Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references. Also available in electronic version.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (Ph.D.)--Montana State University--Bozeman, 2004. / Typescript. Chairperson, Graduate Committee: Edwin H. Abbott. Includes bibliographical references (leaves 264-268).

Thesis (M.S. in chemical engineering)--Washington State University, May 2007. / Includes bibliographical references.

Thesis (D.Eng.)--University of Delaware, 2009. / Principal faculty advisor: John W. Gillespie, Dept. of Materials Science. Includes bibliographical references.

Thesis (M.S. in materials science and engineering)--Washington State University, December 2008. / Title from PDF title page (viewed on Mar. 3, 2009). "Department of Mechanical and Materials Engineering." Includes bibliographical references.

Nanohybrid materials have been prepared and examined for their electrocatalytic activity. The nanocomposites have been prepared from carbon nanomaterials (multiwalled carbon nanotubes (MWCNTs) and graphene nanosheets), cadmium selenide quantum dots and metallophthalocyanines (MPcs). The MPcs used in this work are cobalt tetraamino-phthalocyanine (CoTAPc) and tetra (4-(4,6-diaminopyrimidin-2-ylthio) phthalocyaninatocobalt (II)) (CoPyPc). Their activity has also been explored in different forms; polymeric MPcs, iodine doped MPcs and covalently linked MPcs. The premixed drop-dry, sequential drop-dry and electropolymerisation electrode modification techniques were used to prepare nanocomposite catalysts on the glassy carbon electrode (GCE) surface. The sequential drop dry technique for MPc and MWCNTs gave better catalytic responses in terms of limit of detection, catalytic and electron transfer rate constants relative to the premixed. MWCNTs and CdSe-QDs have been used as intercalating agents to reduce restacking of graphene nanosheets during nanocomposite preparation. Voltammetry, chronoamperometry, scanning electrochemical microscopy and electrochemical impedance spectroscopy methods are used for electrochemical characterization modified GCE. X-ray photoelectron spectroscopy, X-ray diffractometry, transmission electron microscopy, scanning electron microscopy, infra-red spectroscopy, Raman spectroscopy were used to explore surface functionalities, morphology and topography of the nanocomposites. Electrocatalytic activity and possible applications of the modified electrodes were tested using oxygen reduction reaction, l-cysteine oxidation and paraquat reduction. Activity of nanocomposites was found superior over individual nanomaterials in these applications.

Epidemiological studies highlight a direct association between the decline in respiratory health of the human population and increased environmental ultrafine particulate (UFP) exposure. This evidence, coupled with research identifying shared characteristics and toxicity between UFP and engineered nanomaterial (ENM), suggests that increased levels of ENM associated with the nanotechnology revolution could have a detrimental effect on human health. Although the link between respiratory disease and air pollution is well-established, toxicological data for ENM is limited. Current methods for the assessment of particle toxicity utilise a combination of both in vitro assays and in vivo animal testing. In some cases, these conventional assays provide unreliable results on account of nanoparticle interference. In this thesis, assays were undertaken to more fully understand the impact of a panel of ENMs on alveolar epithelial cell function and survival, as well as to assess the potential value of an alternative method for nanotoxicological screening. Eicosanoid profiling was used to assess both toxicity and inflammatory markers associated with a panel of ENMs, this technique is novel for the use in testing of ENM and the results show it has potential to be introduced/applied as an effective tool to predict a broad spectrum of detrimental effects of ENM in lung function. Submerged A549 cells, were used as a model of lung epithelial cells throughout. The secondary cell line is commonly used in in vitro research to examine the effect of toxins on respiratory health, specifically the alveolar region. A panel of ENM (SiO2, TiO2, NiO, ZnO and CuO) were selected to span from the benign to the highly toxic. ENM prepared in suspension were applied to the cells at 100cm2/mL for 24 h. This doctoral thesis focused on addressing the following aims: 1. To assess whether metallic ENM of differing chemical composition damage the cell membrane and/or mitochondria. 2. To determine whether ENM induce mitochondrial dysfunction through delivery or over-production of harmful reactive oxygen species (ROS) and, if so, to determine whether mitochondrial dysfunction results in activation of apoptosis. 3. To ascertain whether ENM alter the release of lipid inflammatory mediators using eicosanoid profiling. Mitochondrial function and membrane integrity assays revealed that CuO and ZnO induced mitochondrial dysfunction (~ 100% reduction in mitochondrial function), and promoted cell death (85 ± 7.5% cell lysis, ***P<0.001), respectively, when compared to control. In addition, superoxide production was increased by TiO2 alone (~ 100% increase, 0.0394 ± 0.0081 AU, **P<0.01), creating a discrepancy between assays. Analysis also revealed that metallic ENMs, specifically ZnO and CuO, significantly increased the production of prostaglandin E2 (~ 50%, 828 ± 119pg/sample, **P<0.01) and ~ 100%, 1439 ± 248pg/sample, ***P< 0.001), a pro-inflammatory eicosanoid, and elevated generation of a range of hydroxy-eicosatetraenoic acids (HETEs), suggesting induction of lipid peroxidation by these oxide derived ENMs. In conclusion, through the use of in vitro assays and eicosanoid analysis it was determined that ZnO and CuO ENM induce cell damage and death. However, although traditional in vitro assays are able to identify highly toxic ENM from the rest, they lack the ability to identify more subtle changes and, in some cases, are unreliable. By contrast, eicosanoid profiling has the ability to provide more detailed information regarding generation of both pro- and anti-inflammatory mediators, as well as oxidative stress, whilst avoiding the issues that are encountered through the use of current in vitro tests.

M.Sc. (Chemistry) / Please refer to full text to view abstract

Nanomaterials, in particular carbon nanotubes have been shown to exhibit favourable properties for the enhancement of electrochemical detection of target analytes in complex matrices. There is however scope for improvement in terms of the optimization thereof in electrochemical sensors surface modification. The aim of this thesis was to examine methods that would result in increased current response, lowered passivation and application of such modified surfaces with application to pharmaceutically and industrially relevant analytes. Current methods for enhancing the performance of carbon nanotubes include acid functionalization which not only increases the hydrophilicity of the nanotubes, and consequently their ability to provide stable (aqueous) suspensions, but also introduces electrochemically active sites. This particular approach is however not normalized in the literature. Over-exposure to acid treatment results in loss of structural integrity of the carbon nanotubes, and as such a fine balance exists between achieving these dual outcomes. Guided by high resolution scanning electron microscopy, atomic force microscopy, voltammetric and impedance studies, this thesis examined the role of the length of time of the acid functionalization process as well as the impact of activation of carbon nanotubes and fullerenes on electrochemical sensor performance. Based on desired charge transfer resistances, rate transfer coefficients and sensitivity towards redox probes the optimal length of acid functionalization for multiwalled carbon nanotubes was 9 hours and 4 hours for single-walled carbon nanotubes. Further improvements in the desired outcomes were achieved through electrochemical activation of the modified electrode surface by cycling in the presence of catechol, in a novel approach. By employing electrochemical impedance spectroscopy it was observed that catechol activation resulted in lowered charge transfer resistance, before and after activation, with functionalized multi-walled carbon nanotubes (9 hours) exhibiting the greatest decrease of 90 % and functionalized single-walled carbon nanotubes (4 hours), a 50 % decrease. Corresponding increases in the heterologous rate transfer coefficient showed a 770 % increase for functionalized multi-walled carbon nanotubes (9 hours), following catechol activation. Comparative observations for fullerenes following partial reduction in potassium hydroxide yielded a 30 % decrease in charge transfer resistance, with an increased heterologous rate transfer coefficient at a fullerene modified surface The performance of the nanomaterial modified electrodes was applied to the detection of wortmannin with applications in bioprocess control and in the pharmaceutical sector as well as to the detection and monitoring of the industrial dye Reactive red. Of particular relevance to these analytes was the assessment of the nanomaterial modified electrodes for enhanced stability, reproducibility, sensitivity and decreased passivation effects. In this study the first known account of wortmannin detection through electrochemical methods is reported. Voltammetric characterization of wortmannin revealed an irreversible cathodic process with a total number of 4 electrons and a diffusion coefficient of 1.19 x 10-7 cm².s⁻¹. At a functionalized multiwalled carbon nanotubes modified glassy carbon electrode a limit of detection of 0.128 nmol.cm⁻³ was obtained, and with limited surface passivation the detection scheme afforded pertinent analyses in biological media representing a substantial improvement over chromatographic detection methods. This study also provided the first account of the voltammetric detection of reactive red, competing favourably with traditional spectroscopic methods for monitoring biodegradation of this compound in real time.