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Type: Theses
Title: Carbon nanotube composites: advanced properties for emerging applications
Author: Altalhi, Tariq Ateeq
Issue Date: 2014
School/Discipline: School of Chemical Engineering
Abstract: Carbon nanotubes (CNTs) have been considered as an outstanding nanomaterial, envisaged for developing a new generation of membranes for advanced molecular separation as a result of their unique transport properties and ability to mimic biological protein channels. Nevertheless, the excellent physical and chemical properties of CNTs make this material attractive for other potential applications. For example, free-standing or liberated CNTs are nanostructures with excellent properties to develop smart nanocarriers for targeted and localized drug delivery. Before these applications become feasible, however, the fabrication process of CNTs must be entirely understood in order to produce nanostructures with totally controlled dimensions and properties. So far, some approaches have been used to synthesise CNTs, the most representative of which are arc discharge, laser ablation and catalytic chemical vapor deposition (C-CVD). However, these fabrication methods present many fundamental disadvantages (e.g. expensive equipment, high temperature of synthesis, use of toxic and hazardous materials, impurities/contaminations, etc.). Therefore, the physical and chemical properties of the resulting CNTs rely both on fabrication method and manufacturer, thus preventing the production of standardized CNTs. In this scenario, this thesis puts forward a catalyst-free CVD approach for fabricating CNTs with totally controlled properties (e.g. geometry, shape, chemical composition, surface chemistry, etc.) by using nanoporous templates with well-defined chemistry and geometry. As a result of its simplicity, versatility, scalability and cost-competitive fabrication process, this approach is envisaged for producing CNTs featuring standardized properties, which are required for a broad range of applications (e.g. separations, drug delivery, etc.). To develop this CVD approach, the optimal conditions for the fabrication of catalyst-free CNTs were determined by varying such parameters as temperature, reaction path length, absence or presence of catalyst, type of nanoporous template (i.e. nanoporous anodic alumina (NAA) or titania nanotubes (TNTs)) and type of carbon source. The most relevant aspects of this study were: 1 – Carbon Source: Two unconventional carbon sources were explored: namely, a mixed solution of toluene and ethanol and non-degradable grocery plastic bags. 2 – Nanoporous Template: To understand the mechanism of this catalyst-free CVD approach using nanoporous templates, a set of experiments comparing the growth of CNTs inside NAA and TNTs were performed. This made it possible to understand the role of the nanoporous template in the growth of CNTs as well as to establish of the mechanism of growth of CNTs inside these nanoporous templates. 3 – Geometry and Shape: CNTs with different geometries and shapes (e.g. periodically modulated diameters) were fabricated by using NAA templates featuring different geometries and shapes. This confirmed the capability of the proposed CVD approach to synthesise CNTs with desired shapes and geometries, offering new opportunities to develop innovative nanostructures for emerging applications. 4 – Chemical Composition: The presence of heteroatoms has a direct impact over the synthesis of CNTs. To throw light on this question, the effect of such heteroatoms as nitrogen (N), sulfur (S), phosphorus (P) and co-doped sulfur/phosphorus (S/P) on the quality of the resulting CNTs was investigated. 5 – Surface Chemistry Functionalization: Chemical modification of the inner surface of CNTs was achieved through gas-phase and solvent-free functionalization with different functional compounds (i.e. 1-octadecylamine (ODA), 1,8-diaminooctane (DO) and polyethyleneimine (PEI)). 6 – Applications: Finally, CNT membranes and free-standing CNTs obtained by the above-mentioned CVD approach were used in two significant applications: ◆ Sophisticated separation nanodevices (separation): To demonstrate the capability of these membranes to selectively tune molecular transport as a function of the interaction between molecules and inner surface of CNTs, the transport performance of these membranes was analyzed when transporting several dye molecules with positive, negative and neutral charge. ◆ Smart nano-carriers for delivering chemotherapeutic drugs (drug delivery): Free standing CNTs with hydrophilic core were used as nanocontainers for delivering anti-cancer drug. These CNTs were loaded with doxorubicin (Dox) and its external surface was chemically functionalized with a biodegradable polymer (chitosan) by anchoring its polymeric chains to functional groups on the external surface of CNTs. The presented results are expected to be the starting point of the development of new nanodevices based on innovative CNTs featuring totally controlled properties (i.e. standardized product), which could be used in a broad range of research fields and commercial applications.
Advisor: Losic, Dusan
Santos, Abel
Dissertation Note: Thesis (Ph.D.) -- University of Adelaide, School of Chemical Engineering, 2014.
Keywords: CNTs
Provenance: This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at:
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