Book/Dissertation / PhD Thesis

FZJ-2020-03282

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Nanoparticle assemblies: Order by self-organization and collective magnetism

Qdemat, A. (Corresponding author)FZJ*

2021
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-95806-542-0

Please use a persistent id in citations: http://hdl.handle.net/2128/26781  urn:nbn:de:0001-2021052765

Abstract: Assembly of nanoparticles into highly ordered two- or three-dimensional arraysis a prerequisite to achieve their application in novel functional devices. The unique properties of such ensembles differ significantly from those of individual nanoparticles. The assembly techniques have to be able to control the arrangement of nanoparticles over large areas and should be suitable for industrial applications. In the present work, novel, simple and in expensive assembly approaches used to achieve highly ordered two- and three-dimensional arrangements of nanoparticles, are presented. Also, an extensive determination of the structural and the magnetic correlations of the obtained systems has been performed using advanced scattering methods. Among a variety of common assembly techniques, drop-casting is one of the prospective approaches because of its simplicity. Although drop casting has shown its potential to form ordered nanoparticle arrangements, the formation of uniform nanoparticle arrays over large areas remains a challenging subject. Here, we introduce an improved variant of the drop-casting method and demonstrate the formation of large-area highly ordered monolayers of silica nanospheres on asilicon substrate. In our method, the addition of stearyl alcohol to the colloidal nanoparticle dispersion assists the assembly of SiO$_{2}$ nanospheres with a size of 50 nm into a highly ordered arrangement. We reveal that the NPs concentration, the stearyl alcohol concentration, the volume of the droplet, and the annealing time are key factors in the self-assembly in our method. The SiO$_{2}$ nanosphere monolayers contain almost no cracks and voids. Structural characterization of the obtained silica NP monolayer was done locally by Scanning Electron Microscopy (SEM), and globally by X-Ray Reflectivity (XRR) and Grazing Incidence Small-Angle X-ray Scattering (GISAXS), where the data is reproduced by simulation within the Distorted Wave Born Approximation (DWBA). This allows one to make unbiased conclusions that the heat treatment in combination with a compatible additive with a melting point significantly below that of theparticles, can be a general method to improve the ordering between particles inmonolayers as well as in multilayers. Also, in this thesis, 2D arrays of cobalt ferrite (COF) nanodots on silicon substrates were used to determine the effects of dipolar interparticle interactions on the magnetic properties of self- assembled structures of magnetic nanoparticles. GISAXS and SEM confirm a close-packed hexagonal order of the NP monolayer. Atomic force microscopy (AFM) provides information about the interparticle distance and XRR provides the depth profile of the 2D nanodots monolayer. Simulation of the GISAXS pattern reveals that the particles have a hemispherical shape with a height of 10 nm, a radius of 8.5 nm and a hexagonal ...

Note: Dissertation, RWTH Aachen, 2020

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Contributing Institute(s):

1. Streumethoden (JCNS-2)
2. Streumethoden (PGI-4)
3. JARA-FIT (JARA-FIT)

Research Program(s):

1. 899 - ohne Topic (POF4-899) (POF4-899)

Experiment(s):

1. MARIA: Magnetic reflectometer with high incident angle (NL5N)

Appears in the scientific report 2020

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Database coverage:
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