Graphene, the material of the future

 It is transparent, flexible, extraordinarily strong, waterproof, abundant, economical and conducts electricity better than any other known metal. We are talking about single layer graphene powder, the material that fascinates scientists and industry because of its fantastic properties.

Although it was first synthesized in 2004, it rose to fame in 2010 when its discoverers, researchers of Russian origin Andre Geim (Sochi, 1958) and Konstantin Novoselov (Nizhny Tagil, 1974) received the Nobel Prize in Physics . As Andre Geim pointed out at the time, the potential applications of graphene are so many that they were not even able to list them.

This versatile material will allow manufacturing from electronic devices with flexible and transparent screens and ultra-fast batteries to powerful solar panels, not forgetting applications in aeronautics, medicine and other sectors that are currently being researched. In addition, it is an excellent basis for creating new custom materials , depending on specific needs. That is, something like on-demand materials.

The study of the properties of graphene keeps busy a large number of scientists around the world, including the contributions of Spanish theoretical physicists.

In the development phase

Everyone talks about this material although few have seen it. And is that, despite its promising applications, is still in the development phase . Graphene is an extremely thin film composed of carbon (only one atom thick). The graphite that is obtained is the same that is extracted from coal mines and used to make pencils, car brakes or steel, so it is a raw material very abundant in nature. Graphene can be made from natural graphite(Spanish mines are rich in this mineral) or from synthetic graphite .

The main obstacle at present is that it is not yet possible to manufacture graphene on a large scale, according to Jesús de la Fuente, director of the Spanish company Graphenea Nanomaterials , one of the few companies that currently produces this material. Avanzare and GranphNanotech are two other Spanish companies that work with him.

There are several ways to produce graphene. The adhesive tape(mechanical exfoliation) was the method that Geim used to isolate it for the first time and can be used for some experiments , but it is not valid for the industry. Basically it is marketed in two ways: in foil and powder format.

Graphene in foil

Graphenea, based in San Sebastian, is one of the three main producers of sheet graphene worldwide (its two main competitors are American): "Graphene is high purity and has the best properties . battery electrodes, touch screens, solar cells, digital and analog high frequency electronics or advanced composites for aeronautics ", explains De la Fuente in a telephone conversation.

To produce it does not use graphite, but methane gas , which is transformed by a technology called chemical vapor deposition (Chemical Vapor Deposition, CVD): "It is one of the great advantages, because we do not depend on any mineral product," he says.

"It is carried out in a CVD reactor where a carbon gas is introduced, by applying the energy, the carbon atoms are deposited on a metal substrate The next step is to transfer the graphene sheet to the final substrate, which can be a polymer, glass, silicon or others, depending on the application ", explains

The price varies according to sizes and properties . In recent years it has already fallen in half. A sheet of graphene costs between 300 and 1,000 euros , a figure very affordable for research consumption but high for other uses. De la Fuente explains that they expect the price to continue to fall progressively and, "in the medium term (about five years), it is cheaper than silicon, which currently costs around 50 euros." "As the market moves forward, the price will go down, it costs almost the same to produce a sheet than 100,000," he says.

This company supplies material to its customers since the summer of 2011, both to research centers and large companies. "99% of our production is sold abroad , although in Spain there is a lot of research activity, and start-up companies are carrying out some initiatives while large companies are waiting," he adds.

Much more durable batteries

"The graphene we sell is mainly used for testing, much energy is being worked on, in ultracapacitors (for cars, electric trains and to improve the performance of electric distribution lines) and in batteries. that graphene electrodes get ten times more durable batteries. "

In fact, this material could solve one of the great disadvantages of smartphones, whose batteries hardly last a day. The prototypes of batteries made with graphene electrodes are ten times more durablethan those carried by telephones that are sold in the market and are charged in much less time (approximately half an hour).

However, it will be necessary to wait some years to enjoy these batteries. According to De la Fuente, Nokia (its main client) does not plan to market devices made with graphene for five years.

Graphene can also be used in OLED TVs (Organic LED), which will be manufactured with organic materials, more respectful with the environment : "Now rare earths, such as Indian, are used, which have a very large environmental impact. has multiplied by ten. " The industry is looking for a more economical and sustainable substitute , which is why graphene is emerging as one of the alternatives.

Regarding solar panels, De la Fuente explains that the objective is to obtain cells with 42% efficiency (that is, they convert 42% of the solar energy they receive into electricity). Those that are now in the market have an efficiency of approximately 16%.

Graphene powder

Graphene powder is used in applications that require a cheaper material, such as composite for construction . The most frequent is to mix it with other materials. "The process of graphene production in powder form starts from graphite as a raw material and basically consists in carrying out a violent oxidation and an ultrasound process to separate the small sheets of graphene that make up the graphite," explains Jesús de la Fuente.

Its properties are not as good as sheet metal graphene and electricity conducts worse. The demand for this product, whose price depends on its purity, remains small. The low quality costs less than 10 euros per gram while the high quality round 100 euros.

"We also work with high sailing competition teams that need complements for carbon fibers (graphene improves them)". Some laboratory tests have also been done to incorporate it into the construction. However, De la Fuente sees its use in this sector complicated because "they require very large volumes and cheap prices".

The scientists also study the possible applications in medicine . For example, to manufacture biosensors and detect DNA. "There is also speculation about the possibility of producing neuronal implants and regenerating damaged nerve tissues," says De la Fuente. However, even if these medical advances come to fruition, he believes that it would take years to implement them.

For its part, Elsa Prada, researcher at the Institute of Materials Science of Madrid (CSIC), said that graphene could also be used in biodevices, in bactericidal wrappings for medicines and food or to manufacture lighter and more resistant composite materials (for airplanes, cars, etc.).

Artificial grapheme

Despite its extraordinary qualities, graphene is not perfect. Yes it seems a very suitable base to develop new materials inspired by it and that incorporate new advantages. That is, something like an improved graphene. One of the latest developments in this line is the so-called artificial graphene, a research recently published in the journal 'Nature' and in which participates the Spanish Paco Guinea, one of the world's leading experts in this material.

Along with American colleagues at Stanford University (California), the researcher of the Institute of Materials Science of Madrid has managed to make a material that, as he explains to this newspaper, "allows to manipulate the most exotic properties of graphene with great precision" . The so-called artificial graphene is a first step to synthesize on a large scale materials with properties qualitatively similar to that found in nature . "You can study properties that have not yet been observed in real graphene because they do not have the necessary purity," he says in an e-mail.

This new material has been manufactured by placing and moving carbon oxide molecules on a copper surface, although according to Guinea, "other metals can be used". For now, "the artificial is more expensive to produce than the other graphene . "

Before seeing products made with graphene, Guinea believes that it will be necessary to "reduce costs". The researcher hopes "that the demonstration that artificial graphene can be manufactured leads other groups to contribute to improving production techniques."

Inspirador of other materials

Among the other two-dimensional materials that graphene has inspired, Elsa Prada highlights fluorografne (two-dimensional analogue of Teflon, with extraordinary lubricating and insulating properties), hexagonal boronnitride (crystalline and transparent, very hard insulation, which combined with graphene improves its electromechanical properties), molybdenum disulfide (another two-dimensional crystal with promising properties for the construction of a new class of transistors) or silicon (Graphene's version made of silicon.) It has some properties in common with graphene, and as an advantage it could be easily integrated with current electronics based on silicon).

Prada, who has worked with Konstantin Novoselov, one of the discoverers of graphene, highlights the high level of Spanish science in the study of this material: "The Spanish node of the Flagship project of the EU is one of the most active, and promotes basic research at the same time as the transfer of this knowledge to the industry ". A task that, if successful, "will involve a large amount of funds for the research and development of graphene technology in Spain," adds Prada.

"In these times of crisis, our country has to bet on becoming a producer (and not just a consumer) of solutions with potential and demand.In particular, graphene can offer us the possibility of being leaders and exporters worldwide of a technology of future, "he concludes.