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“Engineering Structural Diversity in Gold Nanocrystals by Ligand-Mediated Interface Control”. Wang Y, Sentosun K, Li A, Coronado-Puchau M, Sánchez-Iglesias A, Li S, Su X, Bals S, Liz-Marzán LM, Chemistry of materials 27, 8032 (2015). http://doi.org/10.1021/acs.chemmater.5b03600
Abstract: Surface and interface control is fundamentally important for crystal growth engineering, catalysis, surface enhanced spectroscopies, and self-assembly, among other processes and applications. Understanding the role of ligands in regulating surface properties of plasmonic metal nanocrystals during growth has received considerable attention. However, the underlying mechanisms and the diverse functionalities of ligands are yet to be fully addressed. In this contribution,
we report a systematic study of ligand-mediated interface control in seeded growth of gold nanocrystals, leading to diverse and exotic nanostructures with an improved surface enhanced Raman scattering (SERS) activity. Three dimensional transmission electron microscopy (3D TEM) revealed an intriguing gold shell growth process mediated by the bifunctional ligand 1,4-benzenedithiol (BDT), which leads to a unique crystal growth mechanism as compared to other ligands, and subsequently to the concept of interfacial energy control mechanism. Volmer-Weber growth mode was proposed to be responsible for BDT-mediated seeded growth, favoring the strongest interfacial energy and generating an asymmetric island growth pathway with internal crevices/gaps. This additionally favors incorporation of BDT at the plasmonic nanogaps, thereby generating strong SERS activity with a maximum efficiency for a core-semishell configuration obtained along seeded growth. Numerical modeling was used to explain this observation. Interestingly, the same strategy can be used to engineer the structural diversity of this system, by using gold nanoparticle seeds with various sizes and shapes, and varying the [Au3+]/[Au0] ratio. This rendered a series of diverse and exotic plasmonic nanohybrids such as semishell-coated gold nanorods, with embedded Raman-active tags and Janus surface with distinct surface functionalities.
These would greatly enrich the plasmonic nanostructure toolbox for various studies and applications such as anisotropic nanocrystal engineering, SERS, and high-resolution Raman bioimaging or nanoantenna devices.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 18
DOI: 10.1021/acs.chemmater.5b03600
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“A La2−xGdxZr2O7layer deposited by chemical solution: a promising seed layer for the fabrication of high Jcand low cost coated conductors”. Muguerra H, Pescheux A-C, Meledin A, Van Tendeloo G, Soubeyroux J-L, Journal of materials chemistry C : materials for optical and electronic devices 3, 11766 (2015). http://doi.org/10.1039/C5TC03365A
Abstract: We deposited La2-xGdxZr2O7 seed layers by a chemical solution method on a Ni-5%W substrate to study the influence of these layers on the growth process of a 60 nm-thick La2Zr2O7 layer. We measured the performances of these new buffer layers integrated in a coated conductor with a 300 nm-thick Y0.5Gd0.5Ba2Cu3O7-x layer. For the seed layers{,} we considered two different gadolinium contents (x = 0.2 and x = 0.8) and three different thicknesses for these compositions (20 nm{,} 40 nm{,} and 60 nm). The most promising buffer layer stacks are those with 20 nm of the La1.8Gd0.2Zr2O7 layer or La1.2Gd0.8Zr2O7. Indeed the La2-xGdxZr2O7/La2Zr2O7 films are highly textured{,} similar to a 100 nm-thick La2Zr2O7 layer{,} but their roughness is four times lower. Moreover they contain less and smaller pores in the seed layer than a pure La2Zr2O7 layer. The surface of La2Zr2O7 is also homogenous and crystalline with an orientation deviation from the ideal ?011? (100) direction below 10[degree]. With the 20 nm La2-xGdxZr2O7 seed layers we obtain in the coated conductors an efficiently textured transfer with no gradual degradation from the substrate throughout the superconducting layer. The highest Tc and Jc values are achieved with the La1.8Gd0.2Zr2O7 layer and are{,} respectively{,} 91 K and 1.4 MA cm-2. This trend seems to be due to an improvement of the surface quality of the Ni5%W substrate by the addition of a thin seed layer. Our results offer the potential of the La2-xGdxZr2O7 seed layers as promising alternatives for the classic Ni-5%W/LZO/CeO2/YBCO architectures.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.256
Times cited: 4
DOI: 10.1039/C5TC03365A
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“Combination of HAADF-STEM and ADF-STEM Tomography for Core-Shell Hybrid Materials”. Sentosun K, Sanz Ortiz MN, Batenburg KJ, Liz-Marzán LM, Bals S, Particle and particle systems characterization 32, 1063 (2015). http://doi.org/10.1002/ppsc.201500097
Abstract: Characterization of core-shell type nanoparticles in 3D by transmission electron microscopy (TEM) can be very challenging. Especially when both heavy and light elements co-exist within the same nanostructure, artefacts in the 3D reconstruction are often present. A representative example would be a particle comprising an anisotropic metallic (Au) nanoparticle coated with a (mesoporous) silica shell. To obtain a reliable 3D characterization of such an object, we propose a dose-efficient strategy to simultaneously acquire high angle annular dark field scanning TEM and annular dark field tilt series for tomography. The 3D reconstruction is further improved by applying an advanced masking and interpolation approach to the acquired data. This new methodology enables us to obtain high quality reconstructions from which also quantitative information can be extracted. This approach is broadly applicable to investigate hybrid core-shell materials.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Vision lab
Impact Factor: 4.474
Times cited: 13
DOI: 10.1002/ppsc.201500097
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“Epitaxial YBa2Cu3O7−xnanocomposite thin films from colloidal solutions”. Cayado P, De Keukeleere K, Garzón A, Perez-Mirabet L, Meledin A, De Roo J, Vallés F, Mundet B, Rijckaert H, Pollefeyt G, Coll M, Ricart S, Palau A, Gázquez J, Ros J, Van Tendeloo G, Van Driessche I, Puig T, Obradors X, Superconductor science and technology 28, 124007 (2015). http://doi.org/10.1088/0953-2048/28/12/124007
Abstract: A methodology of general validity to prepare epitaxial nanocomposite films based on the use of colloidal solutions containing different crystalline preformed oxide nanoparticles ( ex situ nanocomposites) is reported. The trifluoroacetate (TFA) metal–organic chemical solution deposition route is used with alcoholic solvents to grow epitaxial YBa 2 Cu 3 O 7 (YBCO) films. For this reason stabilizing oxide nanoparticles in polar solvents is a challenging goal. We have used scalable nanoparticle synthetic methodologies such as thermal and microwave-assisted solvothermal techniques to prepare CeO 2 and ZrO 2 nanoparticles. We show that stable and homogeneous colloidal solutions with these nanoparticles can be reached using benzyl alcohol, triethyleneglycol, nonanoic acid, trifluoroacetic acid or decanoic acid as protecting ligands, thereby allowing subsequent mixing with alcoholic TFA solutions. An elaborate YBCO film growth analysis of these nanocomposites allows the identification of the different relevant growth phenomena, e.g. nanoparticles pushing towards the film surface, nanoparticle reactivity, coarsening and nanoparticle accumulation at the substrate interface. Upon mitigation of these effects, YBCO nanocomposite films with high self-field critical currents ( J c ∼ 3–4 MA cm −2 at 77 K) were reached, indicating no current limitation effects associated with epitaxy perturbation, while smoothed magnetic field dependences of the critical currents at high magnetic fields and decreased effective anisotropic pinning behavior confirm the effectiveness of the novel developed approach to enhance vortex pinning. In conclusion, a novel low cost solution-derived route to high current nanocomposite superconducting films and coated conductors has been developed with very promising features.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.878
Times cited: 32
DOI: 10.1088/0953-2048/28/12/124007
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“Advanced electron crystallography through model-based imaging”. Van Aert S, De Backer A, Martinez GT, den Dekker AJ, Van Dyck D, Bals S, Van Tendeloo G, IUCrJ 3, 71 (2016). http://doi.org/10.1107/S2052252515019727
Abstract: The increasing need for precise determination of the atomic arrangement of non-periodic structures in materials design and the control of nanostructures explains the growing interest in quantitative transmission electron microscopy. The aim is to extract precise and accurate numbers for unknown structure parameters including atomic positions, chemical concentrations and atomic numbers. For this purpose, statistical parameter estimation theory has been shown to provide reliable results. In this theory, observations are considered purely as data planes, from which structure parameters have to be determined using a parametric model describing the images. As such, the positions of atom columns can be measured with a precision of the order of a few picometres, even though the resolution of the electron microscope is still one or two orders of magnitude larger. Moreover, small differences in average atomic number, which cannot be distinguished visually, can be quantified using high-angle annular dark-field scanning transmission electron microscopy images. In addition, this theory allows one to measure compositional changes at interfaces, to count atoms with single-atom sensitivity, and to reconstruct atomic structures in three dimensions. This feature article brings the reader up to date, summarizing the underlying theory and highlighting some of the recent applications of quantitative model-based transmisson electron microscopy.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Vision lab; Engineering Management (ENM)
Impact Factor: 5.793
Times cited: 30
DOI: 10.1107/S2052252515019727
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“Efficient Chemical Modification of Carbon Nanotubes with Metallacarboranes”. Cabana L, Gonzalez-Campo A, Ke X, Van Tendeloo G, Nunez R, Tobias G, Chemistry: a European journal 21, 16792 (2015). http://doi.org/10.1002/chem.201503096
Abstract: As-produced single-walled carbon nanotubes (SWCNTs) tend to aggregate in bundles due to pi-pi interactions. Several approaches are nowadays available to debundle, at least partially, the nanotubes through surface modification by both covalent and noncovalent approaches. Herein, we explore different strategies to afford an efficient covalent functionalization of SWCNTs with cobaltabisdicarbollide anions. Aberration-corrected HRTEM analysis reveals the presence of metallacarboranes along the walls of the SWCNTs. This new family of materials presents an outstanding water dispersibility that facilitates its processability for potential applications.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.317
Times cited: 5
DOI: 10.1002/chem.201503096
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“Surface-Facet-Dependent Phonon Deformation Potential in Individual Strained Topological Insulator Bi2Se3 Nanoribbons”. Yan Y, Zhou X, Jin H, Li C-Z, Ke X, Van Tendeloo G, Liu K, Yu D, Dressel M, Liao Z-M, ACS nano 9, 10244 (2015). http://doi.org/10.1021/acsnano.5b04057
Abstract: Strain is an important method to tune the properties of topological insulators. For example, compressive strain can induce superconductivity in Bi2Se3 bulk material. Topological insulator nanostructures are the superior candidates to utilize the unique surface states due to the large surface to volume ratio. Therefore, it is highly desirable to monitor the local strain effects in individual topological insulator nanostructures. Here, we report the systematical micro-Raman spectra of single strained Bi2Se3 nanoribbons with different thicknesses and different surface facets, where four optical modes are resolved in both Stokes and anti-Stokes Raman spectral lines. A striking anisotropy of the strain dependence is observed in the phonon frequency of strained Bi2Se3 nanoribbons grown along the ⟨112̅0⟩ direction. The frequencies of the in-plane Eg2 and out-of-plane A1g1 modes exhibit a nearly linear blue-shift against bending strain when the nanoribbon is bent along the ⟨112̅0⟩ direction with the curved {0001} surface. In this case, the phonon deformation potential of the Eg2 phonon for 100 nm-thick Bi2Se3 nanoribbon is up to 0.94 cm–1/%, which is twice of that in Bi2Se3 bulk material (0.52 cm–1/%). Our results may be valuable for the strain modulation of individual topological insulator nanostructures.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 13.942
Times cited: 14
DOI: 10.1021/acsnano.5b04057
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“Hematite iron oxide nanorod patterning inside COK-12 mesochannels as an efficient visible light photocatalyst”. Wee LH, Meledina M, Turner S, Custers K, Kerkhofs S, Van Tendeloo G, Martens JA, Journal of materials chemistry A : materials for energy and sustainability 3, 19884 (2015). http://doi.org/10.1039/C5TA05075H
Abstract: The uniform dispersion of functional oxide nanoparticles on the walls of ordered mesoporous silica to tailor optical, electronic, and magnetic properties for biomedical and environmental applications is a scientific challenge. Here, we demonstrate homogeneous confined growth of 5 nanometer-sized hematite iron oxide (α-Fe2O3) inside mesochannels of ordered mesoporous COK-12 nanoplates. The three-dimensional inclusion of the α-Fe2O3 nanorods in COK-12 particles is studied using high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray (EDX) spectroscopy and electron tomography. High resolution imaging and EDX spectroscopy provide information about the particle size, shape and crystal phase of the loaded α-Fe2O3 material, while electron tomography provides detailed information on the spreading of the nanorods throughout the COK-12 host. This nanocomposite material, having a semiconductor band gap energy of 2.40 eV according to diffuse reflectance spectroscopy, demonstrates an improved visible light photocatalytic degradation activity with rhodamine 6G and 1-adamantanol model compounds.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 8.867
Times cited: 9
DOI: 10.1039/C5TA05075H
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“Damage evaluation in graphene underlying atomic layer deposition dielectrics”. Tang X, Reckinger N, Poncelet O, Louette P, Urena F, Idrissi H, Turner S, Cabosart D, Colomer J-F, Raskin J-P, Hackens B, Francis LA, Scientific reports 5, 13523 (2015). http://doi.org/10.1038/srep13523
Abstract: Based on micro-Raman spectroscopy (muRS) and X-ray photoelectron spectroscopy (XPS), we study the structural damage incurred in monolayer (1L) and few-layer (FL) graphene subjected to atomic-layer deposition of HfO2 and Al2O3 upon different oxygen plasma power levels. We evaluate the damage level and the influence of the HfO2 thickness on graphene. The results indicate that in the case of Al2O3/graphene, whether 1L or FL graphene is strongly damaged under our process conditions. For the case of HfO2/graphene, muRS analysis clearly shows that FL graphene is less disordered than 1L graphene. In addition, the damage levels in FL graphene decrease with the number of layers. Moreover, the FL graphene damage is inversely proportional to the thickness of HfO2 film. Particularly, the bottom layer of twisted bilayer (t-2L) has the salient features of 1L graphene. Therefore, FL graphene allows for controlling/limiting the degree of defect during the PE-ALD HfO2 of dielectrics and could be a good starting material for building field effect transistors, sensors, touch screens and solar cells. Besides, the formation of Hf-C bonds may favor growing high-quality and uniform-coverage dielectric. HfO2 could be a suitable high-K gate dielectric with a scaling capability down to sub-5-nm for graphene-based transistors.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 4.259
Times cited: 18
DOI: 10.1038/srep13523
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“Fe2O3-TiO2Nano-heterostructure Photoanodes for Highly Efficient Solar Water Oxidation”. Barreca D, Carraro G, Gasparotto A, Maccato C, Warwick MEA, Kaunisto K, Sada C, Turner S, Gönüllü, Y, Ruoko T-P, Borgese L, Bontempi E, Van Tendeloo G, Lemmetyinen H, Mathur S, Advanced Materials Interfaces 2, 1500313 (2015). http://doi.org/10.1002/admi.201500313
Abstract: Harnessing solar energy for the production of clean hydrogen by photoelectrochemical water splitting represents a very attractive, but challenging approach for sustainable energy generation. In this regard, the fabrication of Fe2O3–TiO2 photoanodes is reported, showing attractive performances [≈2.0 mA cm−2 at 1.23 V vs. the reversible hydrogen electrode in 1 M NaOH] under simulated one-sun illumination. This goal, corresponding to a tenfold photoactivity enhancement with respect to bare Fe2O3, is achieved by atomic layer deposition of TiO2 over hematite (α-Fe2O3) nanostructures fabricated by plasma enhanced-chemical vapor deposition and final annealing at 650 °C. The adopted approach enables an intimate Fe2O3–TiO2 coupling, resulting in an electronic interplay at the Fe2O3/TiO2 interface. The reasons for the photocurrent enhancement determined by TiO2 overlayers with increasing thickness are unraveled by a detailed chemico-physical investigation, as well as by the study of photogenerated charge carrier dynamics. Transient absorption spectroscopy shows that the increased photoelectrochemical response of heterostructured photoanodes compared to bare hematite is due to an enhanced separation of photogenerated charge carriers and more favorable hole dynamics for water oxidation. The stable responses obtained even in simulated seawater provides a feasible route in view of the eventual large-scale generation of renewable energy.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4.279
Times cited: 56
DOI: 10.1002/admi.201500313
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“Pyramid-Shaped Wurtzite CdSe Nanocrystals with Inverted Polarity”. Ghosh S, Gaspari R, Bertoni G, Spadaro MC, Prato M, Turner S, Cavalli A, Manna L, Brescia R, ACS nano 9, 8537 (2015). http://doi.org/10.1021/acsnano.5b03636
Abstract: We report on pyramid-shaped wurtzite cadmium selenide (CdSe) nanocrystals (NCs), synthesized by hot injection in the presence of chloride ions as shape-directing agents, exhibiting reversed crystal polarity compared to former reports. Advanced transmission electron microscopy (TEM) techniques (image-corrected high-resolution TEM with exit wave reconstruction and probe-corrected high-angle annular dark field-scanning TEM) unequivocally indicate that the triangular base of the pyramids is the polar (0001) facet and their apex points toward the [0001] direction. Density functional theory calculations, based on a simple model of binding of Cl(-) ions to surface Cd atoms, support the experimentally evident higher thermodynamic stability of the (0001) facet over the (0001) one conferred by Cl(-) ions. The relative stability of the two polar facets of wurtzite CdSe is reversed compared to previous experimental and computational studies on Cd chalcogenide NCs, in which no Cl-based chemicals were deliberately used in the synthesis or no Cl(-) ions were considered in the binding models. Self-assembly of these pyramids in a peculiar clover-like geometry, triggered by the addition of oleic acid, suggests that the basal (polar) facet has a density and perhaps type of ligands significantly different from the other three facets, since the pyramids interact with each other exclusively via their lateral facets. A superstructure, however with no long-range order, is observed for clovers with their (0001) facets roughly facing each other. The CdSe pyramids were also exploited as seeds for CdS pods growth, and the peculiar shape of the derived branched nanostructures clearly arises from the inverted polarity of the seeds.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 13.942
Times cited: 16
DOI: 10.1021/acsnano.5b03636
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“Electron Microscopy of Probability Currents at Atomic Resolution”. Lubk A, Béché, A, Verbeeck J, Physical review letters 115, 176101 (2015). http://doi.org/10.1103/PhysRevLett.115.176101
Abstract: Atomic resolution transmission electron microscopy records the spatially resolved scattered electron density to infer positions, density, and species of atoms. These data are indispensable for studying the relation between structure and properties in solids. Here, we show how this signal can be augmented by the lateral probability current of the scattered electrons in the object plane at similar resolutions and fields of view. The currents are reconstructed from a series of three atomic resolution TEM images recorded under a slight difference of perpendicular line foci. The technique does not rely on the coherence of the electron beam and can be used to reveal electric, magnetic, and strain fields with incoherent electron beams as well as correlations in inelastic transitions, such as electron magnetic chiral dichroism.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 8.462
Times cited: 12
DOI: 10.1103/PhysRevLett.115.176101
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“Chemical stability of YBiO3 buffer layers for implementation in YBa2Cu3O7-&delta, coated conductors”. Pollefeyt G, Meledin A, Pop C, Ricart S, Hühne R, Van Tendeloo G, Van Driessche I, Acta materialia 100, 224 (2015). http://doi.org/10.1016/j.actamat.2015.08.023
Abstract: In this work, the chemical and microstructural stability of YBiO3 buffer layers during the growth of YBa2Cu3O7-δ (YBCO) was studied. The superconducting YBCO films were deposited via both Pulsed Laser Deposition as well as Chemical Solution Deposition. Although excellent superconducting properties are obtained in both cases, self-field critical current densities of 3.6 and 1.2 MA/cm2 respectively, chemical instability of the YBiO3 buffer layer is observed. An elaborate transmission electron microscopy study showed that in the case of vacuum deposited YBCO, the YBiO3 becomes unstable and Bi2O3 sublimates out of the architecture. Due to this structural instability, an intermediate Y2O3 layer is obtained which maintains it microstructural orientation relation with the substrate and acts as growth template for YBCO. For chemical solution deposited YBCO, reaction of YBCO with the YBiO3 buffer layer is observed, leading to large grains of YBa2BiO6 which are pushed towards the surface of the films and strongly reduce the superconducting properties. Upon using high growth temperatures for the superconducting layer, these secondary phases decompose, which subsequently leads to Bi2O3 sublimation and a textured YBCO film which directly nucleated onto the LaAlO3 single crystal substrate. Hence, this electron microscopy study indicates that bismuth-based buffer layers systems are not suitable for implementation in coated conductors.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 5.301
DOI: 10.1016/j.actamat.2015.08.023
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“Novel 3DOM BiVO4/TiO2nanocomposites for highly enhanced photocatalytic activity”. Zalfani M, van der Schueren B, Hu Z-Y, Rooke JC, Bourguiga R, Wu M, Li Y, Van Tendeloo G, Su B-L, Journal of materials chemistry A : materials for energy and sustainability 3, 21244 (2015). http://doi.org/10.1039/C5TA00783F
Abstract: Novel 3DOM BiVO4/TiO2 nanocomposites with intimate contact were for the first time synthesized by a hydrothermal method in order to elucidate their visible-light-driven photocatalytic performances. BiVO4 nanoparticles and 3DOM TiO2 inverse opal were fabricated respectively. These materials were characterized by XRD, XPS, SEM, TEM, N2 adsorption–desorption and UV-vis diffuse (UV-vis) and photoluminescence spectroscopies. As references for comparison, a physical mixture of BiVO4 nanoparticles and 3DOM TiO2 inverse opal powder (0.08 : 1), and a BiVO4/P25 TiO2 (0.08 : 1) nanocomposite made also by the hydrothermal method were prepared. The photocatalytic performance of all the prepared materials was evaluated by the degradation of rhodamine B (RhB) as a model pollutant molecule under visible light irradiation. The highly ordered 3D macroporous inverse opal structure can provide more active surface areas and increased mass transfer because of its highly accessible 3D porosity. The results show that 3DOM BiVO4/TiO2 nanocomposites possess a highly prolonged lifetime and increased separation of visible light generated charges and extraordinarily high photocatalytic activity. Owing to the intimate contact between BiVO4 and large surface area 3DOM TiO2, the photogenerated high energy charges can be easily transferred from BiVO4 to the 3DOM TiO2 support. BiVO4 nanoparticles in the 3DOM TiO2 inverse opal structure act thus as a sensitizer to absorb visible light and to transfer efficiently high energy electrons to TiO2 to ensure long lifetime of the photogenerated charges and keep them well separated, owing to the direct band gap of BiVO4 of 2.4 eV, favourably positioned band edges, very low recombination rate of electron–hole pairs and stability when coupled with photocatalysts, explaining the extraordinarily high photocatalytic performance of 3DOM BiVO4/TiO2 nanocomposites. It is found that larger the amount of BiVO4 in the nanocomposite, longer the duration of photogenerated charge separation and higher the photocatalytic activity. This work can shed light on the development of novel visible light responsive nanomaterials for efficient solar energy utilisation by the intimate combination of an inorganic light sensitizing nanoparticle with an inverse opal structure with high diffusion efficiency and high accessible surface area.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 8.867
Times cited: 88
DOI: 10.1039/C5TA00783F
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“3D Magnetic Induction Maps of Nanoscale Materials Revealed by Electron Holographic Tomography”. Wolf D, Rodriguez LA, Béché, A, Javon E, Serrano L, Magen C, Gatel C, Lubk A, Lichte H, Bals S, Van Tendeloo G, Fernández-Pacheco A, De Teresa JM, Snoeck E, Chemistry of materials 27, 6771 (2015). http://doi.org/10.1021/acs.chemmater.5b02723
Abstract: The investigation of three-dimensional (3D) ferromagnetic nanoscale materials constitutes one of the key research areas of the current magnetism roadmap, and carries great potential to impact areas such as data storage, sensing and biomagnetism. The properties of such nanostructures are closely connected with their 3D magnetic nanostructure, making their determination highly valuable. Up to now, quantitative 3D maps providing both the internal magnetic and electric configuration of the same specimen with high spatial resolution are missing. Here, we demonstrate the quantitative 3D reconstruction of the dominant axial component of the magnetic induction and electrostatic potential within a cobalt nanowire (NW) of 100 nm in diameter with spatial resolution below 10 nanometers by applying electron holographic tomography. The tomogram was obtained using a dedicated TEM sample holder for acquisition, in combination with advanced alignment and tomographic reconstruction routines. The powerful approach presented here is widely applicable to a broad range of 3D magnetic nanostructures and may trigger the progress of novel spintronic non-planar nanodevices.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 50
DOI: 10.1021/acs.chemmater.5b02723
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“Co-Rich ZnCoO Nanoparticles Embedded in Wurtzite Zn1-xCoxO Thin Films: Possible Origin of Superconductivity”. Zeng Y-J, Gauquelin N, Li D-Y, Ruan S-C, He H-P, Egoavil R, Ye Z-Z, Verbeeck J, Hadermann J, Van Bael MJ, Van Haesendonck C, ACS applied materials and interfaces 7, 22166 (2015). http://doi.org/10.1021/acsami.5b06363
Abstract: Co-rich ZnCoO nanoparticles embedded in wurtzite Zn0.7Co0.3O thin films are grown by pulsed laser deposition on a Si substrate. Local superconductivity with an onset Tc at 5.9 K is demonstrated in the hybrid system. The unexpected superconductivity probably results from Co(3+) in the Co-rich ZnCoO nanoparticles or from the interface between the Co-rich nanoparticles and the Zn0.7Co0.3O matrix.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.504
Times cited: 13
DOI: 10.1021/acsami.5b06363
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“Near-Infrared Emitting CuInSe/CuInS Dot Core/Rod Shell Heteronanorods by Sequential Cation Exchange”. van der Stam W, Bladt E, Rabouw FT, Bals S, de Mello Donega C, ACS nano 9, 11430 (2015). http://doi.org/10.1021/acsnano.5b05496
Abstract: The direct synthesis of heteronanocrystals (HNCs) combining different ternary semiconductors is challenging and has not yet been successful. Here, we report a sequential topotactic cation exchange (CE) pathway that yields CuInSe2/CuInS2 dot core/rod shell nanorods with near-infrared luminescence. In our approach, the Cu+ extraction rate is coupled to the In3+ incorporation rate by the use of a stoichiometric trioctylphosphine-InCl3 complex, which fulfills the roles of both In-source and Cu-extracting agent. In this way, Cu+ ions can be extracted by trioctylphosphine ligands only when the In-P bond is broken. This results in readily available In3+ ions at the same surface site from which the Cu+ is extracted, making the process a direct place exchange reaction and shifting the overall energy balance in favor of the CE. Consequently, controlled cation exchange can occur even in large and anisotropic heterostructured nanocrystals with preservation of the size, shape, and heterostructuring of the template NCs into the product NCs. The cation exchange is self-limited, stopping when the ternary core/shell CuInSe2/CuInS2 composition is reached. The method is very versatile, successfully yielding a variety of luminescent CuInX2 (X = S, Se, and Te) quantum dots, nanorods, and HNCs, by using Cd-chalcogenide NCs and HNCs as templates. The approach reported here thus opens up routes toward materials with unprecedented properties, which would otherwise remain inaccessible.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 13.942
Times cited: 88
DOI: 10.1021/acsnano.5b05496
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“Templated Growth of Surface Enhanced Raman Scattering -Active Branched Au Nanoparticles within Radial Mesoporous Silica Shells”. Sanz-Ortiz MN, Sentosun K, Bals S, Liz-Marzan LM, ACS nano 9, 10489 (2015). http://doi.org/10.1021/acsnano.5b04744
Abstract: Noble metal nanoparticles are widely used as probes or substrates for surface-enhanced Raman scattering (SERS), due to their characteristic plasmon resonances in the visible and NIR spectral ranges. Aiming at obtaining a versatile system with high SERS performance we developed the synthesis of quasi-monodisperse, non-aggregated gold nanoparticles protected by radial mesoporous silica shells. The radial channels of such shells were used as templates for the growth of gold tips branching from the cores, thereby improving the plasmonic performance of the particles while favoring the localization of analyte molecules at high electric field regions: close to the tips, inside the pores. The method, which allows control over tip length, was successfully applied to various gold nanoparticle shapes, leading to materials with highly efficient SERS performance. The obtained nanoparticles are stable in ethanol and water upon thermal consolidation and can be safely stored as a powder.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 13.942
Times cited: 110
DOI: 10.1021/acsnano.5b04744
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“Focused electron beam induced deposition as a tool to create electron vortices”. Béché, A, Winkler R, Plank H, Hofer F, Verbeeck J, Micron 80, 34 (2015). http://doi.org/10.1016/j.micron.2015.07.011
Abstract: Focused electron beam induced deposition (FEBID) is a microscopic technique that allows geometrically controlled material deposition with very high spatial resolution. This technique was used to create a spiral aperture capable of generating electron vortex beams in a transmission electron microscope (TEM). The vortex was then fully characterized using different TEM techniques, estimating the average orbital angular momentum to be approximately 0.8variant Planck's over 2pi per electron with almost 60% of the beam ending up in the l=1 state.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.98
Times cited: 21
DOI: 10.1016/j.micron.2015.07.011
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“Atomic and electronic structures of BaHfO3-doped TFA-MOD-derived YBa2Cu3O7−δthin films”. Molina-Luna L, Duerrschnabel M, Turner S, Erbe M, Martinez GT, Van Aert S, Holzapfel B, Van Tendeloo G, Superconductor science and technology 28, 115009 (2015). http://doi.org/10.1088/0953-2048/28/11/115009
Abstract: Tailoring the properties of oxide-based nanocomposites is of great importance for a wide range of materials relevant for energy technology. YBa2Cu3O7−δ (YBCO) superconducting thin films containing nanosized BaHfO3 (BHO) particles yield a significant improvement of the magnetic flux pinning properties and a reduced anisotropy of the critical current density. These films were prepared by chemical solution deposition (CSD) on (100) SrTiO3 (STO) substrates yielding critical current densities up to 3.6 MA cm−2 at 77 K and self-field. Transport in-field J c measurements demonstrated a high pinning force maximum of around 6 GN/m3 for a sample annealed at T = 760 °C that has a doping of 12 mol% of BHO. This sample was investigated by scanning transmission electron microscopy (STEM) in combination with electron energy-loss spectroscopy (EELS) yielding strain and spectral maps. Spherical BHO nanoparticles of 15 nm in size were found in the matrix, whereas the particles at the interface were flat. A 2 nm diffusion layer containing Ti was found at the YBCO (BHO)/STO interface. Local lattice deformation mapping at the atomic scale revealed crystal defects induced by the presence of both sorts of BHO nanoparticles, which can act as pinning centers for magnetic flux lines. Two types of local lattice defects were identified and imaged: (i) misfit edge dislocations and (ii) Ba-Cu-Cu-Ba stacking faults (Y-248 intergrowths). The local electronic structure and charge transfer were probed by high energy resolution monochromated electron energy-loss spectroscopy. This technique made it possible to distinguish superconducting from non-superconducting areas in nanocomposite samples with atomic resolution in real space, allowing the identification of local pinning sites on the order of the coherence length of YBCO (~1.5 nm) and the determination of 0.25 nm dislocation cores.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.878
Times cited: 4
DOI: 10.1088/0953-2048/28/11/115009
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“BaHfO3artificial pinning centres in TFA-MOD-derived YBCO and GdBCO thin films”. Erbe M, Hänisch J, Hühne R, Freudenberg T, Kirchner A, Molina-Luna L, Damm C, Van Tendeloo G, Kaskel S, Schultz L, Holzapfel B, Superconductor science and technology 28, 114002 (2015). http://doi.org/10.1088/0953-2048/28/11/114002
Abstract: Chemical solution deposition (CSD) is a promising way to realize REBa2Cu3O7−x (REBCO;RE = rare earth (here Y, Gd))-coated conductors with high performance in applied magnetic fields. However, the preparation process contains numerous parameters which need to be tuned to achieve high-quality films. Therefore, we investigated the growth of REBCO thin films containing nanometre-scale BaHfO3 (BHO) particles as pinning centres for magnetic flux lines, with emphasis on the influence of crystallization temperature and substrate on the microstructure and superconductivity. Conductivity, microscopy and x-ray investigations show an enhanced performance of BHO nano-composites in comparison to pristine REBCO. Further, those measurements reveal the superiority of GdBCO to YBCO—e.g. by inductive critical current densities, Jc, at self-field and 77 K. YBCO is outperformed by more than 1 MA cm−2 with Jc values of up to 5.0 MA cm−2 for 265 nm thick layers of GdBCO(BHO) on lanthanum aluminate. Transport in-field Jc measurements demonstrate high pinning force maxima of around 4 GN m−3 for YBCO(BHO) and GdBCO(BHO). However, the irreversibility fields are appreciably higher for GdBCO. The critical temperature was not significantly reduced upon BHO addition to both YBCO and GdBCO, indicating a low tendency for Hf diffusion into the REBCO matrix. Angular-dependent Jc measurements show a reduction of the anisotropy in the same order of magnitude for both REBCO compounds. Theoretical models suggest that more than one sort of pinning centre is active in all CSD films.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.878
Times cited: 36
DOI: 10.1088/0953-2048/28/11/114002
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“Multifunctional self-assembled composite colloids and their application to SERS detection”. La Porta A, Sanchez-Iglesias A, Altantzis T, Bals S, Grzelczak M, Liz-Marzan LM, Nanoscale 7, 10377 (2015). http://doi.org/10.1039/c5nr01264c
Abstract: We present a simple method for the co-encapsulation of gold nanostars and iron-oxide nanoparticles into hybrid colloidal composites that are highly responsive to both light and external magnetic fields. Self-assembly was driven by hydrophobic interactions between polystyrene capped gold nanostars and iron oxide nanocrystals stabilized with oleic acid, upon addition of water. A block copolymer was then used to encapsulate the resulting spherical colloidal particle clusters, which thereby became hydrophilic. Electron microscopy analysis unequivocally shows that each composite particle comprises a single Au nanostar surrounded by a few hundreds of iron oxide nanocrystals. We demonstrate that this hybrid colloidal system can be used as an efficient substrate for surface enhanced Raman scattering, using common dyes as model molecular probes. The co-encapsulation of iron oxide nanoparticles renders the system magnetically responsive, so that application of an external magnetic field leads to particle accumulation and limits of detection are in the nM range.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 7.367
Times cited: 51
DOI: 10.1039/c5nr01264c
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“Multimodal imaging of micron-sized iron oxide particles following in vitro and in vivo uptake by stem cells: down to the nanometer scale”. Roose D, Leroux F, De Vocht N, Guglielmetti C, Pintelon I, Adriaensen D, Ponsaerts P, Van der Linden A, Bals S, Contrast Media &, Molecular Imaging 9, 400 (2014). http://doi.org/10.1002/cmmi.1594
Abstract: In this study, the interaction between cells and micron-sized paramagnetic iron oxide (MPIO) particles was investigated by characterizing MPIO in their original state, and after cellular uptake in vitro as well as in vivo. Moreover, MPIO in the olfactory bulb were studied 9 months after injection. Using various imaging techniques, cell-MPIO interactions were investigated with increasing spatial resolution. Live cell confocal microscopy demonstrated that MPIO co-localize with lysosomes after in vitro cellular uptake. In more detail, a membrane surrounding the MPIO was observed by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Following MPIO uptake in vivo, the same cell-MPIO interaction was observed by HAADF-STEM in the subventricular zone at 1 week and in the olfactory bulb at 9 months after MPIO injection. These findings provide proof for the current hypothesis that MPIO are internalized by the cell through endocytosis. The results also show MPIO are not biodegradable, even after 9 months in the brain. Moreover, they show the possibility of HAADF-STEM generating information on the labeled cell as well as on the MPIO. In summary, the methodology presented here provides a systematic route to investigate the interaction between cells and nanoparticles from the micrometer level down to the nanometer level and beyond.
Keywords: A1 Journal article; Electron Microscopy for Materials Science (EMAT);
Impact Factor: 3.307
Times cited: 8
DOI: 10.1002/cmmi.1594
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“Zr substituted bismuth uranate”. Vannier R-N, Théry O, Kinowski C, Huvé, M, Van Tendeloo G, Suard E, Abraham F, Journal of materials chemistry 9, 435 (1999). http://doi.org/10.1039/a805829f
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 4
DOI: 10.1039/a805829f
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“ZnO@ZIF-8 : stabilization of quantum confined ZnO nanoparticles by a zinc methylimidazolate framework and their surface structural characterization probed by CO2 adsorption”. Esken D, Noei H, Wang Y, Wiktor C, Turner S, Van Tendeloo G, Fischer RA, Journal of materials chemistry 21, 5907 (2011). http://doi.org/10.1039/c1jm10091b
Abstract: The microporous and activated zeolitic imidazolate framework (Zn(MeIM)2; MeIM = imidazolate-2-methyl; ZIF-8) was loaded with the MOCVD precursor diethyl zinc [Zn(C2H5)2]. Exposure of ZIF-8 to the vapour of the volatile organometallic molecule resulted in the formation of the inclusion compound [Zn(C2H5)2]0.38@ZIF-8 revealing two precursor molecules per cavity. In a second step the obtained material was treated with oxygen (5 vol% in argon) at various temperatures (oxidative annealing) to achieve the composite material ZnO0.35@ZIF-8. The new material was characterized with powder XRD, FT-IR, UV-vis, solid state NMR, elemental analysis, N2 sorption measurements, and transmission electron microscopy. The data give evidence for the presence of nano-sized ZnO particles stabilized by ZIF-8 showing a blue-shift of the UV-vis absorption caused by quantum size effect (QSE). The surface structure and reactivity of embedded ZnO nanoparticles were characterized via carbon dioxide adsorption at different temperatures monitored by ultra-high vacuum FTIR techniques. It was found that the surface of ZnO nanoparticles is dominated by polar OZnO and ZnZnO facets as well as by defect sites, which all exhibit high reactivity towards CO2 activation forming various adsorbed carbonate and chemisorbed CO2δ− species.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 76
DOI: 10.1039/c1jm10091b
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“ZnO nanorod arrays by plasma-enhanced CVD for light-activated functional applications”. Bekermann D, Gasparotto A, Barreca D, Devi A, Fischer RA, Kete M, Štangar UL, Lebedev OI, Maccato C, Tondello E, Van Tendeloo G, ChemPhysChem : a European journal of chemical physics and physical chemistry 11, 2337 (2010). http://doi.org/10.1002/cphc.201000333
Abstract: Switch of the surface properties: Supported ZnO nanorod arrays with tailored roughness and aspect ratios are successfully synthesized by plasma-enhanced chemical vapor deposition. Such nanostructures exhibit significant superhydrophilic and photocatalytic properties tunable as a function of their morphological organization (see picture). This renders them promising building blocks for the fabrication of stimuli-responsive materials.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.075
Times cited: 38
DOI: 10.1002/cphc.201000333
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“Zn-Al layered double hydroxides: synthesis, characterization and photocatalytic application”. Seftel EM, Popovici E, Mertens M, de Witte K, Van Tendeloo G, Cool P, Vansant EF, Microporous and mesoporous materials: zeolites, clays, carbons and related materials 113, 296 (2008). http://doi.org/10.1016/j.micromeso.2007.11.029
Keywords: A1 Journal article; Laboratory of adsorption and catalysis (LADCA); Electron microscopy for materials research (EMAT)
Impact Factor: 3.615
Times cited: 154
DOI: 10.1016/j.micromeso.2007.11.029
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“Zirconia-modified exfoliated graphite”. Afanasov IM, Van Tendeloo G, Inorganic materials 47, 603 (2011). http://doi.org/10.1134/S0020168511050013
Abstract: Zirconia has been incorporated into exfoliated graphite (EG) through the anodic polarization in the natural graphite-ZrO(NO3)2-HNO3-H2O system, followed by flash heating. The thermal properties of the oxidized graphites employed as precursors to EG have been studied by thermogravimetry in combination with differential scanning calorimetry, and the distribution of ZrO2 particles in the EG has been assessed by scanning and transmission electron microscopy. Conditions are described for the preparation of EG with bulk densities in the range 1.34.7 g/l and ZrO2 contents in the range 434 wt %.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 0.62
DOI: 10.1134/S0020168511050013
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“Zinc and copper oxides functionalized with metal nanoparticles : an insight into their nano-organization”. Maccato C, Simon Q, Carraro G, Barreca D, Gasparotto A, Lebedev OI, Turner S, Van Tendeloo G, Journal of advanced microscopy research 7, 84 (2012). http://doi.org/10.1166/jamr.2012.1101
Abstract: Ag/ZnO and Au/CuxO (x = 1, 2) nanocomposites supported on Si(100) and polycrystalline Al2O3 were synthesised by hybrid approaches, combining chemical vapor deposition (either thermal or plasma-assisted) of host oxide matrices and subsequent radio frequency-sputtering of guest metal particles. The influence of the adopted synthetic parameters on the nanocomposite morphological and compositional features was investigated by field emission-scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. Results confirm the synthesis of ZnO and CuxO nanoarchitectures, characterized by a tailored morphology and an intimate metal/oxide contact. A careful control of the processing conditions enabled a fine tuning of the mutual constituent distribution, opening thus attractive perspectives for the engineering of advanced nanomaterials.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
DOI: 10.1166/jamr.2012.1101
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“Zeotile-2: a microporous analogue of MCM-48”. Kremer SPB, Kirschhock CEA, Aerts A, Aerts CA, Houthoofd KJ, Grobet PJ, Jacobs PA, Lebedev OI, Van Tendeloo G, Martens JA, Solid state sciences 7, 861 (2005). http://doi.org/10.1016/j.solidstatesciences.2005.01.021
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 1.811
Times cited: 10
DOI: 10.1016/j.solidstatesciences.2005.01.021
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