Graphene, interrupted

One of the biggest challenges in working with a material whose chemical-binding properties are contingent upon physical construction is getting that material to "stay put" in its physical form long enough to get the material to do its chemical thing.

crinkled graphene

Graphene's physical construction is often likened to chicken wire, one atom thick; but when it is "unrolled" it can easily contract and constrict in upon itself,  "crumpling" like the skin of a grape into a raisin that has been left in the heat and sun too long.    In its crumpled form, graphene behaves differently, and is significantly more difficult to handle.  

But new research by Duke University offers a new technique for getting the graphene to un-crumple itself.   By adhering the graphene to a rubber film, the chicken wire lattice's crumpling can be controlled and flexed on demand: 

"Duke engineers attached the graphene on a rubber film that had been pre-stretched multiple times of its original size. Once the pre-stretch in the rubber film was relaxed, part of the graphene detached from the rubber while other part kept adhering on the rubber, forming an attached-detached pattern with a size of a few nanometers. As the rubber was relaxed, the detached graphene was compressed to crumple. Once the rubber film was stretched back, the adhered graphene will pull on the crumpled graphene to unfold it."  source: http://www.sciencedaily.com/releases/2013/01/130123165042.htm

This process opens up new frontiers for application such as artificial muscle, which needs a large surface area that can be "deformed" as the muscles constrict and relax naturally.

Xuanhe Zhao, one of the engineers researching this application said, "In particular, they promise to greatly improve the quality of life for millions of disabled people by providing affordable devices such as lightweight prostheses and full-page Braille displays. The broad impact of new artificial muscles is potentially analogous to the impact of piezoelectric materials on the global society."    

A sponge to soak up radioactive waste

Flakes of graphene oxide have a "spongelike" quality that can be used to bind to and solidify radioactive waste.  Once in solid form, the contaminated material can be easily collected and cleaned up.

"Capturing radionuclides does not make them less radioactive, just easier to handle. Where you have huge pools of radioactive material, like at Fukushima, you add graphene oxide and get back a solid material from what were just ions in a solution," said chemist James Tour of Rice University. "Then you can skim it off and burn it. Graphene oxide burns very rapidly and leaves a cake of radioactive material you can then reuse."

The large surface area of graphene oxide particles means that they have an increased ability to adsorb and bond with other materials, specifically those with toxic quality which tend to have volatile chemical properties.  The honeycomb lattice of graphene can bond to and essentially stabilize them.     

source: http://www.sciencedaily.com/releases/2013/01/130108112459.htm

Scientists at Rice University and Lomonosov Moscow State University have developed the new method for removing radioactive material. In the flask on the left, the solution contains the particles of graphene oxide (atom thick flakes);  on the right the particles have bonded to simulated radioactive material.

Practical applications range from cleanup of sites such as the Fukushima nuclear power plant to fracking -- or using graphene to filter out contaminants from the water.  "Hot" radioactive water normally needs to be shipped to various containment facilities around the country, which is done so at great expense.