Diblock copolymers like poly(styrene)-block-poly(2-vinylpyridine) pave the way for controllable self-assembled monolayers of nanoparticles. Using particular polymer weights and concentration, spherical micelles of PS-b-P2VP can be constructed with a non-polar PS corona and a polar P2VP core. Various precursor salts can be loaded into the core of the micelles due to interactions with the polar core which forms as the active site for nanoparticle growth. The PS corona protects the core from the atmosphere and non-polar solvents. The micelles can then act as nanobeakers for aqueous chemistry in two ways; spontaneous reactions between precursors result in nanoparticles or the trapping of precursor salts can be oxidized or reduced using polymer removal techniques like gas plasmas. In this way, reverse micelles are a facile method of growing metal, metal oxide or dielectric nanoparticles. Process parameters, such as concentration, molecular weights, nature of solvents and type of precursor salt, offer control over the periodicity and size of the monolayer of nanoparticles. Reverse micelle templating is a potentially useful nanofabrication method for tailor-made nanoparticles for use in electrical and optical devices which is not limited to form-factor of substrates. In this thesis, obstacles are identified that hinder the utility of PS-b-P2VP templated nanoparticles in device fabrication. The polymer is insulating which is detrimental to electrical applications. Additionally, the characterization of a monolayer of polymers, thus far, is limited to structural techniques such as SEM and AFM. This thesis sheds light on the mechanism of precursor loading in the micelle core, discusses the efficiency of different polymer removal techniques and uses vibrational spectroscopy for the characterization of monolayers of polymer, loaded polymer and nanoparticles. We have tested enhanced Raman methods using AFM probes to extend the resolution of normal Raman to view monolayers of empty polymers as well. Moreover, using FeCl3-loaded polymer micelles, the control offered by PS-b-P2VP templated growth on the crystal structure of nanoparticles is laid bare. The usefulness of the technique is further divulged by using ordered gamma-Fe2O3 nanoparticles in water-splitting photoanodes where they show an increased efficiency with the inclusion of nanoparticles and their periodicity. This is just an example of devices using reverse micelle templated nanoparticles, paving the way for future applications. The flexibility of this method is further revealed by constructing self-assembled Au/SnO2 nanojunctions within the PS-b-P2VP micelle cores. This was done by exploiting the spontaneous redox reaction between HAuCl4 and SnCl2 in an aqueous environment, and so can be replicated for other metals and metal oxides like Pt, Pd, Ag, TiO2 and ZnO2. The composite nanoparticles formed exhibit a tunable size and dispersion as typically seen with PS-b-P2VP micelles and so, can be used for various applications which require metal/metal oxide junctions. / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/28144 |
| Date | January 2022 |
| Creators | Arbi, Ramis |
| Contributors | Turak, Ayse, Engineering Physics |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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