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“Optimal experiment design for nanoparticle atom counting from ADF STEM images”. de Backer A, Fatermans J, den Dekker AJ, Van Aert S Advances in imaging and electron physics
T2 – Advances in imaging and electron physics. page 145 (2021).
Abstract: In this chapter, the principles of detection theory are used to quantify the probability of error for atom counting from high-resolution scanning transmission electron microscopy (HRSTEM) images. Binary and multiple hypothesis testing have been investigated in order to determine the limits to the precision with which the number of atoms in a projected atomic column can be estimated. The probability of error has been calculated when using STEM images, scattering cross-sections or peak intensities as a criterion to count atoms. Based on this analysis, we conclude that scattering cross-sections perform almost equally well as images and perform better than peak intensities. Furthermore, the optimal STEM detector design can be derived for atom counting using the expression of the probability of error. We show that for very thin objects the low-angle annular dark-field (LAADF) regime is optimal and that for thicker objects the optimal inner detector angle increases.
Keywords: H2 Book chapter; Electron microscopy for materials research (EMAT); Vision lab
DOI: 10.1016/BS.AIEP.2021.01.005
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“Statistical parameter estimation theory : principles and simulation studies”. de Backer A, Fatermans J, den Dekker AJ, Van Aert S Advances in imaging and electron physics
T2 – Advances in imaging and electron physics. page 29 (2021).
Abstract: In this chapter, the principles of statistical parameter estimation theory for a quantitative analysis of atomic-resolution electron microscopy images are introduced. Within this framework, electron microscopy images are described by a parametric statistical model. Here, parametric models are introduced for different types of electron microscopy images: reconstructed exit waves, annular dark-field (ADF) scanning transmission electron microscopy (STEM) images, and simultaneously acquired ADF and annular bright-field (ABF) STEM images. Furthermore, the Cramér-Rao lower bound (CRLB) is introduced, i.e. a theoretical lower bound on the variance of any unbiased estimator. This CRLB is used to quantify the precision of the structure parameters of interest, such as the atomic column positions and the integrated atomic column intensities.
Keywords: H2 Book chapter; Electron microscopy for materials research (EMAT); Vision lab
DOI: 10.1016/BS.AIEP.2021.01.002
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“Shape from projections via differentiable forward projector for computed tomography”. Koo J, Dahl AB, Bærentzen JA, Chen Q, Bals S, Dahl VA, Ultramicroscopy 224, 113239 (2021). http://doi.org/10.1016/j.ultramic.2021.113239
Abstract: In computed tomography, the reconstruction is typically obtained on a voxel grid. In this work, however, we propose a mesh-based reconstruction method. For tomographic problems, 3D meshes have mostly been studied to simulate data acquisition, but not for reconstruction, for which a 3D mesh means the inverse process of estimating shapes from projections. In this paper, we propose a differentiable forward model for 3D meshes that bridge the gap between the forward model for 3D surfaces and optimization. We view the forward projection as a rendering process, and make it differentiable by extending recent work in differentiable rendering. We use the proposed forward model to reconstruct 3D shapes directly from projections. Experimental results for single-object problems show that the proposed method outperforms traditional voxel-based methods on noisy simulated data. We also apply the proposed method on electron tomography images of nanoparticles to demonstrate the applicability of the method on real data.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
Times cited: 3
DOI: 10.1016/j.ultramic.2021.113239
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“The design of magneto-plasmonic nanostructures formed by magnetic Prussian Blue-type nanocrystals decorated with Au nanoparticles”. Sanchis-Gual R, Susic I, Torres-Cavanillas R, Arenas-Esteban D, Bals S, Mallah T, Coronado-Puchau M, Coronado E, Chemical Communications 57, 1903 (2021). http://doi.org/10.1039/D0CC08034A
Abstract: We have developed a general protocol for the preparation of hybrid nanostructures formed by nanoparticles (NPs) of molecule-based magnets based on Prussian Blue Analogues (PBAs) decorated with plasmonic Au NPs of different shapes. By adjusting the pH, Au NPs can be attached preferentially along the edges of the PBA or randomly on the surface. The protocol allows tuning the plasmonic properties of the hybrids in the whole visible spectrum.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 6.319
Times cited: 5
DOI: 10.1039/D0CC08034A
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“Spatially and temporally non-uniform plasmas: microdischarges from the perspective of molecules in a packed bed plasma reactor”. van ‘t Veer K, van Alphen S, Remy A, Gorbanev Y, De Geyter N, Snyders R, Reniers F, Bogaerts A, Journal Of Physics D-Applied Physics 54, 174002 (2021). http://doi.org/10.1088/1361-6463/abe15b
Abstract: Dielectric barrier discharges (DBDs) typically operate in the filamentary regime and thus exhibit great spatial and temporal non-uniformity. In order to optimize DBDs for various applications, such as in plasma catalysis, more fundamental insight is needed. Here, we consider how the millions of microdischarges, characteristic for a DBD, influence individual gas molecules. We use a Monte Carlo approach to determine the number of microdischarges to which a single molecule would be exposed, by means of particle tracing simulations through a full-scale packed bed DBD reactor, as well as an empty DBD reactor. We find that the fraction of microdischarges to which the molecules are exposed can be approximated as the microdischarge volume over the entire reactor gas volume. The use of this concept provides good agreement between a plasma-catalytic kinetics model and experiments for plasma-catalytic NH3 synthesis. We also show that the concept of the fraction of microdischarges indicates the efficiency by which the plasma power is transferred to the gas molecules. This generalised concept is also applicable for other spatially and temporally non-uniform plasmas.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.588
DOI: 10.1088/1361-6463/abe15b
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“Charge Localization and Magnetic Correlations in the Refined Structure of U3O7”. Leinders G, Baldinozzi G, Ritter C, Saniz R, Arts I, Lamoen D, Verwerft M, Inorganic Chemistry 60, 10550 (2021). http://doi.org/10.1021/acs.inorgchem.1c01212
Abstract: Atomic arrangements in the mixed-valence oxide U3O7 are refined from high-resolution neutron scattering data. The crystallographic model describes a long-range structural order in a U60O140 primitive cell (space group P42/n) containing distorted cuboctahedral oxygen clusters. By combining experimental data and electronic structure calculations accounting for spin–orbit interactions, we provide robust evidence of an interplay between charge localization and the magnetic moments carried by the uranium atoms. The calculations predict U3O7 to be a semiconducting solid with a band gap of close to 0.32 eV, and a more pronounced charge-transfer insulator behavior as compared to the well-known Mott insulator UO2. Most uranium ions (56 out of 60) occur in 9-fold and 10-fold coordinated environments, surrounding the oxygen clusters, and have a tetravalent (24 out of 60) or pentavalent (32 out of 60) state. The remaining uranium ions (4 out of 60) are not contiguous to the oxygen cuboctahedra and have a very compact, 8-fold coordinated environment with two short (2 × 1.93(3) Å) “oxo-type” bonds. The higher Hirshfeld charge and the diamagnetic character point to a hexavalent state for these four uranium ions. Hence, the valence state distribution corresponds to 24/60 × U(IV) + 32/60 U(V) + 4/60 U(VI). The tetravalent and pentavalent uranium ions are predicted to carry noncollinear magnetic moments (with amplitudes of 1.6 and 0.8 μB, respectively), resulting in canted ferromagnetic order in characteristic layers within the overall fluorite-related structure.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.857
DOI: 10.1021/acs.inorgchem.1c01212
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Bahnamiri OS, Verheyen C, Snyders R, Bogaerts A, Britun N (2021) Nitrogen fixation in pulsed microwave discharge studied by infrared absorption combined with modelling. 065007
Abstract: A pulsed microwave surfaguide discharge operating at 2.45 GHz was used for the conversion of molecular nitrogen into valuable compounds in several gas mixtures: N2 :O2 , N2 :O2 :CO2 and N2 :CO2 . The ro-vibrational absorption bands of the molecular species were monitored by a Fourier transform infrared apparatus in the post-discharge region in order to evaluate the relative number density of species, specifically NO production. The effects of specific energy input, pulse frequency, gas flow fraction, gas admixture and gas flow rate were studied for better understanding and optimization of the NO production yield and the corresponding energy cost (EC). By both the experiment and modelling, a highest NO yield is obtained at N2 :O2 (1:1) gas ratio in N2 :O2 mixture. The NO yield reveals a small growth followed by saturation when pulse repetition frequency increases. The energy efficiency start decreasing after the energy input reaches about 5 eV/molec, whereas the NO yield rises steadily at the same time. The lowest EC of about 8 MJ mol−1 corresponding to the yield and the energy efficiency of about 7% and 1% are found, respectively, in an optimum discharge condition in our case.
Keywords: A1 Journal Article;nitrogen fixation; pulsed microwave discharge; FTIR spectroscopy; discharge modelling; vibrational excitation; NO yield; energy cost; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 3.302
DOI: 10.1088/1361-6595/abff0e
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“Lipid Oxidation: Role of Membrane Phase-Separated Domains”. Oliveira MC, Yusupov M, Bogaerts A, Cordeiro RM, Journal Of Chemical Information And Modeling 61, 2857 (2021). http://doi.org/10.1021/acs.jcim.1c00104
Abstract: Lipid oxidation is associated with several inflammatory and neurodegenerative diseases, but many questions to unravel its effects on biomembranes are still open due to the complexity of the topic. For instance, recent studies indicated that phase-separated domains can have a significant effect on membrane function. It is reported that domain interfaces are “hot spots” for pore formation, but the underlying mechanisms and the effect of oxidation-induced phase separation on membranes remain elusive. Thus, to evaluate the permeability of the membrane coexisting of liquid-ordered (Lo) and liquid-disordered (Ld) domains, we performed atomistic molecular dynamics simulations. Specifically, we studied the membrane permeability of nonoxidized or oxidized homogeneous membranes (single-phase) and at the Lo/Ld domain interfaces of heterogeneous membranes, where the Ld domain is composed of either oxidized or nonoxidized lipids. Our simulation results reveal that the addition of only 1.5% of lipid aldehyde molecules at the Lo/Ld domain interfaces of heterogeneous membranes increases the membrane permeability, whereas their addition at homogeneous membranes does not have any effect. This study is of interest for a better understanding of cancer treatment methods based on oxidative stress (causing among others lipid oxidation), such as plasma medicine and photodynamic therapy.
Keywords: A1 Journal Article; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 3.76
DOI: 10.1021/acs.jcim.1c00104
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Bal KM, Neyts EC (2021) Quantifying the impact of vibrational nonequilibrium in plasma catalysis: insights from a molecular dynamics model of dissociative chemisorption. 394004
Abstract: The rate, selectivity and efficiency of plasma-based conversion processes is strongly affected by nonequilibrium phenomena. High concentrations of vibrationally excited molecules are such a plasma-induced effect. It is frequently assumed that vibrationally excited molecules are important in plasma catalysis because their presence lowers the apparent activation energy of dissociative chemisorption reactions and thus increases the conversion rate. A detailed atomic-level understanding of vibrationally stimulated catalytic reactions in the context of plasma catalysis is however lacking. Here, we couple a recently developed statistical model of a plasma-induced vibrational nonequilibrium to molecular dynamics simulations, enhanced sampling methods, and machine learning techniques. We quantify the impact of a vibrational nonequilibrium on the dissociative chemisorption barrier of H2 and CH4 on nickel catalysts over a wide range of vibrational temperatures. We investigate the effect of surface structure and compare the role of different vibrational modes of methane in the dissociation process. For low vibrational temperatures, very high vibrational efficacies are found, and energy in bend vibrations appears to dominate the dissociation of methane. The relative impact of vibrational nonequilibrium is much higher on terrace sites than on surface steps. We then show how our simulations can help to interpret recent experimental results, and suggest new paths to a better understanding of plasma catalysis.
Keywords: A1 Journal Article;plasma catalysis; vibrational nonequilibrium; dissociative chemisorption; free energy barriers; Plasma, laser ablation and surface modeling Antwerp (PLASMANT) ;
Impact Factor: 2.588
DOI: 10.1088/1361-6463/ac113a
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“Reaction mechanisms of C(3PJ) and C+(2PJ) with benzene in the interstellar medium from quantum mechanical molecular dynamics simulations”. Izadi ME, Bal KM, Maghari A, Neyts EC, Physical Chemistry Chemical Physics 23, 4205 (2021). http://doi.org/10.1039/D0CP04542J
Abstract: While spectroscopic data on small hydrocarbons in interstellar media in combination with crossed molecular beam (CMB) experiments have provided a wealth of information on astrochemically relevant species, much of the underlying mechanistic pathways of their formation remain elusive. Therefore, in this work, the chemical reaction mechanisms of C(<sup>3</sup>P<sub>J</sub>) + C<sub>6</sub>H<sub>6</sub>and C<sup>+</sup>(<sup>2</sup>P) + C<sub>6</sub>H<sub>6</sub>systems using the quantum mechanical molecular dynamics (QMMD) technique at the PBE0-D3(BJ) level of theory is investigated, mimicking a CMB experiment. Both the dynamics of the reactions as well as the electronic structure for the purpose of the reaction network are evaluated. The method is validated for the first reaction by comparison to the available experimental data. The reaction scheme for the C(<sup>3</sup>P<sub>J</sub>) + C<sub>6</sub>H<sub>6</sub>system covers the literature data,<italic>e.g.</italic>the major products are the 1,2-didehydrocycloheptatrienyl radical (C<sub>7</sub>H<sub>5</sub>) and benzocyclopropenyl radical (C<sub>6</sub>H<sub>5</sub>–CH), and it reveals the existence of less common pathways for the first time. The chemistry of the C<sup>+</sup>(<sup>2</sup>P<sub>J</sub>) + C<sub>6</sub>H<sub>6</sub>system is found to be much richer, and we have found that this is because of more exothermic reactions in this system in comparison to those in the C(<sup>3</sup>P<sub>J</sub>) + C<sub>6</sub>H<sub>6</sub>system. Moreover, using the QMMD simulation, a number of reaction paths have been revealed that produce three distinct classes of reaction products with different ring sizes. All in all, at all the collision energies and orientations, the major product is the heptagon molecular ion for the ionic system. It is also revealed that the collision orientation has a dominant effect on the reaction products in both systems, while the collision energy mostly affects the charged system. These simulations both prove the applicability of this approach to simulate crossed molecular beams, and provide fundamental information on reactions relevant for the interstellar medium.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.123
DOI: 10.1039/D0CP04542J
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“Flowing Atmospheric Pressure Afterglow for Ambient Ionization: Reaction Pathways Revealed by Modeling”. Aghaei M, Bogaerts A, Analytical Chemistry 93, 6620 (2021). http://doi.org/10.1021/acs.analchem.0c04076
Abstract: We describe the plasma chemistry in a helium flowing atmospheric pressure afterglow (FAPA) used for analytical spectrometry, by means of a quasione-dimensional (1D) plasma chemical kinetics model. We study the effect of typical impurities present in the feed gas, as well as the afterglow in ambient humid air. The model provides the species density profiles in the discharge and afterglow regions and the chemical pathways. We demonstrate that H, N, and O atoms are formed in the discharge region, while the dominant reactive neutral species in the afterglow are O3 and NO. He* and He2* are responsible for Penning ionization of O2, N2, H2O, H2, and N, and especially O and H atoms. Besides, He2+ also contributes to ionization of N2, O2, H2O, and O through charge transfer reactions. From the pool of ions created in the discharge, NO+ and (H2O)3H+ are the dominant ions in the afterglow. Moreover, negatively charged clusters, such as NO3H2O− and NO2H2O−, are formed and their pathway is discussed as well. Our model predictions are in line with earlier observations in the literature about the important reagent ions and provide a comprehensive overview of the underlying pathways. The model explains in detail why helium provides a high analytical sensitivity because of high reagent ion formation by both Penning ionization and charge transfer. Such insights are very valuable for improving the analytical performance of this (and other) ambient desorption/ionization source(s).
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.32
DOI: 10.1021/acs.analchem.0c04076
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“Coincidence Detection of EELS and EDX Spectral Events in the Electron Microscope”. Jannis D, Müller-Caspary K, Béché, A, Verbeeck J, Applied Sciences-Basel 11, 9058 (2021). http://doi.org/10.3390/app11199058
Abstract: Recent advances in the development of electron and X-ray detectors have opened up the possibility to detect single events from which its time of arrival can be determined with nanosecond resolution. This allows observing time correlations between electrons and X-rays in the transmission electron microscope. In this work, a novel setup is described which measures individual events using a silicon drift detector and digital pulse processor for the X-rays and a Timepix3 detector for the electrons. This setup enables recording time correlation between both event streams while at the same time preserving the complete conventional electron energy loss (EELS) and energy dispersive X-ray (EDX) signal. We show that the added coincidence information improves the sensitivity for detecting trace elements in a matrix as compared to conventional EELS and EDX. Furthermore, the method allows the determination of the collection efficiencies without the use of a reference sample and can subtract the background signal for EELS and EDX without any prior knowledge of the background shape and without pre-edge fitting region. We discuss limitations in time resolution arising due to specificities of the silicon drift detector and discuss ways to further improve this aspect.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.679
Times cited: 9
DOI: 10.3390/app11199058
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“Spherical core–shell alumina support particles for model platinum catalysts”. Geerts L, Geerts-Claes H, Skorikov A, Vermeersch J, Vanbutsele G, Galvita V, Constales D, Chandran CV, Radhakrishnan S, Seo JW, Breynaert E, Bals S, Sree SP, Martens JA, Nanoscale 13, 4221 (2021). http://doi.org/10.1039/D0NR08456E
Abstract: γ- and δ-alumina are popular catalyst support materials. Using a hydrothermal synthesis method starting from aluminum nitrate and urea in diluted solution, spherical core–shell particles with a uniform particle size of about 1 μm were synthesized. Upon calcination at 1000 °C, the particles adopted a core–shell structure with a γ-alumina core and δ-alumina shell as evidenced by 2D and 3D electron microscopy and<sup>27</sup>Al magic angle spinning nuclear magnetic resonance spectroscopy. The spherical alumina particles were loaded with Pt nanoparticles with an average size below 1 nm using the strong electrostatic adsorption method. Electron microscopy and energy dispersive X-ray spectroscopy revealed a homogeneous platinum dispersion over the alumina surface. These platinum loaded alumina spheres were used as a model catalyst for bifunctional catalysis. Physical mixtures of Pt/alumina spheres and spherical zeolite particles are equivalent to catalysts with platinum deposited on the zeolite itself facilitating the investigation of the catalyst components individually. The spherical alumina particles are very convenient supports for obtaining a homogeneous distribution of highly dispersed platinum nanoparticles. Obtaining such a small Pt particle size is challenging on other support materials such as zeolites. The here reported and well-characterized Pt/alumina spheres can be combined with any zeolite and used as a bifunctional model catalyst. This is an interesting strategy for the examination of the acid catalytic function without the interference of the supported platinum metal on the investigated acid material.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.367
Times cited: 3
DOI: 10.1039/D0NR08456E
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“NOxproduction in a rotating gliding arc plasma: potential avenue for sustainable nitrogen fixation”. Jardali F, Van Alphen S, Creel J, Ahmadi Eshtehardi H, Axelsson M, Ingels R, Snyders R, Bogaerts A, Green Chemistry 23, 1748 (2021). http://doi.org/10.1039/D0GC03521A
Abstract: The fast growing world population demands food to survive, and nitrogen-based fertilizers are essential to ensure sufficient food production. Today, fertilizers are mainly produced from non-sustainable fossil fuels<italic>via</italic>the Haber–Bosch process, leading to serious environmental problems. We propose here a novel rotating gliding arc plasma, operating in air, for direct NO<sub>x</sub>production, which can yield high nitrogen content organic fertilizers without pollution associated with ammonia emission. We explored the efficiency of NO<sub>x</sub>production in a wide range of feed gas ratios, and for two arc modes: rotating and steady. When the arc is in steady mode, record-value NO<sub>x</sub>concentrations up to 5.5% are achieved which are 1.7 times higher than the maximum concentration obtained by the rotating arc mode, and with an energy consumption of 2.5 MJ mol<sup>−1</sup>(or<italic>ca.</italic>50 kW h kN<sup>−1</sup>);<italic>i.e.</italic>the lowest value so far achieved by atmospheric pressure plasma reactors. Computer modelling, using a combination of five different complementary approaches, provides a comprehensive picture of NO<sub>x</sub>formation in both arc modes; in particular, the higher NO<sub>x</sub>production in the steady arc mode is due to the combined thermal and vibrationally-promoted Zeldovich mechanisms.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 9.125
DOI: 10.1039/D0GC03521A
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“Sustainable gas conversion by gliding arc plasmas: a new modelling approach for reactor design improvement”. Van Alphen S, Jardali F, Creel J, Trenchev G, Snyders R, Bogaerts A, Sustainable energy &, fuels 5, 1786 (2021). http://doi.org/10.1039/D0SE01782E
Abstract: Research in plasma reactor designs is developing rapidly as plasma technology is gaining increasing interest for sustainable gas conversion applications, like the conversion of greenhouse gases into value-added chemicals and renewable fuels, and fixation of N<sub>2</sub>from air into precursors of mineral fertilizer. As plasma is generated by electric power and can easily be switched on/off, these applications allows for efficient conversion and energy storage of intermittent renewable electricity. In this paper, we present a new comprehensive modelling approach for the design and development of gliding arc plasma reactors, which reveals the fluid dynamics, the arc behaviour and the plasma chemistry by solving a unique combination of five complementary models. This results in a complete description of the plasma process, which allows one to efficiently evaluate the performance of a reactor and indicate possible design improvements before actually building it. We demonstrate the capabilities of this method for an experimentally validated study of plasma-based NO<sub>x</sub>formation in a rotating gliding arc reactor, which is gaining increasing interest as a flexible, electricity-driven alternative for the Haber–Bosch process. The model demonstrates the importance of the vortex flow and the presence of a recirculation zone in the reactor, as well as the formation of hot spots in the plasma near the cathode pin and the anode wall that are responsible for most of the NO<sub>x</sub>formation. The model also reveals the underlying plasma chemistry and the vibrational non-equilibrium that exists due to the fast cooling during each arc rotation. Good agreement with experimental measurements on the studied reactor design proves the predictive capabilities of our modelling approach.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
DOI: 10.1039/D0SE01782E
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“Distinctive magnetic properties of CrI3 and CrBr3 monolayers caused by spin-orbit coupling”. Bacaksiz C, Šabani D, Menezes RM, Milošević, MV, Physical Review B 103, 125418 (2021). http://doi.org/10.1103/PhysRevB.103.125418
Abstract: After the discovery of magnetism in monolayer CrI3, the magnetic properties of different 2D materials from the chromium-trihalide family are intuitively assumed to be similar, yielding magnetic anisotropy from the spin-orbit coupling on halide ligands. Here we reveal significant differences between the CrI3 and CrBr3 magnetic monolayers in their magnetic anisotropy, resulting Curie temperature, hysteresis in external magnetic field, and evolution of magnetism with strain, all predominantly attributed to distinctly different interplay of atomic contributions to spin-orbit coupling in two materials.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 18
DOI: 10.1103/PhysRevB.103.125418
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“Increased Performance Improvement of Lithium-Ion Batteries by Dry Powder Coating of High-Nickel NMC with Nanostructured Fumed Ternary Lithium Metal Oxides”. Herzog MJ, Gauquelin N, Esken D, Verbeeck J, Janek J, ACS applied energy materials 4, 8832 (2021). http://doi.org/10.1021/acsaem.1c00939
Abstract: Dry powder coating is an effective approach to protect the surfaces of layered cathode active materials (CAMs) in lithium-ion batteries. Previous investigations indicate an incorporation of lithium ions in fumed Al2O3, ZrO2, and TiO2 coatings on LiNi0.7Mn0.15Co0.15O2 during cycling, improving the cycling performance. Here, this coating approach is transferred for the first time to fumed ternary LiAlO2, Li4Zr3O8, and Li4Ti5O12 and directly compared with their lithium-free equivalents. All materials could be processed equally and their nanostructured small aggregates accumulate on the CAM surfaces to quite homogeneous coating layers with a certain porosity. The LiNixMnyCozO2 (NMC) coated with lithium-containing materials shows an enhanced improvement in overall capacity, capacity retention, rate performance, and polarization behavior during cycling, compared to their lithium-free analogues. The highest rate performance was achieved with the fumed ZrO2 coating, while the best long-term cycling stability with the highest absolute capacity was obtained for the fumed LiAlO2-coated NMC. The optimal coating agent for NMC to achieve a balanced system is fumed Li4Ti5O12, providing a good compromise between high rate capability and good capacity retention. The coating agents prevent CAM particle cracking and degradation in the order LiAlO2 ≈ Al2O3 > Li4Ti5O12 > Li4Zr3O8 > ZrO2 > TiO2. A schematic model for the protection and electrochemical performance enhancement of high-nickel NMC with fumed metal oxide coatings is sketched. It becomes apparent that physical and chemical characteristics of the coating significantly influence the performance of NMC. A high degree of coating-layer porosity is favorable for the rate capability, while a high coverage of the surface, especially in vulnerable grain boundaries, enhances the long-term cycling stability and improves the cracking behavior of NMCs. While zirconium-containing coatings possess the best chemical properties for high rate performances, aluminum-containing coatings feature a superior chemical nature to protect high-nickel NMCs.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Times cited: 15
DOI: 10.1021/acsaem.1c00939
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Van Hoecke L, Laffineur L, Campe R, Perreault P, Verbruggen SW, Lenaerts S (2021) Challenges in the use of hydrogen for maritime applications
Abstract: Maritime shipping is a key factor that enables the global economy, however the pressure it exerts on the environment is increasing rapidly. In order to reduce the emissions of harmful greenhouse gasses, the search is on for alternative fuels for the maritime shipping industry. In this work the usefulness of hydrogen and hydrogen carriers is being investigated as a fuel for sea going ships. Due to the low volumetric energy density of hydrogen under standard conditions, the need for efficient storage of this fuel is high. Key processes in the use of hydrogen are discussed, starting with the production of hydrogen from fossil and renewable sources. The focus of this review is different storage methods, and in this work we discuss the storage of hydrogen at high pressure, in liquefied form at cryogenic temperatures and bound to liquid or solid-state carriers. In this work a theoretical introduction to different hydrogen storage methods precedes an analysis of the energy-efficiency and practical storage density of the carriers. In the final section the major challenges and hurdles for the development of hydrogen storage for the maritime industry are discussed. The most likely challenges will be the development of a new bunkering infrastructure and suitable monitoring of the safety to ensure safe operation of these hydrogen carriers on board the ship.
Keywords: A1 Journal Article;Review article, Hydrogen Production, Hydrogen Storage, Maritime Applications; Sustainable energy, air and water technology (DuEL)
Impact Factor: 29.518
DOI: 10.1039/D0EE01545H
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“Mechanisms of selective nanocarbon synthesis inside carbon nanotubes”. Khalilov U, Neyts EC, Carbon 171, 72 (2021). http://doi.org/10.1016/j.carbon.2020.08.060
Abstract: The possibility of confinement effects inside a carbon nanotube provides new application opportunities, e.g., growth of novel carbon nanostructures. However, the understanding the precise role of catalystfeedstock in the nanostructure synthesis is still elusive. In our simulation-based study, we investigate the Ni-catalyzed growth mechanism of encapsulated carbon nanostructures, viz. double-wall carbon nanotube and graphene nanoribbon, from carbon and hydrocarbon growth precursors, respectively. Specifically, we find that the tube and ribbon growth is determined by a catalyst-vs-feedstock competition effect. We compare our results, i.e., growth mechanism and structure morphology with all available theoretical and experimental data. Our calculations show that all encapsulated nanostructures contain metal (catalyst) atoms and such structures are less stable than their pure counterparts. Therefore, we study the purification mechanism of these structures. In general, this study opens a possible route to the controllable synthesis of tubular and planar carbon nanostructures for today’s nanotechnology.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.337
DOI: 10.1016/j.carbon.2020.08.060
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“Methane to Methanol through Heterogeneous Catalysis and Plasma Catalysis”. Li S, Ahmed R, Yi Y, Bogaerts A, Catalysts 11, 590 (2021). http://doi.org/10.3390/catal11050590
Abstract: Direct oxidation of methane to methanol (DOMTM) is attractive for the increasing industrial demand of feedstock. In this review, the latest advances in heterogeneous catalysis and plasma catalysis for DOMTM are summarized, with the aim to pinpoint the differences between both, and to provide some insights into their reaction mechanisms, as well as the implications for future development of highly selective catalysts for DOMTM.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.082
DOI: 10.3390/catal11050590
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“Oxidative damage to hyaluronan–CD44 interactions as an underlying mechanism of action of oxidative stress-inducing cancer therapy”. Yusupov M, Privat-Maldonado A, Cordeiro RM, Verswyvel H, Shaw P, Razzokov J, Smits E, Bogaerts A, Redox Biology 43, 101968 (2021). http://doi.org/10.1016/j.redox.2021.101968
Abstract: Multiple cancer therapies nowadays rely on oxidative stress to damage cancer cells. Here we investigated the biological and molecular effect of oxidative stress on the interaction between CD44 and hyaluronan (HA), as interrupting their binding can hinder cancer progression. Our experiments demonstrated that the oxidation of HA decreased its recognition by CD44, which was further enhanced when both CD44 and HA were oxidized. The reduction of CD44–HA binding negatively affected the proliferative state of cancer cells. Our multi-level atomistic simulations revealed that the binding free energy of HA to CD44 decreased upon oxidation. The effect of HA and CD44 oxidation on CD44–HA binding was similar, but when both HA and CD44 were oxidized, the effect was much larger, in agreement with our experiments. Hence, our experiments and computations support our hypothesis on the role of oxidation in the disturbance of CD44–HA interaction, which can lead to the inhibition of proliferative signaling pathways inside the tumor cell to induce cell death.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Center for Oncological Research (CORE)
Impact Factor: 6.337
DOI: 10.1016/j.redox.2021.101968
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“First-principles study of defects at Σ3 grain boundaries in CuGaSe2”. Saniz R, Bekaert J, Partoens B, Lamoen D, Solid State Communications , 114263 (2021). http://doi.org/10.1016/j.ssc.2021.114263
Abstract: We present a first-principles computational study of cation–Se 3 (112) grain boundaries in CuGaSe. We discuss the structure of these grain boundaries, as well as the effect of native defects and Na impurities on their electronic properties. The formation energies show that the defects will tend to form preferentially at the grain boundaries, rather than in the grain interiors. We find that in Ga-rich growth conditions Cu vacancies as well as Ga at Cu and Cu at Ga antisites are mainly responsible for having the equilibrium Fermi level pinned toward the middle of the gap, resulting in carrier depletion. The Na at Cu impurity in its +1 charge state contributes to this. In Ga-poor growth conditions, on the other hand, the formation energies of Cu vacancies and Ga at Cu antisites are comparatively too high for any significant influence on carrier density or on the equilibrium Fermi level position. Thus, under these conditions, the Cu at Ga antisites give rise to a -type grain boundary. Also, their formation energy is lower than the formation energy of Na at Cu impurities. Thus, the latter will fail to act as a hole barrier preventing recombination at the grain boundary, in contrast to what occurs in CuInSe grain boundaries. We also discuss the effect of the defects on the electronic properties of bulk CuGaSe, which we assume reflect the properties of the grain interiors.
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Electron microscopy for materials research (EMAT)
Impact Factor: 1.554
Times cited: 1
DOI: 10.1016/j.ssc.2021.114263
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“Controlled Alloying of Au@Ag Core–Shell Nanorods Induced by Femtosecond Laser Irradiation”. González‐Rubio G, Díaz‐Núñez P, Albrecht W, Manzaneda‐González V, Bañares L, Rivera A, Liz‐Marzán LM, Peña‐Rodríguez O, Bals S, Guerrero‐Martínez A, Advanced Optical Materials , 2002134 (2021). http://doi.org/10.1002/adom.202002134
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 6.875
Times cited: 10
DOI: 10.1002/adom.202002134
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“Novel class of nanostructured metallic glass films with superior and tunable mechanical properties”. Ghidelli M, Orekhov A, Bassi AL, Terraneo G, Djemia P, Abadias G, Nord M, Béché, A, Gauquelin N, Verbeeck J, Raskin J-p, Schryvers D, Pardoen T, Idrissi H, Acta Materialia , 116955 (2021). http://doi.org/10.1016/j.actamat.2021.116955
Abstract: A novel class of nanostructured Zr50Cu50 (%at.) metallic glass films with superior and tunable mechanical
properties is produced by pulsed laser deposition. The process can be controlled to synthetize a wide
range of film microstructures including dense fully amorphous, amorphous embedded with nanocrystals
and amorphous nano-granular. A unique dense self-assembled nano-laminated atomic arrangement
characterized by alternating Cu-rich and Zr/O-rich nanolayers with different local chemical enrichment
and amorphous or amorphous-crystalline composite nanostructure has been discovered, while
significant in-plane clustering is reported for films synthetized at high deposition pressures. This unique
nanoarchitecture is at the basis of superior mechanical properties including large hardness and elastic
modulus up to 10 and 140 GPa, respectively and outstanding total elongation to failure (>9%), leading to
excellent strength/ductility balance, which can be tuned by playing with the film architecture. These
results pave the way to the synthesis of novel class of engineered nanostructured metallic glass films
with high structural performances attractive for a number of applications in microelectronics and
coating industry.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 5.301
Times cited: 27
DOI: 10.1016/j.actamat.2021.116955
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“From the Birkeland–Eyde process towards energy-efficient plasma-based NOXsynthesis: a techno-economic analysis”. Rouwenhorst KHR, Jardali F, Bogaerts A, Lefferts L, Energy &, Environmental Science 14, 2520 (2021). http://doi.org/10.1039/D0EE03763J
Abstract: Plasma-based NO<sub>X</sub>synthesis<italic>via</italic>the Birkeland–Eyde process was one of the first industrial nitrogen fixation methods. However, this technology never played a dominant role for nitrogen fixation, due to the invention of the Haber–Bosch process. Recently, nitrogen fixation by plasma technology has gained significant interest again, due to the emergence of low cost, renewable electricity. We first present a short historical background of plasma-based NO<sub>X</sub>synthesis. Thereafter, we discuss the reported performance for plasma-based NO<sub>X</sub>synthesis in various types of plasma reactors, along with the current understanding regarding the reaction mechanisms in the plasma phase, as well as on a catalytic surface. Finally, we benchmark the plasma-based NO<sub>X</sub>synthesis process with the electrolysis-based Haber–Bosch process combined with the Ostwald process, in terms of the investment cost and energy consumption. This analysis shows that the energy consumption for NO<sub>X</sub>synthesis with plasma technology is almost competitive with the commercial process with its current best value of 2.4 MJ mol N<sup>−1</sup>, which is required to decrease further to about 0.7 MJ mol N<sup>−1</sup>in order to become fully competitive. This may be accomplished through further plasma reactor optimization and effective plasma–catalyst coupling.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 29.518
DOI: 10.1039/D0EE03763J
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“Effectiveness of reducing the influence of CTAB at the surface of metal nanoparticles during in situ heating studies by TEM”. De Meyer R, Albrecht W, Bals S, Micron 144, 103036 (2021). http://doi.org/10.1016/j.micron.2021.103036
Abstract: In situ TEM is a valuable technique to offer novel insights in the behavior of nanomaterials under various conditions. However, interpretation of in situ experiments is not straightforward since the electron beam can impact the outcome of such measurements. For example, ligands surrounding metal nanoparticles transform into a protective carbon layer upon electron beam irradiation and may impact the apparent thermal stability during in situ heating experiments. In this work, we explore the effect of different treatments typically proposed to remove such ligands. We found that plasma treatment prior to heating experiments for Au nanorods and nanostars increased the apparent thermal stability of the nanoparticles, while an activated carbon treatment resulted in a decrease of the observed thermal stability. Treatment with HCl barely changed the experimental outcome. These results demonstrate the importance of carefully selecting pre-treatments procedures during in situ heating experiments.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.98
DOI: 10.1016/j.micron.2021.103036
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“From CdSe nanoplatelets to quantum rings by thermochemical edge reconfiguration”. Salzmann BBV, Vliem JF, Maaskant DN, Post LC, Li C, Bals S, Vanmaekelbergh D, Chemistry Of Materials 33, 6853 (2021). http://doi.org/10.1021/ACS.CHEMMATER.1C01618
Abstract: The variation in the shape of colloidal semiconductor nanocrystals (NCs) remains intriguing. This interest goes beyond crystallography as the shape of the NC determines its energy levels and optoelectronic properties. While thermodynamic arguments point to a few or just a single shape(s), terminated by the most stable crystal facets, a remarkable variation in NC shape has been reported for many different compounds. For instance, for the well-studied case of CdSe, close-to-spherical quantum dots, rods, two-dimensional nanoplatelets, and quantum rings have been reported. Here, we report how two-dimensional CdSe nanoplatelets reshape into quantum rings. We monitor the reshaping in real time by combining atomically resolved structural characterization with optical absorption and photoluminescence spectroscopy. We observe that CdSe units leave the vertical sides of the edges and recrystallize on the top and bottom edges of the nanoplatelets, resulting in a thickening of the rims. The formation of a central hole, rendering the shape into a ring, only occurs at a more elevated temperature.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 7
DOI: 10.1021/ACS.CHEMMATER.1C01618
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“Linearized radially polarized light for improved precision in strain measurements using micro-Raman spectroscopy”. Prabhakara V, Nuytten T, Bender H, Vandervorst W, Bals S, Verbeeck J, Optics Express 29, 34531 (2021). http://doi.org/10.1364/OE.434726
Abstract: Strain engineering in semiconductor transistor devices has become vital in the semiconductor industry due to the ever-increasing need for performance enhancement at the nanoscale. Raman spectroscopy is a non-invasive measurement technique with high sensitivity to mechanical stress that does not require any special sample preparation procedures in comparison to characterization involving transmission electron microscopy (TEM), making it suitable for inline strain measurement in the semiconductor industry. Indeed, at present, strain measurements using Raman spectroscopy are already routinely carried out in semiconductor devices as it is cost effective, fast and non-destructive. In this paper we explore the usage of linearized radially polarized light as an excitation source, which does provide significantly enhanced accuracy and precision as compared to linearly polarized light for this application. Numerical simulations are done to quantitatively evaluate the electric field intensities that contribute to this enhanced sensitivity. We benchmark the experimental results against TEM diffraction-based techniques like nano-beam diffraction and Bessel diffraction. Differences between both approaches are assigned to strain relaxation due to sample thinning required in TEM setups, demonstrating the benefit of Raman for nondestructive inline testing.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.307
Times cited: 2
DOI: 10.1364/OE.434726
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“How gas flow design can influence the performance of a DBD plasma reactor for dry reforming of methane”. Uytdenhouwen Y, Hereijgers J, Breugelmans T, Cool P, Bogaerts A, Chemical Engineering Journal 405, 126618 (2021). http://doi.org/10.1016/j.cej.2020.126618
Abstract: DBD plasma reactors are commonly used in a static ‘one inlet – one outlet’ design that goes against reactor design principles for multi-component reactions, such as dry reforming of methane (DRM). Therefore, in this paper we have developed a novel reactor design, and investigated how the shape and size of the reaction zone, as well as gradual gas addition, and the method of mixing CO2 and CH4 can influence the conversion and product com position of DRM. Even in the standard ‘one inlet – one outlet’ design, the direction of the gas flow (i.e. short or long path through the reactor, which defines the gas velocity at fixed residence time), as well as the dimensions of the reaction zone and the power delivery to the reactor, largely affect the performance. Using gradual gas addition and separate plasma activation zones for the individual gases give increased conversions within the same operational parameters, by optimising mixing ratios and kinetics. The choice of the main (pre-activated) gas and the direction of gas flow largely affect the conversion and energy cost, while the gas inlet position during separate addition only influences the product distribution.
Keywords: A1 Journal article; Engineering sciences. Technology; Laboratory of adsorption and catalysis (LADCA); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Applied Electrochemistry & Catalysis (ELCAT)
Impact Factor: 6.216
DOI: 10.1016/j.cej.2020.126618
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“Gate-tuned anomalous Hall effect driven by Rashba splitting in intermixed LaAlO3/GdTiO3/SrTiO3”. Lebedev N, Stehno M, Rana A, Reith P, Gauquelin N, Verbeeck J, Hilgenkamp H, Brinkman A, Aarts J, Scientific Reports 11, 10726 (2021). http://doi.org/10.1038/s41598-021-89767-3
Abstract: The Anomalous Hall Effect (AHE) is an important quantity in determining the properties and understanding the behaviour of the two-dimensional electron system forming at the interface of SrTiO<sub>3</sub>-based oxide heterostructures. The occurrence of AHE is often interpreted as a signature of ferromagnetism, but it is becoming more and more clear that also paramagnets may contribute to AHE. We studied the influence of magnetic ions by measuring intermixed LaAlO<sub>3</sub>/GdTiO<sub>3</sub>/SrTiO<sub>3</sub>at temperatures below 10 K. We find that, as function of gate voltage, the system undergoes a Lifshitz transition while at the same time an onset of AHE is observed. However, we do not observe clear signs of ferromagnetism. We argue the AHE to be due to the change in Rashba spin-orbit coupling at the Lifshitz transition and conclude that also paramagnetic moments which are easily polarizable at low temperatures and high magnetic fields lead to the presence of AHE, which needs to be taken into account when extracting carrier densities and mobilities.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 4.259
Times cited: 5
DOI: 10.1038/s41598-021-89767-3
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