Microbe-Metal Interaction Yields Novel Mineral Nanostructures
Nanotube-producing bacteria show manufacturing promise
3-D reconstruction of arsenic-sulfide precipitates by TEM tomography reveals nanotube-like 3-D features. Enlarged View
A new discovery from scientists at the Pacific Northwest National Laboratory, Gwangju Institute of Science and Technology and Pohang Accelerator Laboratory—both in the Republic of Korea—and University of Minnesota and University of California, Riverside, may help produce semiconductors in more ecologically friendly ways to power electronic devices from computers to solar cells. The research team found that the dissimilatory metal-reducing bacterium Shewanella sp. HN-41 facilitates the formation of arsenic-sulfide nanotubes that have unique physical and chemical properties not produced by chemical agents.
Why it matters: The production of nanotubes by biological, rather than chemical, means opens the door to the possibility of cheaper and “greener” manufacture of electronic materials. The photoactive arsenic-sulfide nanotubes produced by the bacteria behave as metals with electrical and photoconductive properties, which may provide new functionality for the next generation of semiconductors in nano- and opto-electronic devices, such as light-emitting diodes, photodetectors in elevator doors and digital cameras and laser diodes that transmit phone calls through glass fibers.
Methods: Using transmission electron microscope (TEM) tomography capability at the Department of Energy’s (DOE's) Environmental Molecular Sciences Laboratory, a national scientific user facility at PNNL, novel mineral nanostructures formed via microbe-metal interaction were observed in nano-detail and three dimensions. The research team produced and characterized the nanostructures, which were grown using Shewanella HN-41, in the absence of oxygen and in the presence of thiosulfate and arsenate. The team found that the precipitate consisted of extracellular, filamentous, arsenic-sulfide nanotubes, 20 to 100 nm in diameter and up to 30 μm in length (more than 1000 times thinner than a human hair). Further tests for conductivity and photoluminescence revealed that the arsenic-sulfide nanotubes possessed the chemical properties of metals and semiconductors, thereby giving promise for original future applications.
What's next?: Future investigations aim to produce biogenic arsenic-sulfide doped with other elements to enhance their photoluminescence or semiconductivity, which will be tested in a bioreactor for the removal of heavy metals. Several other species of Shewanella currently are being tested to see the differences relative to the morphology and properties of arsenic sulfide—differences that are anticipated because of the diversity of related genes. This fundamental research could lead to the application of this novel material to the development of real-life electronic devices.
Acknowledgments: The research was supported by the Environmental Remediation Sciences Program within DOE’s Office of Biological and Environmental Research, the 21C Frontier Microbial Genomics and Applications Center Program (Ministry of Science and Technology, Republic of Korea) and a National Core Research Center Program Grant.
Reference: Ji-Hoon Lee, Min-Gyu Kim, Bongyoung Yoo, Nosang V Myung, Jongsun Maeng, Takhee Lee, Alice C Dohnalkova, James K Fredrickson, Michael J Sadowsky, and Hor-Gil Hur. "Biogenic Formation of Photoactive Arsenic-Sulfide Nanotubes by Shewanella sp. Strain HN-41." Proceedings of the National Academy of Sciences 104(51):20410-20415.