Processing, Properties and Applications of Double-Walled Carbon Nanotubes

Author: Katherine Elizabeth Moore

Moore, Katherine Elizabeth, 2015 Processing, Properties and Applications of Double-Walled Carbon Nanotubes, Flinders University, School of Chemical and Physical Sciences

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Double-walled carbon nanotubes (DWCNTs) consist of two concentric cylinders of carbon and are a unique structural intermediate between single- (SWCNT) and multi- (MWCNT) walled carbon nanotubes. As such, they share many of the attributes of SWCNTs, such as their unique electronic properties; however as the simplest form of a MWCNT, they also offer insights into inter-wall coupling, which has a significant effect on the overall electronic properties of the nanotube. Furthermore, the concentric structure of DWCNTs enables the outer wall to be selectively functionalized for further chemical processing or sensitization, whilst the inner wall remains in its pristine state and available for signal transduction. The strong coupling between the inner and outer wall, in conjunction with the sensitivity of nanotubes to their surrounding environment, enable the inner wall to indirectly sense chemical changes to the outer wall, without compromising its own structure. In this thesis, a preliminary investigation into the electrochemical properties of as-prepared DWCNTs was conducted, where they appeared to be advantageous compared to their single-walled counter parts. This advantage arises from the secondary wall, which allows for covalent modification without compromising the sp2 structure of the inner wall. Despite these observations, the inherent inhomogeneity of as-prepared DWCNT material remained a significant challenge for incorporation into sophisticated electronic and sensor devices. As such, the main focus of this thesis was to overcome the inherent inhomogeneity of DWCNT samples through the use of gel permeation, a well-established technique for separating SWCNTs by diameter, length, electronic character and chirality. Upon successfully producing enriched DWCNT samples free of SWCNT and MWCNT contaminants, the technique was then further extended to sort DWCNTs according to the electronic character of the outer wall. Enriched metallic and semiconducting outer walled DWCNTs were then incorporated into single nanotube field effect transistors, where the electronic behavior of the four DWCNT types could be directly measured without the uncertainty associated with bulk nanotube films of unknown composition.

Keywords: carbon nanotubes,double-walled,separation,Sephacryl gel

Subject: Physics thesis

Thesis type: Doctor of Philosophy
Completed: 2015
School: School of Chemical and Physical Sciences
Supervisor: Prof. Michael Brunger