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978-3-8439-2151-0, Reihe Ingenieurwissenschaften
Synthesis and Characterization of Anisotropic Noble Metal Nanostructures for Applications in Nanotechnology
196 Seiten, Dissertation Universität Erlangen-Nürnberg (2015), Softcover, A5
In this thesis, a facile approach for preparation of regular one-dimensional metal nanostructures is presented which may have significant implications for the fabrication of functional devices in nanotechnology, like optical, electronic and catalytic components. The formation of one-dimensional silver nanoparticle assemblies on sub-micron silica spheres appeared to happen naturally via the liquid phase treatment of colloidal silica with diamminesilver(I) complex followed by washing, deposition on a substrate and ageing under ambient conditions. Electron microscopy reveals that, despite the lack of addition of reducing or templating agents, 5 – 10 nm silver nanoparticles are formed that are arranged in necklace-like assemblies on the silica spheres and up to a certain distance from them on the substrate. The random and irregular occurrence of these nanostructures was improved by developing a strategy to control homogeneity of diamminesilver(I) complex treatment and drying. This enabled the reproducible preparation of coatings on silicon wafers over a square centimetre range, which is the basis for further studies to exploit the potential optical and electronic properties of these nanostructures.
Since the shape stability of anisotropic nanostructures is essential to preserve structure-related properties and thus function, dynamic reshaping processes on the nanoscale were studied for anisotropic silver and gold nanoparticle systems. A new evaluation method for quantification of such shape transformation dynamics was developed, and it could be shown that surface passivation agents are necessary to stabilize the interface. This prevents the nanoparticles from transforming to spheres, being the thermodynamically most stable shape.
Furthermore, the gained knowledge of Stöber silica surface chemistry was used to coat them with Co3O4, a material being highly relevant for applications in lithium ion batteries. The acquired synthesis method can in future be transferred to bio-templated silica nanowires made from cellulose nanofibres being a promising candidate for a sustainable nanomaterial made from renewable biological sources.