| 1. |
- Saini, Apurve, et al.
(författare)
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Magnetic particle self-assembly at functionalized interfaces
- 2021
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 37:14, s. 4064-4071
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Tidskriftsartikel (refereegranskat)abstract
- We study the assembly of magnetite nanoparticles in water-based ferrofluids in wetting layers close to silicon substrates with different functionalization without and with an out-of-plane magnetic field. For particles of nominal sizes 5, 15, and 25 nm, we extract density profiles from neutron reflectivity measurements. We show that self-assembly is only promoted by a magnetic field if a seed layer is formed at the silicon substrate. Such a layer can be formed by chemisorption of activated N-hydroxysuccinimide ester-coated nanoparticles at a (3-aminopropyl)triethoxysilane functionalized surface. Less dense packing is reported for physisorption of the same particles at a piranha-treated (strongly hydrophilic) silicon wafer, and no wetting layer is found for a self-assembled monolayer of octadecyltrichlorosilane (strongly hydrophobic) at the interface. We show that once the seed layer is formed and under an out-of-plane magnetic field further wetting layers assemble. These layers become denser with time, larger magnetic fields, higher particle concentrations, and larger moment of the nanoparticles.
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| 2. |
- Theis-Bröhl, Katharina, et al.
(författare)
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Self-Assembled Layering of Magnetic Nanoparticles in a Ferrofluid on Silicon Surfaces
- 2018
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 10:5, s. 5050-5060
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Tidskriftsartikel (refereegranskat)abstract
- This article describes the three-dimensional self assembly of monodisperse colloidal magnetite nanoparticles (NPs) from a dilute water-based ferrofluid onto a silicon surface and the dependence of the resultant magnetic structure on the applied field. The NPs assemble into close-packed layers on the surface followed by more loosely packed ones. The magnetic field-dependent magnetization of the individual NP layers depends on both the rotational freedom of the layer and the magnetization of the adjacent layers. For layers in which the NPs are more free to rotate, the easy axis of the NP can readily orient along the field direction. In more dense packing, free rotation of the NPs is hampered, and the NP ensembles likely build up quasi-domain states to minimize energy, which leads to lower magnetization in those layers. Detailed analysis of polarized neutron reflectometry data together with model calculations of the arrangement of the NPs within the layers and input from small-angle scattering measurements provide full characterization of the core/shell NP dimensions, degree of chaining, arrangement of the NPs within the different layers, and magnetization depth profile.
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| 3. |
- Wolff, Max, et al.
(författare)
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Grazing incidence neutron scattering for the study of solid–liquid interfaces
- 2023
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Ingår i: Reference Module in Chemistry, Molecular Sciences and Chemical Engineering. - : Elsevier.
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Bokkapitel (refereegranskat)abstract
- Neutrons are characterized by a low absorption in many engineering materials. At the same time the scattering cross section of light elements, such as hydrogen and deuterium, may be large. These properties make neutron scattering experiments performed under grazing incidence geometry an excellent tool for the study of solid–liquid interfaces. In this review we describe the basic concepts of neutron reflection and grazing incidence scattering experiments as well as experimental procedures and sample cells. The full power of the method is exemplified on a range of science areas, including polymers, bio- and ionic liquid lubricants, electrolytes as well as bio-membranes or magnetic liquids.
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| 4. |
- Wolff, Max, et al.
(författare)
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Grazing incidence neutron scattering for the study of solid–liquid interfaces
- 2023
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Ingår i: Encyclopedia of Solid-Liquid Interfaces. - : Elsevier. ; , s. 1-1
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Neutrons are characterized by a low absorption in many engineering materials. At the same time the scattering cross section of light elements, such as hydrogen and deuterium, may be large. These properties make neutron scattering experiments performed under grazing incidence geometry an excellent tool for the study of solid–liquid interfaces. In this review we describe the basic concepts of neutron reflection and grazing incidence scattering experiments as well as experimental procedures and sample cells. The full power of the method is exemplified on a range of science areas, including polymers, bio- and ionic liquid lubricants, electrolytes as well as bio-membranes or magnetic liquids.
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