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Processing of Single-Walled Carbon Nanotubes by Reduction in Metal-Ammonia Solutions

Buckley, DJ; (2015) Processing of Single-Walled Carbon Nanotubes by Reduction in Metal-Ammonia Solutions. Doctoral thesis , UCL (University College London). Green open access

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Abstract

In this thesis, metal-ammonia reduction is used to induce the spontaneous dissolution of single-walled carbon nanotubes (SWCNTs) in polar aprotic solvents. The aim of the project is to quantify the dissolution of SWCNTs and to characterise the solutions by purity compared to the starting material as well as by separation based on the geometry and electronic structure of the nanotubes. The work focuses on an improvement of the dissolution process by careful stoichiometric control of the reduction chemistry to obtain a yields of >90 %, and a quantitative analysis using complementary techniques of UV-Vis-NIR, Raman spectroscopy and photoluminescence to show that the population of metallic SWCNT species can be enriched from 26.3 % to 55.9 % of the overall SWCNT species. An enhancement of larger diameter tubes in the dissolved fraction is also observed within the semiconducting species. A low charge regime is used to show the preferential dissolution of the impurities over that of the SWCNTs to leave a cleaner material with an enhanced sp2 electronic structure. In the highest charge regime, it is shown the salt phase becomes favourable and that the favourable dissolution of smaller diameter nanotubes can be achieved. The dissolution of longer and larger diameter SWCNTs is also characterised, showing the power of this method to achieve tailored, high quality and high concentration solutions of nanotubes. Monte Carlo simulations are used to calculate the enthalpy to explain the selectivity. The simulations show the favourable enthalpy of dissolution for the lesser charged nanotubes and the unfavourable dissolution for both high charge and zero charge regimes. The larger diameter nanotubes are shown to be more favourable to dissolve at lower charge and less favourable at higher charge than smaller diameter nanotubes, in agreement with the experimental data.

Type: Thesis (Doctoral)
Title: Processing of Single-Walled Carbon Nanotubes by Reduction in Metal-Ammonia Solutions
Event: UCL (University College London)
Open access status: An open access version is available from UCL Discovery
Language: English
Keywords: SWCNTs, Characterisation, Raman, Photoluminescence, UV-VIs-NIR, Monte Carlo
UCL classification: UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
URI: http://discovery.ucl.ac.uk/id/eprint/1472025
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