Making Graphene More Useful

By applying a classic organic chemistry reaction to graphene, researchers at MIT have come up with a customizable route to covalently modify this ultrathin form of carbon. The work may lead to procedures for attaching various functional groups to graphene and hence altering its chemical and physical properties—a prerequisite to broadening the material’s applications.

The research was led by MIT chemistry professor Timothy M. Swager, who reported on the work last week at the American Chemical Society national meeting in Denver. The group also published the study in Angewandte Chemie International Edition (DOI: 10.1002/anie.201101371).

Because of graphene’s outstanding mechanical, electronic, thermal, and other properties, scientists in many countries are working on ways to exploit it in microelectronics, energy storage, and other applications. In many cases, the scope or performance of graphene-based applications or simply the ease of handling the material could be improved by chemically modifying it. Yet only a few such modifications have been developed.

The MIT group has just extended that list by demonstrating that graphene can be functionalized via Claisen rearrangement chemistry. Specifically, the team showed that allylic alcohol groups on the surface of graphite oxide, a common starting material in graphene research, can be directly converted into carbon-bound N,N-dimethylamide groups by reacting graphite oxide with the commercial vinyl transfer agent N,N-dimethylacetamide dimethyl acetal. The results were confirmed by X-ray photoelectron spectroscopy measurements and other types of analyses.

Then the group showed that additional functionality could be imparted to the graphene derivative by reacting the newly installed amide groups with potassium hydroxide solution. That process converted the amides into surface carboxylate groups, which increased the graphene derivative’s water solubility and its colloidal stability.

“This method offers a powerful means to covalently attach functional groups to the surface of graphene,” said University of Texas, Austin, chemistry professor Christopher W. Bielawski. “It is likely to pave the way to new carbon functionalization schemes.”

Bielawski added that despite graphene’s extraordinary properties, it remains challenging to manipulate the material. “There is good reason to believe that chemical modification will alleviate these challenges and enhance performance in some applications,” he said.

Elaborating on that point, Bielawski noted that by modifying graphene with water-solubilizing functional groups, Swager’s team improved the material’s solubility in aqueous media. “Now we can think about new ways of transferring graphene between various substrates—a basic manipulation that may accelerate development of graphene-based applications,” he said.