This thesis describes the design and characterisation of self-assembled systems that employ Coulombic interactions as the primary means for driving assembly. Hierarchical self-assembly is sought in three different areas: mesoporous materials, two-dimensional polymers, and peptide fibres. Chapter 1 presents a general introduction to the rationale for using self-assembly to achieve nanotechnology, the basic principles of self-assembly, and an introduction to charge-based assembly, mesoporous materials, two dimensional polymers, and peptide fibres. Chapter 2 describes a new method to synthesise mesoporous membranes, which may contain silica, using ionic self-assembly. These materials result from combining polyelectrolytes with surfactants and inorganic precursors at liquid-liquid interfaces to give a columnar structure perpendicular to their surface. Chapter 3 describes the theoretical design requirements for a tecton that assembles to form a two-dimensional self-assembled polymer. Based on these rules a peptide-based building block is designed, synthesised, and characterised along with the resulting two-dimensional sheets. Chapter 4 continues the topic of 20 polymers with two next-generation systems for studying the assembly of two-dimensional peptide sheets. Chapter 5 describes research towards achieving hierarchical assembly with Self-Assembled Peptide Fibres using layer-by-layer self-assembly and electrophoretic deposition

The work described in this thesis is concerned with the development of fullerenes and single-walled carbon nanotubes (SWNTs) derivatives by novel chemistries for two main objectives: (i) use of fullerenes derivatives and single-walled carbon nanotubes (SWNTs) as a platform for drug delivery; (ii) use of functionalised SWNTs in nanoparticles catalysts for low temperature fuel cells applications. Chapter 1 gives an overview of structure, synthesis, properties and potential applications of carbon nanotubes, Also, reviews on functionalisation and filling of carbon nanotubes are presented. The latter part of this chapter summarises the most update studies of carbon nanotubes as supports for fuel cells applications. Chapter 2 demonstrates the synthetic methods for chemical functionalized fullerenes (Pf-C6o) which are employed as reversible nano-corks for single-walled carbon nanotubes (SWNTs). In this proof-of-the-principle study, SWNTs are filled with copper acetate or uranyl acetate materials. These encapsulated materials are then blocked by pf-C6o to avoid their leaching from the SWNTs. The use of pf-C6o as corks allows the cleanup of the acetates deposited exterior of the SWNTs without leaching the filled material. The concept of a pH-triggered cascade release of encapsulated materials in SWNTs is also demonstrated. Chapter 3 presents the chemical functionalisations of sidewalls of single-walled carbon nanotubes via diaryldiazomethanes: bis( 4( dimethylamino )phenyl)diazomethane, bis( 4- methoxypheny I )diazomethane, ( 4-(hydroxymethy I )pheny I ) (pheny l)diazomethane and bis( 4-iodophenyl)diazomethane, etc. Covalent functionalisation of SWNTs is carried out using thermolysis of diaryldiazomethane compounds to generate reactive carbene as an intermediate which can then directly couple to benzoidal ring of the tubular graphitic walls. The resulting functionalised products are characterised by TGA, FTIR, and Raman, HRTEM and STEM techniques. The chemical functionalisations are shown to enhance dispersibility of the SWNTs in THF. Their immobilization with gold colloid with high electron diffraction is then conducted in order to increase the contrast during the TEM imaging of the composite material. The gold colloids were covalent attached to the sidewalls of carboxylated SWNTs via cysteine coupling. The covalent tagging of f-SWNT carboxylates are also confirmed by a high-resolution AFM. Chapter 4 describes synthesis, characterisation and testing of chemical functionalized SWNTs as support materials for fuel cells applications. First, various chemical functional groups are immobilized on the sidewalls of SWNTs which are subsequently used as nuclei to allow the growth of palladium nanoparticles thereupon. In this study, formic acid adsorption strengths in term of chemical shifts on these supported palladium nanoparticles on SWNTs are for the first time evaluated by 13C-NMR solution spectroscopy. It is shown that the higher chemical shift (higher adsorption strength) gives higher activity for the formic electro-oxidation which depends on the electronic donating ability of a particular functional group when the size, shape, loading of palladium nanoparticles are well controlled.

In this work, domain wall (DW) formation in patterned nanowires has been investigated with Magnetic Force Microscopy (MFM) measurement and Object Oriented MicroMagnetic Framework (OOMMF) simulations. There has been intensive research interest into the behaviour of individual DWs in patterned nanostructures for potential applications in memory storage, logic gates and sensors. For memory applications, DWs can be pinned in patterned notched nanowires, creating multiple domains and hence multiple memory states which could be read out either in shift registers or directly if an entire nanowire forms the free layer of an MRAM (Magnetoresistive Random-Access Memory). For logic applications, simple geometric designed planer magnetic wires that are less than a micrometer in width can be used to construct DW logic element architecture and they can be integrated together into one circuit. For sensor applications, biosensors in particular, DWs can be pinned in the free layer of GMR (Giant Magnetoresistance) or MTJ (Magnetic Tunnel Junction) arrays, by magnetic membrane coated nanotags, with different states when the nanotag is absent. In this study, zigzag-shaped nanowires and twin pinning sites in nanowire have been investigated for potential RM (Racetrack Memory) applications, and notched fork- shaped nanowires have been considered in order to perform AND/OR logic functions. Also, the shape effect of the nanotag and its interaction with the free layer of the biosensor have been simulated quantitatively and qualitatively. Polycrystalline Permalloy (NisoFe2o) has been the material choice for the investigations of patterned magnetic elements in this study, due to its very high magnetic permeability, low coercivity, negligible magnetocrystalline anisotropy, significant anisotropy magnetoresistance and small magnetostriction. Consequently the magnetization can be largely constrained by shape anisotropy so as to lie along the long axis of the wire with spins parallel to the surfaces and edges.

The effects of various parameters influencing the electrostatic and hydrophobic interactions oc'curring during the adsorption process of ferritin onto Au or PS- PFEMS (polystyrene-block-poly(ferroceny1ethylmethylsilane)) nanopatterned diblock copolymer surfaces have been investigated. The effects of pH change of the buffering media and applied potential change have been studied in-situ on the Au surface. The influence of a chemically nanopatterned surface and the change of ionic strength have been investigated by ex-situ methods. For ex-situ measurements an AFM (atomic force microscope) and for in-situ measurements an EQCM (electrochemical quartz crystal microbalance) were used. Sudden changes in the pH of the buffering solution enabled control over the amount of ferritin adsorbed on the Au surface. More reliable control over adsorption was achieved by controlling the potential applied to the Au surface. By changing the applied potential the electrostatic and hydrophobic properties are changed simultaneously, in-situ. Under the conditions studied, the electrostatic forces had greater influence on the adsorption and desorption behaviour of ferritin than the hydrophobic interactions. To investigate the effect of potential control on the nanoscale, ex-situ AFM measurements were made. These measurements supported the data gained by EQCM. Furthermore they showed that there is no observable ordering during adsorption. Comparison of the adsorption and desorption behaviour of ferritin monomers, dimers and agglomerates controlled by potential change showed that our technique is sensitive enough to distinguish among them . . The dependence of the affinity of adsorption of ferritin on the electrostatic and hydrophobic interactions made it possible to try to pattern ferritin with the help of a chemically patterned surface. It has been shown that there is preference of adsorption to one of the blocks, and that this can be influenced by controlling the pH and ionic strength.

Due to the unique ability of metallic nanoparticles to change their optical properties depending on their size and morphology there is an ever increreasing need to not only discover new methods for their anisotropic synmthesis but also to understand more fully the processes which lead to this shape directed growth The aim of this research was both the wet chemical and the electrochemical synthesis of metallic nanoparticles and nanorods for the construction of films appropriate for their use in Surface Enhanced Raman Spectroscopy in analytical applications. For this, a controlled nucleation and growth strategy coupled to ultrasonic pulses has been investigated. The kinetics of the electrochemical phase transformation of silver onto both platinum and glassy carbon along with the influence of pulse parameters on current density in varying conditions were systematically studied by means of cyclic voltammetry and potential step experiments. Nucleation and growth were controlled independently and electrodeposited small clusters were dislodged using an ultrasonic pulse at an appropriate time of the nucleation-growth sequence. Monodisperse silver nanoparticles of varing sizes stabilised by polyvinylpyrrohdone have been synthesised and were characterised by UV-Vis Spectroscopy and Transmission Electron Microscopy.

Conductive nano-composites have the potential to replace traditional conductive materials due to the enhanced mechanical, electrical and chemical properties that lend themselves to a plethora of applications. In this work, conductive nano-composites of poly (3,4-ethylenedioxythiophene)-poly(styrenesulfonate) with multi-walled carbon nanotubes (PEDOT:PSS/MWCNT) and PEDOT:PSS with silver nanowires (PEDOT:PSS/Ag NW) were prepared, characterized and tested for gas sensing and lighting applications. Carbon nanotubes were functionalized covalently with carboxylic acid and non-covalently with surfactant and polymer molecules. The functionalized nanotubes were mixed with PEDOT:PSS at different concentrations and printed using inkjet printing techniques. The effect of the concentration of these nanotubes on the electrical properties of the nano-composite samples was investigated. The results show that the electrical conductivity of the printed structures strongly depends on the concentration of the nanotubes in the sample. Furthermore. the electrical properties strongly depend on the wetting of the substrate and by controlling the wettability, the conductivity of the nano-composite samples can be improved. Based on polymer conductivity, the electrical conductivity of the composite fi lm can be improved or degraded by orders of magnitude with the incorporation of the MWCNT. Moreover, electrical measurements show strong correlation between the conductivity of the carbon nanotube nehvork and the resulting nano-composite films. Excellent alignment of the nanotubes with improvement in the conductivity of the printed sample was also achieved using a novel and simple methodology. Carbon nanotube gas sensors were fully printed on flexible substrates and tested as ethanol sensors. The performance shows significant enhancement in the sensitivity of the PEDOT:PSSIMWCNT based sensor, in comparison to the pristine nanotubes and pristine polymer based sensors with enhancement factor greater than 2.5. Moreover, a remarkable improvement in the response and recovery time of the sensor after polymer functionalization is also reported.

Organic photovoltaics (OPV) is one of the most dynamic and rapidly developing solar cell technologies leading to renewable I green energy. OPVs arc based on organic semiconductors such as conjugated polymers, ful1erenes and other small molecules. Such devices can be fabricated by low-cost, roil-ta-roil printing techniques by layering extremely thin photoactive coatings on lightweight, flexible substrates which maybe organic in nature as well. Various OPV technologies are being developed in industrial and academic research fields where OPVs are on its way to broad commercialisation. To improve the power conversion efficiencies (PCEs) further researchers have looked into embedding nano-scale materials in OPVs over the last few years. The leading potential candidates being, carbon nanotubes (CNTs) and graphene, due to their extraordinary electronic properties and quantum dots with their tunable size dependant electronic properties. In this thesis, the effect of utilising single walled carbon nanotubes (SWNTs) as hole transport layers in bulk-hetero junction (BHJ) OPVs has been studied using a polymer wrapping technique of SWNTs for dispersion purposes. Supramolecular interactions based on π-π stacking between poly(3-hexylthiophcnc-2,5-diyl)poly(3-hcxylthiophene) (rr-P3HT) and SWNTs are exploited to prepare self-assembled networks of nanohybrid structures for hole extraction in OPVs. The effectiveness of such a network for hole transport is demol1strated, with the hole extraction capability shown to be associated with the potential of SWNTs being hole-doped by the surrounding rr-P3IlT sheath.

One-dimensional nanomaterials have many useful properties for the development of future electronic devices. Single walled carbon nanotubes (SWCNTs) and nanowires (NW) exhibit excellent charge carrier transport characteristics and are efficient for electronic conduction as both semiconductors and conductors in thin films. With this change of materials comes an opportunity to also change device production techniques. Printing offers a fast and easy method for the deposition of materials for electronics, but printing systems require solutions of materials to act as inks. One of the main barriers to using carbon nanotubes (CNTs) in the field of printed electronics is the problem of creating reproducible films due to the poor dispersion in typical solution deposited CNT films. This random orientation of CNT within the film leads to a loss of charge carrier mobility as it is difficult to produce a conjugated path between electrodes and so charge carriers have to 'jump' the gap between neighbouring tubes. Two routes have been investigated as a part of this project to solve these problems. Firstly, composite films of CNT and polymerisable conjugated liquid crystals (Le) have been fabricated, which use the self assembly and crosslinking properties of the LC to create an aligned array of CNT in a semiconducting polymer. This is the first time this route to aligned, patterned composite semiconducting films has been performed and we have shown that this method provides an increase in conductivity and mobility of three orders of magnitude over a pure LC or CNT film. The fabrication of semiconducting field effect transistor devices has been achieved for the first time with such a composite system with the result of mobility increases of three orders of magnitude and a 60 % increase in the reliability of the device fabrication process over unaligned SWCNT films. Secondly, a functionalization/defunctionalisation system has been developed for SWCNTs to allow the effective solution deposition of thin films of CNTs while being able to recover the original electronic properties of the tubes. This defunctionalisation process adds an octadecylamine functional group for solubilisation and then uses a 200°C anneal process to remove the group after thin film deposition. The use of this process creates a decrease of five orders of magnitude in the sheet resistance between un-annealed and annealed films. Evidence is also presented to show that the defunctionalisation process has an effect on the number of defects on the SWCNT walls. Finally, potential mechanisms for this process are discussed. The process developed in this work takes places at far lower temperature, pressure and less caustic chemical conditions that any previously reported system for the removal of functional groups and healing of defects in CNT.

In this work, the fabrication of noble metal nanostructures with interesting and useful optical properties was investigated. Nanoporous alumina templates were used as a basis for the production of gold nanowire and nanotube arrays, and the fabrication conditions can be changed to alter the array dimensions. The structures were characterised optically and the modes observed were described using finite element analysis; nanowires support a transverse and longitudinal resonance at non-zero angles, and nanotubes have a broad resonance at normal incidence. These resonances are highly sensitive to the dielectric environment surrounding their surface. Additionally, polymer nanodome arrays were created using a process of soft nanoimprint lithography, leading to the creation of uniform nanostructures over a large area. The domes were then coated in a thin film of gold or silver which allowed the domes to support localised surface plasmon resonances which were also found to be highly sensitive to the surrounding medium. Throughout this work, the potential for each nanostructure to be applied to plasmonic sensing was realised. The advantages of using arrays of nanowires and nanotubes is that, unlike label-based techniques which only confirm the presence or absence of a detector molecule, they are label-free methods which provide direct information on analyte binding to the target molecules via a change in the observed optical properties. The optical properties of the nanostructures produced in this work have been studied extensively and the effect of changing the dimensions of these are well understood. This means that the nanostructures used in this work show great potential for applications which involve sensing on the molecular level, particularly due to the tunability of their resonance peaks and the ability to produce the nanostructures uniformly over large areas.

This thesis reports the preparation and characterization of ZnO films and nanostructures and their incorporation in simple devices. The characterization includes imaging techniques - atomic force-, scanning electron- and transmission electron- microscopies (and accompanying analysis) - as well as X-ray diffraction (confirming wurzite structure in all the form of ZnO), photoluminescence (elucidating exciton and defect bands), Raman spectroscopy (dopent incorporation, including defects) and, importantly, optical absorption since it is crucial to confirm the various forms of ZnO as transparent conducting oxide. Also, electron scanning tunnelling microscopy reveals interesting bias- and polarity-dependent changes in 'topography' images originating with different density-of-states contributions from the conduction band, valence band and defect (surface) states. A new fabrication methodology, based on metal-salt decomposition, is introduced to prepare un doped and Co-doped thin films and nanowires on quartz where the doped ZnO exhibited Co2+ substitution of Zn2+ while retaining good optical transmission. Extending the wet-chemical approach synthesis a simple change in reaction temperature led to two quite different forms of ZnO-nanostructure:- nanocrystals and nanosheets. The potential of ZnO-nanosheets as a phosphor coating for producing (bluish-) white light from UV-LEDs is demonstrated. The nanocrystals were used in poly(3, 4- ethylenedioxythiophene)-poly(styrenesulfonate)(pEDOT:PSS) host matrix to form a nanocomposite exhibiting the fascinating property of negative photoconduction, explained in terms of decreased conductivity of the ZnO stemming from a charge transfer interaction with the PEDOT:PSS. The well-known difficulty in forming stable p-type 2nO films was confirmed by fabricating Li-doped 2nO/n-type 2nO homojunctions which failed to show rectifying behaviour, where the oxygen vacancies may indicate extinction of p-type behavior. However, a number of successful n-2nO (Ga- and In-doped 2nO films, honeycomb structured intrinsic .n-2nOIPEDOT:PSS and Ag-doped 2nO nanorods/p-Si heterojunctions were fabricated and their photoresponse examined in detail - these data, in particular polarity-dependent wavelength selectivity, are discussed and analysed in terms of basic band structure and carrier transport properties.