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Title: Dispersion, adsorption properties and separation of nanoparticles
Author: Kastrisianki-Guyton, Emma
ISNI:       0000 0004 5919 0515
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2015
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Recent years have seen a surge in interest into the properties of new materials, and their application in electronic devices. This project has used techniques common for colloidal systems in order to gain insight into these systems. The work has mainly focussed on single-walled carbon nanotubes (SWCNTs), however silicon nanowires have also briefly been studied. Pluronic block copolymers are commonly used to stabilise SWCNTs in water, most commonly F127. Such dispersions were studied using small-angle neutron scattering (SANS) experiments performed at a range of solvent contrast systems. The data were successfully fitted to a relatively simple core-shell cylinder model. Data fitting was consistent with SWCNTs present in small bundles in dispersion, with an average radius of 10 A, surrounded by a water-swollen F127 layer of 61 A thickness, with a water content of 94% in the adsorbed layer. Increasing the temperature of F127 /SWCNT /D20 systems so that they were above the critical micellisation temperature (CMT) of the polymer was seen to have only a small impact on the polymer adsorption, with the adsorbed layer thickness increasing from ~55 to 65 A, and the adsorbed amount increasing by between 50 and 100% (from ~ 1 to 1.5 mg m- 2). Dispersions of SWCNTs in surfactant mixtures of SDS and sodium cholate (SC) are often used to separate SWCNTs by electronic type. SWCNTs were dispersed with SDS and studied using small-angle scattering techniques at various contrasts. Data were fitted to a core-shell cylinder model, and the fits were consistent with small SWCNT bundles of an average radius of 10 A, surrounded by an adsorbed layer of thickness 18 A. The adsorbed amount of SDS at the SWCNT surface was calculated to be 2.5 mg m-2 , however the adsorbed amount at the SDS headgroup/water interface was calculated to be 0.85 mg m- 2 , a value closer to previously reported values for the adsorption of SDS on carbon surfaces. Subsequently, SWCNTs dispersed with SC and mixtures of SDS and SC (1:4 and 3:2 volume ratios of SDS:SC) were studied with SANS, and the dimensions of the decorated SWCNTs were not seen to vary greatly between the different surfactants studied. Finally, the separation of nanoparticles has been investigated. The separation of SWCNTs based on their electronic properties using aqueous PEG/dextran twophase polymer systems was studied. Although absorbance spectra suggested that an electronic separation of SWCNTs had occurred, the process was found to be highly irreproducible. Additionally, variations in temperature were found to have little effect on partitioning and no separation by electronic type was seen when F127-dispersed SWCNTs rather than SC-stabilised SWCNTs were used, suggesting that, unlike F127, SC adsorbs differently to SWCNTs depending on their electronic type. Silicon nanowires (SiNWs) have also been briefly studied, and separating the nanowires by length was attempted using glass bead columns, however no significant separation by length was achieved.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available