RESUMEN
Single-atom catalysis of carbon monoxide oxidation on metal-oxide surfaces is crucial for greenhouse recycling, automotive catalysis, and beyond, but reports of the atomic-scale mechanism are still scarce. Here, using scanning probe microscopy, we show that charging single gold atoms on oxidized rutile titanium dioxide surface, both positively and negatively, considerably promotes adsorption of carbon monoxide. No carbon monoxide adsorption is observed on neutral gold atoms. Two different carbon monoxide adsorption geometries on gold atoms are identified. We demonstrate full control over the redox state of adsorbed gold single atoms, carbon monoxide adsorption geometry, and carbon monoxide adsorption/desorption by the atomic force microscopy tip. On charged gold atoms, we activate Eley-Rideal oxidation reaction between carbon monoxide and a neighboring oxygen adatom by the tip. Our results provide unprecedented insights into carbon monoxide adsorption and suggest that the gold dual activity for carbon monoxide oxidation after electron or hole attachment is also the key ingredient in photocatalysis under realistic conditions.
RESUMEN
The costs of eye-tracking technologies steadily decrease. This allows research institutions to obtain multiple eye-tracking devices. Already, several multiple eye-tracker laboratories have been established. Researchers begin to recognize the subfield of group eye-tracking. In comparison to the single-participant eye-tracking, group eye-tracking brings new tech-nical and methodological challenges. Solutions to these challenges are far from being established within the research community. In this paper, we present the Group Studies system, which manages the infrastructure of the group eye-tracking laboratory at the User Experience and Interaction Research Center (UXI) at the Slovak University of Technology in Bratislava. We discuss the functional and architectural characteristics of the system. Furthermore, we illustrate our infrastructure with one of our past studies. With this paper, we also publish the source code and the documentation of our system to be re-used.
RESUMEN
Linear conductance of junctions formed by graphene flakes with the order of the nanometer-thick electrodes attached at the corners of the flakes is studied. The explored structures have sizes up to 20,000 atoms and the conductance is studied as a function of applied gate voltage varied around the Fermi level. The finding, obtained computationally, is that junctions formed by armchair-edge flakes with the electrodes connected at the acute-angle corners block the electron transport while only junctions with such electrodes at the obtuse-angle corners tend to provide the high electrical conductance typical for metallic GNRs. The finding in the case of zig-zag edges is similar with the exception of a relatively narrow gate voltage interval in which each studied junction is highly conductive as mediated by the edge states. The contrast between the conductive and insulating setups is typically several orders of magnitude in terms of ratio of their conductances. The main results of the paper also remain to a large extent valid in the presence of edge disorder.
RESUMEN
Optical, purely mechanical, and combined opto-mechanical switching cycles of a molecular switch embedded in a metal junction are investigated using density functional theory and (excited state) ab initio molecular dynamics. The nanomechanical simulations are done on realistic models of gold electrode tips bridged by a single dithioazobenzene molecule. Comparison of different tip models shows that the nature of the tips affects switching processes both qualitatively and quantitatively. The study predicts that purely photochemical cisâtrans switching cycles of suspended azobenzene bridges are mechanically hindered; combined opto-mechanical as well as purely mechanochemical forward and backward switching is, however, feasible.
RESUMEN
Most chemical reactions require activation which is conventionally supplied by heat. In stark contrast, mechanical activation by applied external forces opens intriguing novel possibilities. Here, the first direct comparison of mechanical versus thermal activation of bond breaking is provided. Studying both thiolate-copper interfaces and junctions provides evidence for vastly different reaction pathways and product classes. This is understood in terms of directional mechanical manipulation of coordination numbers and system fluctuations in the process of mechanical activation.
RESUMEN
The relationship between structure, interfacial electrostatics, bonding, and dynamics of organic molecules on metals is studied using a self-assembled monolayer of methylthiolate, CH3S, on Cu(111). The flat adsorption energy landscape of CH(3)S/Cu(111) results from metal-to-molecule charge redistribution which allows for a high mobility of CH3S. This contributes a nonuniform diffuse background to Bragg scattering, which needs to be considered in diffraction analyses. Ramifications on the interpretation of experimental data and the potential impact on the design of metal-organic interfaces are discussed.
RESUMEN
The interaction of alkanethiolates with small coinage metal clusters of copper and gold was studied based on density functional theory with a focus on the metal-thiolate junction. Calculation of fragmentation energies indicate that for Cu(n)-thiolate (n = 1,3,5,7, and 9) there is a progressive lowering in energy for the fragmentation of the S-C bond in the thiolate from a value of 2.9 eV for n = 1 to 1.4 eV for n = 9. The detailed electronic origins of this specific weakening are attributed to a polarization of electron density in the S-C bond as induced by bonding with the Cu(n) cluster. For the gold analogues, this effect is not observed and fragmentation at the S-C bond experiences only a slight 10% destabilization as n increases from 3 to 9. The relativistic origin of this difference between Cu and Au is discussed, and an analysis of bonding considerations is presented.
