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Graphene Films Enabling Miracle Nanomaterials

R. Colin Johnson | Date: 02-16-11 | Comments

Pure carbon thin-films just nanometers thick are enabling a new era of miracle applications, from windshields so slick they don't require wipers to thermoelectric materials that drastically reduce energy generation costs by harvesting waste heat.

Graphene�pure carbon thin-film�has a wide variety of uses beyond its potential in semiconductor manufacturing, from reducing the drag on ships' hulls to recovering lost energy at coal-fired electricity generation plants, according to separate research projects at Vanderbilt University and the Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN) at Trinity College (Dublin, Ireland).

Physicist James Dickerson, left, and graduate student Saad Hasan (Photo by Daniel Dubois)

Vanderbilt physicist James Dickerson, working with doctoral candidate Saad Hasan, claims to be perfecting a method of depositing ultrathin films of graphene that impart remarkable qualities to surfaces. For example, the team claims to be able to coat glass with a transparent graphene coating so slick that automobile windshields would not need wipers, or so "wettable" that they wick moisture across their entire surface.

The Vanderbilt process alters the surface roughness of graphene-oxide films in one of two configurations�either "brick" or "rug"�the former causes water to bead up and slide off and the latter causes water to spread out evenly on its surface. These configurations are called super-hydrophobic and super-hydrophilic, respectively. Both techniques can create free-standing graphene films using inexpensive methods suitable for mass production, according to the Vanderbilt researchers.

James Dickerson can tweak the process for creating films of graphene oxide so they are formed by "rug" process, above, which is extremely smooth and "water loving," or by "brick" process, below, which is rough and "water hating." (Image courtesy of James Dickerson)

Based on the same electrophoretic deposition method already used to create coatings on ceramics, the technique applies an electric field within a liquid medium, causing the nanoparticle film to be transferred to the surface. With an adjustment to the pH of the liquid and the electric voltage causing deposition to take place, either the brick or rug arrangement can be imparted to a wide variety of surfaces, from self-cleaning glasses and clothing to antifogging windshields to corrosion and snow-load protection for building roofs.

Next, the group wants to apply its technique to a fluorinated, two-dimensional version of Teflon called fluorographene, which the researchers predict will enhance these surface effects even further.

Separately, professor Jonathan Coleman, principal investigator at CRANN and the School of Physics at Trinity College, together with professor Valeria Nicolosi in the Department of Materials at the University of Oxford, claims to have adapted graphene films for thermoelectric power generation�harvesting waste heat to generate electricity. The new technique slices graphene into ultrathin nanosheets using ultrasound together with common solvents, resulting in a two-dimensional material that can be manufactured on an industrial scale.

Professor Jonathan Coleman (left) pictured with CRANN Director, Professor John Boland.

Currently, the team is adapting its splitting technique to other materials, such as boron nitride, molybdenum disulfide, and bismuth telluride, to create a new family of supermaterials that enhance the structural, electronic and thermoelectric properties of those compounds, too. The technique is also being adapted to supercapacitors, an alternative to batteries in applications that do not require electricity to be stored for long periods, such as electric cars.