said. As a solid, the product also would be easier than a liquid to clean up after it had done its job of decontaminating a building.

As viewed on his Web site, Aakeroy's work shows delicate chains suspended like jewelry against black backgrounds. He uses hydrogen bonds, the same connection that allows DNA to replicate, to direct the crystallization of molecular building blocks. Aakeroy's Web site is available at:

sporesMaking crystals sounds straightforward, but Aakeroy points out that the difference between a pencil lead and a diamond lies in how they crystallized: Both are pure carbon. Control molecular recognition and assembly, Aakeroy said, and you control a wide range of the above-mentioned physical properties and behaviors.

"A sad fact of pharmaceuticals is that many potentially invaluable compounds are poorly soluble," Aakeroy said. Eliminate that obstacle, and a boom in new and more effective drugs could result. Make an existing drug more stable, and it could endure the humidity at a rain forest clinic.

Other possibilities? A net of metallic ions could be designed to trap molecules of nerve gas while allowing oxygen in and carbon dioxide out. Presto, a suit of biochemical armor. The same principles could lead to filters that would detoxify aging stockpiles of banned herbicides, Aakeroy suggested.

Note the "could" and "would." Though grant money from the military and private industry is funding research into biochemical defense and pharmaceutical applications, Aakeroy said, "we have to demonstrate proof and process" before any nanofactories break ground.

"We've made this field up in the last 10 years," he said, "and we started by looking at problems that were far too complicated."

Aakeroy seems relaxed about a slow trip toward a distant horizon.

"I like the little, simple steps" around which an experiment can be designed, he said. "I like listening in on molecular conversations. If it takes us a bit of time to translate their communications, I'm absolutely fine with that."


Images: (Top) Control of Bacillus anthracis spores, delta sterne strain. (Bottom) Treated spores.

Spring/Summer 2007