Nanoscale investigation of molecular scaffolding

This collaborative research project between the University of Vienna and the Wigner Research Centre in Budapest investigates carbon-based structures held together by molecular scaffolding. Scaffolds consist of novel forms of carbon, graphene and carbon nanotubes, respectively, connected by small organic molecules adhering to the scaffolds. The project builds on the recent advances in high-resolution electron microscopy and near-field optical spectroscopy. Both laboratories are in the process of installing state-of-the-art equipment which promises unique and novel insight into the structural and dynamical properties of these systems; combining the two will contribute significant added value to the project: The combination of high-resolution transmission electron microscopy and near-field optical microscopy will yield information with spatial resolution of a few angstroms and energy resolution of a few meV on the same structures. From the collaborative effort we expect a direct advance in the understanding of structure-property relationships in these molecular composites. This knowledge will provide the basis for specifically targeted, functional materials with new properties.

This collaborative research project between the University of Vienna and the Wigner Research Centre in Budapest has investigated carbon-based structures held together by molecular scaffolding. At the University of Vienna, these structures were studied by high- resolution electron microscopy, while at the Wigner Research Centre in Budapest they were investigated by near-field optical spectroscopy.The research group at the University of Vienna has started the project by a theoretical study of how the very radiation sensitive molecules that are bound to the graphene sheet can be imaged by electron microscopy. They discovered a new method where the dose is distributed over many identical copies of the molecule and then a representative structure is reconstructed in the computer (Ultramicroscopy 145, p. 13, 2014, http://dx.doi.org/1.1016/j.ultramic.2013.11.010). A second initial work considered the carbon scaffolds that are the basis for the planned molecular attachment (Scientific Reports 4, Art. # 4060, http://dx.doi.org/1.1038/srep04060 ). The work provided the basis for introducing a controlled amount of disorder in the graphene membrane, and also shed light into the transitional states between crystalline and amorphous materials.A high amount of charge transfer could be demonstrated in a hybrid structure consisting of carbon nanotubes as the conducting matrix and graphene oxide (GO) platelets as molecular scale dopant objects (Carbon 72, p. 224232, http://dx.doi.org/10.1016/j.carbon.2014.02.006). In this work show that the presence of electrically insulating GO within a SWCNT network strongly enhances electrical conductivity, whereas reduced rGO, even though electrically conductive, suppresses electrical conductivity within a composite network with single-walled carbon nanotubes.Imaging molecular structures on a carbon support (graphene) was successful for the case of fullerenes on graphene, fullerenes encapsulated between graphene layers, and for chlorinated copper phtalocyanine molecules on graphene. For the fullerene sandwich, Figure1 shows an illustration and a high-resolution scanning transmission electron microscopy image of the structure (this work is currently under review for publication). We could follow the dynamics of entire molecules as well as reactions between the molecules under irradiation.