Scientists spin up graphene in a kitchen blender

 

Bottles filled with water, detergent and graphene flakes – the graphene absorbs a small amount of light, leading to the darkened appearance of the mixture (Photo: CRANN)

It is one atom thick and touted to be stronger than steel. Graphene has captured the scientific and public imagination as the wonder material of the 21st century. Now, researchers at Trinity College Dublin have found a way to extract the substance from graphite – using a kitchen blender and some liquid soap.

Since Konstantin Novoselov and Andre Geim of Manchester University managed to extract graphene (which is a two-dimensional slice of graphite) using a piece of transparent tape, the buzz around this super-strong, super-conductive material has tended toward the superlative. Novoselov and Geim received the Nobel Prize for their discoveries in 2010, but still the quest continues for a method of scaling up graphene extraction to an industrial, or even a vaguely practical level.

Now, researchers at Trinity College Dublin have found a new and relatively quick way to obtain graphene from a sample of graphite, and their revolutionary equipment consists of a modest kitchen blender and liquid detergent. According to Dr. Keith Paton, who worked on the project, this was a "sighting" experiment, which was carried out "to test the feasibility of using shear mixing to exfoliate graphene."

Method

In their experiment, the Trinity College Dublin team describe how they took a high-power (400-watt) kitchen blender and added half a liter of water, 10-25 milliliters of detergent and 20-50 grams of graphite powder (found in pencil leads). They turned the machine on for 10-30 minutes. The process resulted in a large number of micrometer-sized flakes of graphene, suspended in the water.

Kitchen-sink solutions

The cheapest shear-mixing appliance is a regular kitchen blender, Dr. Paton explains, which was why the team chose to employ it in the first trials. Though adding liquid to the blender with the graphite allowed the graphene to shear off, at the end of the process the material would just settle at the bottom of the blender and re-aggregate.

The researchers realized they needed a surfactant to keep the flakes separated and dispersed in the liquid. Again, they decided to begin with the most available source, regular liquid dish-washing detergent, and they found that this worked nearly as well as an industrial product.

A standard kitchen blender, and transmission electron microscope images of graphene flakes (Photo: CRANN)

Scaling up

While the kitchen blender and dish soap experiment proved the concept, the researchers are keen to emphasize that this method is not easily scalable for industrial or commercial use. As their relatively low-tech trial was successful, they then moved to more sophisticated equipment. The rotor-stator mixer is a laboratory-quality device that has rotating blades and a stationary screen. There is a very small gap between the elements through which the liquid and graphite are squeezed, and this yields very high rates of shearing and exfoliation of graphene from the graphite.

Dr. Paton likens the process to "sliding your hands across a deck of cards," causing them to spread and separate. After being exfoliated in flakes, the graphene can be recovered in a number of ways, including using filtering processes or by allowing the liquid to evaporate. The experiment with the rotor-stator proved that the blender method could be scaled up to an industrial level of production, and this is what is getting people excited.

 

The stronger, lighter, super-conductor

The excitement is generated by the potential for the new material, graphene. The marvel is in its strength (said to be 200 times that of a comparable quantity of steel), the fact that it is extremely lightweight, and because it is highly conductive. According to Dr. Paton, this means that "commercial printing techniques, such as ink-jet or screen-printing, could be used to create very thin, flexible electronics, including batteries and super-capacitors.” There is also talk of a folding touchscreen device that uses graphene for the screen or for the connecting circuit.

Graphene could also be used for very thin, flexible, perhaps more efficient and transparent solar cells. And there is significant potential in strengthening plastics. Since a very minute amount of graphene can improve the strength of PET (plastic used widely in drink bottles) by around 40 percent, this could result in a huge reduction in the amount of plastic required.

All that having been said, two separate studies have recently raised concerns about the dangers that graphene could pose both to ourselves, and to the environment.

While it may seem to have burst onto the scene, experiments with graphene go back at least to 2004, when Novoselov and Geim conducted their tape experiment. This latest discovery was the outcome of a collaborative project between Thomas Swan (manufacturer of specialty chemicals) and CRANN (the Centre for Research on Adaptive Nanostructures and Nanodevices) at Trinity College Dublin. The work was carried out at CRANN where the team was led by Professor Jonathan Coleman.

Source: Nature.com