A model Cu catalyst surface oxidises to Cu2O when methanol, oxygen and water vapour are all present during methanol conversion.

Under ambient conditions, surfaces are rapidly modified and contaminated by absorbance of molecules and a variety of nanoparticles that drastically change their chemical and physical properties. The atomic force microscope tip–sample system can be considered a model system for investigating a variety of nanoscale phenomena. In the present work we use atomic force microscopy to directly image nanoscale contamination on surfaces, and to characterize this contamination by using multidimensional spectroscopy techniques. By acquisition of spectroscopy data as a function of tip–sample voltage and tip–sample distance, we are able to determine the contact potential, the Hamaker constant and the effective thickness of the dielectric layer within the tip–sample system. All these properties depend strongly on the contamination within the tip–sample system. We propose to access the state of contamination of real surfaces under ambient conditions using advanced atomic force microscopy techniques.

No abstract

Using atomic force microscopy in the pressure range of 10 –10 mbar to several tens of mbar at room temperature, we demonstrate the restructuring of nanostructured KBr surfaces assisted by the presence of water, methanol, and ethanol vapors and the formation of solvation islands. On a flat KBr surface, the two-dimensional solvation islands start nucleating at the step edges and grow with time and with increasing relative pressure. Solvation islands of water wet the terraces; however, solvation islands of methanol and ethanol are localized around the step edges and do not wet the terraces. Two processes are observed on nanostructured KBr surfaces: the movement of the atomic steps and the formation of solvation islands. The first process takes place at comparatively lower pressures at around 1% relative pressure, whereas the second process starts at higher pressures at around 25% relative pressure and above. Furthermore, the second process takes place only after the complete relocation of the step edges and thereby formation of a nearly flat surface. This implies that there is a competition between the restructuring of the atomic steps and solvation layer formation, as both processes require solvated ions. Unlike in the case of a flat surface, solvation islands of alcohols wet the restructured surface due to a higher density of low-coordination sites.