Chemical and topological functionalization of graphitic surfaces: open challenges for computational modeling
CECAM-HQ-EPFL, Lausanne, Switzerland
A broad sector of present and future nanotechnologies is relying on the very large variety of sp2 carbon forms and on their flexibility towards chemical functionalization. The occurrence of stable 0-, 1-, 2- and 3-dimensional sp2 structures belonging to the wide families of fullerenes, nanotubes, graphene and random schwarzites, respectively, provides the building blocks for assembling carbon-based architectures with tailored physical and/or chemical properties. The synthesis of these C-based materials is now turning into a maturity stage, and can deliver graphitic materials with desired structure and defect content at a continually increasing rate. The structural and electronic properties C-based materials have already been the subject of several CECAM workshops in the past years, the last one in 2009.
In contrast, the chemical and topological functionalization of the graphitic surfaces exposed by these nanostructured materials is currently an open challenge, both for experimental measurement and for computational modeling. Some important challenges, which fully emerged in the last 1-2 years, and which will constitute key topics of the proposed workshop include: i) the use of atomic/molecular adsorbates to control the electronic, chemical, optical, and catalytic properties; ii) the controlled anchoring of semiconductor/metallic nanoparticles on 2D carbon supports; iii) the dynamics, stability, clustering, thermal evolution, as well as chemical reactivity of these atomic/molecular/metallic adsorbates at graphitic surfaces; iv) the epitaxial growth/support of high-purity graphene on metallic/insulating surfaces and the precise characterization of structural, electronic and (electro)-catalytic properties.
In addition, the topology of the two-dimensional space hosting the electron gas also offers the opportunity for reproducing and investigating on the ordinary scale of lab experiments and atomistic simulations fundamental issues of electronic-structure theory and their interplay with the surface functionalization.
Numerical modeling can play an important role in clarifying this structure/property interplay, but there are several fundamental shortcomings that limit the predictive power of both quantum and empirical approaches. On the one hand, much of the complexity arises from the way functionality is affected by two key aspects: i) the intrinsic properties of the supporting graphitic surface (topology, mechanical stability, elastic, vibrational and electronic properties) and ii) the almost endless way in which atomic/molecular/metallic adsorbates distribute, aggregate and react on these graphitic surfaces (patterned formation of defects, thermal stability and evolution, oxidative unzipping and cutting, surface gasification, catalytic activation of supported metal clusters …). On the other hand, the complexity in modeling accurately the functionalized graphitic surfaces is closely related to the long-range electronic effects involved when the regular pi-conjugated sp2 C-C bonding is perturbed by the presence of surface adsorbates and interfaces. Here is where most of the challenges for computational modeling nestle.
The present CECAM workshop, bringing together experimental and theoretical scientists working on these issues, aims at a timely uplift to the field.
Giorgio Benedek (University of Milano-Bicocca) - Organiser
Stefano Fabris (CNR-IOM DEMOCRITOS Simulation Center and SISSA, Trieste) - Organiser