Carbon nanotubes have been found to have extraordinary properties, such as ballistic electrical conductivity, extremely high thermal conductivity and they can be metallic or semiconducting with a wide range of band gaps. There are however several issues that have to be solved before these properties can be fully utilised. One of these issues is that the nanotube growth temperature must be lowered in order to make the synthesis compatible with the fabrication processes used in electronics. The whole environment is heated to temperatures typically higher than 500 °C in the standard growth techniques whereas only a very localised area is heated in the technique developed here. This technique thus provides a way around the temperature issue. In the method developed here, the catalyst is deposited on top of a small metal (molybdenum) wire on the substrate. The high temperature required for nanotube growth is then reached by Joule heating by sending a current through the metal wire. This process eliminates the furnace which is used in conventional chemical vapour deposition and localises the high temperature to a very small and controlled area of the sample. Consequently, this technique is compatible with the semiconductor technology used today. Another advantage of this technique is that, since no furnace is required, a small growth chamber, which fits under a microscope, can be used. This allows in situ studies of the growth by optical microscopy and by Raman spectroscopy. By changing the carbon precursor, single- or multiwalled nanotubes can be grown. This can be important when producing devices since single-walled nanotubes predominantly are semiconducting whereas multi-walled mainly are metallic. The multi-walled nanotubes grow in a rapid and concerted process. This growth was monitored through an optical microscope. It was found that the thickness of the support layer and especially the catalyst are even more crucial parameters for nanotube growth using this local heating technique than in conventional processes. The activation energy could be extracted and was found to be 1.1-1.3 eV. The carbon nanotube growth was investigated by in situ Raman spectroscopy. The growth evolution could be well described by a model using the initial growth rate and the catalyst lifetime as parameters. The process was found to be limited by the mass transport of the carbon precursor. It was found that the molybdenum wire creates an additional pathway for the carbon cycle from gas to nanotube formation. The Raman spectra were studied at elevated temperatures. A decrease in intensity and a shift towards lower wavenumbers with increasing temperature was observed for the Stokes signal. It was found that the laser used for the Raman measurements could heat the nanotubes to high temperatures without any other heat source. Vertically aligned arrays of nanotubes were grown by conventional CVD. These arrays were actuated by applying a DC voltage between them. An effective Young's modulus of the arrays was found to be similar to that of rubber, which is orders of magnitude lower than for individual nanotubes. The capacitance between the arrays was measured to be tens of fF with a tunability of over 20%.

<p> Advancements in science and technology increasingly involve systems operating at the nanoscale. Interfaces are often present in these systems. Nanoscopic interfaces are ubiquitous in biological systems, nanofluidic devices, and integrated circuits. Properties at the interface may be quite different from the bulk, and in fact a true bulk may not be present in these systems. At the nanoscale the ratio of interface to volume is large, and the interface may have the dominant role in determining system behavior. Interfacial characteristics and their connection to interfacial properties are the focus of my thesis. Using molecular simulations of model interfaces we characterize how properties like chemistry, composition, and topography affect such phenomena such as hydrophobicity, heat transfer, and momentum transport at the nanoscale. An interface is defined simply as where two materials meet and a change in some structure or order parameter is observed. In aqueous systems, the type studied here, these changes are relatively sharp and occur within a distance of nanometers. Water molecules near the interface are expected to display sensitivity to the underlying surface. Indeed, water near a hydrophobic surface is more deformable and has greater fluctuations. The hydrophobicity of chemically heterogeneous surfaces and proteins are characterized using these nanoscopic measures. We find the effect of mixing hydrophobic and hydrophobic head group chemistries is asymmetric, i.e., it is easier to make a hydrophobic surface hydrophilic than the reverse. The role of hydrogen bonding in hydrophobic and ion hydration is also characterized using a short range water model. Hydrophobic and ion hydration are reasonably captured with the short range water model. These studies show the importance of chemical composition and local hydrogen bonding in determining surface hydrophobicity. Interfaces also lead to anomalous behavior in heat and momentum transport. Interfaces disrupt local structure and create boundary resistances that manifest in temperature discontinuities and interfacial slip. We explore the effects of chemical heterogeneity, nanoscale surface roughness, and directionality on thermal conductance across model solid-water interfaces. Interfacial conductance is directly influenced by the coupling strength or wettability of the surface. For chemically mixed surfaces, interfacial conductance does not precisely match with wettability. Surface roughness in general enhances conductance, but the improvement cannot be completely attributed to increased solvent accessible surfaced area. Momentum transport displays similar discontinuities at aqueous interfaces. These effects can be reduced through the use of osmolytes. Collectively this work highlights the influence of interfaces on heat and momentum transport. Insights are provided for modifying interfacial behavior and altering the property of interest.</p>

As of 2010, cancer remains the leading cause of death in Canada, and second in the United States of America. This is despite decades of research into development of chemotherapeutics and diagnostics. A number of major challenges have prevented new discoveries from translating into a reduction in mortality rates. One challenge is the poor efficiency with which anti-cancer agents (diagnostic contrast agents and therapeutics) reach deregulated cells in the body. Therefore, development of new methods and technologies for improving efficiency of delivery has been a focus of research. Nanoparticles are leading candidates for improving the efficiency of delivery because they can act as payload vehicles for anti-cancer agents, because it is possible to mediate their interaction with biological systems and thus their pharmaockinetics, and because they can exploit inherent vulnerabilities of tumours. This thesis describes the results from a series of research projects designed to progress our understanding of how nanoparticles behave in vivo, and how their design can be optimized to improve tumour targeting.

Nucleic acid analysis is one of the most important disease diagnostic approaches in medical practice, and has been commonly used in cancer biomarker detection, bacterial speciation and many other fields in laboratory. Currently, the application of powerful research methods for genetic analysis, including the polymerase chain reaction (PCR), DNA sequencing, and gene expression profiling using fluorescence microarrays, are not widely used in hospitals and extended-care units due to high-cost, long detection times, and extensive sample preparation. Bioassays, especially chip-based electrochemical sensors, may be suitable for the next generation of rapid, sensitive, and multiplexed detection tools. Herein, we report three different microelectrode platforms with capabilities enabled by nano- and microtechnology: nanoelectrode ensembles (NEEs), nanostructured microelectrodes (NMEs), and hierarchical nanostructured microelectrodes (HNMEs), all of which are able to directly detect unpurified RNA in clinical samples without enzymatic amplification. Biomarkers that are cancer and infectious disease relevant to clinical medicine were chosen to be the targets. Markers were successfully detected with clinically-relevant sensitivity. Using peptide nucleic acids (PNAs) as probes and an electrocatalytic reporter system, NEEs were able to detect prostate cancer-related gene fusions in tumor tissue samples with 100 ng of RNA. The development of NMEs improved the sensitivity of the assay further to 10 aM of DNA target, and multiplexed detection of RNA sequences of different prostate cancer-related gene fusion types was achieved on the chip-based NMEs platform. An HNMEs chip integrated with a bacterial lysis device was able to detect as few as 25 cfu bacteria in 30 minutes and monitor the detection in real time. Bacterial detection could also be performed in neat urine samples. The development of these versatile clinical diagnostic tools could be extended to the detection of various cancers, genetic, and infectious diseases.

DNA cages are polyhedra self-assembled from synthetic oligonucleotides in a one-pot process. The main system described in this thesis is a reconfigurable, wire-framed DNA tetrahedron in nanometre-scale. On one of its vertices this tetrahedron has an overhang that can hybridise with a specific sequence of nucleic acids and open the cage. We describe the design of a reconfigurable cage that remained closed under physiological conditions and only opened in the presence of an appropriate signal in solution. Fluorescence techniques were employed to distinguish the open and closed states of the cage. We used flow cytometry and confocal microscopy to successfully established the open and closed states of the cage inside live cultured mammalian cells. Further experiments revealed that the DNA cage could be opened by a separately transfected signalling strand. Hybridisation between two separately transfected systems was possible. The DNA cage was then simplified to a DNA duplex so that the intracellular interactions between the two nucleic acids systems could be studied more efficiently. Microscopy images showed that the interaction occurred in membrane-bound compartments. We describe an investigation into the use of various cellular RNAs, including full-length mRNA and tRNA-RNA fusion, to actuate the DNA cages. Choosing an appropriate cellular opening signal remains a challenge. Analysis showed that bulky cellular RNA experienced steric hindrance with the rigid DNA cage. Finally, other potential biological applications of DNA cages, such as using DNA nanostructures as the carriers for genetic therapeutic agents, were also presented.

Dans cette thèse, trois approches différentes ont été étudiées pour des dispositifs photoniques accordables basés sur la technologie MEMS. Premièrement, la structure à double barrière optique a été étudiée numériquement et expérimentalement, sous forme de commutateur thermo-optique, polariseur commutable et de jonctions tunnel optiques intégrées en tant que système WDM reconfigurable. Le dispositif est fabriqué sur substrat silicium SOI utilisant le procédé de gravure profonde. Les dispositifs optiques tunnel sont contrôlés électro-thermiquement, le temps de commutation mesuré correspondant est de plusieurs microsecondes. Deuxièmement, des structures de propagation de lumière lente à base de méta matériaux constitués de cellules unitaires sous forme d’anneaux fendus couplés, sont numériquement analysés. Les résultats des simulations montrent que la conception de SRRs (Split Ring Resonator) couplés améliore l'accordabilité de la permittivité et de la perméabilité effectives de 70 et 200 fois, respectivement. On peut trouver des applications potentielles dans le stockage de données, des circuits photoniques, les communications optiques et les biocapteurs. Enfin, un méta matériau accordable magnétique est démontré en utilisant la technologie MEMS. Il démontre une approche unique pour contrôler les propriétés optiques des méta matériaux par l'évolution des dimensions géométriques et les formes des cellules unitaires / In this PhD project, three different approaches have been studied for tunable photonic devices based on MEMS technology. First, the optical double barrier structure has been numerically studied and experimentally demonstrated as the thermo-optical switch, switchable polarizer and optical tunneling junctions integrated as reconfigurable WDM system. Second, the slow light structure using metamaterial with coupled split ring unit cells is numerically analyzed. Finally, a tunable magnetic metamaterial is demonstrated using MEMS technology. The first major work is to use the optical tunneling effects to design MEMS based photonic devices. Three different tunable photonic devices has been demonstrated using thermo-optical tuning. a thermo-optic switch is realized using MEMS technology. The device is fabricated on silicon-on-isolator wafer using deep etching process. The transmission of the optical switch is controlled by the optical length of the central rib which is thermally controlled by the external pumping current. In experiment, it measures a switching speed of 1 us and an extinction ratio of 30 dB. A switchable polarizer is demonstrated using the double optical barrier structure which transmit the light with one polarization state and filter out the others. In experiment it measures a PER of lager than 23 dB when the pumping current is above 60mA. The switching time is shorter than 125 us which is limited by the polarization analyzer used in the experiment. A MEMS reconfigurable add-drop multiplexer is realized by applied the optical tunneling structure to the ribbed waveguide. The tunable add-drop multiplexer is based on Y-shape optical double barriers tunneling junction which are realized by MEMS technology

This thesis reports magnetotransport measurements in graphene Hall bar devices. Graphene samples fabricated from different techniques (epitaxial growth on silicon carbide, exfoliation, and CVD) are measured and compared. Measurements are taken primarily using a 21T magnet, at liquid Helium 4 temperatures. The first three chapters present the background for the work. Chapter One details the motivation for the thesis, and gives a general background to carbon and the state of carbon research. Chapter Two covers the theoretical background of graphene, including the anomalous quantum Hall effect and weak localization. Chapter Three covers the synthesis of graphene and a typical procedure undertaken for device fabrication. The next three chapters report experimental results. Chapter Four presents measurements of the energy loss rates in exfoliated graphene. The mechanism of carrier energy loss is investigated, and compared to theory. Further, the breakdown of the quantum Hall effect in the device is investigated, demonstrating peak current densities far in excess of those found in the literature for exfoliated graphene. Chapter Five shows measurements comparing the carrier energy loss rates in graphene derived from the epitaxial, exfoliated and CVD fabrication techniques. An unconventional method for measuring the energy loss rate based on measuring the weak localization peak is developed, and trends in the energy loss rates with carrier density are investigated for a wide range of devices. Chapter Six reports a comparison of the decomposed weak localization scattering lengths from graphene devices derived from the epitaxial and CVD methods, and compares these to measurements from the literature. Further, a previously reported saturation of the weak localization in graphene is investigated, and demonstrated to be an experimental artefact. This thesis provides a development of the understanding, and an experimental verification, of several aspects of heat transfer in graphene. An understanding of heat transfer is of critical importance to proposed high-density nano-electronics, and bolometry applications. The high breakdown currents and observed trends in carrier density are also of significant assistance in the design of low-cost resistance metrology devices based on graphene.

No description available.

Doctor of Philosophy / Department of Chemical Engineering / Vikas Berry / Placidus Amama / The evolution of unique electrical, optical, thermal, mechanical, and chemical properties in two-dimensional (2D) nanomaterials due to the atomic confinement in the z-direction has ignited tremendous technology promises. With that promise comes a challenge of incorporating 2D nanomaterials into practical applications, enabling their large-area growth and using covalent or van der Waal bonding to extent and control their properties in electronic applications. This PhD thesis establishes the following results: (a) successfully developing of scalable processes for direct growth of large-area graphene, h-BN, and MoS₂-on-h-BN on SiO₂/Si substrate, (b) demonstrating an electronic sensor for the defection of molecular motion by covalently interfacing 2D nanomaterials with photo-mechanical molecules, and (c) establishing the modulation of structural, electrical, thermal properties of 2D nanomaterials by covalently interfacing metal nanoparticles with 2D nanomaterials. A promising scalable route for large-area growth of 2D nanomaterial on a dielectric substrate is to perform chemical vapor deposition (CVD). Via two patented processes, we have synthesized graphene films directly on a SiO₂ substrate via carbon-diffusion through copper grains, and h-BN film on SiO₂ substrate via surface oxide assisted mechanism. The continuous graphene film grown with large coverage on SiO₂ substrate possessed a crystalline sp² domain size of 140 nm with low defect density (as indicated by low Raman I[subscript]D/I[subscript]G~0.1). The sheet resistance of this turbostratic stacking graphene was ~4 kOhm/sq, with a charge carrier mobility of ~250 cm²V⁻¹s⁻¹. Unprecedented, large coverage of directly grown h-BN film on SiO₂ substrate was demonstrated. This h-BN film showed a 6-fold smoothness enhancement compared to that of SiO₂ substrate. Such smoothness and the nature of free dangling bond of h-BN film reduced Coulombic long range scattering, leading to the 5-fold enhancement in the conductivity of the MoS₂, which is directly grown on the underlying h-BN platform. The next-generation molecular electromechanical systems require controlled manipulation and detection of molecular motion to build systems which respond to molecular mechanics. To achieve this, we covalently interfaced photo-mechanical molecules (azobenzene) (density = 2.5 nm⁻²) onto trilayer graphene (37.5% sp² coverage), where high sensitivity of this trilayer graphene due to high quantum capacitance (6.3 microF/cm²) and carrier confinement was leveraged. This enabled graphene to sensitively detect azobenzene isomerization, where one hundred molecules generated one charged carriers in the graphenic platform (2.44 x 10¹² holes/cm²). As mentioned before, surface modification of 2D nanomaterials opens an avenue to incorporate them into rational applications. We demonstrated the ability to interface noble metal nanoparticles (gold, silver) selectively onto a MoS₂ lattice (60° angular displacement) via both diffusion limited aggregation and instantaneous reaction arresting (using microwaves). Such gold nanoparticle interfaces allowed the modulation of electrical, and thermal properties, confirmed by Raman, electrical, and thermal studies. Consequently, a remarkably capacitive interaction between gold and thin MoS₂ sheet showed a 9-fold increase of effective gate capacitance with low Schottky barrier (14.52 meV), and a 1.5-fold increase in thermal conductivity with a low carrier-transport thermal-barrier (44.18 meV). This long-term work has established the following points: 1) Scalable routes for the growth of 2D nanomaterials, which can be extended to synthesize complex hetero/lateral architectures for integrated thin film circuitries. Furthermore, 2) covalent functionalization of 2D nanomaterials with nanoparticles and molecular systems can futuristically develop rational interfaces with other 2D heterostructures, and molecular machines.

>Magister Scientiae - MSc / Cancer is one of the leading causes of death, worldwide. Mortality tolls are estimated to reach approximately 13.1 million in 2030. These statistics suggest that current therapeutic strategies are not effective. This is partly due to the fact that the drugs used in the treatment of cancer lack selectivity and specificity, which lead to undesirable side effects and reduced drug efficacy. There is therefore a need for alternative therapeutic approaches. In view of this, the therapeutic goal of chemotherapy has shifted towards targeted drug delivery systems, which have been successfully demonstrated using nanotechnology. The nano-based drug delivery vehicles that specifically target diseased cells are appealing as they could reduce drug toxicity towards healthy tissues and be more effective at lower dosages. The main aim of this study was to develop gold nanorods (AuNRs) capable of inducing cell death in cancer cells specifically. Selectivity of the AuNRs (denoted as AGK) for cancer cells was achieved by conjugating the AuNRs to a peptide (Adipose Homing Peptide or AHP) that has high affinity and specificity for a cell surface receptor (prohibitin or PHB) that is expressed on some cancer cells. Cell death was achieved through conjugating the AuNRs to a pro-apoptotic peptide, D(KLAKLAK)2. Spherical AuNPs (AuNSs) conjugated with AHP and D(KLAKLAK)2, capable of selectively inducing apoptosis in cancer cells that express PHB, was previously reported. However, in this study the AuNSs were replaced with AuNRs. AuNRs has the ability to absorb light in the near infrared (NIR) light spectrum and converts this light energy into heat. This property of AuNRs has been used in several studies to demonstrate the application of AuNRs for the treatment of cancer using photothermal therapy (PTT). Consequently, the AuNRs described in this study can also be used for PTT. These AuNRs can induce cell death through the target specific delivery of the pro-apoptotic peptide D(KLAKLAK)2 as well as through PTT. The study showed that three human cancer cell lines (PC-3, Caco-2 and U-87) express PHB. The cytotoxicity testing of AGK AuNPs on PC-3 cells showed that these AuNRs could induce apoptosis in these cells without exposure to a NIR light source. The study also shows that AuNRs conjugated with the targeting peptide only (denoted as AG) can induce cell death in Caco-2 through PTT. This study demonstrates the potential of the AuNRs described in this study for application in the targeted elimination of cancer cells through the selective induction of PTT and apoptosis.