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“Current fluctuations in boundary driven diffusive systems in different dimensions : a numerical study”. Becker T, Nelissen K, Cleuren B, New journal of physics 17, 055023 (2015). http://doi.org/10.1088/1367-2630/17/5/055023
Abstract: We use kinetic Monte Carlo simulations to investigate current fluctuations in boundary driven generalized exclusion processes, in different dimensions. Simulation results are in full agreement with predictions based on the additivity principle and the macroscopic fluctuation theory. The current statistics are independent of the shape of the contacts with the reservoirs, provided they are macroscopic in size. In general, the current distribution depends on the spatial dimension. For the special cases of the symmetric simple exclusion process and the zero-range process, the current statistics are the same for all spatial dimensions.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.786
Times cited: 5
DOI: 10.1088/1367-2630/17/5/055023
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“Selective nickel-catalyzed conversion of model and lignin-derived phenolic compounds to cyclohexanone-based polymer building blocks”. Schutyser W, Van den Bosch S, Dijkmans J, Turner S, Meledina M, Van Tendeloo G, Debecker DP, Sels BF, Chemsuschem 8, 1805 (2015). http://doi.org/10.1002/cssc.201403375
Abstract: Valorization of lignin is essential for the economics of future lignocellulosic biorefineries. Lignin is converted into novel polymer building blocks through four steps: catalytic hydroprocessing of softwood to form 4-alkylguaiacols, their conversion into 4-alkylcyclohexanols, followed by dehydrogenation to form cyclohexanones, and Baeyer-Villiger oxidation to give caprolactones. The formation of alkylated cyclohexanols is one of the most difficult steps in the series. A liquid-phase process in the presence of nickel on CeO2 or ZrO2 catalysts is demonstrated herein to give the highest cyclohexanol yields. The catalytic reaction with 4-alkylguaiacols follows two parallel pathways with comparable rates: 1) ring hydrogenation with the formation of the corresponding alkylated 2-methoxycyclohexanol, and 2) demethoxylation to form 4-alkylphenol. Although subsequent phenol to cyclohexanol conversion is fast, the rate is limited for the removal of the methoxy group from 2-methoxycyclohexanol. Overall, this last reaction is the rate-limiting step and requires a sufficient temperature (> 250 degrees C) to overcome the energy barrier. Substrate reactivity (with respect to the type of alkyl chain) and details of the catalyst properties (nickel loading and nickel particle size) on the reaction rates are reported in detail for the Ni/CeO2 catalyst. The best Ni/CeO2 catalyst reaches 4-alkylcyclohexanol yields over 80 %, is even able to convert real softwood-derived guaiacol mixtures and can be reused in subsequent experiments. A proof of principle of the projected cascade conversion of lignocellulose feedstock entirely into caprolactone is demonstrated by using Cu/ZrO2 for the dehydrogenation step to produce the resultant cyclohexanones (approximate to 80%) and tin-containing beta zeolite to form 4-alkyl-e-caprolactones in high yields, according to a Baeyer-Villiger-type oxidation with H2O2.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 7.226
Times cited: 71
DOI: 10.1002/cssc.201403375
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“An envelope function formalism for lattice-matched heterostructures”. Van de Put ML, Vandenberghe WG, Magnus W, Sorée B, Physica: B : condensed matter 470-471, 69 (2015). http://doi.org/10.1016/j.physb.2015.04.031
Abstract: The envelope function method traditionally employs a single basis set which, in practice, relates to a single material because the k.p matrix elements are generally only known in a particular basis. In this work, we defined a basis function transformation to alleviate this restriction. The transformation is completely described by the known inter-band momentum matrix elements. The resulting envelope function equation can solve the electronic structure in lattice matched heterostructures without resorting to boundary conditions at the interface between materials, while all unit-cell averaged observables can be calculated as with the standard envelope function formalism. In the case of two coupled bands, this heterostructure formalism is equivalent to the standard formalism while taking position dependent matrix elements. (C) 2015 Elsevier B.V. All rights reserved
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 1.386
Times cited: 5
DOI: 10.1016/j.physb.2015.04.031
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“Electronic band structures and native point defects of ultrafine ZnO nanocrystals”. Zeng Y-J, Schouteden K, Amini MN, Ruan S-C, Lu Y-F, Ye Z-Z, Partoens B, Lamoen D, Van Haesendonck C, ACS applied materials and interfaces 7, 10617 (2015). http://doi.org/10.1021/acsami.5b02545
Abstract: Ultrafine ZnO nanocrystals with a thickness down to 0.25 nm are grown by a metalorganic chemical vapor deposition method. Electronic band structures and native point defects of ZnO nanocrystals are studied by a combination of scanning tunneling microscopy/spectroscopy and first-principles density functional theory calculations. Below a critical thickness of nm ZnO adopts a graphitic-like structure and exhibits a wide band gap similar to its wurtzite counterpart. The hexagonal wurtzite structure, with a well-developed band gap evident from scanning tunneling spectroscopy, is established for a thickness starting from similar to 1.4 nm. With further increase of the thickness to 2 nm, V-O-V-Zn defect pairs are easily produced in ZnO nanocrystals due to the self-compensation effect in highly doped semiconductors.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 7.504
Times cited: 15
DOI: 10.1021/acsami.5b02545
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“Stable half-metallic monolayers of FeCl2”. Torun E, Sahin H, Singh SK, Peeters FM, Applied physics letters 106, 192404 (2015). http://doi.org/10.1063/1.4921096
Abstract: The structural, electronic, and magnetic properties of single layers of Iron Dichloride (FeCl2) were calculated using first principles calculations. We found that the 1T phase of the single layer FeCl2 is 0.17 eV/unit cell more favorable than its 1H phase. The structural stability is confirmed by phonon calculations. We found that 1T-FeCl2 possess three Raman-active (130, 179, and 237 cm(-1)) and one infrared-active (279 cm(-1)) phonon branches. The electronic band dispersion of the 1T-FeCl2 is calculated using both gradient approximation of Perdew-Burke-Ernzerhof and DFT-HSE06 functionals. Both functionals reveal that the 1T-FeCl2 has a half-metallic ground state with a Curie temperature of 17 K. (C) 2015 AIP Publishing LLC.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 3.411
Times cited: 84
DOI: 10.1063/1.4921096
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“Direct-synthesis method towards copper-containing periodic mesoporous organosilicas : detailed investigation of the copper distribution in the material”. Lin F, Meng, Kukueva E, Altantzis T, Mertens M, Bals S, Cool P, Van Doorslaer S, Journal of the Chemical Society : Dalton transactions 44, 9970 (2015). http://doi.org/10.1039/c4dt03719g
Abstract: Three-dimensional cubic Fm (3) over barm mesoporous copper-containing ethane-bridged PMO materials have been prepared through a direct-synthesis method at room temperature in the presence of cetyltrimethylammonium bromide as surfactant. The obtained materials have been unambiguously characterized in detail by several sophisticated techniques, including XRD, UV-Vis-Dr, TEM, elemental mapping, continuous- wave and pulsed EPR spectroscopy. The results show that at lower copper loading, the Cu2+ species are well dispersed in the Cu-PMO materials, and mainly exist as mononuclear Cu2+ species. At higher copper loading amount, Cu2+ clusters are observed in the materials, but the distribution of the Cu2+ species is still much better in the Cu-PMO materials prepared through the direct-synthesis method than in a Cu-containing PMO material prepared through an impregnation method. Moreover, the evolution of the copper incorporation during the PMO synthesis has been followed by EPR. The results show that the immobilization of the Cu2+ ion/complex and the formation of the PMO materials are taking place simultaneously. The copper ions are found to be situated on the inner surface of the mesopores of the materials and are accessible, which will be beneficial for the catalytic applications.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA)
Impact Factor: 4.029
Times cited: 11
DOI: 10.1039/c4dt03719g
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“Optical conductivity of topological insulator thin films”. Li LL, Xu W, Peeters FM, Journal of applied physics 117, 175305 (2015). http://doi.org/10.1063/1.4919429
Abstract: We present a detailed theoretical study on the optoelectronic properties of topological insulator thin film (TITFs). The k . p approach is employed to calculate the energy spectra and wave functions for both the bulk and surface states in the TITF. With these obtained results, the optical conductivities induced by different electronic transitions among the bulk and surface states are evaluated using the energy-balance equation derived from the Boltzmann equation. We find that for Bi2Se3-based TITFs, three characteristic regimes for the optical absorption can be observed. (i) In the low radiation frequency regime (photon energy (h) over bar omega < 200 meV), the free-carrier absorption takes place due to intraband electronic transitions. An optical absorption window can be observed. (ii) In the intermediate radiation frequency regime (200 < (h) over bar omega < 300 meV), the optical absorption is induced mainly by interband electronic transitions from surface states in the valance band to surface states in the conduction band and an universal value sigma(0) = e(2) / (8<(h)over bar>) for the optical conductivity can be obtained. (iii) In the high radiation frequency regime ((h) over bar omega > 300 meV), the optical absorption can be achieved via interband electronic transitions from bulk and surface states in the valance band to bulk and surface states in the conduction band. A strong absorption peak can be observed. These interesting findings indicate that optical measurements can be applied to identify the energy regimes of bulk and surface states in the TITF. (C) 2015 AIP Publishing LLC.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 2.068
Times cited: 9
DOI: 10.1063/1.4919429
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“Phase problem in the B-site ordering of La2CoMnO6 : impact on structure and magnetism”. Egoavil R, Huehn S, Jungbauer M, Gauquelin N, Béché, A, Van Tendeloo G, Verbeeck, Moshnyaga V, Nanoscale 7, 9835 (2015). http://doi.org/10.1039/c5nr01642h
Abstract: Epitaxial double perovskite La2CoMnO6 (LCMO) films were grown by metalorganic aerosol deposition on SrTiO3(111) substrates. A high Curie temperature, T-C = 226 K, and large magnetization close to saturation, M-S(5 K) = 5.8 mu(B)/f.u., indicate a 97% degree of B-site (Co,Mn) ordering within the film. The Co/Mn ordering was directly imaged at the atomic scale by scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy (STEM-EDX). Local electron-energy-loss spectroscopy (EELS) measurements reveal that the B-sites are predominantly occupied by Co2+ and Mn4+ ions in quantitative agreement with magnetic data. Relatively small values of the (1/2 1/2 1/2) superstructure peak intensity, obtained by X-ray diffraction (XRD), point out the existence of ordered domains with an arbitrary phase relationship across the domain boundary. The size of these domains is estimated to be in the range 35-170 nm according to TEM observations and modelling the magnetization data. These observations provide important information towards the complexity of the cation ordering phenomenon and its implications on magnetism in double perovskites, and similar materials.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.367
Times cited: 37
DOI: 10.1039/c5nr01642h
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“Ion current rectification, limiting and overlimiting conductances in nanopores”. van Oeffelen L, Van Roy W, Idrissi H, Charlier D, Lagae L, Borghs G, PLoS ONE 10, e0124171 (2015). http://doi.org/10.1371/journal.pone.0124171
Abstract: Previous reports on Poisson-Nernst-Planck (PNP) simulations of solid-state nanopores have focused on steady state behaviour under simplified boundary conditions. These are Neumann boundary conditions for the voltage at the pore walls, and in some cases also Donnan equilibrium boundary conditions for concentrations and voltages at both entrances of the nanopore. In this paper, we report time-dependent and steady state PNP simulations under less restrictive boundary conditions, including Neumann boundary conditions applied throughout the membrane relatively far away from the nanopore. We simulated ion currents through cylindrical and conical nanopores with several surface charge configurations, studying the spatial and temporal dependence of the currents contributed by each ion species. This revealed that, due to slow co-diffusion of oppositely charged ions, steady state is generally not reached in simulations or in practice. Furthermore, it is shown that ion concentration polarization is responsible for the observed limiting conductances and ion current rectification in nanopores with asymmetric surface charges or shapes. Hence, after more than a decade of collective research attempting to understand the nature of ion current rectification in solid-state nanopores, a relatively intuitive model is retrieved. Moreover, we measured and simulated current-voltage characteristics of rectifying silicon nitride nanopores presenting overlimiting conductances. The similarity between measurement and simulation shows that overlimiting conductances can result from the increased conductance of the electric double-layer at the membrane surface at the depletion side due to voltage-induced polarization charges.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 2.806
Times cited: 11
DOI: 10.1371/journal.pone.0124171
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“Vacancy formation and oxidation characteristics of single layer TiS3”. Iyikanat F, Sahin H, Senger RT, Peeters FM, The journal of physical chemistry: C : nanomaterials and interfaces 119, 10709 (2015). http://doi.org/10.1021/acs.jpcc.5b01562
Abstract: The structural, electronic, and magnetic properties of pristine, defective, and oxidized monolayer TiS3 are investigated using first-principles calculations in the framework of density functional theory. We found that a single layer of TiS3 is a direct band gap semiconductor, and the bonding nature of the crystal is fundamentally different from other transition metal chalcogenides. The negatively charged surfaces of single layer TiS3 makes this crystal a promising material for lubrication applications. The formation energies of possible vacancies, i.e. S, Ti, TiS, and double S, are investigated via total energy optimization calculations. We found that the formation of a single S vacancy was the most likely one among the considered vacancy types. While a single S vacancy results in a nonmagnetic, semiconducting character with an enhanced band gap, other vacancy types induce metallic behavior with spin polarization of 0.3-0.8 mu(B). The reactivity of pristine and defective TiS3 crystals against oxidation was investigated using conjugate gradient calculations where we considered the interaction with atomic O, O-2, and O-3. While O-2 has the lowest binding energy with 0.05-0.07 eV, O-3 forms strong bonds stable even at moderate temperatures. The strong interaction (3.9-4.0 eV) between atomic O and TiS3 results in dissociative adsorption of some O-containing molecules. In addition, the presence of S-vacancies enhances the reactivity of the surface with atomic O, whereas it had a negative effect on the reactivity with O-2 and O-3 molecules.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 4.536
Times cited: 51
DOI: 10.1021/acs.jpcc.5b01562
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“Structural transitions in monolayer MOS2 by lithium adsorption”. Esfahani, Leenaerts O, Sahin H, Partoens B, Peeters FM, The journal of physical chemistry: C : nanomaterials and interfaces 119, 10602 (2015). http://doi.org/10.1021/jp510083w
Abstract: Based on first-principles calculations, we study the structural stability of the H and T phases of monolayer MoS2 upon Li doping. Our calculations demonstrate that it is possible to stabilize a distorted T phase of MoS2 over the H phase through adsorption of Li atoms on the MoS2 surface. Through molecular dynamics and phonon calculations, we show that the T phase of MoS2 is dynamically unstable and undergoes considerable distortions. The type of distortion depends on the concentration of adsorbed Li atoms and changes from zigzag-like to diamond-like when increasing the Li doping. There exists a substantial energy barrier to transform the stable H phase to the distorted T phases, which is considerably reduced by increasing the concentration of Li atoms. We show that it is necessary that the Li atoms adsorb on both sides of the MoS2 monolayer to reduce the barrier sufficiently. Two processes are examined that allow for such two-sided adsorption, namely, penetration through the MoS2 layer and diffusion over the MoS2 surface. We show that while there is only a small barrier of 0.24 eV for surface diffusion, the amount of energy needed to pass through a pure MoS2 layer is of the order of similar or equal to 2 eV. However, when the MoS2 layer is covered with Li atoms the amount of energy that Li atoms should gain to penetrate the layer is drastically reduced and penetration becomes feasible.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 4.536
Times cited: 96
DOI: 10.1021/jp510083w
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“VEGF-targeted magnetic nanoparticles for MRI visualization of brain tumor”. Abakumov MA, Nukolova NV, Sokolsky-Papkov M, Shein SA, Sandalova TO, Vishwasrao HM, Grinenko NF, Gubsky IL, Abakumov AM, Kabanov AV, Chekhonin VP;, Nanomedicine: nanotechnology, biology and medicine 11, 825 (2015). http://doi.org/10.1016/j.nano.2014.12.011
Abstract: This work is focused on synthesis and characterization of targeted magnetic nanoparticles as magnetic resonance imaging (MRI) agents for in vivo visualization of gliomas. Ferric oxide (Fe3O4) cores were synthesized by thermal decomposition and coated with bovine serum albumin (BSA) to form nanoparticles with D-eff of 53 +/- 9 nm. The BSA was further cross-linked to improve colloidal stability. Monoclonal antibodies against vascular endothelial growth factor (mAbVEGF) were covalently conjugated to BSA through a polyethyleneglycol linker. Here we demonstrate that 1) BSA coated nanoparticles are stable and non-toxic to different cells at concentration up to 2.5 mg/mL; 2) conjugation of monoclonal antibodies to nanoparticles promotes their binding to VEGF-positive glioma C6 cells in vitro; 3) targeted nanoparticles are effective in MRI visualization of the intracranial glioma. Thus, mAbVEGF-targeted BSA-coated magnetic nanoparticles are promising MRI contrast agents for glioma visualization. (C) 2015 Elsevier Inc. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 5.72
Times cited: 62
DOI: 10.1016/j.nano.2014.12.011
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“Increasing the cost-effectiveness of EU agri-environment policy measures through evaluation of farm and field-level environmental and economic performance”. Pacini GC, Merante P, Lazzerini G, Van Passel S, Agricultural Systems 136, 70 (2015). http://doi.org/10.1016/J.AGSY.2015.02.004
Abstract: A lot of attention in the debate on the 2014-2020 programming period of the EU CAP and rural development policy revolves around the policy's contribution to enhancing resource use efficiency, decreasing environmental impact, restoring ecosystems and how to ensure more efficient and effective agrienvironmental measures (AEMs). Nevertheless, studies that simultaneously address multiple measures with multiple environmental objectives and targets are underrepresented in the scientific literature. The objectives of the present article are (i) to present an integrated tool-kit for AEM design resulting from the combination of farm modelling with the Sustainable Value Approach (SVA), and (ii) to evaluate the potential of the tool-kit to support AEM design through an application to estimate cost-effective organic agriculture payments for the dairy sector in Mugello, northern Tuscany. Sustainability assessment of organic and conventional farming systems (OFS and CFS, respectively.) under the 2007-2013 EU CAP support schemes and a no EU support scenario show better OFS performances regarding nitrogen leaching (-52% and -47% under the current CAP and the no EU support scenarios, respectively), soil erosion (-24% and -34%), potential pesticide risks (-100%), biodiversity (+13% and +30%). Income foregone for the production of environmental benefits from organic agriculture under a no EU support scenario is equal to 210 Euro/ha. Sustainable value calculations combined with modelling results indicate soil erosion and nitrogen leaching as the environmental processes to be addressed with specific policy measures to further increase the efficiency of organic farming. A new organic agriculture support scheme designed based on such indications further increases the OFS SV and almost closes the GAP with a benchmark farm of the area, featured with ideal performances in terms of environmental and economic indicators. The payment scheme we designed with the support of the integrated tool-kit shows to be more cost-effective and efficient of current AEMs. (C) 2015 Elsevier Ltd. All rights reserved.
Keywords: A1 Journal article; Economics; Engineering Management (ENM)
Impact Factor: 2.571
Times cited: 12
DOI: 10.1016/J.AGSY.2015.02.004
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“Using agro-environmental models to design a sustainable benchmark for the sustainable value method”. Merante P, Van Passel S, Pacini C, Agricultural Systems 136, 1 (2015). http://doi.org/10.1016/J.AGSY.2015.02.001
Abstract: Farms contribute heavily to overall sustainability. To date, various frameworks, approaches, methods and indicators have been developed to appraise how much corporations (firms, farms) contribute to sustainability. Among these, the Sustainable Value (SV) method helps to determine by which economic entity resources should be used in order to achieve the highest contributions to sustainability, by comparing company's efficiency of capital use against the efficiency of a benchmark. In this work we argue that the SV benchmark does not include certain crucial environmental concepts, such as the carrying capacity of an ecosystem or the multiple vital functions provided by ecosystem services. Thus, it is not a suitable reference for companies to evaluate their contribution to sustainability. As an alternative benchmark to standard SV applications, we propose a farm whose resource use productivity is correlated to the fulfilment of pre-determined environmental constraints: the Environmentally Sustainable Farm (ESF). To design this farm, we created an agro-environmental farm modelling framework that includes: (i) methods and approaches to assess indicators concerning specific environmental issues; (ii) an integrated ecological-economic model based on linear programming. This farm modelling framework is employed to determine both the environmental performance and the economic returns of two farming systems, conventional (CFS) and organic (OFS), which are compared using the Sustainable Value approach. Despite the fact that the OFS environmentally outperforms the CFS, none of them reaches the sustainable performances achieved by the ESF, both performing a negative Sustainable Value. The environmental constraints forced the ESF towards management choices that, although decreasing the economic performance, increase its environmental sustainability behaviour. Hence, the ESF is a viable benchmark that can be used to evaluate llllfarms' environmental sustainability. (C) 2015 Elsevier Ltd. All rights reserved.
Keywords: A1 Journal article; Economics; Engineering Management (ENM)
Impact Factor: 2.571
Times cited: 6
DOI: 10.1016/J.AGSY.2015.02.001
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“Scanning tunneling microscopy and density functional theory study on zinc(II)-phthalocyanine tetrasulfonic acid on bilayer epitaxial graphene on silicon carbide(0001)”. Nicholls D, Li RR, Ware B, Pansegrau C, Çakir D, Hoffmann MR, Oncel N, The journal of physical chemistry: C : nanomaterials and interfaces 119, 9845 (2015). http://doi.org/10.1021/acs.jpcc.5b00864
Abstract: Zinc(II)-phthalocyanine tetrasulfonic acid (Zn-PcS) molecules physisorbed on bilayer epitaxial graphene on silicon carbide (SiC(0001)) were studied by using scanning tunneling microscopy/spectroscopy (STM/STS) and density functional theory (DFT). Two different methods were used to deposit Zn-PcS molecules and regardless of the method being used, the surface coverage stayed very low indicating the weakness of surface-molecule interaction. STS measurements revealed that derivative of tunneling current with respect to voltage (dI/dV) measured on Zn-PcS molecules did not exhibit the characteristic dip observed on dI/dV curves of pristine bilayer epitaxial graphene. DFT calculations show that the energy of the lowest unoccupied molecular orbital (LUMO) of the Zn-PcS molecule is below the Dirac point of graphene which enhances local density of states (LDOS). We attribute the disappearance of the dip in the dI/dV curves measured on the Zn-PcS/bilayer system to the LUMO of Zn-PcS. Charge density calculations along Zn-PcS/graphene interface reveal that there is a small charge transfer from graphene to the molecule. Calculated adsorption energy (3.13 eV) of the molecule is notably low and is consistent with the observed low surface coverage at room temperature.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 4.536
Times cited: 3
DOI: 10.1021/acs.jpcc.5b00864
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“From olivine to ringwoodite : a TEM study of a complex process”. Pittarello L, Ji G, Yamaguchi A, Schryvers D, Debaille V, Claeys P, Meteoritics and Planetary Science 50, 944 (2015). http://doi.org/10.1111/maps.12441
Abstract: The study of shock metamorphism of olivine might help to constrain impact events in the history of meteorites. Although shock features in olivine are well known, so far, there are processes that are not yet completely understood. In shock veins, olivine clasts with a complex structure, with a ringwoodite rim and a dense network of lamellae of unidentified nature in the core, have been reported in the literature. A highly shocked (S5-6), L6 meteorite, Asuka 09584, which was recently collected in Antarctica by a Belgian-Japanese joint expedition, contains this type of shocked olivine clasts and has been, therefore, selected for detailed investigations of these features by transmission electron microscopy (TEM). Petrographic, geochemical, and crystallographic studies showed that the rim of these shocked clasts consists of an aggregate of nanocrystals of ringwoodite, with lower Mg/Fe ratio than the unshocked olivine. The clast's core consists of an aggregate of iso-oriented grains of olivine and wadsleyite, with higher Mg/Fe ratio than the unshocked olivine. This aggregate is crosscut by veinlets of nanocrystals of olivine, with extremely low Mg/Fe ratio. The formation of the ringwoodite rim is likely due to solid-state, diffusion-controlled, transformation from olivine under high-temperature conditions. The aggregate of iso-oriented olivine and wadsleyite crystals is interpreted to have formed also by a solid-state process, likely by coherent intracrystalline nucleation. Following the compression, shock release is believed to have caused opening of cracks and fractures in olivine and formation of olivine melt, which has lately crystallized under postshock equilibrium pressure conditions as olivine.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.391
Times cited: 8
DOI: 10.1111/maps.12441
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“An improved electrochemical aptasensor for chloramphenicol detection based on aptamer incorporated gelatine”. Hamidi-Asl E, Dardenne F, Blust R, De Wael K, Sensors 15, 7605 (2015). http://doi.org/10.3390/S150407605
Abstract: Because of the biocompatible properties of gelatine and the good affinity of aptamers for their targets, the combination of aptamer and gelatine type B is reported as promising for the development of biosensing devices. Here, an aptamer for chloramphenicol (CAP) is mixed with different types of gelatine and dropped on the surface of disposable gold screen printed electrodes. The signal of the CAP reduction is investigated using differential pulse voltammetry. The diagnostic performance of the sensor is described and a detection limit of 1.83 x 10(-10) M is found. The selectivity and the stability of the aptasensor are studied and compared to those of other CAP sensors described in literature.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 2.677
Times cited: 21
DOI: 10.3390/S150407605
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“Governing the morphology of PtAu heteronanocrystals with improved electrocatalytic performance”. Mourdikoudis S, Chirea M, Zanaga D, Altantzis T, Mitrakas M, Bals S, Marzán LM, Pérez-Juste J, Pastoriza-Santos I, Nanoscale 7, 8739 (2015). http://doi.org/10.1039/C4NR07481E
Abstract: Platinumgold heteronanostructures comprising either dimer (PtAu) or coresatellite (Pt@Au) configurations were synthesized by means of a seeded growth procedure using platinum nanodendrites as seeds. Careful control of the reduction kinetics of the gold precursor can be used to direct the nucleation and growth of gold nanoparticles on either one or multiple surface sites simultaneously, leading to the formation of either dimers or coresatellite nanoparticles, respectively, in high yields. Characterization by electron tomography and high resolution electron microscopy provided a better understanding of the actual three-dimensional particle morphology, as well as the AuPt interface, revealing quasi-epitaxial growth of Au on Pt. The prepared PtAu bimetallic nanostructures are highly efficient catalysts for ethanol oxidation in alkaline solution, showing accurate selectivity, high sensitivity, and improved efficiency by generating higher current densities than their monometallic counterparts.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.367
Times cited: 41
DOI: 10.1039/C4NR07481E
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“Realization of a p-n junction in a single layer boron-phosphide”. Çakir D, Kecik D, Sahin H, Durgun E, Peeters FM, Physical chemistry, chemical physics 17, 13013 (2015). http://doi.org/10.1039/c5cp00414d
Abstract: Two-dimensional (2D) materials have attracted growing interest due to their potential use in the next generation of nanoelectronic and optoelectronic applications. On the basis of first-principles calculations based on density functional theory, we first investigate the electronic and mechanical properties of single layer boron phosphide (h-BP). Our calculations show that h-BP is a mechanically stable 2D material with a direct band gap of 0.9 eV at the K-point, promising for both electronic and optoelectronic applications. We next investigate the electron transport properties of a p-n junction constructed from single layer boron phosphide (h-BP) using the non-equilibrium Green's function formalism. The n-and p-type doping of BP are achieved by substitutional doping of B with C and P with Si, respectively. C(Si) substitutional doping creates donor (acceptor) states close to the conduction (valence) band edge of BP, which are essential to construct an efficient p-n junction. By modifying the structure and doping concentration, it is possible to tune the electronic and transport properties of the p-n junction which exhibits not only diode characteristics with a large current rectification but also negative differential resistance (NDR). The degree of NDR can be easily tuned via device engineering.
Keywords: A1 Journal article; Condensed Matter Theory (CMT)
Impact Factor: 4.123
Times cited: 104
DOI: 10.1039/c5cp00414d
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“Neutron activation autoradiography and scanning macro-XRF of Rembrandt van Rijn's Susanna and the Elders (Gemaldegalerie Berlin) : a comparison of two methods for imaging of historical paintings with elemental contrast”. Alfeld M, Laurenze-Landsberg C, Denker A, Janssens K, Noble P, Applied physics A : materials science &, processing 119, 795 (2015). http://doi.org/10.1007/S00339-015-9081-8
Abstract: Imaging methods with elemental contrast are of great value for the investigation of historical paintings, as they allow for study of sub-surface layers that provide insight into a painting's creation process. Two of the most important methods are neutron activation autoradiography (NAAR) and scanning macro-XRF (MA-XRF). Given the differences between these methods in the fundamental physical phenomena exploited, a theoretical comparison of their capabilities is difficult and until now a critical comparison of their use on the same painting is missing. In this paper, we present a study of Rembrandt van Rijn's painting Susanna and the Elders from the Gemaldegalerie in Berlin employing both techniques. The painting features a considerable number of overpainted features and a wide range of pigments with different elemental tracers, including earth pigments (Mn/Fe), Azurite (Cu), lead white (Pb), vermilion (Hg) and smalt (Co, As). MA-XRF can detect all elements above Si (Z = 14), suffers from few spectral overlaps and can be performed in a few tens of hours in situ, i.e. in a museum. NAAR requires the stay of the painting at a research facility for several weeks, and inter-element interferences can be difficult to resolve. Also, only a limited number of elements contribute to the acquired autoradiographs, most notably Mn, Cu, As, Co, Hg and P. However, NAAR provides a higher lateral resolution and is less hindered by absorption in covering layers, which makes it the only method capable of visualizing P in lower paint layers.
Keywords: A1 Journal article; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 1.455
Times cited: 11
DOI: 10.1007/S00339-015-9081-8
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“Emergent phenomena in multicomponent superconductivity: an introduction to the focus issue”. Milošević, MV, Perali A, Superconductor Science &, Technology 28, 060201 (2015). http://doi.org/10.1088/0953-2048/28/6/060201
Keywords: A1 Journal article; CMT
Impact Factor: 2.878
Times cited: 41
DOI: 10.1088/0953-2048/28/6/060201
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“Dynamic identifiability analysis-based model structure evaluation considering rating curve uncertainty”. Van Hoey S, Nopens I, van der Kwast J, Seuntjens P, Journal of hydrologic engineering 20, 04014072 (2015). http://doi.org/10.1061/(ASCE)HE.1943-5584.0000995
Abstract: When applying hydrological models, different sources of uncertainty are present, and evaluations of model performances should take these into account to assess model outcomes correctly. Furthermore, uncertainty in the discharge observations complicates the model identification, both in terms of model structure and parameterization. In this paper, the authors compare two different lumped model structures (PDM and NAM) considering uncertainty coming from the rating curve. Limits of acceptability for the model simulations were determined based on derived uncertainty bounds of the discharge observations. The authors applied the DYNamic Identifiability Approach (DYNIA) to identify structural failure of both models and to evaluate the configuration of their structures. In general, similar model performances are observed. However, the model structures tend to behave differently in the course of time, as revealed by the DYNIA approach. Based on the analyses performed, the probability based soil storage representation of the PDM model outperforms the NAM structure. The incorporation of the observation error did not prevent the DYNIA analysis to identify potential model structural deficiencies that are limiting the representation of the seasonal variation, primarily indicated by shifting regions of parameter identifiability. As such, the proposed approach is able to indicate where deficiencies are found and model improvement is needed.
Keywords: A1 Journal article; Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.1061/(ASCE)HE.1943-5584.0000995
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“Vapor phase processing of \alpha-Fe2O3 photoelectrodes for water splitting : an insight into the structure/property interplay”. Warwick MEA, Kaunisto K, Barreca D, Carraro G, Gasparotto A, Maccato C, Bontempi E, Sada C, Ruoko TP, Turner S, Van Tendeloo G;, ACS applied materials and interfaces 7, 8667 (2015). http://doi.org/10.1021/acsami.5b00919
Abstract: Harvesting radiant energy to trigger water photoelectrolysis and produce clean hydrogen is receiving increasing attention in the search of alternative energy resources. In this regard, hematite (alpha-Fe2O3) nanostructures with controlled nano-organization have been fabricated and investigated for use as anodes in photoelectrochemical (PEC) cells. The target systems have been grown on conductive substrates by plasma enhanced-chemical vapor deposition (PE-CVD) and subjected to eventual ex situ annealing in air to further tailor their structure and properties. A detailed multitechnique approach has enabled to elucidate between system characteristics and the generated photocurrent. The present alpha-Fe2O3 systems are characterized by a high purity and hierarchical morphologies consisting of nanopyramids/organized dendrites, offering a high contact area with the electrolyte. PEC data reveal a dramatic response enhancement upon thermal treatment, related to a more efficient electron transfer. The reasons underlying such a phenomenon are elucidated and discussed by transient absorption spectroscopy (TAS) studies of photogenerated charge carrier kinetics, investigated on different time scales for the first time on PE-CVD Fe2O3 nanostructures.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.504
Times cited: 51
DOI: 10.1021/acsami.5b00919
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“Tuning carrier confinement in the MoS2/WS2 lateral heterostructure”. Kang J, Sahin H, Peeters FM, The journal of physical chemistry: C : nanomaterials and interfaces 119, 9580 (2015). http://doi.org/10.1021/acs.jpcc.5b00814
Abstract: To determine and control the spatial confinement of charge carriers is of importance for nanoscale optoelectronic device applications. Using first-principles calculations, we investigate the tunability of band alignment and Charge localization in lateral and combined lateral vertical heterostructures of MoS2 and WS2. First, we Show that a type-II to type-I band alignment transition takes place when tensile strain is applied on the WS2 region. This band alignment transition is a result of the different response of the band edge states with strain and is caused by their different wave function characters. Then we show that the presence of the grain boundary introduces localized in-gap states. The boundary at the armchair interface significantly modifies the charge distribution of the valence band maximum (VBM) state, whereas in a heterostructure with tilt grain domains both conducation band maximum (CBM) and VBM are found to be localized around the grain boundary. We also found that the thickness of the constituents in a lateral heterostructure also determines how the electrons and holes are confined. Creating combined lateral vertical heterostructures of MOS2/WS2 provides another way cif tuning the charge confinement. These results provide possible ways to tune the carrier confinement in MoS2/WS2 heterostructures, which are interesting for its practical: applications in the future.
Keywords: A1 Journal article; Engineering sciences. Technology; Condensed Matter Theory (CMT)
Impact Factor: 4.536
Times cited: 73
DOI: 10.1021/acs.jpcc.5b00814
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“Competing forces in the self-assembly of coupled ZnO nanopyramids”. Javon E, Gaceur M, Dachraoui W, Margeat O, Ackermann J, Ilenia Saba M, Delugas P, Mattoni A, Bals S, Van Tendeloo G, ACS nano 9, 3685 (2015). http://doi.org/10.1021/acsnano.5b00809
Abstract: Self-assembly (SA) of nanostructures has recently gained increasing interest. A clear understanding of the process is not straightforward since SA of nanoparticles is a complex multiscale phenomenon including different driving forces. Here, we study the SA between aluminum doped ZnO nanopyramids into couples by combining inorganic chemistry and advanced electron microscopy techniques with atomistic simulations. Our results show that the SA of the coupled nanopyramids is controlled first by morphology, as coupling only occurs in the case of pyramids with well-developed facets of the basal planes. The combination of electron microscopy and atomistic modeling reveals that the coupling is further driven by strong ligandligand interaction between the bases of the pyramids as dominant force, while screening effects due to Al doping or solvent as well as corecore interaction are only minor contributions. Our combined approach provides a deeper understanding of the complex interplay between the interactions at work in the coupled SA of ZnO nanopyramids.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 13.942
Times cited: 21
DOI: 10.1021/acsnano.5b00809
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“Li2Cu2O(SO4)2: a possible electrode for sustainable Li-based batteries showing a 4.7 V redox activity vs Li+/Li0”. Sun M, Rousse G, Abakumov AM, Saubanere M, Doublet M-L, Rodriguez-Carvajal J, Van Tendeloo G, Tarascon J-M, Chemistry of materials 27, 3077 (2015). http://doi.org/10.1021/acs.chemmater.5b00588
Abstract: Li-ion batteries rely on the use of insertion positive electrodes with performances scaling with the redox potential of the 31) metals accompanying Liuptake/removal. Although not commonly studied, the Cu2+/Cu3+ redox potential has been predicted from theoretical calculations to possibly offer a high operating voltage redox couple. We herein report the synthesis and crystal structure of a hitherto-unknown oxysulfate phase, Li2Cu2O(SO4)(2), which contains infinite edgesharing CuO4 chains and presents attractive electrochemical redox activity with respect to Li+/Li, namely amphoteric characteristics. Li2Cu2O(SO4)(2) shows redox activity at 4.7 V vs Li+/Li corresponding to the oxidation of Cu2+ to Cu3+ enlisting ligand holes and associated with the reversible uptake-removal of 0.3 Li. Upon reduction, this compound reversibly uptakes similar to 2 Li at an average potential of about 2.5 V vs Li+/Li, associated with the Cu2+/Cu+ redox couple. The mechanism of the reactivity upon reduction is discussed in detail, with particular attention to the occasional appearance of an oscillation wave in the discharge profile. Our work demonstrates that Cu-based compounds can indeed be fertile scientific ground in the search for new high-energy-density electrodes.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 20
DOI: 10.1021/acs.chemmater.5b00588
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“Layered oxychlorides [PbBiO2]An+1BnO3n-1Cl2(A = Pb/Bi, B = Fe/Ti) : intergrowth of the hematophanite and sillen phases”. Batuk M, Batuk D, Tsirlin AA, Filimonov DS, Sheptyakov DV, Frontzek M, Hadermann J, Abakumov AM, Chemistry of materials 27, 2946 (2015). http://doi.org/10.1021/acs.chemmater.5b00233
Abstract: New layered structures corresponding to the general formula [PbBiO2]A(n+1)B(n)O(3n-1)Cl(2) Were prepared. Pb5BiFe3O10Cl2 (n = 3) and Pb5Bi2Fe4O13Cl2 (n = 4) are built as a stacking of truncated A(n+1)B(n)O(3n-1) perovskite blocks and alpha-PbO-type [A(2)O(2)](2+) (A = Pb, Bi) blocks combined with chlorine sheets. The alternation of these structural blocks can be represented as an intergrowth between the hematophanite and Sullen-type structural blocks. The crystal and-Magnetic structures of Pb5BiFe3O10Cl2 and Pb5Bi2Fe4O13Cl2 were investigated in the temperature range of 1.5-700 K using X-ray and neutron powder diffraction, transmission electron microscopy and Fe-57 Mossbauer spectroscopy. Both compounds crystallize in the I4/mmm space group with the unit cell parameters a approximate to a(p) approximate to 3.92 angstrom (a unit-cell parameter of the perovskite-structure), c approximate to 43.0 angstrom for the n = 3 member and c approximate to 53.5 angstrom for the n = 4 member. Despite the large separation between the slabs containing the Fe3+ ions (nearly 14 angstrom), long-range antiferromagnetic order sets in below similar to 600 K with the G-type arrangement of the Fe magnetic moments aligned along the c-axis. The possibility of mixing d(0) and d(n) cations at the B sublattice of these structures was also demonstrated by preparing the Ti-substituted n = 4 member Pb6BiFe3TiO13Cl2.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 11
DOI: 10.1021/acs.chemmater.5b00233
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“Soft chemical control of the crystal and magnetic structure of a layered mixed valent manganite oxide sulfide”. Blandy JN, Abakumov AM, Christensen KE, Hadermann J, Adamson P, Cassidy SJ, Ramos S, Free DG, Cohen H, Woodruff DN, Thompson AL, Clarke SJ;, APL materials 3, 041520 (2015). http://doi.org/10.1063/1.4918973
Abstract: Oxidative deintercalation of copper ions from the sulfide layers of the layered mixed-valent manganite oxide sulfide Sr2MnO2Cu1.5S2 results in control of the copper-vacancy modulated superstructure and the ordered arrangement of magnetic moments carried by the manganese ions. This soft chemistry enables control of the structures and properties of these complex materials which complement mixed-valent perovskite and perovskite-related transition metal oxides. (C) 2015 Author(s).
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 4.335
Times cited: 5
DOI: 10.1063/1.4918973
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“Effect of the burn-out step on the microstructure of the solution-processed Cu(In,Ga)Se2 solar cells”. Batuk M, Buffiere M, Zaghi AE, Lenaers N, Verbist C, Khelifi S, Vleugels J, Meuris M, Hadermann J, Thin solid films : an international journal on the science and technology of thin and thick films 583, 142 (2015). http://doi.org/10.1016/j.tsf.2015.03.063
Abstract: For the development of the photovoltaic industry cheap methods for the synthesis of Cu(In,Ga)Se-2 (CIGSe) based solar cells are required. In this work, CIGSe thin films were obtained by a solution-based method using oxygen-bearing derivatives. With the aimof improving the morphology of the printed CIGSe layers, we investigated two different annealing conditions of the precursor layer, consisting of (1) a direct selenization step (reference process), and (2) a pre-treatment thermal step prior to the selenization. We showed that the use of an Air/H2S burn-out step prior to the selenization step increases the CIGSe grain size and reduces the carbon content. However, it leads to the reduction of the solar cell efficiency from 4.5% in the reference sample down to 0.5% in the annealed sample. Detailed transmission electron microscopy analysis, including high angle annular dark field scanning transmission electron microscopy and energy dispersive X-ray mapping, was applied to characterize the microstructure of the film and to determine the relationship between microstructure and the solar cell performance. We demonstrated that the relatively low efficiency of the reference solar cells is related not only to the nanosize of the CIGSe grains and presence of the pores in the CIGSe layer, but also to the high amount of secondary phases, namely, In/Ga oxide (or hydroxide) amorphous matter, residuals of organicmatter (carbon), and copper sulfide that is formed at the CIGSe/MoSe2 interface. The annealing in H2S during the burn-out step leads to the formation of the copper sulfide at all grain boundaries and surfaces in the CIGSe layer, which results in the noticeably efficiency drop. (C) 2015 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.879
Times cited: 5
DOI: 10.1016/j.tsf.2015.03.063
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“Direct observation and structural characterization of natural and metal ion-exchanged HEU-type zeolites”. Filippousi M, Turner S, Katsikini M, Pinakidou F, Zamboulis D, Pavlidou E, Van Tendeloo G, Microporous and mesoporous materials: zeolites, clays, carbons and related materials 210, 185 (2015). http://doi.org/10.1016/j.micromeso.2015.01.043
Abstract: The atomic structure of natural HEU-type zeolite and two ion-exchanged variants of the zeolite, Ag+ (Ag-HEU) and Zn2+ (Zn-HEU) ion exchanged HEU-type zeolites, are investigated using advanced transmission electron microscopy techniques in combination with X-ray powder diffraction and X-ray absorption fine structure measurements. In both ion-exchanged materials, loading of the natural HEU zeolite is confirmed. Using low-voltage, aberration-corrected transmission electron microscopy at low-dose conditions, the local crystal structure of natural HEU-type zeolite is determined and the interaction of the ion-exchanged natural zeolites with the Ag+ and Zn2+ ions is studied. In the case of Ag-HEU, the presence of Ag+ ions and clusters at extra-framework sites as well as Ag nanoparticles has been confirmed. The Ag nanoparticles are preferentially positioned at the zeolite surface. For Zn-HEU, no large Zn(O) nanopartides are present, instead, the HEU channels are evidenced to be decorated by small Zn(O) clusters. (c) 2015 Elsevier Inc. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 3.615
Times cited: 5
DOI: 10.1016/j.micromeso.2015.01.043
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