Good Things in Very Small Packages

November 15, 2012—With research focused on nanomaterials, Assistant Chemistry Professor Jong-in Hahm gets big results from the smallest of packages.

Hahm recently received the 2013 Rising Star Award from the American Chemical Society’s Women Chemists Committee (WCC). This spring, she will present some of her latest research on one-dimensional nanomaterials to the WCC. “I will showcase all of the nanomaterials that we grow and synthesize in the lab. And how we tweak their properties to help biomedical sensing,” she said.

Although many of her projects have applications in medicine, Hahm always investigates the many ways that her materials can be used. “Since you can tweak the physical, electrical, optical, or magnetic properties of these materials, it comes down to where you need [them] the most. You’re trying to design your materials to fit that purpose,” she continued.

Before they can make any changes, Hahm and her lab group start with a fundamental understanding of each material. “We spend a lot of time trying to understand the basic principles that are relevant to different properties of these nanomaterials,” she said. “These properties are interrelated, so if you change one property, it may affect another one,” she explained.

Hahm is currently working with carbon nanotubes, which measure about 1.5 nanometers in diameter. (A nanometer is 1 billionth of a meter.) “[They are] about the width of double-stranded DNA,” she said. Hahm uses the size and sharpness of a carbon nanotube to enhance biomedical sensing. Spotting genetic variances or markers can be difficult because each individual has DNA from their mother and father. “There’s really no good way to differentiate two copies of the chromosome—which came from where.

“The physical nature of the carbon nanotube will allow us to look at any sort of variance on the gene under investigation. Without it, you can’t really see the mutations sites on the gene.”

Whether working with carbon nanotubes or zinc oxide nanorods, Hahm can alter significant properties by changing the diameter of the material. According to Hahm, this process has been around from some time and can easily been seen in many stained-glass windows.

“Those colors are coming from nanoparticles, [but] they didn’t call them nanoparticles then,” she said. Flecks of gold and silver in the windows demonstrate how properties can change by making things smaller. “These gold particles, if you make them 25 nanometers in size, all of sudden they glow red. But double the size to 50 nanometers, and they glow green,” she explained. However, these changes in optical properties do not occur after the gold particles are more than several hundreds of nanometers in diameter. “It only happens at the very small scale.”

The process is now easily explained in modern scientific terms. “When things become smaller—smaller to the one thousandth of hair thickness—materials’ properties can be manipulated by fine-tuning the size and shapes of materials,” she explained.

Nanoparticles are not only in our stained-glass windows but in a variety of consumer products. Zinc oxide nanoparticles in sunscreen absorb UV rays and protect the skin. Carbon nanotubes are used to strengthen the frames of tennis rackets and bicycles. Hahm’s own research materials have been applied mainly in the biomedical field: improving protein arrays, enhancing biomedical sensors, and establishing more determinative and quantitative medical experiments.

After two years at Georgetown, Hahm is continuing to grow relationships with other faculty on campus. These collaborations sometimes happen formally, but they often happen from casual conversations about research problems. “All of a sudden you realize that some of your materials can help them solve [their] problem.”

With the ability to change the physical, optical, magnetic, or electrical properties of materials, Hahm is looking at new applications. “Although our main focus in terms of nanomaterials’ applications is currently in the areas of biomedical detection, we have recently expanded our nanomaterials research to the areas of energy.”

—Elizabeth Wilson