<p> In this dissertation, as a monitoring technology for cyanotoxins, a multiwalled carbon nanotube (MWCNT)-based electrochemical biosensor was developed to determine microcystin-LR (MC-LR), a potent cyanobacterial toxin, in sources of drinking water supplies. The performance of the MWCNT array biosensor is evaluated using micro-Raman spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, optical microscopy, and Faradaic electrochemical impedance spectroscopy. A linear dependence of the electron-transfer resistance on the MC-LR concentration is observed in the range of 0.05 to 20 &micro;g L^-1, which enables cyanotoxin monitoring well below the World Health Organization provisional concentration limit of 1 &micro;g L^-1 for MC-LR in drinking water. </p><p> In addition to the development of monitoring tools for cyanotoxins, visible light-activated (VLA) TiO₂ and monodisperse TiO₂ were developed and evaluated for treatment of water contaminants of emerging concern. These materials were synthesized using modified sol-gel methods (i.e., wet chemistry-based methods) such as self-assembly-based and ionic strength-assisted techniques. For this study, first, VLA-sulfur-doped TiO₂ (S-TiO₂) nanocrystalline films were synthesized by a self-assembly-based sol-gel method using nonionic surfactant to control nanostructure and an inorganic sulfur source for decomposing MC-LR under visible light illumination. Second, the effects of solvent on the synthesis of VLA-S-TiO₂ films were scrutinized. Four different polar, protic solvents, isopropanol, 1-butanol, ethanol, and methanol, were chosen as the solvent in four titania sol-gel preparations. Third, monodisperse anatase titania nanoparticles with controllable sizes (typically 10-300 nm) were synthesized using an efficient and straightforward protocol via fine tuning of the ionic strength in the devised sol-gel methodology. Finally, noble metal Ag-decorated, monodisperse TiO₂ (TiO₂-Ag) aggregates were successfully synthesized by an ionic strength-assisted, simple sol-gel method and were used for the photocatalytic degradation of the pharmaceutical oxytetracycline (OTC) under both UV and visible light irradiation. With a self-assembly-based sol-gel method, nanostructured anatase S-TiO₂ with high surface area (> 100 m² g^-1) and porosity (> 30 %) was synthesized and the sample calcined at 350 ^oC demonstrated the highest visible light absorption and visible light-induced photocatalytic activity in the decomposition of MC-LR. The structural and morphological properties of S-TiO₂ could be also tailor-designed using different solvents in the sol-gel synthesis, while inducing negligible effects on the sulfur doping and the visible light activation of TiO₂. Thus, it can be concluded that the enhancement of photocatalytic activity of S-TiO₂ films can be achieved by judicious choice of the main solvent for the sol-gel method. With an ionic strength-assisted sol-gel method, monodisperse spherical anatase TiO₂ (10-300 nm in diameter) as well as monodisperse TiO₂-Ag aggregates with 350 nm of diameter were synthesized. For TiO₂-Ag, its visible light absorption increased due to the presence of Ag on the surface of monodisperse TiO₂, which resulted in the enhancement of the photocatalytic degradation of OTC under both UV-visible light and visible light irradiation compared to pure TiO₂. There was an optimal Ag content to obtain the highest photocatalytic degradation of OTC. These newly developed materials demonstrated the efficient decomposition of water contaminants of emerging concern, especially MC-LR and OTC, under UV-visible light and visible light illumination.</p>

<p> The tumor microenvironment has been demonstrated to be a key determinant in the progression of cancer. Unfortunately, the mechanisms behind the different microenvironments (cytokine gradients, hypoxia, hypoglycemia, etc) have not been fully elucidated. Identifying these mechanisms can lead to targeted, individualized therapy to prevent metastasis. The Nano Intravital Device (NANIVID) is a microfabricated, implantable device designed to initiate specific microenvironments <i> in vivo</i> so that the time course of the effects can be observed. With both spatial and temporal control over the induced environments, the affected regions of the tumor can be compared to the rest of the tumor. The NANIVID was first used to establish cytokine gradients to monitor the migration of invasive cancer cells. The three projects that comprise this work expand the applications of the NANIVID to establish the device as a robust platform for investigating tumor microenvironment interactions. The first project released chemical mimics from the device to induce the cellular hypoxic response in tumors to determine how hypoxia affects the fate of disseminated tumor cells. The second project used the NANIVID in combination with an atomic force microscope to investigate the altered mechanics of migrating invasive cancer cells. The final project was to develop a cell counter to monitor the isolation of the invasive subpopulation of cells that were drawn into the device using a chemoattractant. These three projects demonstrate the potential of the NANIVID as a platform for investigating the tumor microenvironment.</p>

<p>This thesis focuses on energy considerations in the MOSFET when we supply a bias to it. We also notice that the length of the MOSFET gets smaller and smaller then for a small release or exchange of energy that may take place in a MOS transistor which can cause a change in the temperature. We have investigated that there is a change in the temperature of the MOSFET when we supply bias to it as we keep reducing the length of the channel. The change in the temperature of the MOSFET is calculated theoretically. </p>

Carbon nanotubes have been subject to a great many theoretical and experimental investigations and have many interesting properties. However, the caps found at the ends of nanotubes have been rather neglected. Previous work has established the possible caps for a given nanotube. This thesis seeks to build on this work to determine which caps are probable. Three representative nanotubes are considered: the (5,5) tube (an example of a metal); the (10,0) tube (an example of an insulator) and the (11,2) tube (for which experimental data is available). A linear scaling density matrix method based on orthogonal tight-binding theory is used for a systematic study of doubly capped nanotubes. The energetically most stable caps are found for all three tubes and the isolated pentagon rule established for fullerenes is shown to be valid for nanotube caps. No simple rule governing the stability of isolated pentagon caps is found, although the stability of (11,2) caps correlates well with the number of hexagons adjacent to just one pentagon. The local densities of states (LDOS) are calculated for the most stable cap for each nanotube. A localised state is found for the capped (5,5) tube and a resonant state is observed for the capped (11,2) tube. The LDOS for the capped (11,2) tube is compared with experimental observations and questions are raised concerning the nature of the tube observed and the limitations of STM as a method for identifying nanotube caps.

<p>The development of practical and sensitive techniques for screening early biomarkers such as nucleic acid targets related to medical diseases and cancers is critical for early diagnosis, prevention and effective interventions. Recent advances in molecular profiling technology have made significant progress in the discovery of various biomarkers that could serve as important predictors of cancer risk and progression. Fast and precise measurement of biomarkers will help identify molecular signatures critical for the evaluation of cancer risk and early detection. Recently, there has been great interest in the design and fabrication of plasmonics-active biosensing platforms for a wide variety of applications ranging from biomedical diagnostics, food safety, environmental monitoring, to homeland defense. In particular, DNA-functionalized metal nanoparticles (e.g. gold and silver) have been utilized in the development of novel plasmonics-based analytical techniques for the detection of nucleic acid targets. In this study, two novel label-free approaches named "molecular sentinel (MS) nanoprobes", and "plasmonic coupling interference (PCI) nanoprobes" have been developed for multiplex detection of disease biomarkers using surface-enhanced Raman scattering (SERS). The MS approach has been further extended into a unique "molecular sentinel-on-chip" (MSC) technology based on a SERS-active nanowire array substrate, leading to the development of a unique diagnostic tool having multiplexing and high-throughput screening capabilities. Finally, a novel nanoparticle-based colorimetric assay has been developed and implemented for the detection of microRNAs (miRNAs). Direct detection of miRNAs in RNA samples from breast cancer cell lines has been demonstrated. Furthermore, the PCI technique has successfully detected miRNA biomarkers in biopsies of gastrointestinal cancer patients and the results are consistent with established techniques such qRT-PCR. The results of this study demonstrate that these plasmonics-based nanoprobes have great potential as useful point-of-care diagnostic tools for medical applications.</p> / Dissertation

No description available.

Electron transport and recombination are two competing factors within Dye-Sensitized Solar-Cells (DSSCs) which have a great influence on their performance. By drastically increasing the speed of electron transport to the electrode, it is believed that these cells could reach new record efficiencies. To achieve this result, an all-in-one integrated DSSC was attempted, in which the electrode material is extended into the active area of the solar cell material. The research conducted can be separated into two stages. The first stage is the production of a three-dimensional macroporous electrode. The second stage is the production of an all-in-one DSSC by a simplified co-casting technique. The structures and materials presented were examined using electron microscopy, X-ray Diffraction, 4-point and 2-point probe electrical measurements as well as experimentally by the testing of solar cells. The methods of fabrication, characterization, experimental results and future directions are also presented.

Electron transport and recombination are two competing factors within Dye-Sensitized Solar-Cells (DSSCs) which have a great influence on their performance. By drastically increasing the speed of electron transport to the electrode, it is believed that these cells could reach new record efficiencies. To achieve this result, an all-in-one integrated DSSC was attempted, in which the electrode material is extended into the active area of the solar cell material. The research conducted can be separated into two stages. The first stage is the production of a three-dimensional macroporous electrode. The second stage is the production of an all-in-one DSSC by a simplified co-casting technique. The structures and materials presented were examined using electron microscopy, X-ray Diffraction, 4-point and 2-point probe electrical measurements as well as experimentally by the testing of solar cells. The methods of fabrication, characterization, experimental results and future directions are also presented.

Interactions between surfactants and polymeric nanostructures have gained increasing attention due to their potential application in many disciplines. In this study, a well-defined random copolymer containing 2-(2-methoxyethoxy) ethyl methacrylate (MEO2MA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA2080) (poly(MEO2MA-co-PEGMA2080)) was synthesized using the atom transfer radical polymerization (ATRP) process, and its thermo-responsive behaviors in aqueous solution were investigated. In comparison to other thermo-sensitive random copolymers based on oligo(ethylene glycol) methacrylates (OEGMA), this copolymer exhibited an unusual thermal induced two-stage aggregation process. The copolymer chains associated at the first thermal transition followed by a rearrangement process at the second thermal transition to produce a stable core-shell micellar structure. Furthermore, the binding interactions between cationic surfactants and this copolymer were examined below and above its cloud point. In general, the binding interactions between cationic surfactants and neutral polymers are weak and cationic surfactants are very selective and only bind to those polymers with specific hydrophobic groups. Significant hydrophobic interactions were observed between surfactant monomers and the polymer backbone. The binding occurred uncooperatively at low surfactant concentration, which was confirmed by electromotive force (EMF) measurements. Moreover, the binding affinity of three cationic surfactants follows the sequence: CTAB > TTAB > DoTAB. Cellulose Nanocrystals (CNC) with diameter of 10-20 nm and length of 200-400 nm, derived from native cellulose, is a promising new class of nanomaterials due to its high specific strength, high surface area, and unique optical properties. Currently, most of researches focused on the improvement of its steric stability, dispersability and compatibility in different solvents or matrices. A thermo-responsive polymer, namely Jeffamine M600 (a 600 Da polypropylene glycol) was grafted on the surface of cellulose nanocrystals (CNC) via a peptide coupling reaction. The better dispersion of the modified CNC in water was demonstrated, and the interactions between surfactants and M600-grafted CNC were investigated via isothermal titration calorimetry (ITC). Three types of surfactants with dodecyl alkyl chain and different head groups, namely cationic dodecyltrimethylammonium bromine (DoTAB), anionic sodium dodecyl sulfate (SDS), and nonionic poly(ethylene glycol) dodecyl ether (Brij 30) were studied. Physical mechanisms describing the interactions of cationic, anionic and nonionic surfactants and M600-grafted CNC were proposed. Chitosan molecules are water-soluble in acidic media due to the protonation of amino groups. However, some applications of chitosan are restricted by its poor solubility in basic media. A biocompatible derivative of chitosan, N-carboxyethylchitosan (CECh) was synthesized by Michael addition reactions, which possessed high solubility in both acidic and basic media due to the modification by carboxyl groups. The aggregation behavior of CECh in aqueous solution under the effects of pH, polymer concentration, as well as a gemini surfactant, was investigated by turbidity, zeta potential, fluorescence spectroscopy, viscosity, and surface tension measurements. This research demonstrates that nanostructures comprising of thermo-responsive copolymers can be controlled and manipulated by temperature and surfactants, and they play an important role in the physical properties of surfactants-polymeric complexes. The results from this research provide the fundamental knowledge on the self-assembly behavior and the binding mechanism of various novel polymeric systems and surfactants, which can be utilized to design and develop systems for personal care formulations and drug delivery systems.

<p>The development of finely dispersed powders and superfine-grained materials intended for application in various areas of science and engineering is one of the challenges facing modern nanotechnology. Thus, specific fundamental and applied research was required in order to consolidate advancement made in preparing nano- and submicron crystalline composite materials.</p> <p><br /> Useful templates for electrochemical deposition of nanowires include porous alumina films formed by anodic oxidation of aluminium, nuclear track-etched porous membranes, nanochannel array-glass and mesoporous channel hosts. The properties of the nanowires are directly related to the properties of the nanoporous templates such as, the relative pore orientations in the assembly, the pore size distribution, and the surface roughness of the pores. The template synthesis method, based on the use of porous polymeric and inorganic matrixes, is now actively used for synthesis of such composite materials. The method allows the chemical and/or electrochemical synthesis of nano- and microstructured tubes and wires consisting of conducting polymers, metals and semiconductors.</p> <p><br /> In this study various technological challenges relating to template synthesis and development of nickel nano- and microstructures on adequately strong and durable substrates were investigated. The two methods used were the electrochemical and chemical deposition. &ldquo / Hard nickel&rdquo / bath solution was used for optimal nickel deposition. This optimization included investigating variables such as the template structure, type of electrolyte and form of electrolytic deposition. Scanning Electron Microscopy was used to investigate the structures of template matrixes and the resultant materials. The cyclic voltammetry method was applied for the analysis of electrochemical properties and hydrogen evaluation reaction of nano- and microstructured nickel based electrodes. The activity of composite nano- and microstructured materials in various configurations resulting from pore filling of template matrices by nickel was explored. Studies of the physical structure and chemical properties of the nanostructured materials included investigating the necessary parameters of template matrices. The optimum conditions of synthesis, which allowed development of materials with the highest catalytic activity, were determined.&nbsp / The effect of the template structure on microcrystallinity of the catalyst particles was established using the XRD method. Different new types of non-commercial asymmetric ion track membranes has been tested for nanostructure preparation. The catalytic activity of the new developed nanomaterials is higher as compared to materials using commercial templates. The procedures to modify the newly developed nickel catalyst with Pt, Pd and Pt-Pd alloy have been developed. The Pt and Pt-Pd alloy containing catalyst showed the best performance in water electrolysis. In this work, the promising role for specific application of the new materials in hydrogen economy has been demonstrated.</p>