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Bacteria Recruited to Produce Graphene

Anne Meyer

Anne Meyer (J. Adam Fenster, University of Rochester)

11 July 2019. Labs in the U.S. and the Netherlands developed techniques to sustainably produce high-quality graphene with more capabilities, using a strain of bacteria. Researchers from University of Rochester in New York and Delft University of Technology describe their process in the 4 July issue of the journal ChemistryOpen.

A team led by Rochester biologist and materials scientist Anne Meyer and quantum-nanomaterials professor Herre van der Zant in Delft are seeking more sustainable and scalable methods to produce graphene, a material with many desirable qualities for a range of industries. The material is very light, strong, chemically stable, and only one atom in thickness, arrayed in a hexagonal pattern. Graphene can conduct both heat and electricity, with many applications in electronics, energy, and health care. In 2010, two researchers at University of Manchester in the U.K. received the Nobel Prize in physics for their discoveries on graphene.

But producing graphene safely in high volumes is difficult. Current production methods using chemical vapor deposition can produce single layers of graphene. While this technique produces a high-quality material, it’s a slow process requiring a controlled environment to grow the graphene, and continued problems separating graphene from its growing surface. Another technique uses exfoliation, or shredding layers, of graphite, as found in pencils, to graphene oxide, then chemically reducing graphene oxide to pure graphene. While the process is faster and more scalable than chemical vapor deposition, it requires use of highly toxic and unstable (i.e., explosive) hydrazine to reduce graphene oxide to graphene.

The Rochester-Delft team investigated an alternative process, to replace the use of hydrazine with a safer and more sustainable method that can still result in high-quality graphene. Their process employs a bacteria known as Shewanella oneidensis found in deep-sea environments, as well as soil. Shewanella oneidensis has an unusual characteristic for microbes, namely an appetite for heavy metals. These bacteria oxidize the carbon in heavy metals, and thus are studied as a method for environmental clean-up of chemical spills.

In this project, Meyer, van der Zant, and colleagues used Shewanella oneidensis in a biological process instead of the chemical hydrazine to reduce flakes of graphene oxide to pure graphene. The results show their microbial process can produce both flakes and bulk graphene with at least comparable physical properties of chemically-produced graphene. In addition, microbe-produced graphene outperforms chemically-produced graphene in some respects. The bacterial graphene is thinner than chemically-produced graphene and more stable, which allows for longer storage.

Moreover, the researchers found bacterial graphene has specialized qualities not found in chemically-produced varieties, including an affinity for biological molecules. This property makes bacterial graphene suitable for field-effect transistors, or FETs, electronic components found in biosensors and medical devices. “When biological molecules bind to the device,” says Meyer in a University of Rochester statement, “they change the conductance of the surface, sending a signal that the molecule is present.”

Meyer notes, “To make a good FET biosensor you want a material that is highly conductive but can also be modified to bind to specific molecules,” and adds that bacterial graphene has left-over carbon-oxygen bonds that can bind to target molecules. Bacterial graphene can be formulated as well into conductive inks for printing graphene circuits in electronic components or into fabrics or paper.

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