In this work, carbon nanotubes (CNTs) have been synthesized by microwave chemical vapor deposition technique using Ni as catalyst and at different experimental parameters. Catalysts Ni plays an important role in the process of synthesizing carbon nanotubes. Sputtered Ni film can agglomerate into uniformly distributed nanometer size particles, which can be employed to assist the growth of carbon nanotubes. The effect of Ni catalyst on CNTs growth have been investigated and an optima Ni thickness has been found. There are series experiments performed in order to improve the CNT growth environment and a characteristics for CNTs under the condition at 30 torr, 800¢J, 600W and ¡V 350V was observed. The growth characteristics was evaluated with TEM, SEM, Raman and FTIR. From Raman spectra, the degree of graphitization is proportional to growth temperature and microwave power. In addition to extending the growth time, the length of CNT did not increase.

One-dimension (1D) nanostructures such as wires, rods, belts and tubes have become the focus of intensive researches for investigating structure-property relationships and related scientific and technological applications. Few-walled carbon nanotubes (FWNTs), a special type of small diameter multi-walled carbon nanotubes with superb structural perfection, are first discovered in our laboratory and systemically studied in this dissertation, including the synthesis by chemical vapor deposition (CVD) method, the purification and their applications. Moreover, iron phosphide nanorods/nanowires with controlled structures have been synthesized in solution phase and their magnetic properties have been investigated. The first parts of this dissertation are mainly focused on the studies of FWNTs synthesized by CVD method using binary catalyst Co (or Fe) with Mo (or W) supported on MgO made by modified combustion method. The structures of as-grown FWNTs can be controlled by three basic growth parameters: temperature, catalyst composition and carbon feeding rate. It is found that the as-grown FWNT materials prepared from W-containing catalysts are much more easily purified than those from Mo-containing catalysts. Both raw and purified FWNTs show enhanced electron field emission characteristics compared to other current commercial nanotubes. The highly pure FWNTs are then used to prepare composite materials with polymers and noble metal nanocrystals. Furthermore, the structures of FWNTs are attempted to be controlled by adjusting the growth parameters of carbon monoxide CVD. Highly pure DWNTs (over 95%) are obtained and well characterized by TEM, Raman and fluorescence spectrum. The optical properties of DWNTs and their application in bio-imaging are primarily investigated. In addition, conducing films are fabricated using highly pure FWNTs and the relationship between the structure and the conductivity is surveyed and further possible improvements are discussed. The second parts of this dissertation describe a solution-phase route for the preparation of single-crystalline iron phosphide nanorods and nanowires. The mixture of trioctylphosphine oxide (TOPO) and trioctylphosphine (TOP) which are commonly used as the solvents for semiconductor nanocrystal synthesis is not entirely inert. TOP serves as phosphor source and reacts with Fe precursors to generate iron phosphide nanostructures with large aspect ratios. In addition, the morphology of the produced iron phosphide structures can be controlled by the ratio of TOPO/TOP. A possible growth mechanism is discussed. / Dissertation

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Thorough understanding of the electronic and optical properties of single-walled carbon nanotubes (SWCNTs) will no doubt benefit future technological applications. Since the discovery of band gap photoluminescence from isolated semiconducting SWCNTs, significant progresses in studying the optical properties of SWCNTs have been made (e.g. linear polarization along the tube axis for the absorption and emission of light, excitonic nature in SWCNT excitation). However, there are still several controversial parameters of SWCNTs (e.g. quantum efficiency, absorption cross section, radiative lifetime, and Auger recombination lifetime). With the advancement in SWCNT sample preparation, studies of SWCNT intrinsic properties have shifted from ensemble to a single tube level, in which the ambiguities in elucidating intrinsic properties posed by the assortment of different tube species can be minimized. By examining individual SWCNTs suspended in air, in contrast to micelle-encapsulated SWCNTs, we believe that the environmental effects can be reduced. This thesis will demonstrate the capability of doing spectroscopy on a single semiconducting air-suspended SWCNT. In continuous-wave excitation, the photoluminescence excitation map and high resolution photoluminescence (PL) image of a SWCNT can be constructed, and PL polarization is proven. Quantum efficiency of 5% is experimentally estimated for (9,8) and (10,8) chiral SWCNTs. Pulse excitation allows us to study the intrinsic exciton dynamics of a SWCNT. To gain insight into exciton nonlinear decay processes, PL saturation in pump power dependence measurement is investigated and compared to the simulated results from stochastic models of exciton dynamics. Femtosecond excitation correlation spectroscopy with 150 fs time resolution is employed to time-resolve the PL of a single tube suspended in air. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2008-08-29 13:10:49.045

This thesis describes the development and testing of a range of electrodes designed to be able to measure electrical current produced by the respiration of bacteria in direct contact with the electrode surface. The electrodes are designed to directly wire into redox processes in the cytoskeleton of the bacteria so that electron transfer can be measured in real time without the need for solution based mediator molecules. The rate of electron transfer from the bacteria is enhanced by nanostructuring the surface of graphite electrodes with vertically aligned single and multiwalled carbon nanotubes (CNTs) and covalently coupling mediator molecules to the CNT tips. A selection of the prepared electrodes are tested with the non-electrogenic bacteria Proteus vulgaris and Bacillus subtilis to demonstrate the potential of the electrode designs to be used with a wide range of microbial species.

The aim of the thesis is to fabricate Schottky contact carbon nanotube field effect transistor (CNFET) using the dielectrophoresis (DEP) to resolve the alignment issue and show its transistor behaviour. The work presented is a combination of fabrication and simulation of CNFET. Fabrication of the device electrode had been done using the electron beam lithography to achieve a channel length of 150nm and analysis was done on an optical microscope, SEM, AFM and Raman spectroscopy. Second half of the thesis provides a solution to “bottleneck communication” between microprocessor and memory to increase the computation for applications like AI, IoT etc and 3D monolithic memories. As a solution, we propose a novel CNFET based processing in-memory architecture using a novel CNFET dual port single-ended SRAM bit cell. The combination of the CNFET and processing in-memory can be a new phase for memory and computation.

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Carbon nanotubes (CNTs) have been the subject of intensive research for nearly two decades, and this is due to their exceptional lightness, large aspect ratio, extraordinary mechanical, electrical, thermal properties and additional multi-functional characteristics. Ceramics have high stiffness and good thermal stability with a relatively low density, and they are an important constituent in the fabrication of advanced composites where high thermal and chemical stability are important. However, brittleness has limited their application in many structural applications. The combination of ceramic (alumina in particular) and CNTs, endeavouring to develop functional composites, offers a very attractive system for research and development. The fabrication of such alumina-CNT composites at bulk scale is therefore highly desirable for industrial applications. However, the synthesis of such composites possesses many technical challenges which need to be addressed. Poor synergy between the matrix and CNTs, potential damage to CNTs, obtaining a uniform and agglomeration-free distribution of CNTs within the matrix, and high cost of CNTs and processes involved in their composite fabrication have proved to be the significant challenges. In this thesis, the focuses are laid on addressing these issues and on the fabrication of specially engineered composites for particular applications such as filter and composites with improved mechanical properties. In this regard, it has been tried to directly fabricate CNTs in different ceramic matrices based on the application requirements. After that, the critical issues and challenges in the fabrication of these functional materials have been clearly investigated and by introducing novel methods and approaches, it has been tried to solve these problems. Also, a new polymer-ceramic-CNT composite has been fabricated by using two different thermoset (epoxy resin) and thermoplastic (polyamide 12) matrices. In this regard, good interfacial bonding between the composite elements along with good wettability of ceramic and CNTs with polymer had to be addressed as critical issues and challenges in the fabrication process. If the adherence at the interface is not strong enough, the material will tear and fail easier. In contrary, a tailored functionalization of CNTs can lead to an improved wettability and as the results, strong interfacial adhesion and bonding between the composite elements. These dominating factors will improve the degree of filling which results in existence of fewer voids inside the composite. These voids will act later as stress points and reduce the composite strength. At the end, the mechanical properties of the fabricated samples have been assessed. The CNT filters have been tested in the removal of bioorganic (yeast cells) and inorganic (heavy metal ions) contaminants from water, and of particulates from air, and they all showed very promising results. More than 99.6% of the air particles (size ranges from 0.3 to 10 µm) were filtered using 300 mm long CNT filter. A complete removal of heavy metal ions from water was reported particularly for single ion. 98% of the yeast cells were filtered. Different factors involved in the filtration efficiency such as ceramic pore size, length of filters, CNT loading and injection rates have also been discussed. Furthermore, the mechanical properties (compression test, hardness and impact test) of the composite materials (including ceramic-CNT, epoxy resin-ceramic-CNT and polyamide-ceramic-CNT composites) have been assessed. During impact test, the epoxy resin-ceramic-CNT composite absorbed 117.2% and 32.7% more energy compared to the pure epoxy resin and epoxy resin-ceramic composite, respectively. The epoxy resin-ceramic-CNT composite sustained 40% more elastic deformation before breakage compared to the epoxy resin-ceramic composite as a result of the CNT reinforcement. The addition of CNTs to the polyamide12-ceramic composite increased its yield stress by 41%. All of these results represent a big leap towards practical applications for the composite reported in the thesis, which may open up new opportunities for CNT engineering at industrial scales, due to the easy fabrication methods introduced and the promising performance they have exhibited.

Thesis advisor: Thomas Chiles / Molecular recognition is an important area of research as it has far reaching applications in sensors, molecular separations, and medicine. Molecularly imprinted polymers offer an option for developing high resolution tools of detection that are both selective and sensitive. As a platform, carbon nanotubes offer a highly conductive surface and their growth and unique magnetic properties can be manipulated for our purposes. Such carbon-nanotube based sensors can afford high sensitivity, while molecular imprinting provides the selectivity of detection with the flexibility of fabrication. In order to fabricate a molecular imprint, monomeric compounds are polymerized in the presence of a target molecule of interest, which acts as the template. Once the template molecule has been removed an imprint capable of “recapturing” the target molecule is left behind. In this work we used cyclic voltammetry as a means of depositing polymer coatings doped with a target molecule. We fabricated a molecularly imprinted polymer sensor specific for ferritin using polyphenol as the polymer. The development of our imprint was monitored based on changes in impedance levels calculated by electrochemical impedance spectroscopy. After depositing ferritin-doped polyphenol layers we evaluated the effectiveness of different eluant solutions. Ultimately, deionized water was determined to be the developing solution of choice because it effectively removed the ferritin while not compromising the integrity of the remaining polymer coating. The sensor was capable of detecting ferritin at a concentration of 1x10-9 g/L (1 pg/mL). In parallel we evaluated the stability of the polyphenol coating. / Thesis (BS) — Boston College, 2009. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: College Honors Program. / Discipline: Biology.