Green Nanotech; Bacteria -Shewanella sp., make filamentous (arsenic sulphide) nanotubes 08-066
Current Situation & Problem
It is known that some bacteria found in geothermal fluids of hot springs can precipitate arsenic trisulphide particles. This important infrared-transparent inorganic material has been used for many different optoelectronic applications, such as waveguides and photonic crystals. Traditionaly, these nanotubes have been manufactured in a very chemical-intensive and not so "green" process.
Improved Smart Solution
Now, researchers in Korea and the US have discovered that, under the correct conditions, a special strain of bacteria can produce arsenic sulphide nanotubes, which may prove useful for making nanoscale devices.
The team, lead by Hor-Gil Hur from the Gwangju Institute of Science and Technology, found that in the absence of oxygen, cultures of Shewanella sp. - a strain of bacteria that can reduce arsenic through respiration and detoxification reactions - can produce long (30 m) filamentous arsenic sulphide nanotubes with diameters ranging from 20-100 nm. X-ray diffraction analysis showed that freshly produced nanotubes were amorphous, but became crystalline over time. These tubes could conduct electricity like metals, were sensitive to UV light, and showed photoluminescence similar to the bulk material, suggesting their potential as building blocks for optoelectronic nanodevices.
Control experiments revealed that a polymeric substance on the outside of the bacteria may serve as a template for the nucleation of the nanotubes.
Although the process is not yet fully understood, these bacteria may prove to be an ecologically friendly alternative to making semiconducting nanotubes without needing additional chemical agents.
Source: Proc. Natl Acad. Sci. USA 104, 20410-20415 (2007)
Comments