Juan Casado Cordón, Professor of Physical Chemistry at the University of Malaga, considers graphene –an infinite layer of carbon atoms– as one of the greatest discoveries of the last twenty years due to its “unique properties” such as high electrical and thermal conductivity or its great flexibility and, also, resistance. Qualities that become exceptional, he explains, with a recently found evolution consisting in joining two layers of this material –bilayer graphene.

Researchers from the University of Malaga, led by Casado Cordón, and from the Complutense University, under the coordination of Professor Nazario Martín, have taken a step further and created an unprecedented molecular model of bilayer graphene that is capable of controlling rotation, which in turn allows controlling conductivity and achieving “potentially spectacular semiconducting properties”.

The result is a new model molecule of bilayer graphene. “By designing covalently bound molecular nanographenes we can simulate the search for the magic angle between graphene-like sheets, which is where semiconductivity is achieved, a key property in, for example, the construction of transistors, the basic units of computers”, explains this scientist from the Faculty of Science. This finding has been published in the scientific journal Nature Chemistry.

Greater efficiency and durability

In addition, this UMA-developed model allows the formation of ionic bonding between organic molecules –one atom dominates another in the charge separation–, when the vast majority of cases that have been so far studied on organic molecules focus on covalent bonding. “Finding a metastable and lasting state of matter with electron transfer is a unique case between carbon molecules”, assures Casado Cordón, who adds that this is a unique example of a ‘quantum-mechanical’ molecule with electrostatic bonding, this being ‘pre-quantum’ if desired or ‘classical’ due to its coulombic character.

Thus, this research lays the foundations for the creation of artificial molecules capable of mimicking the efficiency of photosynthetic processes –converting light energy into electrostatic and then chemical energy–, since the designed nanographene bilayer, as a consequence of the electronic transfer, mimics the biological molecules involved in photosynthesis, which will allow the development of custom-designed artificial photovoltaic applications.

The study ‘Synthesis of zwitterionic open-shell bilayer spironanographenes’ was conducted for more than six years, with the participation of the scientists from the Department of Physical Chemistry of the University of Malaga Samara Medina, who assumed the experimental part, and Daniel Aranda, in charge of theoretically modeling the charge transfer process. Likewise, the study was conducted with the collaboration of international laboratories of Japan and Singapore and researchers at the Complutense University of Madrid led by Professor Nazario Martín, an ‘Enrique Moles’ National Research Award winner in Chemical Science and Technology.