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Title: Electrochemical processing of single-walled carbon nanotubes and related materials
Author: Hodge, Stephen Anthony
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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The remarkable properties of single-walled carbon nanotubes (SWNTs) and potential applications are hindered by current solution-phase processing strategies. The initial dissolution of SWNTs remains a fundamental challenge, reliant on aggressive chemistry or ultrasonication and lengthy ultracentrifugation. In this thesis, a simple non-aqueous electrochemical reduction process that leads to spontaneous dissolution of individualised SWNTs from raw, unprocessed powders is outlined. The intrinsic electrochemical stability and conductivity of these nanoparticles allows their electrochemical dissolution from a pure SWNT cathode to form solutions of well-defined nanoparticle anions with characteristic charge density. Other than a reversible change in redox/solvation state, there is no obvious chemical functionalisation of the structure, suggesting an analogy to conventional atomic electrochemical dissolution. The heterogeneity of as-synthesised SWNT samples leads to the sequential dissolution of distinct fractions over time. Initial preferential dissolution of defective nanotubes and carbonaceous debris provides a simple, non-destructive means to purify raw materials without recourse to the usual, damaging, competitive oxidation reactions. During early stage developments, the process showed remarkable affinity for dissolving metallic SWNTs, providing a potentially scalable route for separation by electronic character, vital for many applications. However, selectivity was lost with significantly increased process yields (complete dissolution) following several optimisations. Subsequently, the electrochemical deposition of SWNTs is proposed as a new route to selectively plate specific SWNT species and avoid unwanted functionalisations that occur when exposing reduced SWNTs to different atmospheres. Finally, the extension of electrochemical processing to related materials including activated and graphitic nanocarbons, metallic and metal chalcogenide nanomaterials was also investigated, with great promise for the development of new applications.
Supervisor: Shaffer, Milo Sponsor: LSI Logic Corporation
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral