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Title: Purification, dispersion and separation of single walled carbon nanotubes
Author: Fogden, Sian
ISNI:       0000 0004 2680 5691
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2009
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In this thesis, the purification, dispersion and separation of Single Walled Carbon Nanotubes (SWNTs) are explored. The motivation for this work arose from the basic desire to understand and further develop the underlying chemistry of SWNTs, thus enabling the extraordinary properties of SWNTs to be used to their full potential. Achieving highly pure SWNT samples on which further chemistry can be undertaken is of critical importance; purification must be able to be performed in a reliable and repeatable manner. As such, a new method of SWNT purification was developed. This method introduced a new base washing step that removed a significant fraction of the impurities created during the standard acid reflux purification. This finding has implications for many existing reports on nanotube chemistry. Separation of SWNTs by their electronic properties is extremely important if SWNTs are to fulfil their potential in a wide range of applications, from optoelectronics to molecular sensing. In order to separate metallic and semiconducting SWNTs, two novel methods were developed, both of which are relatively cheap and easily scalable. First, SWNTs were reduced in liquid ammonia containing an alkali metal. The reduced tube salts were then spontaneously dissolved in dry solvents to form stable dispersions which were found to contain primarily metallic SWNTs; hence, separation was achieved. The second method investigated the separation of SWNTs reduced by electrochemical means. When a voltage was passed through a SWNT sample in a suitable electrolyte, SWNTs were reduced and therefore dissolved. These dissolved SWNTs were deposited as a thin carbon film, in which metallic SWNTs were found to preferentially present; once again, separation was achieved.
Supervisor: Shaffer, Milo Sponsor: EPSRC ; Thomas Swan
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral