ARKHANGELSK, July 28. /TASS/. Russian scientists developed an effective method to make multilayer graphene from plant biopolymers, senior researcher at the Ioffe Institute of Physics and Technology's Laboratory of Cluster Structures' Physics, Candidate of Chemical Sciences, Alexey Voznyakovsky told TASS. High-quality graphene is made of woodworking industry's waste.

Graphene is carbon's modification that has a single atom layer. In 2010, Konstantin Novoselov and Andre Geim received the Nobel Prize for graphene research. Low-layer graphene, consisting of several layers, is of record strength - it is 200 times stronger than steel, and it has a thermal conductivity. Its use in various fields is highly promising, though producers need technologies to make inexpensive, high-quality, low-layer graphene on an industrial scale.

"Right now, low-layer graphene is a very expensive material. Thus, its use is simply unprofitable at the moment. We have learned to make multilayer graphene in big amounts, cheap and of high quality. We use various waste products of the woodworking industry, for example, lignin, tree bark, and hogweed stalks, thus cutting the cost. As of now, we produce up to 10 kg per month and we are ready to synthesize many times more," the scientist said.

The new method results from work of several scientific centers: the Institute of Physics and Technology, the Research Institute of Synthetic Rubber, the Northern Arctic Federal University, Komi's Institute of Biology, Komi's Institute of Geology, the Timiryasov Innovative University in Kazan, he added. "We are a big team of diverse specialists, which allows us to achieve serious results."

From biopolymer into graphene

The method is about re-arranging biopolymer molecules into the graphene plane. "You know, its' very interesting - if you squeeze and heat graphite very hard, you will get a diamond. This is about what we are doing. The difference is that we don't compress, we give a lot of energy to biopolymer molecules to make them become graphene," the expert said.

Energy for the reaction is released during self-propagating high-temperature synthesis (SHS), where the wave temperature is 2,000 degrees. "It gives this impetus, this effect to have the biopolymer "want" to become graphene," the scientist told TASS.

The result is a low-layer graphene according to the international classification, that is, it contains up to five layers. The method's biggest achievement is that the material does not have Stone-Wales defects. Those are connected carbon rings with five and seven atoms, resulting from a 90-degree rotation of neighboring carbon atoms with respect to the midpoint. Such defects drop graphene's quality and affect the material's possible use.

"It's like with some simple products: we know high-quality steel, and cheap low-quality grades unsuitable for a can opener. So here, we've learned to make high-quality graphene, which satisfies expectations. We know other methods to make graphene nanostructures in big amounts and cheaply, but they are of poor quality. Other methods are to make high-quality graphene with high efficiency, though very expensive. We have combined both approaches. We make a lot, cheaply, and efficiently," the scientist said in conclusion. The material may be used to create polymer composites, coatings, sorbents, and it may be used in the military industry.

The scientist's developments were supported by grants from the Russian Science Foundation.