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Title: Studies on optical characterisation of carbon nanotube suspensions
Author: Nish, Adrian
ISNI:       0000 0001 3447 5758
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2008
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This thesis reports studies done on single-walled carbon nanotubes (SWNTs) using optical spectroscopy as the primary investigative technique. It focuses on advances in sample preparation which have been made possible through improvements to the method of photo-luminescence excitation (PLE) mapping of nanotubes. An introduction to the field and some theoretical models are presented initially to provide a background to the experimental chapters which follow. A description of the standard procedure for sample preparation in aqueous surfactants is then followed by a detailed introduction to PLE mapping, including modeling of SWNT spectra. The next chapter discusses improvements to the sample preparation method by using organic polymer solutions instead of aqueous surfactants for suspending the nanotubes. The results show reductions in the distribution of SWNT species which are solubilised, leading to significant improvements in the resolution of the optical absorbance spectra and an increased photoluminescence yield. Two experiments which were performed on the novel polymer-SWNT systems are then described. The first shows (via PLE mapping) that energy is transfered to the SWNTs when the polymer is photo-excited. The possible mechanisms behind this, as well as the implications for using carbon nanotubes as an additive in polymer photovoltaics, are discussed. The second experiment details a recent magneto-PL study of SWNTs embedded in films produced from the polymer solutions. Here, the improved optical signatures and absence of strain at low temperatures have revealed a previously unseen high field intensity dependence. The behavior has been explained by the magnetic field induced mixing of the excitonic states.
Supervisor: Nicholas, Robin J. Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Physical Sciences ; Advanced materials ; Nanomaterials ; Materials Sciences ; Nanostructures ; Physics ; Condensed Matter Physics ; carbon nanotubes ; photoluminescence spectroscopy ; excitons