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Researchers ease preparation of graphene for industrial use

17 Dec 2013

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Graphene is used by many manufacturers in creating electronic devices for industries such as medicine, solar energy and consumer electronics. To prepare the compound for electronic device production, graphene is added with oxygen atoms and treated with chemicals or at high temperatures, which can cause adverse environmental effects. In an effort to make graphene more cost-effective and environmentally friendly, researchers at the Massachusetts Institute of Technology (MIT) and the University of California at Berkeley developed a "mild thermal approach" to modifying the material.

"We've been very interested in graphene, graphene oxide, and other two-dimensional materials for possible use in solar cells, thermoelectric devices, and water filtration, among a number of other applications," said MIT professor Jeffrey Grossman.

"Having oxygen atoms on graphene is so important for so many applications," study co-author Priyank Kumar said. But present methods leave oxygen atoms distributed unpredictably across the graphene's surface, and involve treatment with harsh chemicals, or at temperatures of 700 to 900°C.

The group's new approach involves exposing the material to relatively low temperatures, just 50 to 80°C, with no need for additional chemical treatment. The treatment does not produce harmful byproducts and is suitable for large-scale, commercial applications, according to researcher Neelkanth Bardhan.

The low-temperature annealing process modifies the distribution of the oxygen atoms, causing them to form clusters and leaving areas of pure graphene between them, without introducing any disorder to the overall graphene structure—and most importantly, preserving the oxygen content.

Kumar says the new treatment allows the electrical resistance of the material to decrease by four to five orders of magnitude, which could be important for electronics, catalysis, and sensing applications. This is a result of the oxygen clustering, which renders the oxygen-rich regions insulating, but leaves the pure graphene areas in between conducting.

In addition, the pure graphene regions naturally have properties of "quantum dots", which could find use as highly efficient light emitters, among other applications. The treatment also greatly enhances the material's ability to absorb visible light, the team says. "It produces a 38 per cent improvement in the collection of photons," Grossman says, compared to untreated graphene oxide, "which is a significant improvement that could be important for its use in a number of applications, such as solar cells."

While Grossman's group is looking at the potential use of graphene in solar cells, thermoelectric devices, solar thermal fuels, and desalination filters, MIT scientist Angela Belcher and her team is exploring biological applications, such as sensors for disease agents in the bloodstream, or delivery systems for targeting insoluble drugs to specific areas of the body.




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