Abstract: In this paper, two types of melanoma and glioblastoma cancer cell lines are treated with cold atmospheric plasma to assess the effect of several parameters on the cell viability. The cell viability decreases with treatment duration and time until analysis in all cell lines with varying sensitivity. The majority of dead cells stains both AnnexinV (AnnV) and propidium iodide, indicating that the plasma-treated non-viable cells are mostly late apoptotic or necrotic. Genetic mutations might be involved in the response to plasma. Comparing the effects of two gas mixtures, as well as indirect plasma-activated medium versus direct treatment, gives different results per cell line. In conclusion, this study confirms the potential of plasma for cancer therapy and emphasizes the influence of experimental parameters on therapeutic outcome.

Abstract: The catalytic oxidative dehydrogenation of hydrocarbons is an industrially important process, in which selectivity is a key issue. We here investigate the conversion of methanol to formaldehyde on a vanadia surface employing long timescale simulations, reaching a time scale of seconds. In particular, we compare the thermal process to the case where an additional external electric field is applied, as would be the case in a direct plasma-catalysis setup. We find that the electric field influences the retention time of the molecules at the catalyst surface. These simulations provide an atomic scale insight in the thermal catalytic oxidative dehydrogenation process, and in how an external electric field may affect this process.

Abstract: Plasma catalysis is gaining increasing interest for various environmental applications, but the crucial question is whether plasma can be created inside catalyst pores and under which conditions. In practice, various catalytic support materials are used, with various dielectric constants. We investigate here the influence of the dielectric constant on the plasma properties inside catalyst pores and in the sheath in front of the pores, for various pore sizes. The calculations are performed by a two-dimensional fluid model for an atmospheric pressure dielectric barrier discharge in helium. The electron impact ionization rate, electron temperature, electron and ion density, as well as the potential distribution and surface charge density, are analyzed for a better understanding of the discharge behavior inside catalyst pores. The results indicate that, in a 100 μm pore, the electron impact ionization in the pore, which is characteristic for the plasma generation inside the pore, is greatly enhanced for dielectric constants below 300. Smaller pore sizes only yield enhanced ionization for smaller dielectric constants, i.e., up to εr = 200, 150, and 50 for pore sizes of 50, 30, and 10 μm. Thus, the most common catalyst supports, i.e., Al2O3 and SiO2, which have dielectric constants around εr = 8−11 and 4.2, respectively, should allow more easily that microdischarges can be formed inside catalyst pores, even for smaller pore sizes. On the other hand, ferroelectric materials with dielectric constants above 300 never seem to yield plasma enhancement inside catalyst pores, not even for 100 μm pore sizes. Furthermore, it is clear that the dielectric constant of the material has a large effect on the extent of plasma enhancement inside the catalyst pores, especially in the range between εr = 4 and εr = 200. The obtained results are explained in detail based on the surface charge density at the pore walls,
and the potential distribution and electron temperature inside and above the pores. The results obtained with this model are
important for plasma catalysis, as the production plasma species in catalyst pores might affect the catalyst properties, and thus
improve the applications of plasma catalysis.

Abstract: We present a 3D and 2D Cartesian quasi-neutral plasma model for a low current argon gliding arc discharge, including strong interactions between the gas flow and arc plasma column.
The 3D model is applied only for a short time of 0.2 ms due to its huge computational cost. It mainly serves to verify the reliability of the 2D model. As the results in 2D compare well with those in 3D, they can be used for a better understanding of the gliding arc basic characteristics. More specifically, we investigate the back-breakdown phenomenon induced by an artificially controlled plasma channel, and we discuss its effect on the gliding arc characteristics. The
back-breakdown phenomenon, or backward-jump motion of the arc, as observed in the experiments, results in a drop of the gas temperature, as well as in a delay of the arc velocity with respect to the gas flow velocity, allowing more gas to pass through the arc, and thus increasing the efficiency of the gliding arc for gas treatment applications.

Abstract: In this tutorial review paper, we illustrate how computer modeling can contribute to a better insight in inductively coupled plasma-mass spectrometry (ICP-MS). We start with a brief overview on previous efforts, studying the fundamentals of the ICP and ICP-MS, with main focus on previous modeling activities. Subsequently, we explain in detail the model that we developed in previous years, and we show typical calculation results, illustrating the plasma characteristics, gas flow patterns and the sample transport, evaporation and ionization. We also present the effect of various experimental parameters, such as operating conditions, geometrical aspects and sample characteristics, to illustrate how modeling can help to elucidate the optimal conditions for improved analytical performance.

Abstract: Unlocking the enormous technological potential of carbon nanotubes strongly depends on our ability to specifically produce metallic or semiconducting tubes. While selective etching of both has already been demonstrated, the underlying reasons, however, remain elusive as yet. We here present computational and experimental evidence on the operative mechanisms at the atomic scale. We demonstrate that during the adsorption of H atoms and their coalescence, the adsorbed ortho hydrogen pairs on single-walled carbon nanotubes induce higher shear stresses than axial stresses, leading to the elongation of HC–CH bonds as a function of their alignment with the tube chirality vector, which we denote as the γ-angle. As a result, the C–C cleavage occurs more rapidly in nanotubes containing ortho H-pairs with a small γ-angle. This phenomenon can explain the selective etching of small-diameter semiconductor nanotubes with a similar curvature. Both theoretical and experimental results strongly indicate the important role of the γ-angle in the selective etching mechanisms of carbon nanotubes, in addition to the nanotube curvature and metallicity effects and lead us to clearly understand the onset of selective synthesis/removal of CNT-based materials.

Abstract: tWe investigated the plasma-assisted catalytic reactions for the production of value-added chemicalsfrom Ni-catalyzed plasma dry reforming of methane by means of density functional theory (DFT). Weinspected many activation barriers, from the early stage of adsorption of the major chemical fragmentsderived fromCH4andCO2molecules up to the formation of value-added chemicals at the surface, focusingon the formation of methanol, as well as the hydrogenation of C1and C2hydrocarbon fragments. Theactivation barrier calculations show that the presence of surface-bound H atoms and in some cases alsoremaining chemical fragments at the surface facilitates the formation of products. This implies that thehydrogenation of a chemical fragment on the hydrogenated crystalline surface is energetically favouredcompared to the simple hydrogenation of the chemical fragment at the bare Ni(111) surface. Indeed, thepresence of hydrogen modifies the electronic structure of the surface and the course of the reactions.We therefore conclude that surface-bound H atoms, and to some extent also the remaining chemicalfragments at the crystalline surface, induce the following effects: they facilitate associative desorption ofmethanol and ethane by increasing the rate of H-transfer to the adsorbed fragments while they impedehydrogenation of ethylene to ethane, thus promoting again the desorption of ethylene. Overall, they thusfacilitate the catalytic conversion of the formed fragments from CH4and CO2, into value-added chemicals.Finally, we believe that the retention of methane fragments, especially CH3, in the presence of surface-boundHatoms (as observed here for Ni) can be regarded as an identifier for the proper choice of a catalystfor the production of value-added chemicals.

Abstract: In this work, the electrostatic control in metal-oxide-semiconductor field-effect transistors based on MoS2 is studied, with respect to the number of MoS2 layers in the channel and to the equivalent oxide thickness of the gate dielectric, using first-principles calculations combined with a quantum transport formalism. Our simulations show that a compromise exists between the drive current and the electrostatic control on the channel. When increasing the number of MoS2 layers, a degradation of the device performances in terms of subthreshold swing and OFF currents arises due to the screening of the MoS2 layers constituting the transistor channel. Published by AIP Publishing.

Abstract: Here, we present routes to increase CO2 conversion into CO using an atmospheric pressure dielectric-barrier discharge. The change in conversion as a function of simple plasma parameters, such as power, flow rate, but also frequency, on-and-off power pulse, thickness and the chemical nature of the dielectric, wall and gas temperature, are described. By means of an in-depth electrical characterization of the discharge (effective plasma voltage, dielectric voltage, plasma current, number and lifetime of the microdischarges), combined with infrared analysis of the walls of the reactor, optical emission spectroscopy for the gas temperature, and mass spectrometry for the CO2 conversion, we propose a global interpretation of the effect of all the experimental parameters on the conversion and efficiency of the reaction.

Abstract: Cold atmospheric pressure plasmas in and in contact with liquids represent a growing field of research for various applications. Understanding the interactions between the plasma generated species and the liquid is crucial. In this work we perform molecular dynamics (MD) simulations based on a quantum mechanical method, i.e. density-functional based tight-binding (DFTB), to examine the interactions of OH radicals and O atoms in bulk water. Our calculations reveal that the transport of OH radicals through water is not only governed by diffusion, but also by an equilibrium reaction of H-abstraction with water molecules. Furthermore, when two OH radicals encounter each other, they either form a stable cluster, or react, resulting in the formation of a new water molecule and an O atom. In addition,
the O atoms form either oxywater (when in singlet configuration) or they remain stable in solution (when in triplet configuration), stressing the important role that O atoms can play in aqueous solution, and in contact with biomolecules. Our observations are in line with both experimental and ab initio results from the literature.

Abstract: In this paper, we show that the apparent delocalization of the conduction band reported from first-principles simulations for the high-mobility amorphous oxide semiconductor InGaZnO4 (a-IGZO) is an artifact induced by the periodic conditions imposed to the model. Given a sufficiently large unit-cell dimension (over 40 angstrom), the conduction band becomes localized. Such a model size is up to four times the size of commonly used models for the study of a-IGZO. This finding challenges the analyses done so far on the nature of the defects and on the interpretation of numerous electrical measurements. In particular, we re-interpret the meaning of the computed effective mass reported so far in literature. Our finding also applies to materials such as SiZnSnO, ZnSnO, InZnSnO, In2O3 or InAlZnO4 whose models have been reported to display a fully delocalized conduction band in the amorphous phase.

Abstract: Excessive CO2 emissions in the atmosphere from anthropogenic activity can be divided into point sources and diffuse sources. The capture of CO2 from flue gases of large industrial installations and its conversion into fuels and chemicals with fast catalytic processes seems technically possible. Some emerging technologies are already being demonstrated on an industrial scale. Others are still being tested on a laboratory or pilot scale. These emerging chemical technologies can be implemented in a time window ranging from 5 to 20 years. The massive amounts of energy needed for capturing processes and the conversion of CO2 should come from low-carbon energy sources, such as tidal, geothermal, and nuclear energy, but also, mainly, from the sun. Synthetic methane gas that can be formed from CO2 and hydrogen gas is an attractive renewable energy carrier with an existing distribution system. Methanol offers advantages as a liquid fuel and is also a building block for the chemical industry. CO2 emissions from diffuse sources is a difficult problem to solve, particularly for CO2 emissions from road, water, and air transport, but steady progress in the development of technology for capturing CO2 from air is being made. It is impossible to ban carbon from the entire energy
supply of mankind with the current technological knowledge, but a transition to a mixed carbon–hydrogen economy can reduce net CO2 emissions and ultimately lead to a CO2-neutral world.