“Chemical activity of the peroxide/oxide redox couple : case study of Ba5Ru2O11 in aqueous and organic solvents”. Grimaud A, Iadecola A, Batuk D, Saubanere M, Abakumov AM, Freeland JW, Cabana J, Li H, Doublet M-L, Rousse G, Tarascon J-M, Chemistry of materials 30, 3882 (2018). http://doi.org/10.1021/ACS.CHEMMATER.8B01372
Abstract: The finding that triggering the redox activity of oxygen ions within the lattice of transition metal oxides can boost the performances of materials used in energy storage and conversion devices such as Li-ion batteries or oxygen evolution electrocatalysts has recently spurred intensive and innovative research in the field of energy. While experimental and theoretical efforts have been critical in understanding the role of oxygen nonbonding states in the redox activity of oxygen ions, a clear picture of the redox chemistry of the oxygen species formed upon this oxidation process is still missing. This can be, in part, explained by the complexity in stabilizing and studying these species once electrochemically formed. In this work, we alleviate this difficulty by studying the phase Ba5Ru2O11, which contains peroxide O-2(2-) groups, as oxygen evolution reaction electrocatalyst and Li-ion battery material. Combining physical characterization and electrochemical measurements, we demonstrate that peroxide groups can easily be oxidized at relatively low potential, leading to the formation of gaseous dioxygen and to the instability of the oxide. Furthermore, we demonstrate that, owing to the stabilization at high energy of peroxide, the high-lying energy of the empty sigma* antibonding O-O states limits the reversibility of the electrochemical reactions when the O-2(2-)/O2- redox couple is used as redox center for Li-ion battery materials or as OER redox active sites. Overall, this work suggests that the formation of true peroxide O-2(2-) states are detrimental for transition metal oxides used as OER catalysts and Li-ion battery materials. Rather, oxygen species with O-O bond order lower than 1 would be preferred for these applications.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 2
DOI: 10.1021/ACS.CHEMMATER.8B01372
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“Role of graphene inter layer on the formation of the MoS2 –, CZTS interface during growth”. Vishwakarma M, Thota N, Karakulina O, Hadermann J, Mehta BR, (icc-2017) (2018). http://doi.org/10.1063/1.5033000
Abstract: The growth of MoS2 layer near the Mo/CZTS interface during sulphurization process can have an impact on back contact cell parameters (series resistance and fill factor) depending upon the thickness or quality of MoS2. This study reports the dependence of the thickness of interfacial MoS2 layer on the growth of graphene at the interface between molybdenum back contact and deposited CZTS layer. The graphene layer reduces the accumulation of Zn/ZnS, Sn/SnO2 and formation of pores near the MoS2-CZTS interface. The use of graphene as interface layer can be potentially useful for improving the quality of Mo/MoS2/CZTS interface.
Keywords: P1 Proceeding; Electron microscopy for materials research (EMAT)
Times cited: 1
DOI: 10.1063/1.5033000
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“Tailoring the Ti-C nanoprecipitate population and microstructure of titanium stabilized austenitic steels”. Cautaerts N, Delville R, Stergar E, Schryvers D, Verwerft M, Journal of nuclear materials 507, 177 (2018). http://doi.org/10.1016/J.JNUCMAT.2018.04.041
Abstract: The present work reports on the microstructural evolution of a new heat of 24% cold worked austenitic DIN 1.4970 (15-15Ti) nuclear cladding steel subjected to ageing heat treatments of varying duration between 500 and 800 degrees C (by steps of 100 degrees C). The primary aim was studying the finely dispersed Ti-C nanoprecipitate population, which are thought to be beneficial for creep and swelling resistance during service. Their size distribution and number density were estimated through dark field imaging and bright field Moire imaging techniques in the transmission electron microscope. Nanoprecipitates formed at and above 600 degrees C, which is a lower temperature than previously reported. The observed nucleation, growth and coarsening behavior of the nanoprecipitates were consistent with simple diffusion arguments. The formation of nanoprecipitates coincided with significant dissociation of dislocations as evidenced by weak beam dark field imaging. Possible mechanisms, including Silcock's stacking fault growth model and Suzuki segregation, are discussed. Recrystallization observed after extended ageing at 800 degrees C caused the redissolution of nanoprecipitates. Large primary Ti(C,N) and (Ti,Mo)C precipitates that occur in the as-received material, and M23C6 precipitates that nucleate on grain boundaries at low temperatures were also characterized by a selective dissolution procedure involving filtration, X-ray diffraction and quantitative Rietveld refinement. The partitioning of key elements between the different phases was derived by combining these findings and was consistent with thermodynamic considerations and the processing history of the steel. (C) 2018 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 2.048
Times cited: 1
DOI: 10.1016/J.JNUCMAT.2018.04.041
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“Demonstration of a 2 × 2 programmable phase plate for electrons”. Verbeeck J, Béché, A, Müller-Caspary K, Guzzinati G, Luong MA, Den Hertog M, Ultramicroscopy 190, 58 (2018). http://doi.org/10.1016/j.ultramic.2018.03.017
Abstract: First results on the experimental realisation of a 2 × 2 programmable phase plate for electrons are presented. The design consists of an array of electrostatic elements that influence the phase of electron waves passing through 4 separately controllable aperture holes. This functionality is demonstrated in a conventional transmission electron microscope operating at 300 kV and results are in very close agreement with theoretical predictions. The dynamic creation of a set of electron probes with different phase symmetry is demonstrated, thereby bringing adaptive optics in TEM one step closer to reality. The limitations of the current design and how to overcome these in the future are discussed. Simulations show how further evolved versions of the current proof of concept might open new and exciting application prospects for beam shaping and aberration correction.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
Times cited: 73
DOI: 10.1016/j.ultramic.2018.03.017
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“Characterization of silver-polymer core–shell nanoparticles using electron microscopy”. Claes N, Asapu R, Blommaerts N, Verbruggen SW, Lenaerts S, Bals S, Nanoscale 10, 9186 (2018). http://doi.org/10.1039/C7NR09517A
Abstract: Silver-polymer core–shell nanoparticles show interesting optical properties, making them widely applicable in the field of plasmonics. The uniformity, thickness and homogeneity of the polymer shell will affect the properties of the system which makes a thorough structural characterization of these core–shell silver-polymer nanoparticles of great importance. However, visualizing the shell and the particle simultaneously is far from straightforward due to the sensitivity of the polymer shell towards the electron beam. In this study, we use different 2D and 3D electron microscopy techniques to investigate different structural aspects of the polymer coating.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 7.367
Times cited: 11
DOI: 10.1039/C7NR09517A
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“Removal of arsenic and mercury species from water by covalent triazine framework encapsulated \gamma-Fe2O3 nanoparticles”. Leus K, Folens K, Nicomel NR, Perez JPH, Filippousi M, Meledina M, Dirtu MM, Turner S, Van Tendeloo G, Garcia Y, Du Laing G, Van Der Voort P, Journal of hazardous materials 353, 312 (2018). http://doi.org/10.1016/J.JHAZMAT.2018.04.027
Abstract: The covalent triazine framework, CTF-1, served as host material for the in situ synthesis of Fe2O3 nanoparticles. The composite material consisted of 20 +/- 2 m% iron, mainly in gamma-Fe2O3 phase. The resulting gamma-Fe2O3@CTF-1 was examined for the adsorption of As-III, As-V and H-II from synthetic solutions and real surface-, ground- and wastewater. The material shows excellent removal efficiencies, independent from the presence of Ca2+, Mg2+ or natural organic matter and only limited dependency on the presence of phosphate ions. Its adsorption capacity towards arsenite (198.0 mg g(-1)), arsenate (102.3 mg g(-1)) and divalent mercury (165.8 mg g(-1)) belongs amongst the best-known adsorbents, including many other iron-based materials. Regeneration of the adsorbent can be achieved for use over multiple cycles without a decrease in performance by elution at 70 degrees C with 0.1 M NaOH, followed by a stirring step in a 5 m% H2O2 solution for As or 0.1 M thiourea and 0.001 M HCl for Hg. In highly contaminated water (100 mu gL(-1)), the adsorbent polishes the water quality to well below the current WHO limits.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 6.065
Times cited: 22
DOI: 10.1016/J.JHAZMAT.2018.04.027
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“Strain analysis from nano-beam electron diffraction : influence of specimen tilt and beam convergence”. Grieb T, Krause FF, Schowalter M, Zillmann D, Sellin R, Müller-Caspary K, Mahr C, Mehrtens T, Bimberg D, Rosenauer A, Ultramicroscopy 190, 45 (2018). http://doi.org/10.1016/J.ULTRAMIC.2018.03.013
Abstract: Strain analyses from experimental series of nano-beam electron diffraction (NBED) patterns in scanning transmission electron microscopy are performed for different specimen tilts. Simulations of NBED series are presented for which strain analysis gives results that are in accordance with experiment. This consequently allows to study the relation between measured strain and actual underlying strain. A two-tilt method which can be seen as lowest-order electron beam precession is suggested and experimentally implemented. Strain determination from NBED series with increasing beam convergence is performed in combination with the experimental realization of a probe-forming aperture with a cross inside. It is shown that using standard evaluation techniques, the influence of beam convergence on spatial resolution is lower than the influence of sharp rings around the diffraction disc which occur at interfaces and which are caused by the tails of the intensity distribution of the electron probe. (C) 2018 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.843
Times cited: 1
DOI: 10.1016/J.ULTRAMIC.2018.03.013
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“Asymmetric Modulation on Exchange Field in a Graphene/BiFeO3Heterostructure by External Magnetic Field”. Song H-D, Wu Y-F, Yang X, Ren Z, Ke X, Kurttepeli M, Tendeloo GV, Liu D, Wu H-C, Yan B, Wu X, Duan C-G, Han G, Liao Z-M, Yu D, Nano letters 18, 2435 (2018). http://doi.org/10.1021/acs.nanolett.7b05480
Abstract: Graphene, having all atoms on its surface, is favorable to extend the functions by introducing the spin–orbit coupling and magnetism through proximity effect. Here, we report the tunable interfacial exchange field produced by proximity coupling in graphene/BiFeO3 heterostructures. The exchange field has a notable dependence with external magnetic field, and it is much larger under negative magnetic field than that under positive magnetic field. For negative external magnetic field, interfacial exchange coupling gives rise to evident spin splitting for N ≠ 0 Landau levels and a quantum Hall metal state for N = 0 Landau level. Our findings suggest graphene/BiFeO3 heterostructures are promising for spintronics.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 12.712
Times cited: 9
DOI: 10.1021/acs.nanolett.7b05480
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“Near-Infrared-Emitting CuInS2/ZnS Dot-in-Rod Colloidal Heteronanorods by Seeded Growth”. Xia C, Winckelmans N, Prins PT, Bals S, Gerritsen HC, de Mello Donegá, C, Journal of the American Chemical Society 140, 5755 (2018). http://doi.org/10.1021/jacs.8b01412
Abstract: Synthesis protocols for anisotropic CuInX2 (X = S, Se, Te)-based heteronanocrystals (HNCs) are scarce due to the difficulty in balancing the reactivities of multiple precursors and the high solid-state diffusion rates of the cations involved in the CuInX2 lattice. In this work, we report a multistep seeded growth synthesis protocol that yields colloidal wurtzite CuInS2/ZnS dot core/rod shell HNCs with photoluminescence in the NIR (∼800 nm). The wurtzite CuInS2 NCs used as seeds are obtained by topotactic partial Cu+ for In3+ cation exchange in template Cu2–xS NCs. The seed NCs are injected in a hot solution of zinc oleate and hexadecylamine in octadecene, 20 s after the injection of sulfur in octadecene. This results in heteroepitaxial growth of wurtzite ZnS primarily on the Sulfur-terminated polar facet of the CuInS2 seed NCs, the other facets being overcoated only by a thin (∼1 monolayer) shell. The fast (∼21 nm/min) asymmetric axial growth of the nanorod proceeds by addition of [ZnS] monomer units, so that the polarity of the terminal (002) facet is preserved throughout the growth. The delayed injection of the CuInS2 seed NCs is crucial to allow the concentration of [ZnS] monomers to build up, thereby maximizing the anisotropic heteroepitaxial growth rates while minimizing the rates of competing processes (etching, cation exchange, alloying). Nevertheless, a mild etching still occurred, likely prior to the onset of heteroepitaxial overgrowth, shrinking the core size from 5.5 to ∼4 nm. The insights provided by this work open up new possibilities in designing multifunctional Cu-chalcogenide based colloidal heteronanocrystals.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 13.858
Times cited: 43
DOI: 10.1021/jacs.8b01412
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“Exploring possibilities of band gap measurement with off-axis EELS in TEM”. Korneychuk S, Partoens B, Guzzinati G, Ramaneti R, Derluyn J, Haenen K, Verbeeck J, Ultramicroscopy 189, 76 (2018). http://doi.org/10.1016/J.ULTRAMIC.2018.03.021
Abstract: A technique to measure the band gap of dielectric materials with high refractive index by means of energy electron loss spectroscopy (EELS) is presented. The technique relies on the use of a circular (Bessel) aperture and suppresses Cherenkov losses and surface-guided light modes by enforcing a momentum transfer selection. The technique also strongly suppresses the elastic zero loss peak, making the acquisition, interpretation and signal to noise ratio of low loss spectra considerably better, especially for excitations in the first few eV of the EELS spectrum. Simulations of the low loss inelastic electron scattering probabilities demonstrate the beneficial influence of the Bessel aperture in this setup even for high accelerating voltages. The importance of selecting the optimal experimental convergence and collection angles is highlighted. The effect of the created off-axis acquisition conditions on the selection of the transitions from valence to conduction bands is discussed in detail on a simplified isotropic two band model. This opens the opportunity for deliberately selecting certain transitions by carefully tuning the microscope parameters. The suggested approach is experimentally demonstrated and provides good signal to noise ratio and interpretable band gap signals on reference samples of diamond, GaN and AlN while offering spatial resolution in the nm range. (C) 2018 Elsevier B.V. All rights reserved.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 2.843
Times cited: 7
DOI: 10.1016/J.ULTRAMIC.2018.03.021
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“Role of the carbon support on the oxygen reduction and evolution activities in LaNiO3 composite electrodes in alkaline solution”. Alexander CT, Abakumov AM, Forslund RP, Johnston KP, Stevenson KJ, ACS applied energy materials 1, 1549 (2018). http://doi.org/10.1021/ACSAEM.7B00339
Abstract: Metal-air batteries and fuel cells show a great deal of promise in advancing low-cost, high-energy-density charge storage solutions for sustainable energy applications. To improve the activities and stabilities of electrocatalysts for the critical oxygen reduction and evolution reactions (ORR and OER, respectively), a greater understanding is needed of the catalyst/carbon interactions and carbon stability. Herein, we report how LaNiO3 (LNO) supported on nitrogen-doped carbon nanotubes (N-CNT) made from a high-yield synthesis lowers the overpotential for both the OER and ORR markedly to enable a low bifunctional window of 0.81 V at only a 51 mu g cm(-2) mass loading. Furthermore, the addition of LNO to the N-CNTs improves the galvanostatic stability for the OER by almost 2 orders of magnitude. The nanoscale geometries of the perovskites and the CNTs enhance the number of metal-support and charge transfer interactions and thus the activity. We use rotating ring disk electrodes (RRDEs) combined with Tafel slope analysis and ICP-OES to quantitatively separate current contributions from the OER, carbon oxidation, and even anodic iron leaching from carbon nanotubes.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
DOI: 10.1021/ACSAEM.7B00339
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“Subtissue plasmonic heating monitored with CaF2:Nd3+,Y3+ nanothermometers in the second biological window”. Quintanilla M, Zhang Y, Liz-Marzan LM, Chemistry of materials 30, 2819 (2018). http://doi.org/10.1021/ACS.CHEMMATER.8B00806
Abstract: Measuring temperature in biological environments is an ambitious goal toward supporting medical treatment and diagnosis. Minimally invasive techniques based on optical probes require very specific properties that are difficult to combine within a single material. These include high chemical stability in aqueous environments, optical signal stability, low toxicity, high emission intensity, and, essential, working at wavelengths within the biological transparency windows so as to minimize invasiveness while maximizing penetration depth. We propose CaF2:Nd3+,Y3+ as a candidate for thermometry based on an intraband ratiometric approach, fully working within the biological windows (excitation at 808 nm; emission around 1050 nm). We optimized the thermal probes through the addition of Y3+ as a dopant to improve both emission intensity and thermal sensitivity. To define the conditions under which the proposed technique can be applied, gold nanorods were used to optically generate subtissue hot areas, while the resulting temperature variation was monitored with the new nanothermometers.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 28
DOI: 10.1021/ACS.CHEMMATER.8B00806
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“Synthesis of high-oxidation Y-Ba-Cu-O phases in superoxygenated thin films”. Zhang H, Gauquelin N, McMahon C, Hawthorn DG, Botton GA, Wei JYT, Physical review materials 2, 033803 (2018). http://doi.org/10.1103/PHYSREVMATERIALS.2.033803
Abstract: It is known that solid-state reaction in high-pressure oxygen can stabilize high-oxidation phases of Y-Ba-Cu-O superconductors in powder form. We extend this superoxygenation concept of synthesis to thin films which, due to their large surface-to-volume ratio, are more reactive thermodynamically. Epitaxial thin films of YBa2Cu3O7-delta grown by pulsed laser deposition are annealed at up to 700 atm O-2 and 900 degrees C, in conjunction with Cu enrichment by solid-state diffusion. The films show the clear formation of Y2Ba4Cu7O15-delta and Y2Ba4Cu8O16 as well as regions of YBa2Cu5O9-delta and YBa2Cu6O10-delta phases, according to scanning transmission electron microscopy, x-ray diffraction, and x-ray absorption spectroscopy. Similarly annealed YBa2Cu3O7-delta powders show no phase conversion. Our results demonstrate a route of synthesis towards discovering more complex phases of cuprates and other superconducting oxides.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 2
DOI: 10.1103/PHYSREVMATERIALS.2.033803
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“Pushing the limits of applicability of REBCO coated conductor films through fine chemical tuning and nanoengineering of inclusions”. Rizzo F, Augieri A, Kursumovic A, Bianchetti M, Opherden L, Sieger M, Huehne R, Haenisch J, Meledin A, Van Tendeloo G, MacManus-Driscoll JL, Celentano G, Nanoscale 10, 8187 (2018). http://doi.org/10.1039/C7NR09428K
Abstract: An outstanding current carrying performance (namely critical current density, J(c)) over a broad temperature range of 10-77 K for magnetic fields up to 12 T is reported for films of YBa2Cu3O7-x with Ba2Y(Nb,Ta)O-6 inclusion pinning centres (YBCO-BYNTO) and thicknesses in the range of 220-500 nm. J(c) values of 10 MA cm(-2) were measured at 30 K – 5 T and 10 K – 9 T with a corresponding maximum of the pinning force density at 10 K close to 1 TN m(-3). The system is very flexible regarding properties and microstructure tuning, and the growth window for achieving a particular microstructure is wide, which is very important for industrial processing. Hence, the dependence of J(c) on the magnetic field angle was readily controlled by fine tuning the pinning microstructure. Transmission electron microscopy (TEM) analysis highlighted that higher growth rates induce more splayed and denser BYNTO nanocolumns with a matching field as high as 5.2 T. Correspondingly, a strong peak at the B||c-axis is noticed when the density of vortices is lower than the nanocolumn density. YBCO-BYNTO is a very robust and reproducible composite system for high-current coated conductors over an extended range of magnetic fields and temperatures.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.367
Times cited: 9
DOI: 10.1039/C7NR09428K
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“Interplay between surface chemistry, precursor reactivity, and temperature determines outcome of ZnS shelling reactions on CuInS2 nanocrystals”. Berends AC, van der Stam W, Hofmann JP, Bladt E, Meeldijk JD, Bals S, de Donega CM, Chemistry of materials 30, 2400 (2018). http://doi.org/10.1021/ACS.CHEMMATER.8B00477
Abstract: ZnS shelling of I-III-VI(2 )nanocrystals (NCs) invariably leads to blue-shifts in both the absorption and photoluminescence spectra. These observations imply that the outcome of ZnS shelling reactions on I-III-VI2 colloidal NCs results from a complex interplay between several processes taking place in solution, at the surface of, and within the seed NC. However, a fundamental understanding of the factors determining the balance between these different processes is still lacking. In this work, we address this need by investigating the impact of precursor reactivity, reaction temperature, and surface chemistry (due to the washing procedure) on the outcome of ZnS shelling reactions on CuInS2 NCs using a seeded growth approach. We demonstrate that low reaction temperatures (150 degrees C) favor etching, cation exchange, and alloying regardless of the precursors used. Heteroepitaxial shell overgrowth becomes the dominant process only if reactive S- and Zn-precursors (S-ODE/OLAM and ZnI2 ) and high reaction temperatures (210 degrees C) are used, although a certain degree of heterointerfacial alloying still occurs. Remarkably, the presence of residual acetate at the surface of CIS seed NCs washed with ethanol is shown to facilitate heteroepitaxial shell overgrowth, yielding for the first time CIS/ZnS core/shell NCs displaying red-shifted absorption spectra, in agreement with the spectral shifts expected for a type-I band alignment. The insights provided by this work pave the way toward the design of improved synthesis strategies to CIS/ZnS core/shell and alloy NCs with tailored elemental distribution profiles, allowing precise tuning of the optoelectronic properties of the resulting materials.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 85
DOI: 10.1021/ACS.CHEMMATER.8B00477
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“Control of the interfacial wettability to synthesize highly dispersed PtPd nanocrystals for efficient oxygen reduction reaction”. Wei H, Hu Z-Y, Xiao Y-X, Tian G, Ying J, Van Tendeloo G, Janiak C, Yang X-Y, Su B-L, Chemistry: an Asian journal 13, 1119 (2018). http://doi.org/10.1002/ASIA.201800191
Abstract: Highly dispersed PtPd bimetallic nanocrystals with enhanced catalytic activity and stability were prepared by adjusting the interfacial wettability of the reaction solution on a commercial carbon support. This approach holds great promise for the development of high-performance and low-cost catalysts for practical applications.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.083
Times cited: 3
DOI: 10.1002/ASIA.201800191
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“Detection of amyloid fibrils in Parkinson’s disease using plasmonic chirality”. Kumar J, Eraña H, López-Martínez E, Claes N, Martín VF, Solís DM, Bals S, Cortajarena AL, Castilla J, Liz-Marzán LM, Proceedings of the National Academy of Sciences of the United States of America 115, 3225 (2018). http://doi.org/10.1073/pnas.1721690115
Abstract: Amyloid fibrils, which are closely associated with various neurodegenerative
diseases, are the final products in many protein aggregation pathways. The identification of fibrils at low concentration is, therefore, pivotal in disease diagnosis and development of therapeutic strategies. We report a methodology for the specific identification of amyloid fibrils using chiroptical effects in plasmonic nanoparticles. The formation of amyloid fibrils based on α-synuclein was probed using gold nanorods, which showed no
apparent interaction with monomeric proteins but effective adsorption onto fibril structures via noncovalent interactions. The amyloid structure drives a helical nanorod arrangement, resulting in intense optical activity at the surface plasmon resonance wavelengths. This sensing technique was successfully applied to human brain homogenates of patients affected by Parkinson’s disease,
wherein protein fibrils related to the disease were identified through chiral signals from Au nanorods in the visible and near IR, whereas healthy brain samples did not exhibit any meaningful optical activity. The technique was additionally extended to the specific detection of infectious amyloids formed by prion proteins, thereby confirming the wide potential of the technique. The intense chiral response driven by strong dipolar coupling in helical Au nanorod arrangements allowed us to detect amyloid fibrils down to nanomolar concentrations.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 9.661
Times cited: 187
DOI: 10.1073/pnas.1721690115
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“Martensite crystallography and chemistry in dual phase and fully martensitic steels”. Du C, Hoefnagels JPM, Kolling S, Geers MGD, Sietsma J, Petrov R, Bliznuk V, Koenraad PM, Schryvers D, Amin-Ahmadi B, Materials characterization 139, 411 (2018). http://doi.org/10.1016/j.matchar.2018.03.011
Abstract: Lath martensite is important in industry because it is the key strengthening component in many advanced high strength steels. The study of crystallography and chemistry of lath martensite is extensive in the literature, however, mostly based on fully martensitic steels. In this work, lath martensite in dual phase steels is investigated with a focus on the substructure identification of the martensite islands and microstructural bands using electron backscattered diffraction, and on the influence of the accompanied tempering process during industrial coating process on the distribution of alloying elements using atom probe tomography. Unlike findings for the fully martensitic steels, no martensite islands with all 24 Kurdjumov-Sachs variants have been observed. Almost all martensite islands contain only one main packet with all six variants and minor variants from the remaining three packets of the same prior austenite grain. Similarly, the martensite bands are typically composed of connected domains originating from prior austenite grains, each containing one main packets (mostly with all variants) and few separate variants. The effect of tempering at similar to 450 degrees C (due to the industrial zinc coating process) has also been investigated. The results show a strong carbon partitioning to lath boundaries and Cottrell atmospheres at dislocation core regions due to the thermal process of coating. In contrast, auto-tempering contributes to the carbon redistribution only in a limited manner. The substitutional elements are all homogenously distributed. The phase transformation process has two effects on the material: mechanically, the earlier-formed laths are larger and softer and therefore more ductile (as revealed by nanoindentation); chemically, due to the higher dislocation density inside the later-formed laths, which are generally smaller, carbon Cottrell atmospheres are predominantly observed.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 2.714
DOI: 10.1016/j.matchar.2018.03.011
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“Controlled Growth of Supported ZnO Inverted Nanopyramids with Downward Pointing Tips”. Barreca D, Carraro G, Maccato C, Altantzis T, Kaunisto K, Gasparotto A, Crystal growth &, design , acs.cgd.8b00198 (2018). http://doi.org/10.1021/acs.cgd.8b00198
Abstract: High purity porous ZnO nanopyramids with controllable properties are grown on their tips on
Si(100) substrates by means of a catalyst-free vapor phase deposition route in a wet oxygen
reaction environment. The system degree of preferential [001] orientation, as well as
nanopyramid size, geometrical shape and density distribution, can be finely tuned by varying the
growth temperature between 300 and 400°C, whereas higher temperatures lead to more compact
systems with a three-dimensional (3D) morphology. A growth mechanism of the obtained ZnO
nanostructures based on a self-catalytic vapor-solid (VS) mode is proposed, in order to explain
the evolution of nanostructure morphologies as a function of the adopted process conditions. The
results obtained by a thorough chemico-physical characterization enable to get an improved
control over the properties of ZnO nanopyramids grown by this technique. Taken together, they
are of noticeable importance not only for fundamental research on ZnO nanomaterials with
controlled nano-organization, but also to tailor ZnO functionalities in view of various potential
applications.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.055
Times cited: 6
DOI: 10.1021/acs.cgd.8b00198
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“Nanoscale Characterization of Growth of Secondary Phases in Off-Stoichiometric CZTS Thin Films”. Vishwakarma M, Karakulina OM, Abakumov AM, Hadermann J, Mehta BR, Journal of nanoscience and nanotechnology 18, 1688 (2018). http://doi.org/10.1166/jnn.2018.14261
Abstract: The presence of secondary phases is one of the main issues that hinder the growth of pure kesterite Cu2ZnSnS4 (CZTS) based thin films with suitable electronic and junction properties for efficient solar cell devices. In this work, CZTS thin films with varied Zn and Sn content have been prepared by RF-power controlled co-sputtering deposition using Cu, ZnS and SnS targets and a subsequent sulphurization step. Detailed TEM investigations show that the film shows a layered structure with the majority of the top layer being the kesterite phase. Depending on the initial thin film composition, either about ~1 μm Cu-rich and Zn-poor kesterite or stoichiometric CZTS is formed as top layer. X-ray diffraction, Raman spectroscopy and transmission electron microscopy reveal the presence of Cu2−x S, ZnS and SnO2 minor secondary phases in the form of nanoinclusions or nanoparticles or intermediate layers.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 1.483
DOI: 10.1166/jnn.2018.14261
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“Blue-edge slow photons promoting visible-light hydrogen production on gradient ternary 3DOM TiO 2 -Au-CdS photonic crystals”. Zhao H, Hu Z, Liu J, Li Y, Wu M, Van Tendeloo G, Su B-L, Nano energy 47, 266 (2018). http://doi.org/10.1016/j.nanoen.2018.02.052
Abstract: The slow photon effect, a structural effect of photonic crystal photocatalyst, is very efficient in the enhancement of photocatalytic reactions. However, slow photons in powdered photonic crystal photocatalyst have rarely been discussed because they are usually randomly oriented when the photocatalytic reaction happens in solution under constant stirring. In this work, for the first time we design a gradient ternary TiO2-Au-CdS photonic crystal based on three-dimensionally ordered macroporous (3DOM) TiO2 as skeleton, Au as electron transfer medium and CdS as active material for photocatalytic H2 production under visible-light. As a result, this gradient ternary photocatalyst is favorable to simultaneously enhance light absorption, extend the light responsive region and reduce the recombination rate of the charge carriers. In particular, we found that slow photons at blue-edge exhibit much higher photocatalytic activity than that at red-edge. The photonic crystal photocatalyst with a macropore size of 250 nm exhibits the highest visible-light H2 production rate of 3.50 mmolh⁻¹g⁻¹ due to the slow photon energy at the blue-edge to significantly enhance the incident photons utilization. This work verifies that slow photons at the blue-edge can largely enhance light harvesting and sheds a light on designing the powdered photonic crystal photocatalyst to promote the photocatalytic H2 production via slow photon effect.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 12.343
Times cited: 33
DOI: 10.1016/j.nanoen.2018.02.052
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“Surface passivation of CIGS solar cells using gallium oxide”. Garud S, Gampa N, Allen TG, Kotipalli R, Flandre D, Batuk M, Hadermann J, Meuris M, Poortmans J, Smets A, Vermang B, Physica status solidi : A : applications and materials science 215, 1700826 (2018). http://doi.org/10.1002/PSSA.201700826
Abstract: This work proposes gallium oxide grown by plasma-enhanced atomic layer deposition, as a surface passivation material at the CdS buffer interface of Cu(In,Ga)Se-2 (CIGS) solar cells. In preliminary experiments, a metal-insulator-semiconductor (MIS) structure is used to compare aluminium oxide, gallium oxide, and hafnium oxide as passivation layers at the CIGS-CdS interface. The findings suggest that gallium oxide on CIGS may show a density of positive charges and qualitatively, the least interface trap density. Subsequent solar cell results with an estimated 0.5nm passivation layer show an substantial absolute improvement of 56mV in open-circuit voltage (V-OC), 1mAcm(-2) in short-circuit current density (J(SC)), and 2.6% in overall efficiency as compared to a reference (with the reference showing 8.5% under AM 1.5G).
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.775
Times cited: 8
DOI: 10.1002/PSSA.201700826
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“Optical enhancement of a printed organic tandem solar cell using diffractive nanostructures”. Mayer JA, Offermans T, Chrapa M, Pfannmöller M, Bals S, Ferrini R, Nisato G, Optics express 26, A240 (2018). http://doi.org/10.1364/OE.26.00A240
Abstract: Solution processable organic tandem solar cells offer a promising approach to achieve cost-effective, lightweight and flexible photovoltaics. In order to further enhance the efficiency of optimized organic tandem cells, diffractive light-management nanostructures were designed for an optimal redistribution of the light as function of both wavelength and propagation angles in both sub-cells. As the fabrication of these optical structures is compatible with roll-to-roll production techniques such as hot-embossing or UV NIL imprinting, they present an optimal cost-effective solution for printed photovoltaics. Tandem cells with power conversion efficiencies of 8-10% were fabricated in the ambient atmosphere by doctor blade coating, selected to approximate the conditions during roll-to-roll manufacturing. Application of the light management structure onto an 8.7% efficient encapsulated tandem cell boosted the conversion efficiency of the cell to 9.5%. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.307
Times cited: 9
DOI: 10.1364/OE.26.00A240
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“Inkjet printing multideposited YBCO on CGO/LMO/MgO/Y2O3/Al2O3/Hastelloy tape for 2G-coated conductors”. Roxana Vlad V, Bartolome E, Vilardell M, Calleja A, Meledin A, Obradors X, Puig T, Ricart S, Van Tendeloo G, Usoskin A, Lee S, Petrykin V, Molodyk A, IEEE transactions on applied superconductivity 28, 6601805 (2018). http://doi.org/10.1109/TASC.2018.2808403
Abstract: We present the preparation of a new architecture of coated conductor by Inkjet printing of low fluorine YBa2Cu3O7-x (YBCO) on top of SuperOx tape: CGO/LMO/IBAD-MgO/Y2O3/Al-2 O-3/Hastelloy. A five-layered multideposited, 475-nm-thick YBCO film was structurally and magnetically characterized. A good texture was achieved using this combination of buffer layers, requiring only a 30-nm-thin ion-beam-assisted deposition (IBAD)-MgO layer. The LF-YBCO CC reaches self-field critical current density values of J(c)(GB) similar to NJ 15.9 MA/cm(2) (5 K), similar to 1.23 MA/cm(2) (77 K) corresponding to an I-c (77 K) = 58.4 A/cm-width. Inkjet printing offers a flexible and cost effective method for YBCO deposition, allowing patterning of structures.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.288
Times cited: 2
DOI: 10.1109/TASC.2018.2808403
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“Reversible Clustering of Gold Nanoparticles under Confinement”. Sánchez-Iglesias A, Claes N, Solís DM, Taboada JM, Bals S, Liz-Marzán LM, Grzelczak M, Angewandte Chemie: international edition in English 57, 3183 (2018). http://doi.org/10.1002/anie.201800736
Abstract: A limiting factor of solvent-induced nanoparticle self-assembly is the need for constant sample dilution in assembly/disassembly cycles. Changes in the nanoparticle concentration alter the kinetics of the subsequent assembly process, limiting optical signal recovery. Herein, we show that upon confining hydrophobic nanoparticles in permeable silica nanocapsules, the number of nanoparticles participating in cyclic aggregation remains constant despite bulk changes in solution, leading to highly reproducible plasmon band shifts at different solvent compositions.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 11.994
Times cited: 53
DOI: 10.1002/anie.201800736
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“Controlling the formation and stability of ultra-thin nickel silicides : an alloying strategy for preventing agglomeration”. Geenen FA, van Stiphout K, Nanakoudis A, Bals S, Vantomme A, Jordan-Sweet J, Lavoie C, Detavernier C, Journal of applied physics 123, 075303 (2018). http://doi.org/10.1063/1.5009641
Abstract: The electrical contact of the source and drain regions in state-of-the-art CMOS transistors is nowadays facilitated through NiSi, which is often alloyed with Pt in order to avoid morphological agglomeration of the silicide film. However, the solid-state reaction between as-deposited Ni and the Si substrate exhibits a peculiar change for as-deposited Ni films thinner than a critical thickness of t(c) = 5 nm. Whereas thicker films form polycrystalline NiSi upon annealing above 450 degrees C, thinner films form epitaxial NiSi2 films that exhibit a high resistance toward agglomeration. For industrial applications, it is therefore of utmost importance to assess the critical thickness with high certainty and find novel methodologies to either increase or decrease its value, depending on the aimed silicide formation. This paper investigates Ni films between 0 and 15 nm initial thickness by use of “thickness gradients,” which provide semi-continuous information on silicide formation and stability as a function of as-deposited layer thickness. The alloying of these Ni layers with 10% Al, Co, Ge, Pd, or Pt renders a significant change in the phase sequence as a function of thickness and dependent on the alloying element. The addition of these ternary impurities therefore changes the critical thickness t(c). The results are discussed in the framework of classical nucleation theory. Published by AIP Publishing.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.068
Times cited: 23
DOI: 10.1063/1.5009641
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“Imaging heterogeneously distributed photo-active traps in perovskite single crystals”. Yuan H, Debroye E, Bladt E, Lu G, Keshavarz M, Janssen KPF, Roeffaers MBJ, Bals S, Sargent EH, Hofkens J, Advanced materials 30, 1705494 (2018). http://doi.org/10.1002/ADMA.201705494
Abstract: Organic-inorganic halide perovskites (OIHPs) have demonstrated outstanding energy conversion efficiency in solar cells and light-emitting devices. In spite of intensive developments in both materials and devices, electronic traps and defects that significantly affect their device properties remain under-investigated. Particularly, it remains challenging to identify and to resolve traps individually at the nanoscopic scale. Here, photo-active traps (PATs) are mapped over OIHP nanocrystal morphology of different crystallinity by means of correlative optical differential super-resolution localization microscopy (Delta-SRLM) and electron microscopy. Stochastic and monolithic photoluminescence intermittency due to individual PATs is observed on monocrystalline and polycrystalline OIHP nanocrystals. Delta-SRLM reveals a heterogeneous PAT distribution across nanocrystals and determines the PAT density to be 1.3 x 10(14) and 8 x 10(13) cm(-3) for polycrystalline and for monocrystalline nanocrystals, respectively. The higher PAT density in polycrystalline nanocrystals is likely related to an increased defect density. Moreover, monocrystalline nanocrystals that are prepared in an oxygen and moisture-free environment show a similar PAT density as that prepared at ambient conditions, excluding oxygen or moisture as chief causes of PATs. Hence, it is conduded that the PATs come from inherent structural defects in the material, which suggests that the PAT density can be reduced by improving crystalline quality of the material.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 19.791
Times cited: 29
DOI: 10.1002/ADMA.201705494
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“Carbon Incorporation and Anion Dynamics as Synergistic Drivers for Ultrafast Diffusion in Superionic LiCB11H12 and NaCB11H12”. Dimitrievska M, Shea P, Kweon KE, Bercx M, Varley JB, Tang WS, Skripov AV, Stavila V, Udovic TJ, Wood BC, Advanced energy materials 8, 1703422 (2018). http://doi.org/10.1002/AENM.201703422
Abstract: The disordered phases of LiCB11H12 and NaCB11H12 possess superb superionic conductivities that make them suitable as solid electrolytes. In these materials, cation diffusion correlates with high orientational mobilities of the CB11H12- anions; however, the precise relationship has yet to be demonstrated. In this work, ab initio molecular dynamics and quasielastic neutron scattering are combined to probe anion reorientations and their mechanistic connection to cation mobility over a range of timescales and temperatures. It is found that anions do not rotate freely, but rather transition rapidly between orientations defined by the cation sublattice symmetry. The symmetry-breaking carbon atom in CB11H12- also plays a critical role by perturbing the energy landscape along the instantaneous orientation of the anion dipole, which couples fluctuations in the cation probability density directly to the anion motion. Anion reorientation rates exceed 3 x 10(10) s(-1), suggesting the underlying energy landscape fluctuates dynamically on diffusion-relevant timescales. Furthermore, carbon is found to modify the orientational preferences of the anions and aid rotational mobility, creating additional symmetry incompatibilities that inhibit ordering. The results suggest that synergy between the anion reorientational dynamics and the carbon-modified cation-anion interaction accounts for the higher ionic conductivity in CB11H12- salts compared with B12H122-.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 16.721
Times cited: 20
DOI: 10.1002/AENM.201703422
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“Influence of artificial pinning centers on structural and superconducting properties of thick YBCO films on ABAD-YSZ templates”. Pahlke P, Sieger M, Ottolinger R, Lao M, Eisterer M, Meledin A, Van Tendeloo G, Haenisch J, Holzapfel B, Schultz L, Nielsch K, Huehne R, Superconductor science and technology 31, 044007 (2018). http://doi.org/10.1088/1361-6668/AAAFBE
Abstract: Recent efforts in the development of YBa2Cu3O7-x (YBCO) coated conductors are devoted to the increase of the critical current I-c in magnetic fields. This is typically realized by growing thicker YBCO layers as well as by the incorporation of artificial pinning centers. We studied the growth of doped YBCO layers with a thickness of up to 7 mu m using pulsed laser deposition with a growth rate of about 1.2 nm s(-1). Industrially fabricated ion-beam textured YSZ templates based on metal tapes were used as substrates for this study. The incorporation of BaHfO3 (BHO) or Ba2Y(Nb0.5Ta0.5)O-6 (BYNTO) secondary phase additions leads to a denser microstructure compared to undoped films. A purely c-axis-oriented YBCO growth is preserved up to a thickness of about 4 mu m, whereas misoriented texture components were observed in thicker films. The critical temperature is slightly reduced compared to undoped films and independent of film thickness. The critical current density J(c) of the BHO- and BYNTO-doped YBCO layers is lower at 77 K and self-field compared to pure YBCO layers; however, I-c increases up to a thickness of 5 mu m. A comparison between films with a thickness of 1.3 mu m revealed that the anisotropy of the critical current density J(c)(theta) strongly depends on the incorporated pinning centers. Whereas BHO nanorods lead to a strong B vertical bar vertical bar c-axis peak, the overall anisotropy is significantly reduced by the incorporation of BYNTO forming a mixture of short c-axis-oriented nanorods and small (a-b)-oriented platelets. As a result, the J(c) values of the doped films outperform the undoped samples at higher fields and lower temperatures for most magnetic field directions.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.878
Times cited: 9
DOI: 10.1088/1361-6668/AAAFBE
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“Hierarchical CdS/m-TiO 2 /G ternary photocatalyst for highly active visible light-induced hydrogen production from water splitting with high stability”. Lu Y, Cheng X, Tian G, Zhao H, He L, Hu J, Wu S-M, Dong Y, Chang G-G, Lenaerts S, Siffert S, Van Tendeloo G, Li Z-F, Xu L-L, Yang X-Y, Su B-L, Nano energy 47, 8 (2018). http://doi.org/10.1016/j.nanoen.2018.02.021
Abstract: Hierarchical semiconductors are the most important photocatalysts, especially for visible light-induced hydrogen production from water splitting. We demonstrate herein a hierarchical electrostatic assembly approach to hierarchical CdS/m-TiO2/G ternary photocatalyst, which exhibits high photoactivity and excellent photostability (more than twice the activity of pure CdS while 82% of initial photoactivity remained after 15 recycles during 80 h irradiation). The ternary nanojunction effect of the photocatalyst has been investigated from orbitals hybrid, bonding energy to atom-stress distortion and nano-interface fusion. And a coherent separation mechanism of charge carriers in the ternary system has been proposed at an atomic/nanoscale. This work offers a promising way to inhibit the photocorrosion of CdS and, more importantly, provide new insights for the design of ternary nanostructured photocatalysts with an ideal heterojunction.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Sustainable Energy, Air and Water Technology (DuEL)
Impact Factor: 12.343
Times cited: 58
DOI: 10.1016/j.nanoen.2018.02.021
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