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“Disordered graphene Josephson junctions”. Muñoz WA, Covaci L, Peeters FM, Physical review : B : condensed matter and materials physics 91, 054506 (2015). http://doi.org/10.1103/PhysRevB.91.054506
Abstract: A tight-binding approach based on the Chebyshev-Bogoliubov-de Gennes method is used to describe disordered single-layer graphene Josephson junctions. Scattering by vacancies, ripples, or charged impurities is included. We compute the Josephson current and investigate the nature of multiple Andreev reflections, which induce bound states appearing as peaks in the density of states for energies below the superconducting gap. In the presence of single-atom vacancies, we observe a strong suppression of the supercurrent, which is a consequence of strong intervalley scattering. Although lattice deformations should not induce intervalley scattering, we find that the supercurrent is still suppressed, which is due to the presence of pseudomagnetic barriers. For charged impurities, we consider two cases depending on whether the average doping is zero, i.e., existence of electron-hole puddles, or finite. In both cases, short-range impurities strongly affect the supercurrent, similar to the vacancies scenario.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 7
DOI: 10.1103/PhysRevB.91.054506
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“Near-Infrared Emitting CuInSe/CuInS Dot Core/Rod Shell Heteronanorods by Sequential Cation Exchange”. van der Stam W, Bladt E, Rabouw FT, Bals S, de Mello Donega C, ACS nano 9, 11430 (2015). http://doi.org/10.1021/acsnano.5b05496
Abstract: The direct synthesis of heteronanocrystals (HNCs) combining different ternary semiconductors is challenging and has not yet been successful. Here, we report a sequential topotactic cation exchange (CE) pathway that yields CuInSe2/CuInS2 dot core/rod shell nanorods with near-infrared luminescence. In our approach, the Cu+ extraction rate is coupled to the In3+ incorporation rate by the use of a stoichiometric trioctylphosphine-InCl3 complex, which fulfills the roles of both In-source and Cu-extracting agent. In this way, Cu+ ions can be extracted by trioctylphosphine ligands only when the In-P bond is broken. This results in readily available In3+ ions at the same surface site from which the Cu+ is extracted, making the process a direct place exchange reaction and shifting the overall energy balance in favor of the CE. Consequently, controlled cation exchange can occur even in large and anisotropic heterostructured nanocrystals with preservation of the size, shape, and heterostructuring of the template NCs into the product NCs. The cation exchange is self-limited, stopping when the ternary core/shell CuInSe2/CuInS2 composition is reached. The method is very versatile, successfully yielding a variety of luminescent CuInX2 (X = S, Se, and Te) quantum dots, nanorods, and HNCs, by using Cd-chalcogenide NCs and HNCs as templates. The approach reported here thus opens up routes toward materials with unprecedented properties, which would otherwise remain inaccessible.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 13.942
Times cited: 88
DOI: 10.1021/acsnano.5b05496
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“Atomic-scale insight into the interactions between hydroxyl radicals and DNA in solution using the ReaxFF reactive force field”. Verlackt CCW, Neyts EC, Jacob T, Fantauzzi D, Golkaram M, Shin Y-K, van Duin ACT, Bogaerts A, New journal of physics 17, 103005 (2015). http://doi.org/10.1088/1367-2630/17/10/103005
Abstract: Cold atmospheric pressure plasmas have proven to provide an alternative treatment of cancer by targeting tumorous cells while leaving their healthy counterparts unharmed. However, the underlying mechanisms of the plasma–cell interactions are not yet fully understood. Reactive oxygen species, and in particular hydroxyl radicals (OH), are known to play a crucial role in plasma driven apoptosis of
malignant cells. In this paper we investigate the interaction of OH radicals, as well as H2O2 molecules and HO2 radicals, with DNA by means of reactive molecular dynamics simulations using the ReaxFF force field. Our results provide atomic-scale insight into the dynamics of oxidative stress on DNA caused by the OH radicals, while H2O2 molecules appear not reactive within the considered timescale. Among the observed processes are the formation of 8-OH-adduct radicals, forming the first stages towards the formation of 8-oxoGua and 8-oxoAde, H-abstraction reactions of the amines, and the partial opening of loose DNA ends in aqueous solution.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.786
Times cited: 18
DOI: 10.1088/1367-2630/17/10/103005
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“The Dominant Pathways for the Conversion of Methane into Oxygenates and Syngas in an Atmospheric Pressure Dielectric Barrier Discharge”. De Bie C, van Dijk J, Bogaerts A, The journal of physical chemistry: C : nanomaterials and interfaces 119, 22331 (2015). http://doi.org/10.1021/acs.jpcc.5b06515
Abstract: A one-dimensional fluid model for a dielectric barrier discharge in CH4/O2 and CH4/CO2 gas mixtures is developed. The model describes the gas-phase chemistry for partial oxidation and for dry reforming of methane. The spatially averaged densities of the various plasma species are presented as a function of time and initial gas mixing ratio. Besides, the conversion of the inlet gases and the selectivities of the reaction products are calculated. Syngas, higher hydrocarbons, and higher oxygenates are typically found to be important reaction products. Furthermore, the main underlying reaction pathways for the formation of syngas, methanol, formaldehyde, and other higher oxygenates are determined.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.536
Times cited: 46
DOI: 10.1021/acs.jpcc.5b06515
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“Hydrogen adsorption on nitrogen and boron doped graphene”. Pizzochero M, Leenaerts O, Partoens B, Martinazzo R, Peeters FM, Journal of physics : condensed matter 27, 425502 (2015). http://doi.org/10.1088/0953-8984/27/42/425502
Abstract: Hydrogen adsorption on boron and nitrogen doped graphene is investigated in detail by means of first-principles calculations. A comprehensive study is performed of the structural, electronic, and magnetic properties of chemisorbed hydrogen atoms and atom pairs near the dopant sites. The main effect of the substitutional atoms is charge doping which is found to greatly affect the adsorption process by increasing the binding energy at the sites closest to the substitutional species. It is also found that doping does not induce magnetism despite the odd number of electrons per atom introduced by the foreign species, and that it quenches the paramagnetic response of chemisorbed H atoms on graphene. Overall, the effects are similar for B and N doping, with only minor differences in the adsorption energetics due to different sizes of the dopant atoms and the accompanying lattice distortions.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.649
Times cited: 20
DOI: 10.1088/0953-8984/27/42/425502
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“Chemical stability of YBiO3 buffer layers for implementation in YBa2Cu3O7-&delta, coated conductors”. Pollefeyt G, Meledin A, Pop C, Ricart S, Hühne R, Van Tendeloo G, Van Driessche I, Acta materialia 100, 224 (2015). http://doi.org/10.1016/j.actamat.2015.08.023
Abstract: In this work, the chemical and microstructural stability of YBiO3 buffer layers during the growth of YBa2Cu3O7-δ (YBCO) was studied. The superconducting YBCO films were deposited via both Pulsed Laser Deposition as well as Chemical Solution Deposition. Although excellent superconducting properties are obtained in both cases, self-field critical current densities of 3.6 and 1.2 MA/cm2 respectively, chemical instability of the YBiO3 buffer layer is observed. An elaborate transmission electron microscopy study showed that in the case of vacuum deposited YBCO, the YBiO3 becomes unstable and Bi2O3 sublimates out of the architecture. Due to this structural instability, an intermediate Y2O3 layer is obtained which maintains it microstructural orientation relation with the substrate and acts as growth template for YBCO. For chemical solution deposited YBCO, reaction of YBCO with the YBiO3 buffer layer is observed, leading to large grains of YBa2BiO6 which are pushed towards the surface of the films and strongly reduce the superconducting properties. Upon using high growth temperatures for the superconducting layer, these secondary phases decompose, which subsequently leads to Bi2O3 sublimation and a textured YBCO film which directly nucleated onto the LaAlO3 single crystal substrate. Hence, this electron microscopy study indicates that bismuth-based buffer layers systems are not suitable for implementation in coated conductors.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 5.301
DOI: 10.1016/j.actamat.2015.08.023
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“Onset, evolution, and magnetic braking of vortex lattice instabilities in nanostructured superconducting films”. Adami O-A, Jelić, ŽL, Xue C, Abdel-Hafiez M, Hackens B, Moshchalkov VV, Milošević, MV, Van de Vondel J, Silhanek AV, Physical review: B: condensed matter and materials physics 92, 134506 (2015). http://doi.org/10.1103/PhysRevB.92.134506
Abstract: In 1976, Larkin and Ovchinnikov [Zh. Eksp. Teor. Fiz. 68, 1915 (1975) [Sov. Phys.–JETP 41, 960 (1976)]] predicted that vortex matter in superconductors driven by an electrical current can undergo an abrupt dynamic transition from a flux-flow regime to a more dissipative state at sufficiently high vortex velocities. Typically, this transition manifests itself as a large voltage jump at a particular current density, so-called instability current density J∗, which is smaller than the depairing current. By tuning the effective pinning strength in Al films, using an artificial periodic pinning array of triangular holes, we show that a unique and well-defined instability current density exists if the pinning is strong, whereas a series of multiple voltage transitions appear in the relatively weaker pinning regime. This behavior is consistent with time-dependent Ginzburg-Landau simulations, where the multiple-step transition can be unambiguously attributed to the progressive development of vortex chains and subsequently phase-slip lines. In addition, we explore experimentally the magnetic braking effects, caused by a thick Cu layer deposited on top of the superconductor, on the instabilities and the vortex ratchet effect.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 21
DOI: 10.1103/PhysRevB.92.134506
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“Ab-initio study of the segregation and electronic properties of neutral and charged B and P dopants in Si and Si/SiO2 nanowires”. Schoeters B, Leenaerts O, Pourtois G, Partoens B, Journal of applied physics 118, 104306 (2015). http://doi.org/10.1063/1.4930048
Abstract: We perform first-principles calculations to investigate the preferred positions of B and P dopants, both neutral and in their preferred charge state, in Si and Si/SiO2 core-shell nanowires (NWs). In order to understand the observed trends in the formation energy, we isolate the different effects that determine these formation energies. By making the distinction between the unrelaxed and the relaxed formation energy, we separate the impact of the relaxation from that of the chemical environment. The unrelaxed formation energies are determined by three effects: (i) the effect of strain caused by size mismatch between the dopant and the host atoms, (ii) the local position of the band edges, and (iii) a screening effect. In the case of the SiNW (Si/SiO2 NW), these effects result in an increase of the formation energy away from the center (interface). The effect of relaxation depends on the relative size mismatch between the dopant and host atoms. A large size mismatch causes substantial relaxation that reduces the formation energy considerably, with the relaxation being more pronounced towards the edge of the wires. These effects explain the surface segregation of the B dopants in a SiNW, since the atomic relaxation induces a continuous drop of the formation energy towards the edge. However, for the P dopants, the formation energy starts to rise when moving from the center but drops to a minimum just next to the surface, indicating a different type of behavior. It also explains that the preferential location for B dopants in Si/SiO2 core-shell NWs is inside the oxide shell just next to the interface, whereas the P dopants prefer the positions next to the interface inside the Si core, which is in agreement with recent experiments. These preferred locations have an important impact on the electronic properties of these core-shell NWs. Our simulations indicate the possibility of hole gas formation when B segregates into the oxide shell.
Keywords: A1 Journal article; Condensed Matter Theory (CMT); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.068
Times cited: 3
DOI: 10.1063/1.4930048
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“Influence of the support material and the resulting particle distribution on the deposition of Ag nanoparticles for the electrocatalytic activity of benzyl bromide reduction”. Vanrenterghem B, Geboes B, Bals S, Ustarroz J, Hubin A, Breugelmans T, Applied catalysis : B : environmental 181, 542 (2016). http://doi.org/10.1016/j.apcatb.2015.08.026
Abstract: tSilver nanoparticles (NPs) were deposited on nickel, titanium and gold substrates using a potentiostaticdouble-pulse method. The influence of the support material on both the morphology and the electro-catalytic activity of Ag NPs for the reduction reaction of benzyl bromide was investigated and comparedwith previous research regarding silver NPs on glassy carbon. Scanning electron microscopy (SEM) dataindicated that spherical monodispersed NPs were obtained on Ni, Au and GC substrate with an averageparticle size of respectively 216 nm, 413 nm and 116 nm. On a Ti substrate dendritic NPs were obtainedwith a larger average particle density of 480 nm. The influence of the support material on the electrocat-alytic activity was tested by means of cyclic voltammetry (CV) for the reduction reaction of benzylbromide(1 mM) in acetonitrile + 0.1 M tetrabutylammonium perchlorate (Bu4NClO4). When the nucleation poten-tial (En) was applied at high cathodic overpotential, a positive shift of the reduction potential was obtained.The nucleation (tn) and growth time (tg) mostly had an influence on the current density whereas longerdeposition times lead to larger current densities. For these three parameters an optimum was present.The best electrocatalytic activity was obtained with Ag NPs deposited on Ni were a shift of the reduc-tion peak potential of 145 mV for the reaction of benzyl bromide was measured in comparance to bulksilver. The deposition on Au substrate yielded a positive shift of 114 mV. There was no indication of analtered reaction mechanism as the reaction was characterized as diffusion controlled and the transfercoefficients were in accordance with bulk silver. There was a beneficial catalitic activity measured due tothe interplay between support and NPs. This resulted in a shift of the reduction peak potential of 34 mV(Ag NPs on Au) and 65 mV (Ag NPs on Ni) compared to Ag NPs on a GC substrate.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Applied Electrochemistry & Catalysis (ELCAT)
Impact Factor: 9.446
Times cited: 16
DOI: 10.1016/j.apcatb.2015.08.026
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“Improving the Conversion and Energy Efficiency of Carbon Dioxide Splitting in a Zirconia-Packed Dielectric Barrier Discharge Reactor”. van Laer K, Bogaerts A, Energy technology 3, 1038 (2015). http://doi.org/10.1002/ente.201500127
Abstract: The use of plasma technology for CO2 splitting is gaining increasing interest, but one of the major obstacles to date for industrial implementation is the considerable energy cost. We demonstrate that the introduction of a packing of dielectric zirconia (ZrO2) beads into a dielectric barrier discharge (DBD) plasma reactor can enhance the CO2 conversion and energy efficiency up to a factor 1.9 and 2.2, respectively, compared to that in a normal (unpacked) DBD reactor. We obtained a maximum conversion of 42 % and a maximum energy efficiency of 9.6 %. However, it is the ability of the packing to almost double both the conversion and the energy efficiency simultaneously at certain input parameters that makes it very promising. The improved conversion and energy efficiency can be explained by the higher values of the local electric field and electron energy near the contact points of the beads and the lower breakdown voltage, demonstrated by 2 D fluid modeling.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.789
Times cited: 59
DOI: 10.1002/ente.201500127
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“Merging Metadynamics into Hyperdynamics: Accelerated Molecular Simulations Reaching Time Scales from Microseconds to Seconds”. Bal KM, Neyts EC, Journal of chemical theory and computation 11, 4545 (2015). http://doi.org/10.1021/acs.jctc.5b00597
Abstract: The hyperdynamics method is a powerful tool to simulate slow processes at the atomic level. However, the construction of an optimal hyperdynamics potential is a task that is far from trivial. Here, we propose a generally applicable implementation of the hyperdynamics algorithm, borrowing two concepts from metadynamics. First, the use of a collective variable (CV) to represent the accelerated dynamics gives the method a very large flexibility and simplicity. Second, a metadynamics procedure can be used to construct a suitable history-dependent bias potential on-the-fly, effectively turning the algorithm into a self-learning accelerated molecular dynamics method. This collective variable-driven hyperdynamics (CVHD) method has a modular design: both the local system properties on which the bias is based, as well as the characteristics of the biasing method itself, can be chosen to match the needs of the considered system. As a result, system-specific details are abstracted from the biasing algorithm itself, making it extremely versatile and transparent. The method is tested on three model systems: diffusion on the Cu(001) surface and nickel-catalyzed methane decomposition, as examples of reactive processes with a bond-length-based CV, and the folding of a long polymer-like chain, using a set of dihedral angles as a CV. Boost factors up to 109, corresponding to a time scale of seconds, could be obtained while still accurately reproducing correct dynamics.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 5.245
Times cited: 41
DOI: 10.1021/acs.jctc.5b00597
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“Defect-induced faceted blue phosphorene nanotubes”. Aierken Y, Leenaerts O, Peeters FM, Physical review : B : condensed matter and materials physics 92, 104104 (2015). http://doi.org/10.1103/PhysRevB.92.104104
Abstract: The properties of a new class of phosphorene nanotubes (PNT) are investigated by performing first-principles calculations. We demonstrate that it is advantageous to use blue phosphorene in order to make small nanotubes and propose a way to create low-energy PNTs by the inclusion of defect lines. Five different types of defect lines are investigated and incorporated in various combinations. The resulting defect-induced faceted PNTs have negligible bending stresses which leads to a reduction in the formation energy with respect to round PNTs. Our armchair faceted PNTs have similar formation energies than the recently proposed multiphase faceted PNTs, but they have a larger variety of possible structures. Our zigzag faceted PNTs have lower formation energies than round tubes and multiphase faceted nanotubes. The electronic properties of the defect-induced faceted PNTs are determined by the defect lines which control the band gap and the shape of the electronic states at the band edges. These band gaps increase with the radius of the nanotubes and converge to those of isolated defect lines.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 24
DOI: 10.1103/PhysRevB.92.104104
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“The ASTRA Toolbox: A platform for advanced algorithm development in electron tomography”. van Aarle W, Palenstijn WJ, De Beenhouwer J, Altantzis T, Bals S, Batenburg KJ, Sijbers J, Ultramicroscopy 157, 35 (2015). http://doi.org/10.1016/j.ultramic.2015.05.002
Abstract: We present the ASTRA Toolbox as an open platform for 3D image reconstruction in tomography. Most of the software tools that are currently used in electron tomography offer limited flexibility with respect to the geometrical parameters of the acquisition model and the algorithms used for reconstruction. The ASTRA Toolbox provides an extensive set of fast and flexible building blocks that can be used to develop advanced reconstruction algorithms, effectively removing these limitations. We demonstrate this flexibility, the resulting reconstruction quality, and the computational efficiency of this toolbox by a series of experiments, based on experimental dual-axis tilt series.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 2.843
Times cited: 562
DOI: 10.1016/j.ultramic.2015.05.002
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“Pyramid-Shaped Wurtzite CdSe Nanocrystals with Inverted Polarity”. Ghosh S, Gaspari R, Bertoni G, Spadaro MC, Prato M, Turner S, Cavalli A, Manna L, Brescia R, ACS nano 9, 8537 (2015). http://doi.org/10.1021/acsnano.5b03636
Abstract: We report on pyramid-shaped wurtzite cadmium selenide (CdSe) nanocrystals (NCs), synthesized by hot injection in the presence of chloride ions as shape-directing agents, exhibiting reversed crystal polarity compared to former reports. Advanced transmission electron microscopy (TEM) techniques (image-corrected high-resolution TEM with exit wave reconstruction and probe-corrected high-angle annular dark field-scanning TEM) unequivocally indicate that the triangular base of the pyramids is the polar (0001) facet and their apex points toward the [0001] direction. Density functional theory calculations, based on a simple model of binding of Cl(-) ions to surface Cd atoms, support the experimentally evident higher thermodynamic stability of the (0001) facet over the (0001) one conferred by Cl(-) ions. The relative stability of the two polar facets of wurtzite CdSe is reversed compared to previous experimental and computational studies on Cd chalcogenide NCs, in which no Cl-based chemicals were deliberately used in the synthesis or no Cl(-) ions were considered in the binding models. Self-assembly of these pyramids in a peculiar clover-like geometry, triggered by the addition of oleic acid, suggests that the basal (polar) facet has a density and perhaps type of ligands significantly different from the other three facets, since the pyramids interact with each other exclusively via their lateral facets. A superstructure, however with no long-range order, is observed for clovers with their (0001) facets roughly facing each other. The CdSe pyramids were also exploited as seeds for CdS pods growth, and the peculiar shape of the derived branched nanostructures clearly arises from the inverted polarity of the seeds.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 13.942
Times cited: 16
DOI: 10.1021/acsnano.5b03636
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“Self-Assembly of Pluronic F127—Silica Spherical Core–Shell Nanoparticles in Cubic Close-Packed Structures”. Kerkhofs S, Willhammar T, Van Den Noortgate H, Kirschhock CEA, Breynaert E, Van Tendeloo G, Bals S, Martens JA, Chemistry of materials 27, 5161 (2015). http://doi.org/10.1021/acs.chemmater.5b01772
Abstract: A new ordered mesoporous silica material (COK-19) with cubic symmetry is synthesized by silicate polycondensation in a citric acid/citrate buffered micellar solution of Pluronic F127 triblock copolymer near neutral pH. SAXS, nitrogen adsorption, TEM, and electron tomography reveal the final material has a cubic close packed symmetry (Fm3̅m) with isolated spherical mesopores interconnected through micropores. Heating of the synthesis medium from room temperature to 70 °C results in a mesopore size increase from 7.0 to 11.2 nm. Stepwise addition of the silicate source allows isolation of a sequence of intermediates that upon characterization with small-angle X-ray scattering uncovers the formation process via formation and aggregation of individual silica-covered Pluronic micelles.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 39
DOI: 10.1021/acs.chemmater.5b01772
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“Thermal properties of black and blue phosphorenes from a first-principles quasiharmonic approach”. Aierken Y, Çakır D, Sevik C, Peeters FM, Physical review : B : condensed matter and materials physics 92, 081408 (2015). http://doi.org/10.1103/PhysRevB.92.081408
Abstract: Different allotropes of phosphorene are possible of which black and blue phosphorus are the most stable. While blue phosphorus has isotropic properties, black phosphorus is strongly anisotropic in its electronic and optical properties due to its anisotropic crystal structure. In this work, we systematically investigated the lattice thermal properties of black and blue phosphorene by using first-principles calculations based on the quasiharmonic approximation approach. Similar to the optoelectronic and electronic properties, we predict that black phosphorene has highly anisotropic thermal properties, in contrast to the blue phase. The linear thermal expansion coefficients along the zigzag and armchair direction differ up to 20% in black phosphorene. The armchair direction of black phosphorene is more expandable as compared to the zigzag direction and the biaxial expansion of blue phosphorene under finite temperature. Our comparative analysis reveals that the inclusion of finite-temperature effects makes the blue phase thermodynamically more stable over the black phase above 135 K.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.836
Times cited: 124
DOI: 10.1103/PhysRevB.92.081408
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“Chabazite : stable cation-exchanger in hyper alkaline concrete pore water”. Van Tendeloo L, Wangermez W, Kurttepeli M, de Blochouse B, Bals S, Van Tendeloo G, Martens JA, Maes A, Kirschhock CEA, Breynaert E, Environmental science and technology 49, 2358 (2015). http://doi.org/10.1021/es505346j
Abstract: To avoid impact on the environment, facilities for permanent disposal of hazardous waste adopt multibarrier design schemes. As the primary barrier very often consists of cement-based materials, two distinct aspects are essential for the selection of suitable complementary barriers: (1) selective sorption of the contaminants in the repository and (2) long-term chemical stability in hyperalkaline concrete-derived media. A multidisciplinary approach combining experimental strategies from environmental chemistry and materials science is therefore essential to provide a reliable assessment of potential candidate materials. Chabazite is typically synthesized in 1 M KOH solutions but also crystallizes in simulated young cement pore water, a pH 13 aqueous solution mainly containing K+ and Na+ cations. Its formation and stability in this medium was evaluated as a function of temperature (60 and 85 °C) over a timeframe of more than 2 years and was also asessed from a mechanistic point of view. Chabazite demonstrates excellent cation-exchange properties in simulated young cement pore water. Comparison of its Cs+ cation exchange properties at pH 8 and pH 13 unexpectedly demonstrated an increase of the KD with increasing pH. The combined results identify chabazite as a valid candidate for inclusion in engineered barriers for concrete-based waste disposal.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 6.198
Times cited: 13
DOI: 10.1021/es505346j
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“Photovoltaic effect and evidence of carrier multiplication in graphene vertical homojunctions with asymmetrical metal contacts”. Chen JJ, Wang Q, Meng J, Ke X, Van Tendeloo G, Bie YQ, Liu J, Liu K, Liao ZM, Sun D, Yu D;, ACS nano 9, 8851 (2015). http://doi.org/10.1021/acsnano.5b02356
Abstract: Graphene exhibits exciting potentials for high-speed wideband photodetection and high quantum efficiency solar energy harvest because of its broad spectral absorption, fast photoelectric response, and potential carrier multiplication. Although photocurrent can be generated near a metalgraphene interface in lateral devices, the photoactive area is usually limited to a tiny one-dimensional line-like interface region. Here, we report photoelectric devices based on vertical graphene two-dimensional homojunction, which is fabricated via vertically stacking four graphene monolayers with asymmetric metal contacts. The devices show excellent photovoltaic output with excitation wavelength ranging from visible light to mid-infrared. The wavelength dependence of the internal quantum efficiency gives direct evidence of the carrier multiplication effect in graphene. The simple fabrication process, easy scale-up, large photoresponsive active area, and broadband response of the vertical graphene device are very promising for practical applications in optoelectronics and photovoltaics.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 13.942
Times cited: 11
DOI: 10.1021/acsnano.5b02356
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“Cation exchange mediated elimination of the Fe-antisites in the hydrothermal synthesis of LiFePO4”. Paolella A, Bertoni G, Hovington P, Feng Z, Flacau R, Prato M, Colombo M, Marras S, Manna L, Turner S, Van Tendeloo G, Guerfi A, Demopoulos GP, Zaghib K;, Nano energy 16, 256 (2015). http://doi.org/10.1016/j.nanoen.2015.06.005
Abstract: In this work we elucidate the elimination of mechanism Fe-antisite defects in lithium iron phosphate (LiFePO4) during the hydrothermal synthesis. Compelling evidence of this effect is provided by combining Neutron Powder Diffraction (NPD), High Resolution (Scanning) Transmission Electron Microscopy (HR-(S)TEM), Electron Energy Loss Spectroscopy (EELS), X-Ray Photoelectron Spectroscopy (XPS) and calculations. We found: i) the first intermediate vivianite inevitably creates Fe-antisite defects in LiFePO4; ii) the removal of these antisite defects by cation exchange is assisted by a nanometer-thick amorphous layer, rich in Li, that enwraps the LiFePO4 crystals.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 12.343
Times cited: 27
DOI: 10.1016/j.nanoen.2015.06.005
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“Advanced electron microscopy characterisation of important precipitation and ordering phenomena in shape memory systems”. Schryvers D, Shape memory and superelasticity 1, 78 (2015). http://doi.org/10.1007/s40830-015-0006-3
Abstract: The present paper discusses some important aspects of precipitation and ordering in alloy systems that show a martensitic transformation and can or are used as shape memory or superelastic metallic systems. The precipitates are investigated by a variety of conventional and advanced electron microscopy techniques, including atomic resolution, 3D slice-and-view, energy loss spectroscopy etc. Depending on the system, such secondary phases can decrease the probability of a displacive transformation by changing the phase stability in the system, such as in the case of NiAl or NiTiPd, or can mechanically hinder the passage of the transformation interface, as in NiTiNb. On the other hand, properly controlling the nucleation and growth of some precipitates can strongly improve the properties of some types of materials, as is the case for the well-known Ni4Ti3 precipitates.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
DOI: 10.1007/s40830-015-0006-3
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“Two-dimensional particle-in cell/Monte Carlo simulations of a packed-bed dielectric barrier discharge in air at atmospheric pressure”. Zhang Y, Wang H-yu, Jiang W, Bogaerts A, New journal of physics 17, 083056 (2015). http://doi.org/10.1088/1367-2630/17/8/083056
Abstract: The plasma behavior in a parallel-plate dielectric barrier discharge (DBD) is simulated by a two-dimensional particle-in-cell/Monte Carlo collision model, comparing for the first time an unpacked (empty) DBD with a packed bed DBD, i.e., a DBD filled with dielectric spheres in the gas gap. The calculations are performed in air, at atmospheric pressure. The discharge is powered by a pulse with a voltage amplitude of −20 kV. When comparing the packed and unpacked DBD reactors with the same dielectric barriers, it is clear that the presence of the dielectric packing leads to a transition in discharge behavior from a combination of negative streamers and unlimited surface streamers on the bottom dielectric surface to a combination of predominant positive streamers and limited surface discharges on the dielectric surfaces of the beads and plates. Furthermore, in the packed bed DBD, the electric field is locally enhanced inside the dielectric material, near the contact points between the beads and the plates, and therefore also in the plasma between the packing beads and between a bead and the dielectric wall, leading to values of $4\times {10}
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.786
Times cited: 22
DOI: 10.1088/1367-2630/17/8/083056
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“2D ZnO mesoporous single-crystal nanosheets with exposed {0001} polar facets for the depollution of cationic dye molecules by highly selective adsorption and photocatalytic decomposition”. Liu J, Hu Z-Y, Peng Y, Huang H-W, Li Y, Wu M, Ke X-X, Van Tendeloo G, Su B-L, Applied catalysis : B : environmental 181, 138 (2016). http://doi.org/10.1016/j.apcatb.2015.07.054
Abstract: Two dimensional (2D) ZnO nanosheets are ideal system for dimensionally confined transport phenomenon investigation owing to specific surface atomic configuration. Therefore, 2D ZnO porous nanosheets with single-crystal nature and {0001} polar facets, likely display some specific physicochemical properties. In this work, for the first time, 2D ZnO mesoporous single-crystal nanosheets (ZnO-MSN) with {0001} polar facets have been designed and prepared via an intriguing colloidal templating approach through controlling the infiltration speed for the suspension of EG-capped ZnO nanoparticles and polymer colloids. The EG-capped ZnO nanoparticles are very helpful for single-crystal nanosheet formation, while the polymer colloids play dual roles on the mesoporosity generation and {0001} polar facets formation within the mesopores. Such special 2D structure not only accelerates the hole-electron separation and the electron transportation owing to the single-crystal nature, but also enhances the selective adsorption of organic molecules owing to the porous structure and the exposed {0001} polar facets with more O-termination (000-1) surfaces: the 2D ZnO-MSN shows highly selective adsorption and significantly higher photodegradation for positively charged rhodamine B than those for negatively charged methyl orange and neutral phenol, comparing with ZnO nanoparticles (ZnO-NP) and ZnO commercial nanoparticles (ZnO-CNP) with high surface areas. This work may shed some light on better understanding the synthesis of 2D porous single-crystal nanosheet with exposed polar surfaces and photocatalytic mechanism of nanostructured semiconductors in a mixed organic molecules system.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.446
Times cited: 60
DOI: 10.1016/j.apcatb.2015.07.054
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“Stabilization and encapsulation of gold nanostars mediated by dithiols”. Wang Y, Belén Serrano A, Sentosun K, Bals S, Liz-Marzán LM, Small 11, 4314 (2015). http://doi.org/10.1002/smll.201500703
Abstract: Surface chemistry plays a pivotal role in regulating the morphology of nanoparticles, maintaining colloidal stability, and mediating the interaction with target analytes toward practical applications such as surface-enhanced Raman scattering (SERS)-based sensing and imaging. The use of a binary ligand mixture composed of 1,4-benzenedithiol (BDT) and hexadecyltrimethylammonium chloride (CTAC) to provide gold nanostars with long-term stability is reported. This is despite BDT being a bifunctional ligand, which usually leads to bridging and loss of colloidal stability. It is found however that neither BDT nor CTAC alone are able to provide sufficient colloidal and chemical stability. BDT-coated Au nanostars are additionally used as seeds to direct the encapsulation with a gold outer shell, leading to the formation of unusual nanostructures including semishell-coated gold nanostars, which are characterized by high-resolution electron microscopy and electron tomography. Finally, BDT is exploited as a probe to reveal the enhanced local electric fields in the different nanostructures, showing that the semishell configuration provides significantly high SERS signals as compared to other coreshell configurations obtained during seeded growth, including full shells.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 8.643
Times cited: 36
DOI: 10.1002/smll.201500703
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“Effect of clay modification on structureproperty relationships and thermal degradation kinetics of \beta-polypropylene/clay composite materials”. Papageorgiou DG, Filippousi M, Pavlidou E, Chrissafis K, Van Tendeloo G, Bikiaris D, Journal of thermal analysis and calorimetry 122, 393 (2015). http://doi.org/10.1007/s10973-015-4705-y
Abstract: The influence of neat and organically modified montmorillonite on the structureproperty relationships of a β-nucleated polypropylene matrix has been thoroughly investigated. High-angle annular dark field scanning transmission electron microscopy revealed that the organic modification of clay facilitated the dispersion of the clay, while X-ray diffractograms showed the α-nucleating effect of the clays on the β-nucleated matrix. The results from tensile tests showed that the organic modification of MMT affected profoundly only the tensile strength at yield and at break. The effect of the organic modification of the clay on the thermal stability of the composites was finally evaluated by thermogravimetric analysis, where the samples filled with oMMT decomposed faster than the ones filled with neat MMT, due to the decomposition of the organic salts that were initially used for the modification of MMT. A kinetics study of the thermal degradation of the composites was also performed, in order to export additional conclusions on the activation energy of the samples.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.953
Times cited: 7
DOI: 10.1007/s10973-015-4705-y
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“A comparative study for the inactivation of multidrug resistance bacteria using dielectric barrier discharge and nano-second pulsed plasma”. Hoon Park J, Kumar N, Hoon Park D, Yusupov M, Neyts EC, Verlackt CCW, Bogaerts A, Ho Kang M, Sup Uhm H, Ha Choi E, Attri P;, Scientific reports 5, 13849 (2015). http://doi.org/10.1038/srep13849
Abstract: Bacteria can be inactivated through various physical and chemical means, and these have always been the focus of extensive research. To further improve the methodology for these ends, two types of plasma systems were investigated: nano-second pulsed plasma (NPP) as liquid discharge plasma and an Argon gas-feeding dielectric barrier discharge (Ar-DBD) as a form of surface plasma. To understand the sterilizing action of these two different plasma sources, we performed experiments with Staphylococcus aureus (S. aureus) bacteria (wild type) and multidrug resistant bacteria (Penicillum-resistant, Methicillin-resistant and Gentamicin-resistant). We observed that both plasma sources can inactivate both the wild type and multidrug-resistant bacteria to a good extent. Moreover, we observed a change in the surface morphology, gene expression and β-lactamase activity. Furthermore, we used X-ray photoelectron spectroscopy to investigate the variation in functional groups (C-H/C-C, C-OH and C=O) of the peptidoglycan (PG) resulting from exposure to plasma species. To obtain atomic scale insight in the plasma-cell interactions and support our experimental observations, we have performed molecular dynamics simulations to study the effects of plasma species, such as OH, H2O2, O, O3, as well as O2 and H2O, on the dissociation/formation of above mentioned functional groups in PG.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.259
Times cited: 32
DOI: 10.1038/srep13849
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“Nanoscale thermodynamic aspects of plasma catalysis”. Neyts EC, Ostrikov K(K), Catalysis today 256, 23 (2015). http://doi.org/10.1016/j.cattod.2015.02.025
Abstract: Plasma catalysis continues to gain increasing scientific interest, both in established fields like toxic waste abatement and emerging fields like greenhouse gas conversion into value-added chemicals. Attention is typically focused on the obtained conversion process selectivity, rates and energy efficiency. Much less attention is usually paid to the underlying mechanistic aspects of the processes that occur. In this contribution, we critically examine a number of fundamentally important nanoscale thermodynamic aspects of plasma catalysis, which are very relevant to these processes but so far have been overlooked or insufficiently covered in the plasma catalysis literature.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.636
Times cited: 14
DOI: 10.1016/j.cattod.2015.02.025
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“Molecular dynamics simulations of supported metal nanocatalyst formation by plasma sputtering”. Brault P, Neyts EC, Catalysis today 256, 3 (2015). http://doi.org/10.1016/j.cattod.2015.02.004
Abstract: Magnetron sputtering is a widely used physical vapor deposition technique for deposition and formation of nanocatalyst thin films and clusters. Nevertheless, so far only few studies investigated this formation process at the fundamental level. We here review atomic scale molecular dynamics simulations aimed at elucidating the nanocatalyst growth process through magnetron sputtering. We first introduce the basic magnetron sputtering background and machinery of molecular dynamics simulations, and then describe the studies conducted in this field so far. We also present a perspective view on how the field may be developed further.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.636
Times cited: 18
DOI: 10.1016/j.cattod.2015.02.004
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“Plasmas for enhanced catalytic processes (ISPCEM 2014)”. Nozaki T, Neyts EC, Sankaran M, Ostrikov K(K), Liu C-J, Catalysis today 256, 1 (2015). http://doi.org/10.1016/j.cattod.2015.08.001
Keywords: Editorial; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.636
Times cited: 2
DOI: 10.1016/j.cattod.2015.08.001
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“Intrinsic thermal instability of methylammonium lead trihalide perovskite”. Conings B, Drijkoningen J, Gauquelin N, Babayigit A, D'Haen J, D'Olieslaeger L, Ethirajan A, Verbeeck J, Manca J, Mosconi E, Angelis FD, Boyen HG;, Laser physics review 5, 1500477 (2015). http://doi.org/10.1002/aenm.201500477
Abstract: Organolead halide perovskites currently are the new front-runners as light absorbers in hybrid solar cells, as they combine efficiencies passing already 20% with deposition temperatures below 100 °C and cheap solution-based fabrication routes. Long-term stability remains a major obstacle for application on an industrial scale. Here, it is demonstrated that significant decomposition effects already occur during annealing of a methylammonium lead triiode perovskite at 85 °C even in inert atmosphere thus violating international standards. The observed behavior supports the view of currently used perovskite materials as soft matter systems with low formation energies, thus representing a major bottleneck for their application, especially in countries with high average temperatures. This result can trigger a broader search for new perovskite families with improved thermal stability.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 16.721
Times cited: 1691
DOI: 10.1002/aenm.201500477
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“KEu(MoO4)2 : polymorphism, structures, and luminescent properties”. Morozov VA, Arakcheeva AV, Pattison P, Meert KW, Smet PF, Poelman D, Gauquelin N, Verbeeck J, Abakumov AM, Hadermann J, Chemistry of materials 27, 5519 (2015). http://doi.org/10.1021/acs.chemmater.5b01622
Abstract: In this paper, with the example of two different polymorphs of KEu(MoO4)2, the influence of the ordering of the A-cations on the luminescent properties in scheelite related compounds (A′,A″)n[(B′,B″)O4]m is investigated. The polymorphs were synthesized using a solid state method. The study confirmed the existence of only two polymorphic forms at annealing temperature range 9231203 K and ambient pressure: a low temperature anorthic α-phase and a monoclinic high temperature β-phase with an incommensurately modulated structure. The structures of both polymorphs were solved using transmission electron microscopy and refined from synchrotron powder X-ray diffraction data. The monoclinic β-KEu(MoO4)2 has a (3+1)-dimensional incommensurately modulated structure (superspace group I2/b(αβ0)00, a = 5.52645(4) Å, b = 5.28277(4) Å, c = 11.73797(8) Å, γ = 91.2189(4)o, q = 0.56821(2)a*0.12388(3)b*), whereas the anorthic α-phase is (3+1)-dimensional commensurately modulated (superspace group I1̅(αβγ)0, a = 5.58727(22) Å, b = 5.29188(18)Å, c = 11.7120(4) Å, α = 90.485(3)o, β = 88.074(3)o, γ = 91.0270(23)o, q = 1/2a* + 1/2c*). In both cases the modulation arises due to Eu/K cation ordering at the A site: the formation of a 2-dimensional Eu3+ network is characteristic for the α-phase, while a 3-dimensional Eu3+-framework is observed for the β-phase structure. The luminescent properties of KEu(MoO4)2 samples prepared under different annealing conditions were measured, and the relation between their optical properties and their structures is discussed.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 26
DOI: 10.1021/acs.chemmater.5b01622
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