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Building the Nano World

Jia Grace Lu, associate professor of physics in USC College. Photo credit Max S. Gerber.
Jia Grace Lu, associate professor of physics in USC College. Photo credit Max S. Gerber.

We can assume by its prefix that a nanometer is small — very small, in fact. One nanometer is equal to one billionth of a meter. In comparison, a single human hair is about 50,000 nanometers wide, and a nanowire diameter is more than 1,000 times smaller than the width of a hair.

Jia Grace Lu has spent the last four years researching nanowires in the College’s Department of Physics and Astronomy. These wires can be used in everything from photodetectors to chemical sensors, with countless applications still awaiting discovery.

In her lab, Lu constructs tightly-packed clusters of nanowires from metals or semiconductors. Some are formed in a disordered mass, like steel wool, and some are vertically aligned like the bristles on a flat hair brush. While some types of nanostructures are solid, others are hollow, and both allow a flow of electric charge.

Lu is researching the characteristics of these structures to gain a comprehensive understanding of their properties. “By studying fundamentals, we gain the potential to apply the technology to different devices,” she said.

Nanowire sensor devices that Lu has worked on include an “electronic nose,” a compact, portable sensor that can be used by civilian or military personnel to identify toxic chemical gases. She is also developing a nanoscale pH probe, a wire that can be inserted into a living cell to measure and detect its in vivo functions.

The wires have a high surface-to-volume ratio, which is one unique aspect that makes them so versatile. “Because the wires are so small, chemicals adsorbed on the surface have a significant effect on the conducting current inside,” Lu said.

Lu is also helping to develop several types of nanowire-based solar cells for the Department of Energy-funded Center for Energy Nanoscience at USC. Working together with researchers from USC Viterbi and fellow College professors, Lu’s goal is to design sustainable and renewable solar cells that achieve high efficiency and low production cost. She is also using nanowire arrays to create a lightweight, flexible solar cell, which could be applied to plastics, fabrics and other substrates.

According to Lu, the applications of nanotechnology are innumerable, and although they are small, these nanowires could soon be making big changes in the way we live.

Read more articles from USC College Magazine's Spring/Summer 2010 issue.