| 1. |
- Agthe, Michael, et al.
(författare)
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Controlling orientational and translational order of iron oxide nanocubes by assembly in nanofluidic containers
- 2015
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 31:45, s. 12537-12543
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that spatial confinement can be used to control the orientational and translational order of cubic nanoparticles. For this purpose we have combined X-ray scattering and scanning electron microscopy to study the ordering of iron oxide nanocubes that have self-assembled from toluene-based dispersions in nanofluidic channels. An analysis of scattering vector components with directions parallel and perpendicular to the slit walls shows that the confining walls induce a preferential parallel alignment of the nanocube (100) faces. Moreover, slit wall separations that are commensurate with an integer multiple of the edge length of the oleic acid-capped nanocubes result in a more pronounced translational order of the self-assembled arrays compared to incommensurate confinement. These results show that the confined assembly of anisotropic nanocrystals is a promising route to nanoscale devices with tunable anisotropic properties.
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| 2. |
- Mayence, Arnaud, 1987-
(författare)
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Design and characterization of nanoparticles and their assemblies : Transmission electron microscopy investigations from atomic to mesoscopic length scales
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Transmission electron microscopy (TEM) is a powerful and versatile tool for investigating nanomaterials. In this thesis, various transmission electron microscopy techniques are used to study the chemical and structural features of different types of inorganic nanoparticles of well-defined morphologies as well as their assemblies. The synthesis of spherical and anisotropic nanoparticles (iron oxide nanocubes and other morphologies, gadolinium orthophosphate nanorods, tungsten oxide nanowires and nanorods, palladium nanospheres, and facetted iron-manganese oxides hybrid nanoparticles) using thermal decomposition of metal complex precursors in high-boiling point organic solvents and hydrothermal process are described in details.Electron diffraction tomography (3D EDT) is a recently developed technique that is used to investigate the 3D structure of crystalline materials. Reciprocal space volume reconstruction of 3D EDT data of thin WO3 nanowires assembled into nanorods revealed single crystal domains of hexagonal symmetry. Moreover, the use of 3D EDT enabled to identify and solve the structures of individual GdPO4 nanorods in a mixed phase powder. The use of 3D EDT was extended using small-angle diffraction mode to investigate the packing arrangements and defects in nanoparticle assemblies. A high concentration of planar defects found in different nanoparticle assemblies highlights the competition between the fcc and hcp arrangements during the assembly process.Iron-manganese oxides hybrid nanoparticles with different three-dimensional configurations, i.e. core|shell and asymmetric facetted dimers, were investigated using a combination of several electron microscopy techniques (HRTEM, SAED, STEM-HAADF, EFTEM, EELS). The growth of the facetted cubic MnO phase onto preformed Fe3O4 seed particles occurs preferentially along the Fe3O4 nanocube edges forming a well-oriented crystalline interface despite the lattice mismatch and defects. Atomic resolution monitoring of the structural changes in Mn3O4|Fe3O4 and Fe3O4|Mn3O4 core|shell nanoparticles induced by the electron beam revealed a strain relief mechanism at the interface involving inhomogeneous diffusion of cations and defects creation.
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| 3. |
- Mayence, Arnaud, et al.
(författare)
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Interfacial strain and defects in asymmetric Fe-Mn oxide hybrid nanoparticles
- 2016
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 8:29, s. 14171-14177
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Tidskriftsartikel (refereegranskat)abstract
- Asymmetric Fe-Mn oxide hybrid nanoparticles have been obtained by a seed-mediated thermal decomposition-based synthesis route. The use of benzyl ether as the solvent was found to promote the orientational growth of Mn1-xO onto the iron oxide nanocube seeds yielding mainly dimers and trimers whereas 1-octadecene yields large nanoparticles. HRTEM imaging and HAADF-STEM tomography performed on dimers show that the growth of Mn1-xO occurs preferentially along the edges of iron oxide nanocubes where both oxides share a common crystallographic orientation. Fourier filtering and geometric phase analysis of dimers reveal a lattice mismatch of 5% and a large interfacial strain together with a significant concentration of defects. The saturation magnetization is lower and the coercivity is higher for the Fe-Mn oxide hybrid nanoparticles compared to the iron oxide nanocube seeds.
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| 4. |
- Mayence, Arnaud, et al.
(författare)
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Phase Identification and Structure Solution by Three-Dimensional Electron Diffraction Tomography : Gd-Phosphate Nanorods
- 2014
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 53:10, s. 5067-5072
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Tidskriftsartikel (refereegranskat)abstract
- Hydrothermal synthesis of GdPO4 in the presence of poly(methacrylic acid) yields nanorods with a diameter of 15 nm and an aspect ratio of 20. Powder X-ray diffraction patterns showed that the GdPO4 nanorods display peaks characteristics for both monoclinic and hexagonal structures. Three-dimensional electron diffraction tomography (3D EDT) was used to determine the structures ab initio on the basis of reciprocal volume reconstruction of electron diffraction data sets collected from single nanorods. The crystal structure of the monoclinic form was shown to be P2(1)/n, corroborating previous work. We were able to solve the 3D structure of the hexagonal P6(2)22 form, which has not been reported previously. Our work shows that 3D EDT is a powerful method that can be used for solving structures of single nano crystals.
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| 5. |
- Mayence, Arnaud, et al.
(författare)
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Probing planar defects in nanoparticle superlattices by 3D small-angle electron diffraction tomography and real space imaging
- 2014
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Ingår i: Nanoscale. - 2040-3364 .- 2040-3372. ; 6:22, s. 13803-13808
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate how the acquisition and processing of 3D electron diffraction data can be extended to characterize structural features on the mesoscale, and show how lattice distortions in superlattices of self-assembled spherical Pd nanoparticles can be quantified by three-dimensional small-angle electron diffraction tomography (3D SA-EDT). Transmission electron microscopy real space imaging and 3D SA-EDT reveal a high density of stacking faults that was related to a competition between fcc and hcp arrangements during assembly. Information on the orientation of the stacking faults was used to make analogies between planar defects in the superlattices and Shockley partial dislocations in metallic systems.
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| 6. |
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| 7. |
- Navarro, Julien R. G., et al.
(författare)
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WO3 Nanorods Created by Self-Assembly of Highly Crystalline Nanowires under Hydrothermal Conditions
- 2014
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 30:34, s. 10487-10492
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Tidskriftsartikel (refereegranskat)abstract
- WO3 nanorods and wires were obtained via hydrothermal synthesis using sodium tungstate as a precursor and either oxalic acid, citric acid, or poly(methacrylic add) as a stabilizing agent. Transmission electron microscopy images showed that the organic acids with different numbers of carboxylic groups per molecule influence the final sizes and stacking nanostructures of WO3 wires. Three-dimensional electron diffraction tomography of a single nanocrystal revealed a hexagonal WO3 structure with preferential growth along the c-axis, which was confirmed by high-resolution transmission electron microscopy. WO3 nanowires were also spin-coated onto an indium tin oxide/glass conducting substrate, resulting in the formation of a film that was characterized by scanning electron microscopy. Finally, cyclic voltammetry measurements performed on the WO3 thin film showed voltammograms typical for the WO3 redox process.
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| 8. |
- Roldan, Manuel A., et al.
(författare)
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Probing the meta-stability of oxide core/shell nanoparticle systems at atomic resolution
- 2021
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947 .- 1873-3212. ; 405
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid nanoparticles allow exploiting the interplay of confinement, proximity between different materials and interfacial effects. However, to harness their properties an in-depth understanding of their (meta)stability and interfacial characteristics is crucial. This is especially the case of nanosystems based on functional oxides working under reducing conditions, which may severely impact their properties. In this work, the in-situ electron-induced selective reduction of Mn3O4 to MnO is studied in magnetic Fe3O4/Mn3O4 and Mn3O4/Fe3O4 core/shell nanoparticles by means of high-resolution scanning transmission electron microscopy combined with electron energy-loss spectroscopy. Such in-situ transformation allows mimicking the actual processes in operando environments. A multi-stage image analysis using geometric phase analysis combined with particle image velocity enables direct monitoring of the relationship between structure, chemical composition and strain relaxation during the Mn3O4 reduction. In the case of Fe3O4/Mn3O4 core/shell the transformation occurs smoothly without the formation of defects. However, for the inverse Mn3O4/Fe3O4 core/shell configuration the electron beam-induced transformation occurs in different stages that include redox reactions and void formation followed by strain field relaxation via formation of defects. This study highlights the relevance of understanding the local dynamics responsible for changes in the particle composition in order to control stability and, ultimately, macroscopic functionality.
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| 9. |
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| 10. |
- Wetterskog, Erik, et al.
(författare)
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Precise control over shape and size of iron oxide nanocrystals suitable for assembly into ordered particle arrays
- 2014
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Ingår i: Science and Technology of Advanced Materials. - : Informa UK Limited. - 1468-6996 .- 1878-5514. ; 15:5
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Tidskriftsartikel (refereegranskat)abstract
- Here we demonstrate how monodisperse iron oxide nanocubes and nanospheres with average sizes between 5 and 27 nm can be synthesized by thermal decomposition. The relative importance of the purity of the reactants, the ratio of oleic acid and sodium oleate, the maximum temperature, and the rate of temperature increase, on robust and reproducible size and shape-selective iron oxide nanoparticle synthesis are identified and discussed. The synthesis conditions that generate highly monodisperse iron oxide nanocubes suitable for producing large ordered arrays, or mesocrystals are described in detail.
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