Fabrication and Application of Carbon Nanotube/Silicon Nanostructures

Author: Cameron James Shearer

Shearer, Cameron James, 2011 Fabrication and Application of Carbon Nanotube/Silicon Nanostructures, Flinders University, School of Chemical and Physical Sciences

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The amazing electrical and mechanical properties of carbon nanotubes (CNTs) make them ideal for use in a variety of applications, many of which require the CNTs to be surface bound. Here the applicability of nanostructures based upon CNTs chemically attached to silicon to the fields of water filtration, field emission and as biomaterial interfaces is investigated. Initial experiments studied the chemical attachment and alignment of different CNT types to silicon. Single-walled carbon nanotubes (SWCNTs) were found to form vertically aligned arrays on both flat silicon and porous silicon (pSi). Double-walled carbon nanotubes (DWCNTs) were found to exhibit both vertical and random alignment while multi-walled carbon nanotubes (MWCNTs) exhibited an exclusive horizontal orientation. The variation in alignment is attributed to the level of crystallinity and functionalisation of each CNT type as determined by Raman spectroscopy. The control of the placement of SWCNTs on silicon was further investigated by fabricating both surface coverage gradients and patterns of SWCNTs. Gradients were fabricated following two protocols, both of which produced surfaces which consist of all possible SWCNT coverages. SWCNT patterns were produced by forming an initial chemical pattern on the silicon surface for subsequent selective SWCNT chemical attachment. CNT membranes for water filtration were fabricated by chemically attaching SWCNTs to permeable pSi membranes. Gaps between the SWCNTs were filled by spin coating polystyrene onto the surface. The SWCNT tips were revealed by etching the polystyrene matrix via water plasma treatment. The fabricated membranes were found to have a water permeability of 0.022 mm3 cm-2 s-1 atm-1. Comparisons to commercial nanofiltration membranes and other published CNT membranes are made and improvements to membrane fabrication are discussed. Field emission experiments were completed for all CNT types chemically attached to silicon. All samples exhibited field emission of electrons with characteristics varying with CNT diameter and vertical alignment. The emission stability of each CNT type was investigated with the SWCNTs exhibiting the most stable emission. Comparison of emission characteristics and stability to other CNT field emission substrates are made. The behaviour of a mammalian neuronal cell line on SWCNTs chemically attached to porous silicon was investigated. Fluorescence microscopy revealed that the cells had a strong affinity for the SWCNT substrate and that the SWCNTs may compromise the cell membrane allowing small fluorescent molecules to enter the nuclear envelope. Experiments to determine if plasmid DNA could be inserted into the cell via the SWCNTs was completed with results indicating the SWCNTs did not promote DNA transfection for the neuronal cell line.

Keywords: carbon nanotube,field emission,water filtration,cell interface,single walled carbon nanotube
Subject: Nanotechnology thesis

Thesis type: Doctor of Philosophy
Completed: 2011
School: School of Chemical and Physical Sciences
Supervisor: Prof Joe Shapter