CO chemisorption at vacancies of supported graphene films: a candidate for a sensor?

We investigate CO adsorption at single vacancies of graphene supported on Ni(111) and polycrystalline Cu. The borders of the vacancies are chemically inert but, on the reactive Ni(111) substrate, CO intercalation occurs. Adsorbed CO dissociates at 380 K, leading to carbide formation and mending of the vacancies, thus preventing their effectiveness in sensor applications

How future surgery will benefit from SARS-COV-2-related measures: a SPIGC survey conveying the perspective of Italian surgeons

COVID-19 negatively affected surgical activity, but the potential benefits resulting from adopted measures remain unclear. The aim of this study was to evaluate the change in surgical activity and potential benefit from COVID-19 measures in perspective of Italian surgeons on behalf of SPIGC. A nationwide online survey on surgical practice before, during, and after COVID-19 pandemic was conducted in March-April 2022 (NCT:05323851). Effects of COVID-19 hospital-related measures on surgical patients' management and personal professional development across surgical specialties were explored. Data on demographics, pre-operative/peri-operative/post-operative management, and professional development were collected. Outcomes were matched with the corresponding volume. Four hundred and seventy-three respondents were included in final analysis across 14 surgical specialties. Since SARS-CoV-2 pandemic, application of telematic consultations (4.1% vs. 21.6%; p < 0.0001) and diagnostic evaluations (16.4% vs. 42.2%; p < 0.0001) increased. Elective surgical activities significantly reduced and surgeons opted more frequently for conservative management with a possible indication for elective (26.3% vs. 35.7%; p < 0.0001) or urgent (20.4% vs. 38.5%; p < 0.0001) surgery. All new COVID-related measures are perceived to be maintained in the future. Surgeons' personal education online increased from 12.6% (pre-COVID) to 86.6% (post-COVID; p < 0.0001). Online educational activities are considered a beneficial effect from COVID pandemic (56.4%). COVID-19 had a great impact on surgical specialties, with significant reduction of operation volume. However, some forced changes turned out to be benefits. Isolation measures pushed the use of telemedicine and telemetric devices for outpatient practice and favored communication for educational purposes and surgeon-patient/family communication. From the Italian surgeons' perspective, COVID-related measures will continue to influence future surgical clinical practice

Influence of Defects on Adsorption\u2014Model Studies With Stepped Surfaces

In this article, we review the latest experimental results on the influence of surface defect in the interaction of different kinds of molecules with metal surfaces, using stepped surfaces as a model system. We will discuss both the adsorption of \u201csimple\u201d molecules of catalytic interest, such as H2, O2, CO, and NO at metal surfaces, and the organic\u2013inorganic interface. The latter is represented, on the one side, by polyaromatic molecules, relevant for nanoelectronics, and on the other side, by amino acids as representative of biological molecules. The substrates are chosen among \u201cnonreactive\u201d noble metals as well as among \u201creactive\u201d transition metals

Ethylene adsorption on clean and oxygen covered flat and stepped Ag(001)

In the present paper we review our findings on ethylene adsorption on clean and oxygen covered Ag(001) surfaces investigated by dosing the gas with a Supersonic Molecular Beam and analysing the adsorption state either by High Resolution Electron Energy Loss Spectroscopy or by High Resolution X Rays Photoemission Spectroscopy. The final adsorption state depends on the translational and on the internal energy of the gas-phase molecules and on the presence of defects. At low translational energy ethylene either physisorbs or very weakly chemisorbs at flat terrace sites. The physisorption probability is thereby hindered by rotational excitation. A more strongly bound, pi bonded, state forms at higher translational energy, the activation barrier being related to the energy needed to form the relevant defect at which chemisorption takes place. A further even more strongly bound state forms only when dosing vibrationally excited molecules from the gas phase

Phonons in Thin Oxide Films

Thin oxide films have physical and chemical properties which may be significantly different from those of the corresponding bulk materials. For their complete characterization the information on the lattice dynamics which can be retrieved by vibrational spectroscopy is mandatory. Here we show that the number of observed phonon modes and their frequencies can indeed provide relevant information about stoichiometry, structure and thickness of the film

Interaction of ethylene and oxygen with stepped Ag surfaces

The active role of defects in some catalytic reactions was predicted in the very early days of surface science. Most of the studies on gas adsorption at solid surfaces dealt, however, so far with nearly perfect low Miller index surfaces, which are rather unlike the active powders employed as catalysts in industrial reactors. The structure gap between the systems studied by surface scientists and the surface structure of real catalyst powders was therefore often indicated as the reason for the failure in reproducing some chemical reactions, which occur readily in industrial reactors, also in controlled conditions. Overcoming this limit without losing control over the experiment at the nanoscopic level is therefore an issue of pivotal importance, which could be addressed only now that the understanding of adsorption processes at flat surfaces is reasonably established. In this paper we shall review our most recent results on O-2 and C2H4 interaction with Ag(410) and Ag(210), which are vicinal surfaces of Ag(100) characterised by open (110)-like steps and narrow (100) terraces. The gases were dosed with a supersonic molecular beam, allowing to perform experiments at selected and well defined angles of incidence of the gas-phase particles. For both gases we find that the open steps affect gas-surface interaction considerably, changing the energy barriers to adsorption as well as the final chemisorption state

Coverage dependence of the sticking probability of ethylene on Ag(410)

The interaction of ethylene with Ag(410), a vicinal surface of Ag(100) characterised by a high density of open steps, is investigated. Energy and angle resolved measurements of the sticking coefficient are performed with the retarded reflector method of King and Wells using a supersonic molecular beam. We find that open steps remove the translational barrier for adsorption into the pi-bonded state present for Ag(100). Steering removes the angle dependence of the initial sticking probability. The coverage dependence of the adsorption probability indicates that a precursor mechanism is present and that adsorbate assisted adsorption is important at hyperthermal energies. With increasing coverage steering becomes ineffective and rotations inhibit adsorption. Admolecules with second nearest neighbours are destabilised and these sites can be populated only by gas-phase molecules impinging along trajectories for which the step heights are exposed

Surface plasmon dispersion on sputtered and nanostructured Ag(001)

The surface plasmon dispersion of ion bombarded Ag(001) is investigated by angle resolved high resolution electron energy loss spectroscopy. We find it to be parabolic and dominated by the quadratic term, contrary to the case of flat Ag(001) where the linear term is dominant. The case is reminiscent of surface plasmon dispersion on the oxygen covered, missing row reconstructed Ag(001) surface, for which case the change of the dispersion from nearly linear to quadratic was attributed to the removal of a surface plasmon decay channel associated to the surface interband transition at (X) over bar. We show moreover, that for the sputtered surface, slope and curvature of the dispersion depend on surface morphology at the nanoscale. When sputtering is performed at low crystal temperature and no ordered superstructure forms, the quadratic term coincides with the isotropic value dictated by bulk properties, reported for flat Ag(110) and Ag(111) and for reconstructed Ag(001). When on the contrary sputtering is performed at room temperature and the checkerboard superstructure develops, the quadratic term becomes twice as large

Springer Handbook of Surface Science

This handbook delivers an up-to-date, comprehensive and authoritative coverage of the broad field of surface science, encompassing a range of important materials such metals, semiconductors, insulators, ultrathin films and supported nanoobjects. Over 100 experts from all branches of experiment and theory review in 39 chapters all major aspects of solid-state surfaces, from basic principles to applications, including the latest, ground-breaking research results. Beginning with the fundamental background of kinetics and thermodynamics at surfaces, the handbook leads the reader through the basics of crystallographic structures and electronic properties, to the advanced topics at the forefront of current research. These include but are not limited to novel applications in nanoelectronics, nanomechanical devices, plasmonics, carbon films, catalysis, astrochemistry and biology. The handbook is an ideal reference guide and instructional aid for a wide range of physicists, chemists, materials scientists and engineers active throughout academic and industrial research

Dynamics of propene adsorption on Ag(001)

The interaction of propene with Ag(001) is investigated by high resolution electron energy loss spectroscopy and supersonic molecular beam methods under ultra high vacuum conditions. Propene adsorbs molecularly at 110 K and desorbs intact leaving a clean surface after annealing to 160 K. Two adsorption sites, characterized by slightly different vibrational modes, exist. The low frequency species is observed already at low coverage for molecules impinging at strongly hyperthermal energies while at lower translational energy it appears only at high coverage. The initial sticking probability S-0 decreases with increasing translational energy, as appropriate for nonactivated adsorption systems. The angle and energy dependence of S-0 indicate that scaling is intermediate between total and normal energy. From the coverage dependence of the sticking probability we infer that both a nonthermal intrinsic and a thermal extrinsic precursor exist