Study Finds Potential in Nanotube-producing Bacteria
Two
engineers at the University of California, Riverside are part of a
binational team that has found semiconducting nanotubes produced by
living bacteria -- a discovery that could help in the creation of a new
generation of nanoelectronic devices.
The research team said this could be the first time nanotubes have
been shown to be produced by biological rather than chemical means. It
opens the door to the possibility of cheaper and more environmentally
friendly manufacture of electronic materials.
Study results appear in the Dec. 7 issue of the early edition of the Proceedings of the National Academy of Sciences.
The team, including Nosang V. Myung (http://www.engr.ucr.edu/faculty/chemenv/myung.html),
associate professor of chemical and environmental engineering in the
Bourns College of Engineering, and his postdoctoral researcher
Bongyoung Yoo, found the bacterium Shewanella facilitates the
formation of arsenic-sulfide nanotubes that have unique physical and
chemical properties not produced by chemical agents.
"We have shown that a jar with a bug in it can create potentially
useful nanostructures," Myung said. "Nanotubes are of particular
interest in materials science because the useful properties of a
substance can be finely tuned according to the diameter and the
thickness of the tubes."
The whole realm of electronic devices, from computers to solar
cells, depend on chemical manufacturing processes that use tremendous
energy, and leave behind toxic metals and chemicals, the researchers
said. Myung said a growing movement in science and engineering is
looking for ways to produce semiconductors in more ecologically
friendly ways.
Two members of the research team, Hor-Gil Hur and Ji-Hoon Lee from
Gwangju Institute of Science and Technology (GIST), Korea, first
discovered something unexpected happening when they attempted to
remediate arsenic contamination using the metal-reducing bacterium
Shewanella. Myung, who specializes in electro-chemical material
synthesis and device fabrication, was able to characterize the
resulting nano-material.
The photoactive arsenic-sulfide nanotubes produced by the bacteria
behave as metals with electrical and photoconductive properties. The
researchers report that these properties may also provide novel
functionality for the next generation of semiconductors in nano- and
opto-electronic devices.
In a process that is not yet fully understood, the Shewanella
bacterium secretes polysacarides that seem to produce the template for
the arsenic sulfide nanotubes, Myung explained. The practical
significance of this technique would be much greater if a bacterial
species were identified that could produce nanotubes of cadmium sulfide
or other superior semiconductor materials, he added.
"This is just a first step that points the way to future investigation," he said. "Each species of Shewanella might have individual implications for manufacturing properties."