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Finding Common Ground in Nanotechnology Research
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Photos A, B, and C show selenium nanospheres
formed by bacteria. D, E, and F show selenium
particles formed by chemical means. Selnium as
nanospheres exhibits vastly different optical
properties than the element's well-known counterpart.
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Working at the nexus of biology and nanotechnology, a researcher and an alumnus from Rensselaer have released findings that could lead to the tailoring of bacterial processes for smaller, faster semiconductors and other electronic devices.
Pulickel Ajayan, professor of materials science and engineering, and geobiologist Ronald Oremland ’68 reported that three different kinds of common bacteria “grow” the element selenium in the form of uniform nanospheres. The nanoscopic balls exhibit vastly different properties than selenium that is a trace mineral found in topsoil.
Selenium is used in photovoltaic and photoconductive technologies. It is incorporated in many electronic and technical applications, such as semiconductors, photocopiers, and photocells.
The findings of Ajayan and Oremland were published in the journal Applied and Environmental Microbiology (an American Society of Microbiology publication) in January. A summary of the research also was featured the same month in the “Editor’s Choice” section of Science magazine.
Oremland, a senior scientist at the U.S. Geological Survey in Menlo Park, Calif., has been studying anaerobic bacteria that respire, or “breathe,” soluble salts, or “oxyanions,” of toxic elements, such as selenium and arsenic. He recently discovered that some of these microbes form distinctive selenium nanoscopic balls, which each measure 300 nanometers in diameter, on the outside of their cell envelopes.
Knowing little about what kinds of properties selenium exhibits on the nanoscale level, Oremland, the paper’s lead author, turned to his alma mater to enlist the help of nanomaterials expert Ajayan,.
Ajayan and his collaborators found that the nanospheres exhibited enhanced optical and semiconducting properties. They also discovered that the nanospheres on each of the three bacteria studied were different from each other and fundamentally different from amorphous selenium particles formed by chemical means.
“Surprisingly, we found different bacteria produce spheres with different arrangements of the selenium atoms and hence different optical properties,” says Ajayan. “Remarkably, these conditions cannot be achieved by current methods of chemical synthesis.”
The research could lead to the production of nanospheres, nanowires, nanorods, and other nanostructures with precise atomic arrangements for smaller, faster semiconductors and other electronic devices.
Other collaborators include researchers from University of Guelph in Canada, the Naval Surface Warfare Center in Virginia, and New Mexico State University.
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