Systematic Study of Parameters Affecting Unconventional Magnetism in Gold Nanostructures
Date
2018-03-09
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Abstract
In this exploratory study we seek to make sense of the conflicting results and interpretations of the novel magnetism of gold, by isolating two variables for testing. They are molecular dipole moment of the thiol that forms a self-assembled monolayer (SAM) on gold nanoparticles and thin-films, and roughness of gold thin-films. The first variable is chosen because the dipole moment of the thiol is believed to affect the ease of charge redistribution from gold to the SAM. The second variable is studied because the domain size of the SAM has been suggested to influence the magnetism of coated gold surfaces, and because nanostructuring of gold could be a source of magnetism itself. In this thesis we study a series of gold nanoparticles coated by different thiols, a series of flat gold thin-films coated by different alkanethiols, and finally, a series of highly porous gold thin-films, which can also be coated by thiols. The first series shows that magnetism of Au NPs does relate to the thiol used to coat it, and that the effect of an electron-withdrawing terminal group of the thiol is much greater than its chain length. The second series establishes that thiolate-coated gold thin-films are indeed magnetic, a notion previously debated. It shows the thin-films to be soft ferromagnets, with evidence emerging for the existence of ferromagnetic exchange in them. The third series finds highly anisotropic magnetization in thiolate-coated nanoporous gold, and shows that the nanoporous gold to be not only magnetic without any coating, but to display magneto-optical Kerr effect as well, which proves the existence of spin polarization in the nanoporous gold. In order to create novel gold nanostructures, low-potential anodization of gold in oxalic acid is studied with the goal of deducing mechanism and improving applicability. Oxalic acid is shown not to be the uniquely suitable electrolyte, with the finding of hydroquinone as a replacement, offering support to our model involving a gold complex participating in catalysis.
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Keywords
nanoparticle, magnetism, gold, thin-film, thiol
Citation
Dong, P. (2018). Systematic study of parameters affecting unconventional magnetism in gold nanostructures (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/31097