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The dissociation of methane is not only an important reaction step in catalytic processes, but also of fundamental interest. Dynamical effects during the dissociative chemisorption of methane on metal surfaces cause significant differences in computed reaction rates, compared to what is predicted by typical transition state theory (TST) models. It is clear that for a good understanding of the catalytic activation of methane dynamical simulations are required. In this paper, a general blueprint is provided for performing dynamical simulations of the dissociative chemisorption of methane on metal surfaces, by employing either the quasi-classical trajectory or ring polymer molecular dynamics approach. If the computational setup is constructed with great care–since results can be affected considerably by the setup – chemically accurate predictions are achievable. Although this paper concerns methane dissociation, the provided blueprint is, so far, applicable to the dissociative chemisorption of most molecules.

The population growth and consequently lack of fresh water resources, are the main concerns of developed communities. Providing water from air humidity is an efficient, clean, and sustainable solution that can supply sweet and fresh water. In this study, different metal surfaces including copper, steel, and aluminum plates have been prepared as a hydrophobic or hydrophilic surfaces through laser, to investigate the amount of collected water at 294.15 K under fully humid environment (100% humidity), at different encounter angles with plates (45, 70, and 90 °). Moreover, the metal plates along with small or large meshes have been also tested. In addition, polytetrafluoroethylene plates have been prepared via laser in order to water harvesting from humid air. It has been shown that all surfaces treated with laser have better efficiency for water harvesting in comparison with the plates without laser. Likewise, the angle of 45° has had the highest amount of collected water on all surfaces. Eventually, it has been observed that steel plate modified with laser 1 has had higher efficiency for producing drinking water.

Introduction. The deterioration of engine oil in an internal combustion engine (ICE) is directly related to the ingress of various pollutants into the crankcase. Depending on the type of contamination, the type of sediment on engine part surfaces varies. It should be noted that the functioning of the motor oil is extremely affected by the oxidation process, and organic acids produced during the process contribute to corrosion of ICE parts. Water, diesel, cooling fluid, soot particles, asphaltenes, etc. also cause irreparable damage.Materials and methods. This paper presents the results of an extensive literature review aimed at studying the main types of motor oil pollutants. Classifications are given for the aggregate state of pollutants, as well as for possible ways of their penetration into the lubricant. Liquid pollutants are the most narrowly considered in this article. To demonstrate the negative effect of contaminants entering the engine oil, photographs of internal combustion engine parts with sediments on the surfaces of the internal combustion engine components are presented.Results. The classification of the main pollutants of motor oils is given; the consequences arising from the ingress of foreign compounds into the lubricant in question are indicated.Conclusion. The effect of contaminants on the parts of the internal combustion engine and the lubricant has been established. On the basis of the classification, it is possible to judge the causes of entry and the possible consequences of the impact of contamination on the operation of the engine.

Introduction. One of the main types of deposits in an internal combustion engine is an emulsion or sludge formed by water, decomposition of fuel residues and solid residues. The sludge usually settles on the colder surfaces of the engine, such as the bottom of the crankcase pan, valve chambers and upper boards. The main problem is that this type of deposits can be collected by the engine oil and transferred to areas such as the oil pump, intake valve or oil channels, where the sludge can interfere with the flow of oil and cause a failure of the lubrication mode. In addition to the disruption in the operation of the above-mentioned systems, the engine oil quality indicators are also undergoing changes for the worse.Materials and methods. To monitor the condition of the engine oil, it is necessary to determine the characteristics of its performance, such as: kinematic viscosity at 40 oC and at 100 oC, acid number, base number and determine the number of elements – indicators of additives and wear products contained in the engine oil. The viscosity was determined using a Stabinger SVM 3000 viscometer. It measures the dynamic viscosity and density of oils and fuels in accordance with ASTM D7042 and automatically calculates the kinematic viscosity, viscosity index and outputs the measurement results. The acid and base numbers were determined using an automatic titrator TitroLine alpha plus, and the presence of indicator elements in engine oil using an inductively coupled plasma optical emission spectrometer of the iCAP 7000 series, designed for analysis and determination of the number of indicator elements in liquid and solid samples.Results. The dynamics of changes in the performance characteristics of the Gazpromneft Diesel Ultra 10W-40 engine oil with an extended replacement interval, which is applicable for equipment operating in severe conditions, depending on the water content in the samples of this lubricant, was analyzed.Conclusion. The consequences that may occur due to water entering the engine oil are indicated.

Rubrene (C42H28) was adsorbed with submonolayer coverage on Pt(111), Au(111), and graphene-covered Pt(111). Adsorption phases and vibronic properties of C42H28 consistently reflect the progressive reduction of the molecule–substrate hybridization. Separate C42H28 clusters are observed on Pt(111) as well as broad molecular resonances. On Au(111) and graphene-covered Pt(111) compact molecular islands with similar unit cells of the superstructure characterize the adsorption phase. The highest occupied molecular orbital of C42H28 on Au(111) exhibits weak vibronic progression while unoccupied molecular resonances appear with a broad line shape. In contrast, vibronic subbands are present for both frontier orbitals of C42H28 on graphene. They are due to different molecular vibrational quanta with distinct Huang–Rhys factors.

We studied the surface-enhanced Raman spectra of amino acids D-alanine and DL-serine and their mixture on silver nanoisland films (SNF) immersed in phosphate-buffered saline (PBS) solution at millimolar amino acid concentrations. It is shown that the spectra from the amino acid solutions differ from the reference spectra for microcrystallites due to the electrostatic orientation of amino acid zwitterions by the metal nanoisland film. Moreover, non-additive peaks are observed in the spectrum of the mixture of amino acids adsorbed on SNF, which means that intermolecular interactions between adsorbed amino acids are very significant. The results indicate the need for a thorough analysis of the Raman spectra from amino acid solutions, particularly, in PBS, in the presence of a nanostructured silver surface, and may also be of interest for studying molecular properties and intermolecular interactions.

In this study, we demonstrate the structural evolution of a two-dimensional (2D) supramolecular assembly system, which is steered by the thermally activated deprotonation of the primary organic building blocks on a Ag(111) surface. Scanning tunneling microscopy revealed that a variety of structures, featuring distinct structural, chiral, and intermolecular bonding characters, emerged with the gradual thermal treatments. According to our structural analysis, in combination with density function theory calculations, the structural evolution can be attributed to the successive deprotonation of the organic building blocks due to the inductive effect. Our finding offers a facile strategy towards controlling the supramolecular assembly pathways and provides a comprehensive understanding of the 2D crystal engineering on surfaces.

Conversion of energy at the gas–solid interface lies at the heart of many industrial applications such as heterogeneous catalysis. Dissipation of parts of this energy into the substrate bulk drives the thermalization of surface species, but also constitutes a potentially unwanted loss channel. At present, little is known about the underlying microscopic dissipation mechanisms and their (relative) efficiency. At metal surfaces, prominent such mechanisms are the generation of substrate phonons and the electronically non-adiabatic excitation of electron–hole pairs. In recent years, dedicated surface science experiments at defined single-crystal surfaces and predictive-quality first-principles simulations have increasingly been used to analyze these dissipation mechanisms in prototypical surface dynamical processes such as gas-phase scattering and adsorption, diffusion, vibration, and surface reactions. In this topical review we provide an overview of modeling approaches to incorporate dissipation into corresponding dynamical simulations starting from coarse-grained effective theories to increasingly sophisticated methods. We illustrate these at the level of individual elementary processes through applications found in the literature, while specifically highlighting the persisting difficulty of gauging their performance based on experimentally accessible observables.

The formation of image-potential states at the interface between a graphene layer and a metal surface is studied by means of model calculations. An analytical one-dimensional model-potential for the combined system is constructed and used to calculate energies and wave functions of the image-potential states at the $\bar{{\rm{\Gamma }}}$ -point as a function of the graphene–metal distance. It is demonstrated how the double series of image-potential states of freestanding graphene evolves into interfacial states that interact with both surfaces at intermediate distances, and finally into a single series of states resembling those of a clean metal surface covered by a monoatomic spacer layer. The model quantitatively reproduces experimental data available for graphene/Ir(111) and graphene/Ru(0001), systems which strongly differ in interaction strength and therefore adsorption distance. Moreover, it provides a clear physical explanation for the different binding energies and lifetimes of the first ( n = 1) image-potential state in the valley and hill areas of the strongly corrugated moiré superlattice of graphene/Ru(0001).