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- Hadi, Seyed Ehsan, et al.
(author)
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Highly magnetic hybrid foams based on aligned tannic acid-coated iron oxide nanoparticles and TEMPO-oxidized cellulose nanofibers
- 2023
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In: RSC Advances. - 2046-2069. ; 13:20, s. 13919-13927
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Journal article (peer-reviewed)abstract
- Lightweight iron oxide nanoparticle (IONP)/TEMPO-oxidized cellulose nanofibril (TOCNF) hybrid foams with an anisotropic structure and a high IONP content were produced using magnetic field-enhanced unidirectional ice-templating. Coating the IONP with tannic acid (TA) improved the processability, the mechanical performance, and the thermal stability of the hybrid foams. Increasing the IONP content (and density) increased the Young's modulus and toughness probed in compression, and hybrid foams with the highest IONP content were relatively flexible and could recover 14% axial compression. Application of a magnetic field in the freezing direction resulted in the formation of IONP chains that decorated the foam walls and the foams displayed a higher magnetization saturation, remanence, and coercivity compared to the ice-templated hybrid foams. The hybrid foam with an IONP content of 87% displayed a saturation magnetization of 83.2 emu g−1, which is 95% of the value for bulk magnetite. Highly magnetic hybrid foams are of potential interest for environmental remediation, energy storage, and electromagnetic interference shielding.
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| 2. |
- Kapuscinski, Martin, 1989-
(author)
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Following nanoparticle self-assembly in real-time : Small-angle X-ray scattering and quartz crystal microbalance study of self-assembling iron oxide nanocubes
- 2020
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Doctoral thesis (other academic/artistic)abstract
- Self-assembly of nanoparticles is a widely used technique to produce nanostructured materials with crystallographic coherence on the atomic scale, i.e. mesocrystals, which can display useful collective properties. This thesis focusses on the underlying mechanism and dynamics of mesocrystal formation by using real-time techniques. Quartz-crystal microbalance with dissipation monitoring (QCM-D) as well as small-angle X-ray scattering (SAXS) in combination with optical microscopy were used to probe the temporal evolution of growing mesocrystals to elucidate the growth mechanism.Time-resolved small-angle X-ray scattering was used to probe the formation and how the structure and defects of the growing mesocrystals in levitating droplets evolve with time. Probing self-assembly of oleate-capped iron oxide nanocubes during evaporation-driven poor-solvent enrichment (EDPSE) showed that a low particle concentration in combination with a short nucleation period can generate large and well-ordered mesocrystals. Information on the formation and transformation of defects in mesocrystals were obtained by analysis of the temporal evolution of crystal strain. A transition from a rapidly increasing isotropic strain to a decreasing anisotropic strain towards the end of the growth stage was observed. The occurrence of anisotropic strain was assigned to the formation of stress-relieving dislocations in the crystal, which were induced by large internal stresses caused by superlattice contraction.Directed assembly of superparamagnetic iron oxide nanocubes, subjected to a weak magnetic field, produced one-dimensional mesocrystal fibers. Real-time SAXS as well as optical microscopy revealed a two-stage growth mechanism. The primary stage involved the growth of cuboidal mesocrystals by nanocube self-assembly. In a secondary stage, the cuboidal mesocrystals were assembled and aligned into fibers by the magnetic field. Evaluation of the magnetic dipole-dipole and van der Waals interactions showed that the dipolar forces arising between two nanocubes in a weak magnetic field are negligible compared to the van der Waals forces, but become the dominant force for larger mesocrystals, which drives the formation of fibers.QCM-D combined with optical microscopy provided simultaneously information on the rheological properties as well as on the mass of an adsorbed self-assembled layer of iron oxide nanocubes. We show that the iron oxide nanocubes rapidly assembled into an array with primarily viscous characteristics. This fluid-like behaviour can be assigned to a layer of solvent surrounding the nanocubes inside the assembly. Expulsion of the thin solvent layer from the assembled array is responsible for the increase in rigidity observed shortly after the beginning of self-assembly.
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| 3. |
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| 4. |
- Lv, Zhong-Peng, et al.
(author)
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Time-Resolved SAXS Study of Polarity- and Surfactant-Controlled Superlattice Transformations of Oleate-Capped Nanocubes During Solvent Removal
- 2022
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In: Small. - : John Wiley and Sons Inc. - 1613-6810 .- 1613-6829. ; 18:22
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Journal article (peer-reviewed)abstract
- Structural transformations and lattice expansion of oleate-capped iron oxide nanocube superlattices are studied by time-resolved small-angle X-ray scattering (SAXS) during solvent removal. The combination of conductor-like screening model for real solvents (COSMO-RS) theory with computational fluid dynamics (CFD) modeling provides information on the solvent composition and polarity during droplet evaporation. Evaporation-driven poor-solvent enrichment in the presence of free oleic acid results in the formation of superlattices with a tilted face-centered cubic (fcc) structure when the polarity reaches its maximum. The tilted fcc lattice expands subsequently during the removal of the poor solvent and eventually transforms to a regular simple cubic (sc) lattice during the final evaporation stage when only free oleic acid remains. Comparative studies show that both the increase in polarity as the poor solvent is enriched and the presence of a sufficient amount of added oleic acid is required to promote the formation of structurally diverse superlattices with large domain sizes. © 2022 The Authors.
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