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Title: Sum frequency generation from Langmuir-Blodgett fatty acid films incorporating semiconductor nanoparticles
Author: Holman, J.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2004
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The principal method of probing the structure of these films was the non-linear optical technique of Sum Frequency Generation (SFG). The experimental techniques used in this work are first introduced together with a theoretical description of SFG. There then follows an overview which describes semiconductor nanoparticle monolayers and the application of SFG to them. The work was subsequently extended to the investigation of multilayers of semiconductor nanoparticles incorporated within fatty acid films. Whilst SFG of monolayers is well understood SFG of multilayer films is not and most of this dissertation has been devoted to providing a systematic description of SFG of multilayer films adsorbed onto both metal and dielectric substrates. The observed multilayer SFG spectrum is shown to be a superposition of SFG signals coming from the surface layer, in contact with air, and the lowermost layer, in contact with the substrate. The SFG spectrum is a simple numerical addition of the two signals when gold is used as a substrate and as a subtle convolution of the two signals when a dielectric substrate is used. Through the incorporation of a single perprotonated fatty acid layer within an otherwise fully per-deuterated film it has been possible to study both the surface layer and buried interfaces. The resonant line shapes of SFG spectra obtained on gold substrates were found to depend on layer thickness, something which has been quantified experimentally and explained theoretically in terms of a nanoscale thin film interference effect. In the final part of the dissertation the capacity of SFG for studying buried interfaces has been exploited to investigate nanoparticle-induced structural changes within fatty acid multilayer films, demonstrating the versatility and potential of this novel application of SFG. It was found that, following nanoparticle formation within the fatty acid film, the surface layer remained highly ordered whilst the buried layers became disordered.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available