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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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“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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“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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“Grain size tuning of nanocrystalline chemical vapor deposited diamond by continuous electrical bias growth : experimental and theoretical study”. Mortet V, Zhang L, Eckert M, D'Haen J, Soltani A, Moreau M, Troadec D, Neyts E, De Jaeger JC, Verbeeck J, Bogaerts A, Van Tendeloo G, Haenen K, Wagner P, Physica status solidi : A : applications and materials science 209, 1675 (2012). http://doi.org/10.1002/pssa.201200581
Abstract: In this work, a detailed structural and spectroscopic study of nanocrystalline diamond (NCD) thin films grown by a continuous bias assisted CVD growth technique is reported. This technique allows the tuning of grain size and phase purity in the deposited material. The crystalline properties of the films are characterized by SEM, TEM, EELS, and Raman spectroscopy. A clear improvement of the crystalline structure of the nanograined diamond film is observed for low negative bias voltages, while high bias voltages lead to thin films consisting of diamond grains of only ∼10 nm nanometer in size, showing remarkable similarities with so-called ultrananocrystalline diamond. These layers arecharacterized by an increasing amount of sp2-bonded carbon content of the matrix in which the diamond grains are embedded. Classical molecular dynamics simulations support the observed experimental data, giving insight in the underlying mechanism for the observed increase in deposition rate with bias voltage. Furthermore, a high atomic concentration of hydrogen has been determined in these films. Finally, Raman scattering analyses confirm that the Raman line observed at ∼1150 cm−1 cannot be attributed to trans-poly-acetylene, which continues to be reported in literature, reassigning it to a deformation mode of CHx bonds in NCD.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 1.775
Times cited: 31
DOI: 10.1002/pssa.201200581
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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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“Luminescent CuInS2 quantum dots by partial cation exchange in Cu2-xS nanocrystals”. van der Stam W, Berends AC, Rabouw FT, Willhammar T, Ke X, Meeldijk JD, Bals S, de Donega CM, Chemistry of materials 27, 621 (2015). http://doi.org/10.1021/cm504340h
Abstract: Here, we show successful partial cation exchange reactions in Cu2-xS nanocrystals (NCs) yielding luminescent CuInS2 (CIS) NCs. Our approach of mild reaction conditions ensures slow Cu extraction rates, which results in a balance with the slow In incorporation rate. With this method, we obtain CIS NCs with photoluminescence (PL) far in the near-infrared (NIR), which cannot be directly synthesized by currently available synthesis protocols. We discuss the factors that favor partial, self-limited cation exchange from Cu2-xS to CIS NCs, rather than complete cation exchange to In2S3. The product CIS NCs have the wurtzite crystal structure, which is understood in terms of conservation of the hexagonal close packing of the anionic sublattice of the parent NCs into the product NCs. These results are an important step toward the design of CIS NCs with sizes and shapes that are not attainable by direct synthesis protocols and may thus impact a number of potential applications.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 119
DOI: 10.1021/cm504340h
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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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“Mapping electronic reconstruction at the metal-insulator interface in LaVO3/SrVO3 heterostructures”. Tan H, Egoavil R, Béché, A, Martinez GT, Van Aert S, Verbeeck J, Van Tendeloo G, Rotella H, Boullay P, Pautrat A, Prellier W, Physical review : B : condensed matter and materials physics 88, 155123 (2013). http://doi.org/10.1103/PhysRevB.88.155123
Abstract: A (LaVO3)6/(SrVO3)(3) superlattice is studied with a combination of sub-A resolved scanning transmission electron microscopy and monochromated electron energy-loss spectroscopy. The V oxidation state is mapped with atomic spatial resolution enabling us to investigate electronic reconstruction at the LaVO3/SrVO3 interfaces. Surprisingly, asymmetric charge distribution is found at adjacent chemically symmetric interfaces. The local structure is proposed and simulated with a double channeling calculation which agrees qualitatively with our experiment. We demonstrate that local strain asymmetry is the likely cause of the electronic asymmetry of the interfaces. The electronic reconstruction at the interfaces extends much further than the chemical composition, varying from 0.5 to 1.2 nm. This distance corresponds to the length of charge transfer previously found in the (LaVO3)./(SrVO3). metal/insulating and the (LaAlO3)./(SrTiO3). insulating/insulating interfaces.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 15
DOI: 10.1103/PhysRevB.88.155123
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“Mapping spin-polarized transitions with atomic resolution”. Schattschneider P, Schaffer B, Ennen I, Verbeeck J, Physical review : B : condensed matter and materials physics 85, 134422 (2012). http://doi.org/10.1103/PhysRevB.85.134422
Abstract: The coupling of angstrom-sized electron probes with spin-polarized electronic transitions shows that the inelastically scattered probe electron is in a mixed state containing electron vortices with nonzero orbital angular momentum. These electrons create an asymmetric intensity distribution in energy filtered diffraction patterns, giving access to maps of the magnetic moments with atomic resolution. A feasibility experiment shows evidence of the predicted effect. Potential applications are column-by-column maps of magnetic ordering, and the creation of angstrom-sized free electrons with orbital angular momentum by inelastic scattering in a thin ferromagnetic foil.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 41
DOI: 10.1103/PhysRevB.85.134422
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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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“Nanoscale ordering in oxygen deficient quintuple perovskite Sm2-\epsilonBa3+\epsilonFe5O15-\delta : implication for magnetism and oxygen stoichiometry”. Volkova NE, Lebedev OI, Gavrilova LY, Turner S, Gauquelin N, Seikh MM, Caignaert V, Cherepanov VA, Raveau B, Van Tendeloo G, Chemistry of materials 26, 6303 (2014). http://doi.org/10.1021/cm503276p
Abstract: The investigation of the system SmBaFe-O in air has allowed an oxygen deficient perovskite Sm2-epsilon Ba3+epsilon Fe5O15-delta (delta = 0.75, epsilon = 0.125) to be synthesized. In contrast to the XRPD pattern which gives a cubic symmetry (a(p) = 3.934 angstrom), the combined HREM/EELS study shows that this phase is nanoscale ordered with a quintuple tetragonal cell, a(p) X a(p) X 5(ap). The nanodomains exhibit a unique stacking sequence of the A-site cationic layers along the crystallographic c-axis, namely SmBaBa/SmBa/SmBaSm, and are chemically twinned in the three crystallographic directions. The nanoscale ordering of this perovskite explains its peculiar magnetic properties on the basis of antiferromagnetic interactions with spin blockade at the boundary between the nanodomains. The variation of electrical conductivity and oxygen content of this oxide versus temperature suggest potential SOFC applications. They may be related to the particular distribution of oxygen vacancies in the lattice and to the 3d(5)(L) under bar configuration of iron.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 16
DOI: 10.1021/cm503276p
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Goorden L, Van Tendeloo G, Lenaerts S, Deblonde M, et al. (2009) Nanotechnologie: gewikt en gewogen. NanoSoc
Keywords: Minutes and reports; Engineering sciences. Technology; Engineering Management (ENM); Sustainable Energy, Air and Water Technology (DuEL); Electron microscopy for materials research (EMAT)
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Goorden L, Van Tendeloo G, Lenaerts S, Deblonde M, van Oudheusden M, et al. (2009) Nanotechnologie op de agenda. NanoSoc
Keywords: Minutes and reports; Engineering sciences. Technology; Engineering Management (ENM); Society and Environment; Sustainable Energy, Air and Water Technology (DuEL); Electron microscopy for materials research (EMAT)
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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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“Novel complex stacking of fully-ordered transition metal layers in Li4FeSbO6 materials”. McCalla E, Abakumov A, Rousse G, Reynaud M, Sougrati MT, Budic B, Mahmoud A, Dominko R, Van Tendeloo G, Hermann RP, Tarascon JM;, Chemistry of materials 27, 1699 (2015). http://doi.org/10.1021/cm504500a
Abstract: As part of a broad project to explore Li4MM'O-6 materials (with M and M' being selected from a wide variety of metals) as positive electrode materials for Li-ion batteries, the structures of Li4FeSbO6 materials with both stoichiometric and slightly deficient lithium contents are studied here. For lithium content varying from 3.8 to 4.0, the color changes from yellow to black and extra superstructure peaks are seen in the XRD patterns. These extra peaks appear as satellites around the four superstructure peaks affected by the stacking of the transition metal atoms. Refinements of both XRD and neutron scattering patterns show a nearly perfect ordering of Li, Fe, and Sb in the transition metal layers of all samples, although these refinements must take the stacking faults into account in order to extract information about the structure of the TM layers. The structure of the most lithium rich sample, where the satellite superstructure peaks are seen, was determined with the help of HRTEM, XRD, and neutron scattering. The satellites arise due to a new stacking sequence where not all transition metal layers are identical but instead two slightly different compositions stack in an AABB sequence giving a unit cell that is four times larger than normal for such monoclinic layered materials. The more lithium deficient samples are found to contain metal site vacancies based on elemental analysis and Mossbauer spectroscopy results. The significant changes in physical properties are attributed to the presence of these vacancies. This study illustrates the great importance of carefully determining the final compositions in these materials, as very small differences in compositions may have large impacts on structures and properties.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 9.466
Times cited: 22
DOI: 10.1021/cm504500a
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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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“Plasmonic nanodiamonds : targeted coreshell type nanoparticles for cancer cell thermoablation”. Rehor I, Lee KL, Chen K, Hajek M, Havlik J, Lokajova J, Masat M, Slegerova J, Shukla S, Heidari H, Bals S, Steinmetz NF, Cigler P, Advanced healthcare materials 4, 460 (2015). http://doi.org/10.1002/adhm.201400421
Abstract: Targeted biocompatible nanostructures with controlled plasmonic and morphological parameters are promising materials for cancer treatment based on selective thermal ablation of cells. Here, coreshell plasmonic nanodiamonds consisting of a silica-encapsulated diamond nanocrystal coated in a gold shell are designed and synthesized. The architecture of particles is analyzed and confirmed in detail using electron tomography. The particles are biocompatibilized using a PEG polymer terminated with bioorthogonally reactive alkyne groups. Azide-modified transferrin is attached to these particles, and their high colloidal stability and successful targeting to cancer cells overexpressing the transferrin receptor are demonstrated. The particles are nontoxic to the cells and they are readily internalized upon binding to the transferrin receptor. The high plasmonic cross section of the particles in the near-infrared region is utilized to quantitatively ablate the cancer cells with a short, one-minute irradiation by a pulse 750-nm laser.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.11
Times cited: 30
DOI: 10.1002/adhm.201400421
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“One-Step Microheterogeneous Formation of Rutile@Anatase Core–Shell Nanostructured Microspheres Discovered by Precise Phase Mapping”. Tarasov A, Hu Z-Y, Meledina M, Trusov G, Goodilin E, Van Tendeloo G, Dobrovolsky Y, The journal of physical chemistry: C : nanomaterials and interfaces 121, 4443 (2017). http://doi.org/10.1021/acs.jpcc.6b12991
Abstract: Nanostructured core−shell microspheres with a rough rutile core and a thin anatase shell are synthesized via a one-step heterogeneous templated hydrolysis process of TiCl4 vapor on the aerosol water−air interface. The rutile-in-anatase core−shell structure has been evidenced by different electron microscopy techniques, including electron energy-loss spectroscopy and 3D electron tomography. A new mechanism for the formation of a crystalline rutile core inside the anatase shell is proposed based on a statistical evaluation of a large number of electron microscopy data. We found that the control over the TiCl4 vapor pressure, the ratio between TiCl4 and H2O aerosol, and the reaction conditions plays a crucial role in the formation of the core−shell morphology and increases the yield of nanostructured microspheres.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 4.536
Times cited: 4
DOI: 10.1021/acs.jpcc.6b12991
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“Preparation, structural and optical characterization of nanocrystalline ZnO doped with luminescent Ag-nanoclusters”. Kuznetsov AS, Lu Y-G, Turner S, Shestakov MV, Tikhomirov VK, Kirilenko D, Verbeeck J, Baranov AN, Moshchalkov VV, Optical materials express 2, 723 (2012). http://doi.org/10.1364/OME.2.000723
Abstract: Nanocrystalline ZnO doped with Ag-nanoclusters has been synthesized by a salt solid state reaction. Three overlapping broad emission bands due to the Ag nanoclusters have been detected at about 570, 750 and 900 nm. These emission bands are excited by an energy transfer from the exciton state of the ZnO host when pumped in the wavelength range from 250 to 400 nm. The 900 nm emission band shows characteristic orbital splitting into three components pointing out that the anisotropic crystalline wurtzite host of ZnO is responsible for this feature. Heat-treatment and temperature dependence studies confirm the origin of these emission bands. An energy level diagram for the emission process and a model for Ag nanoclusters sites are suggested. The emission of nanocrystalline ZnO doped with Ag nanoclusters may be applied for white light generation, displays driven by UV light, down-convertors for solar cells and luminescent lamps.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.591
DOI: 10.1364/OME.2.000723
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“Procedure to count atoms with trustworthy single-atom sensitivity”. Van Aert S, de Backer A, Martinez GT, Goris B, Bals S, Van Tendeloo G, Rosenauer A, Physical review : B : condensed matter and materials physics 87, 064107 (2013). http://doi.org/10.1103/PhysRevB.87.064107
Abstract: We report a method to reliably count the number of atoms from high-angle annular dark field scanning transmission electron microscopy images. A model-based analysis of the experimental images is used to measure scattering cross sections at the atomic level. The high sensitivity of these measurements in combination with a thorough statistical analysis enables us to count atoms with single-atom sensitivity. The validity of the results is confirmed by means of detailed image simulations. We will show that the method can be applied to nanocrystals of arbitrary shape, size, and atom type without the need for a priori knowledge about the atomic structure.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.836
Times cited: 106
DOI: 10.1103/PhysRevB.87.064107
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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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“Pulsed laser deposition of SrTiO3 on a H-terminated Si substrate”. Spreitzer M, Egoavil R, Verbeeck J, Blank DHA, Rijnders G, Journal of materials chemistry C : materials for optical and electronic devices 1, 5216 (2013). http://doi.org/10.1039/c3tc30913d
Abstract: Interfacing oxides with silicon is a long-standing problem related to the integration of multifunctional oxides with semiconductor devices and the replacement of SiO2 with high-k gate oxides. In our study, pulsed laser deposition was used to prepare a SrTiO3 (STO) thin film on a H-terminated Si substrate. The main purpose of our work was to verify the ability of H-termination against the oxidation of Si during the PLD process and to analyze the resulting interfaces. In the first part of the study, the STO was deposited directly on the Si, leading to the formation of a preferentially textured STO film with a (100) orientation. In the second part, SrO was used as a buffer layer, which enabled the partial epitaxial growth of STO with STO(110)parallel to Si(100) and STO[001]parallel to Si[001]. The change in the growth direction induced by the application of a SrO buffer was governed by the formation of a SrO(111) intermediate layer and subsequently by the minimization of the lattice misfit between the STO and the SrO. Under the investigated conditions, approximately 10 nm thick interfacial layers formed between the STO and the Si due to reactions between the deposited material and the underlying H-terminated Si. In the case of direct STO deposition, SiOx formed at the interface with the silicon, while in the case when SrO was used as a buffer, strontium silicate grew directly on the silicon, which improves the growth quality of the uppermost STO.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 5.256
Times cited: 23
DOI: 10.1039/c3tc30913d
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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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“Self-organization of highly symmetric nanoassemblies : a matter of competition”. Galván-Moya JE, Altantzis T, Nelissen K, Peeters FM, Grzelczak M, Liz-Marán LM, Bals S, Van Tendeloo G, ACS nano 8, 3869 (2014). http://doi.org/10.1021/nn500715d
Abstract: The properties and applications of metallic nanoparticles are inseparably connected not only to their detailed morphology and composition but also to their structural configuration and mutual interactions. As a result, the assemblies often have superior properties as compared to individual nanoparticles. Although it has been reported that nanoparticles can form highly symmetric clusters, if the configuration can be predicted as a function of the synthesis parameters, more targeted and accurate synthesis will be possible. We present here a theoretical model that accurately predicts the structure and configuration of self-assembled gold nanoclusters. The validity of the model is verified using quantitative experimental data extracted from electron tomography 3D reconstructions of different assemblies. The present theoretical model is generic and can in principle be used for different types of nanoparticles, providing a very wide window of potential applications.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT)
Impact Factor: 13.942
Times cited: 34
DOI: 10.1021/nn500715d
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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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“Single-step alcohol-free synthesis of coreshell nanoparticles of \gamma-casein micelles and silica”. Kerkhofs S, Leroux F, Allouche L, Mellaerts R, Jammaer J, Aerts A, Kirschhock CEA, Magusin PCMM, Taulelle F, Bals S, Van Tendeloo G, Martens JA;, RSC advances 4, 25650 (2014). http://doi.org/10.1039/C4RA03252G
Abstract: A new, single-step protocol for wrapping individual nanosized β-casein micelles with silica is presented. This biomolecule-friendly synthesis proceeds at low protein concentration at almost neutral pH, and makes use of sodium silicate instead of the common silicon alkoxides. This way, formation of potentially protein-denaturizing alcohols can be avoided. The pH of the citrate-buffered synthesis medium is close to the isoelectric point of β-casein, which favours micelle formation. A limited amount of sodium silicate is added to the protein micelle suspension, to form a thin silica coating around the β-casein micelles. The size distribution of the resulting proteinsilica structures was characterized using DLS and SAXS, as well as 1H NMR DOSY with a dedicated pulsed-field gradient cryo-probehead to cope with the low protein concentration. The degree of silica-condensation was investigated by 29Si MAS NMR, and the nanostructure was revealed by advanced electron microscopy techniques such as ESEM and HAADF-STEM. As indicated by the combined characterization results, a silica shell of 2 nm is formed around individual β-casein micelles giving rise to separate protein coresilica shell nanoparticles of 17 nm diameter. This alcohol-free method at mild temperature and pH is potentially suited for packing protein molecules into bio-compatible silica nanocapsules for a variety of applications in biosensing, therapeutic protein delivery and biocatalysis.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.108
Times cited: 3
DOI: 10.1039/C4RA03252G
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“Smart Align : a new tool for robust non-rigid registration of scanning microscope data”. Jones L, Yang H, Pennycook TJ, Marshall MSJ, Van Aert S, Browning ND, Castell MR, Nellist PD, Advanced Structural and Chemical Imaging 1, 8 (2015). http://doi.org/10.1186/s40679-015-0008-4
Abstract: Many microscopic investigations of materials may benefit from the recording of multiple successive images. This can include techniques common to several types of microscopy such as frame averaging to improve signal-to-noise ratios (SNR) or time series to study dynamic processes or more specific applications. In the scanning transmission electron microscope, this might include focal series for optical sectioning or aberration measurement, beam damage studies or camera-length series to study the effects of strain; whilst in the scanning tunnelling microscope, this might include bias-voltage series to probe local electronic structure. Whatever the application, such investigations must begin with the careful alignment of these data stacks, an operation that is not always trivial. In addition, the presence of low-frequency scanning distortions can introduce intra-image shifts to the data. Here, we describe an improved automated method of performing non-rigid registration customised for the challenges unique to scanned microscope data specifically addressing the issues of low-SNR data, images containing a large proportion of crystalline material and/or local features of interest such as dislocations or edges. Careful attention has been paid to artefact testing of the non-rigid registration method used, and the importance of this registration for the quantitative interpretation of feature intensities and positions is evaluated.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Times cited: 131
DOI: 10.1186/s40679-015-0008-4
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“Soft chemical control of the crystal and magnetic structure of a layered mixed valent manganite oxide sulfide”. Blandy JN, Abakumov AM, Christensen KE, Hadermann J, Adamson P, Cassidy SJ, Ramos S, Free DG, Cohen H, Woodruff DN, Thompson AL, Clarke SJ;, APL materials 3, 041520 (2015). http://doi.org/10.1063/1.4918973
Abstract: Oxidative deintercalation of copper ions from the sulfide layers of the layered mixed-valent manganite oxide sulfide Sr2MnO2Cu1.5S2 results in control of the copper-vacancy modulated superstructure and the ordered arrangement of magnetic moments carried by the manganese ions. This soft chemistry enables control of the structures and properties of these complex materials which complement mixed-valent perovskite and perovskite-related transition metal oxides. (C) 2015 Author(s).
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 4.335
Times cited: 5
DOI: 10.1063/1.4918973
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