Thesis (M.S.) in Mechanical Engineering--University of Maine, 2007. / Includes vita. Includes bibliographical references (leaves 94-100).

Thesis (Ph.D.)--University of Delaware, 2008. / Principal faculty advisor: Douglas J. Doren, Dept. of Physics & Astronomy. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 125-136). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains xiii, 196 p. : ill. (some col.). Includes abstract. Includes bibliographical references.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2006. / On t.p. "2" is subscript. Includes bibliographical references. Also available in electronic version.

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Nanomaterial’s applications have expanded greatly in the last few decades due to their interesting properties. Example of nanomaterials are metal nanoparticles NP. NP have interesting physical and optical properties that make them different and more useful than their bulk counterpart. Some of these properties are the large surface area to mass ratio and their ability to absorb light. NP have been applied in the health, environment, and catalysis fields The main focus of this thesis will be on the applications of nanomaterials in medicine and catalysis. In the first part of the thesis, coated polydispersed and polymorphic silver nanostructures AgNS were synthesized using seed mediated method. The synthesized AgNS were characterized using SEM, TEM, and UV-VIS. The stability of these AgNS were determined by measuring the shift in the plasmon band over time and by measuring their zeta potential. Moreover, the bactericidal properties of coated AgNS were tested on gram negative bacteria such as Escherichia coli and Pseudomonas aeruginosa and gram positive bacteria such as Methicillin- Resistant Staphylococcus aureus (MRSA) and Staphylococcus aureus. The second part of the thesis discusses the field of nanocatalysis where different supported metal nanoparticles on TiO2 were synthesized and characterized by TEM, diffuse reflectance DR, XPS and ICP. The activity of the synthesized catalysts was tested for Ullmann C-C cross coupling reaction. The use of the photoresponisve Pd@TiO2 under the combination of UVA 368 and visible light 465nm irradiation offered the highest selectivity toward the cross coupling product.

Polychlorinated endocrine disrupting chemicals are environmental pollutants that are increasingly found in water sources. As a result of their hydrophobic properties, they generally accumulate in adipocytes of humans and wildlife when ingested. In this study, the feasibility of the advanced oxidation processes (AOPs) such as heterogeneous photocatalysis technology is investigated for the treatment of organochlorides in water systems. Titanium dioxide (TiO2) is the semiconductor catalyst of interest. The literature suggests that the most prominent organochlorides in the region are organochloride pesticides (OCPs). A group of 5 compounds were identified for the investigation; DDT, DDE, heptachlor, chlordane, and a polychlorinated biphenyl compound named 2,3,4-trichlorobiphenyl. Reverse phase solid phase extracted (RP-SPE) surface water organic analytes analysis was conducted using gas chromatography mass spectroscopy (GC-MS). Results from most sampling sites showed high concentration levels of the organochlorides in the environment. Heterogeneous photocatalysed mineralisation processes of organochlorides in aqueous systems were conducted in a batch reactor. Organochloride spiked solutions of differing catalyst concentrations are irradiated using a UV lamp for a period of 30 minutes. The reaction kinetics are determined and weighed against conventional photolysis. Results showed improved photo degradation of organochlorides under photocatalytic imposed conditions in comparison to photolysis. Results also suggest that photocatalytic degradation of organochlorides is less favoured with increased TiO2 catalyst concentrations. Enhanced catalyst performance studies through TiO2 surface property modification were conducted using copper nitrate (CuNO3) as a catalyst dopant. The doped catalyst showed slightly improved degradation of organochlorides at particular catalyst concentrations. Simulated photocatalytic rate of reaction kinetics results are in correlation with the modeled experimental results. They show variability of the degradation constant in the rate of reaction with varied catalyst concentrations. Catalyst concentration efficiency of each compound and the rate of the reactions were determined. / Dissertation (MSc)--University of Pretoria, 2012. / Chemical Engineering / unrestricted

Nanomaterials have a great potential for environmental applications due to their high surface areas and high reactivity. This dissertation investigated the use of electrochemically active biofilms (EABs) as a synthesis approach for the fabrication and environmental applications of different nanomaterials. Bacteria in EABs generate electrons upon consuming electron donor and have the ability to transport these electrons to solid or insoluble substrates through extracellular electron transport (EET) mechanism. The extracellularly transported electrons, once utilized, can lead to nanoparticle synthesis. In this dissertation, noble metal (i.e., Au, Pd, and Pt) ultra-small nanoparticles (USNPs) were first synthesized with the assistance by the EABs. The assynthesized USNPs had a size range between 2 and 7 nm and exhibited excellent catalytic performance in dye decomposition. Also in this research, a two-dimensional (2D) cobalt nanosheet was successfully synthesized in the presence of EABs. A simple biogenic route led to the transformation of cobalt acetate to produce a green, toxic free homogeneous 2D cobalt nanosheet structure. Further, TiO2 nanotubes were successfully combined with the noble metal USNPs to enhance their photocatalytic activity. In this work, for the first time, the noble metal USNPs were directly reduced and decorated on the internal surfaces of the TiO2 nanotubes structure assisted by the EABs. The USNPs modified TiO2 nanotubes generated significantly improved photoelectrocatatlyic performances. This dissertation shines lights on the use of EABs in ultra-small nanoparticle synthesis.

The exploration in the use of nanomaterials for a multitude of different applications has grown within the last few years. This is largely due to the vast number of features exhibited by nanoscale materials when compared to their bulk counterparts. The use of nanomaterials in environmental applications can come in different facets, such as, the production of clean energy in solar cells and the application of nanotechnologies in coatings for building exterior surfaces. The first section of the thesis focuses on the use of nanomaterials for water remediation, since purified groundwater is still not globally accessible. Chapter 2 focuses on the use of Pd nanoparticles supported on TiO₂ (Pd@TiO₂) to photo-generate H₂ while using bacterial cells as sacrificial electron donors (SEDs) rather than chemical reagents. Different conditions were examined to investigate the photo-destruction of gram negative bacteria, E. coli, which is a microbial pollutant often found in a number of different water sources. Samples containing photocatalyst in solution were irradiated using a solar simulator, which is a light source that is similar to the solar spectrum, for applications in a flow system. Chapter 3 is a project in collaboration with Dr. Edith Amuhaya and her research group in Nairobi, Kenya exploring the use of porphyrins, an organic compound, supported on glass wool for water treatment in a flow system. Porphyrins are photosensitizers that generate reactive oxygen species (ROS) when exposed to light and oxygen. However, their high solubility in aqueous media makes it difficult to use them for water remediation and can add an extra step in the process of water purification. Therefore, we suggest attaching the porphyrins to glass wool, which is an inexpensive and inert support that can easily be removed from a flow system. Here, we explore the use of glass wool as a support for a series of different conjugated porphyrins and metalloporphyrins. We have synthesized different porphyrins bearing carboxylic group substituents to enable ease of deposition onto the amino-functionalized glass surface (glass surface modified with (3-Aminopropyl) triethoxysilane, APTES). The characterization of the materials suggests some of the porphyrins retain the ability to absorb solar light and generate reactive oxygen species upon irradiation. Antimicrobial activity and degradation of selected pollutants were also explored. The last section of the thesis discusses a different approach regarding nanoparticles. Typically, nanoparticles are used for their reactivity when they absorb light, often producing a high number of free radicals in the process. However, this high reactivity can become an issue when these free radicals cause unintended damage to biological environments. This is the case for TiO₂ used for photo-protection sunscreens, where there has been some concern regarding the free radical damage to skin. Previously, the group has synthesized TiO₂ particles in a thin shell of lignin, a natural biopolymer. Lignin is an antioxidant that can scavenge the radicals produced by the photo-excited TiO₂ and prevent them from being released into the surrounding media. Here, we further characterize and investigate the properties of the lignin on TiO₂ nanoparticles and attempt to scale up the production of the particles.