"Many companies have started to make graphene and graphene oxide, and I think they're going to be very hard pressed to come up with a cheaper procedure that's this efficient and as safe and environmentally friendly," Tour said.
The researchers suggested the water-soluble product could find use in polymers, ceramics and metals, as thin films for electronics, as drug-delivery devices and for hydrogen storage, as well as for oil and gas recovery.
Though GO is a natural insulator, it could be chemically reduced to a conductor or semiconductor, though not without defects, Tour said.
With so many potential paths into the environment, the fate of GO nanomaterials concerned Tour, who sought the advice of Rice colleague Lttge.
Lttge and Everett Salas, a postdoctoral researcher in his lab and primary author of the second paper, had already been studying the effects of bacteria on carbon, so it was simple to shift their attention to GO. They found bacteria from the genus Shewanella easily convert GO to harmless graphene. The graphene then stacks itself into graphite.
"That's a big plus for green nano, because these ubiquitous bacteria are quickly converting GO into an environmentally benign mineral," Tour said.
Essentially, Salas said, Shewanella have figured out how to "breathe" solid metal oxides. "These bacteria have turned themselves inside out. When we breathe oxygen, the reactions happen inside our cells. These microbes have taken those components and put them on the outside of their cells."
It is this capability that allows them to reduce GO to graphene. "It's a mechanism we don't understand completely because we didn't know it was possible until a few months ago," he said of the process as it relates to GO.
The best news of all, Lttge said, is that these metal-reducing bacteria "are found pretty much everywhere, so there will be no need to 'inoculate' the environment with them," he said. "The
|Contact: David Ruth|