Kislon Voïtchovsky

The Supramolecular Nano-Materials and Interfaces Laboratory SuNMIL, Ecole Polytechnique Fédérale de Lausanne, Lausanne

After receiving a Bachelors and Masters degrees in Physics from the University of Lausanne (CH) – both with honours, Kislon Voïtchovsky obtained in 2007 a DPhil in Biophysics from the University of Oxford (UK) with a thesis on the characterization of biomembranes by using AFM. Part of his thesis was done in collaboration with NTT basic research laboratory, Atsugi, and with the research group of Prof. Ando at Kanazawa University, both in Japan. He was granted the Arthur Cooke Prize of the University of Oxford Physics Department for his work. Dr. Voïtchovsky was 2008 –2010 as SNSF Post-doctoral Research Fellow at the MIT Massachusetts Institute of Technology (USA) where he worked on an experimental approach based on AFM to image and quantifysolid-liquid interfaces with sub-nanometerresolution. He received 2009 the Nature Materials Award and 2011 the Ambizione Career Award of the Swiss National Science Foundation.

His research focused initially on the biomechanics and structure-function relationship of membrane protein studied with scanning probe microscopy. Given the importance of ionic effects on local hydration effects (interfacial effects with the surrounding liquid) he developed a strong interest in solid-liquid interfaces at the molecular level – he was awarded this FEMS prize with a lecture in this area.

Measuring wetting at the nanoscale

Solid-liquid interfaces (SLIs) occupy a central role in many phenomena ranging from surface electrochemistry to heterogeneous catalysis, heat transfer, proteins folding and function, ionic effects and molecular self-assembly. All these processes crucially depend on the particular structural arrangement of the liquid molecules close to the solid. This so-called interfacial liquid tends to be more ordered and dense than bulk liquid due to its interaction with the solid’s surface. At the macroscopic level, these interactions are usually characterized by the work of adhesionW_SL, effectively the work necessary to separate the solid from the liquid. The wetting of the solid by the liquid is quantified by W_SL, with high values indicating good wetting.

Experimentally, SLIs are typically investigated through diffraction techniques and W_SL quantified with contact angle measurements. These techniques generally require averaging over large areas, hence rendering measurements particularly challenging for irregular SLIs, for example if the solid exhibits nanoscale domains with different affinities for the surrounding liquid.

These difficulties can be overcome using an approach based on amplitude-modulation atomic force microscopy (AM-AFM). When operated in a particular regime, AM-AFM can be used to gain semi-quantitative information about the local W_SL with sub-nanometer resolution. The approach effectively provides simultaneous maps of the interface topography and of the local wetting properties, often with atomic- or molecular-level resolution of the solid. The method has been successfully applied to study interfaces formed by liquids with minerals, biological membranes as well as synthetic nanostructures. The results show that molecular-level structural effects within the SLI can lead to unexpected macroscopic changes in the interface properties. This is the case for nano-patterned surfaces where nanoscale domains exhibiting dissimilar affinities for the liquid can to tune the surface wetting properties solely through the particular spatial organization of the different domains.

Vincenzo Palermo

Nanochemistry Laboratory, CNR-Institute for Organic Synthesis and Photoreactivity – ISOF, Bologna, Italy

Vincenzo Palermo received a Masters degree with honours in Industrial Chemistry in 1995 at the University of Bologna (IT). After working as a guest scientist at the University of Utrecht (NL), at Steacie Institute of the National Research Council (CND) and the research division of Procter & Gamble in Rome (IT) he obtained 2003 his Ph.D. in physical chemistry at the University of Bologna (IT) in a joint project with the CNR Istituto dei Composti del Carbonio ICOCEA also in Bologna. Vincenzo Palermo won two graduate student awards at the E-MRS Conference 2003 and at the European Conference on Molecular Electronics 2005; he received in 2006 the Young Scientist Award in materials science of the Italian Society for Microscopical Sciences (S.I.S.M.).

While we often describe graphene with many superlative adjectives, it is difficult to force this (superlative) material within a single chemical class.

The typical size of Graphene is atomistic in one dimension of space, and mesoscopic in the other two. This provides graphene with several, somehow contrasting properties.

Graphene can be can be patterned, etched and coated as a substrate. Though, it can also be processed in solution and chemically functionalized, as a molecule. It could be considered a polymer, obtained by bottom-up assembly of carbon atoms, but it can be obtained from top-down exfoliation of graphite (a mineral) as well. It is not a nano-object, as fullerenes or nanotubes, because it does not have a well-defined shape; conversely, it is a large, highly anisotropic, very flexible object, which can have different shapes and be folded, rolled or bent to high extents.

In this presentation, we will discuss the state of the art and possible applications of graphene in its broader sense with a particular focus on how its “chemical” properties, rather than its well-known electrical ones, can be exploited to develop original science, innovative materials and new technological applications.