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Title: Liquid crystal induced ordering of gold nanorods
Author: Thomas, Michael
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2013
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The main themes of this work cover the preparation, suspension and analysis of functionalised gold nanorods in small molecule nematic liquid crystal solvents as archetypal systems to further the understanding of anisotropic nanoparticle suspensions in anisotropic molecular solvents. The analysis has focussed on the stability of these suspensions towards aggregation and sedimentation as well as their response to electric fields of varying strength and frequency, monitored by Synchrotron Radiation Small Angle X-ray Scattering. The influence of surface functionalities (including short n-alkylthiol monolayers, functionalised silica encapsulation and polar and non-polar polymeric brushes) upon nanorod behaviour has been reported. In doing so, it has been demonstrated that when thin steric layers are employed, nanorods form well-ordered, assembled nanostructures that display excellent orientational ordering upon inclusion in small molecule nematics under the influence of an electric field. If the steric layer is sufficiently thick, the interparticle van der Waals attractive forces can be mediated yielding highly stable dispersed gold nanorods in non-aqueous isotropic solvents. The stability of these nanorod 'inclusions in the nematic phase has been shown to be strongly influenced by both the thickness and the chemical composition of the steric layer. The orientational response of individually dispersed nanorods (modified with polar, covalently ' bound polyethylene glycol brush layers) has been shown to be influenced by aspect ratio and polymer length. Their response to flow and magnetic fields, as well as simulations of the effect of anisotropic dielectric solvents on particle alignment in electric fields, have been used to develop an understanding of the strong orientational response these suspensions. In addition, nanorod fractions that were not freely-dispersed have been characterised, providing insight into the design of future materials that can utilise the extensive understanding developed from these diversely modified nanorod archetypes.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available