Scanning transmission electron microscopy tomography and 4D-stem applied to the study of chiral and self-assembled nanoparticles

Da Silva, Alessandra (2020). Scanning transmission electron microscopy tomography and 4D-stem applied to the study of chiral and self-assembled nanoparticles. University of Birmingham. Ph.D.

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Over recent years, advances in nanotechnology have led to an increased interest towards engineering nanomaterials with defined morphologies, for applications where the nanoparticle shape plays a significant role in processes, such as in catalysis, drug delivery and optics. Therefore, it is essential to resolve the 3D morphology and structure of these materials in order to gain understanding about their physical and chemical properties for further optimization. Following this line of research, this thesis explores a set of experiments that makes use of Scanning Transmission Electron Microscopy (STEM), incorporating both STEM tomography and 4D-STEM techniques. These techniques were used to investigate the origin of
chiral shapes in Tellurium (Te) bipyramidal nanoparticles, where it was determined that the chiral geometries of the nanoparticles arise from growth mediated by screw dislocations rather than chiral ligands used in their synthesis. Gold (Au) nanoparticle self-assembled superlattices were studied by electron tomography and their lattice structure was investigated through determination of the 3D nanoparticle positions. The superlattices were found to have different crystalline structures for different molecular weights of their protective ligands. Finally, gold nanoparticles that seemed to have a twisted bipyramidal geometry were investigated through electron tomography. A model was built from the reconstructed cross-sections which supported the conclusion that the asymmetry in the shape resulted from the arrangement of the facets rather than a twist. The analyses performed in this thesis were custom-developed building upon general electron microscopy and mathematical concepts, enabling their application towards different systems and materials.

Type of Work: Thesis (Doctorates > Ph.D.)
Award Type: Doctorates > Ph.D.
Licence: All rights reserved
College/Faculty: Colleges (2008 onwards) > College of Engineering & Physical Sciences
School or Department: School of Physics and Astronomy
Funders: Other
Other Funders: Brazilian National Council of Technological and Scientific Development (CNPq)
Subjects: Q Science > QC Physics


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