Graphene production could mean advanced touchscreens, more
An international team of researchers has come up with a method for the production of bulk quantities of one-atom-thick sheets of carbon called graphene, a development that could lead to novel carbon composites and touch-screen displays.
The research by scientists from the Technion-Israel Institute of Technology and Rice University is published online in Nature Nanotechnology.
When stacked together, graphene sheets make graphite, which has been commonly used as pencil lead for hundreds of years. But it wasn't until 2004 that stand-alone sheets of graphene were characterized with modern nanotechnological instruments. Graphene has since been intensely studied by materials scientists, in part because it is ultrastrong and highly conductive.
According to co-lead author Prof. Matteo Pasquali of Rice University, the research team found it could dissolve graphite in chlorosulphonic acid, a common industrial solvent. The researchers had to devise new methods to measure the aggregation of the dissolved graphene flakes, but at the end the team was pleasantly surprised to find that the individual graphene layers in the graphite peeled apart spontaneously. The team was able to dissolve as much as two grams of graphene per liter of acid to produce solutions at least 10 times more concentrated than existing methods.
The researchers took advantage of novel cryogenic techniques for electron microscopy that allowed them to directly image the graphene sheets in the chlorosulfonic acid.
"We applied new methods that we had developed to directly image carbon nanotubes in acid," said co-lead author Prof. Yeshayahu "Ishi" Talmon, of the Technion Faculty of Chemical Engineering. "This was no small feat considering the nature of the acid and the difficulty of specimen preparation and imaging."
Using the concentrated solutions of dissolved graphene, the scientists made transparent films that were electrically conductive. Such films could be useful in making touch screens that are less expensive than those used in today's smart phones. In addition, the researchers also produced liquid crystals.
“If you can make liquid crystals, you can spin fibers,” said co-author and Rice Prof. of Chemistry James Tour. “In liquid crystals, the individual sheets align themselves into domains, and having some measure of alignment allows for the flow of the material through narrow openings to create fibers.”
If the method proves useful for making graphene fibers in bulk, it could drive down the cost of the ultrastrong carbon composites used in the aerospace, automotive and construction industries.