Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604308
Title: The structure and stability of colloidal nanoparticle assemblies
Author: Alhummiany, Haya A.
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2012
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Abstract:
Thiol-passivated gold nanoparticies deposited onto a silicon substrate from an organic solvent form a remarkable variety of self-organised nanostructured and microstructured patterns. The work in this thesis focuses on three key aspects of these systems: (i) their environmental stability, (ii) the formation of nanoparticie rings via condensation of water droplets, and (iii) the morphology of nanoparticie mono layers formed at the water-air interface and transferred to silicon substrates using the Langmuir-Blodgett technique. The nanoparticie structures were studied by combined atomic force microscopy (A FM) and contrast-enhanced optical microscopy. Striking changes in the morphology of self-organised nanoparticie patterns are observed during exposure to high humidity or high temperature environment. Annealing the sample at 1200 C leads to a high degree of nanoparticie sintering promoted by break-up of the initial assembly. Conversely, exposing the sample to a high relative humidity (80%) environment induces layer-by-layer assembly of 3D aggregates with no evidence of sintering. We focus also on the formation of rings of thiol-passivated Au nanoparticies, addressing the controversy in the literature regarding the formation of these structures. We provide compelling evidence that nanoparticie rings formed via the adsorption of droplets of condensed water. This so-called "breath figure" effect plays the dominant role in the dynamics of ring formation via iii evaporative dewetting. Different sizes and size distributions of nanoparticle rings have been created under controlled relative humidity environments ranging from ~50% to 80%. Fmthermore, the dynamic behaviour of water droplets on surface has been examined using a contrast-enhanced optical mIcroscope. Analysis of the observed droplet dynamics shows significant differences between the behaviour of droplets formed on top of a silicon substrate and the nanoparticle films. Finally, the formation of gold nanoparticle assemblies at the water-air interface using the Langmuir-Blodgett deposition technique has also been studied. The LB films were transferred to a solid substrate (silicon) and the nanoparticle assemblies fOlmed close to the contact line imaged by AFM and contrastenhanced optical microscopy. The experimental control parameters resulted in the emergence of variety of nanoparticie morphologies. We propose formation mechanisms for a number of these morphologies.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.604308  DOI: Not available
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