In recent decades, there has been a rapid expansion in the use of manufactured nanoparticles (MNPs). Experimental evidence and material flow models predict that MNPs enter wastewater treatment plants and partition to sewage sludge and majority of that sludge is land applied as biosolids. During wastewater treatment and after land application, MNPs undergo biogeochemical transformations (aging). The primary transformation process for silver MNPs (Ag-MNPs) is sulfidation, while zinc oxide MNPs (ZnO-MNPs) most likely undergo phosphatation and sulfidation. Our overall goal was to assess bioavailability and toxicogenomic impacts of both pristine, defined as-synthesized, and aged Ag- and ZnO-MNPs, as well as their respective ions, to a model organism, the soil nematode Caenorhabditis elegans. We first investigated the toxicity of pristine Ag-MNPs, sulfidized Ag-MNPs (sAg-MNPs), and AgNO3 to identify the most sensitive ecologically relevant endpoint in C. elegans. We identified reproduction as the most sensitive endpoint for all treatments with sAg-MNPs being about 10-fold less toxic than pristine Ag-MNPs. Using synchrotron x-ray microspectroscopy we demonstrated that AgNO3 and pristine Ag-MNPs had similar bioavailability while aged sAg-MNPs caused toxicity without being taken up by C. elegans. Comparisons of the genomic impacts of both MNPs revealed that Ag-MNPs and sAg-MNPs have transcriptomic profiles distinct from each other and from AgNO3. The toxicity mechanisms of sAg-MNPs are possibly associated with damaging effects to cuticle. We also investigated the effects pristine zinc oxide MNPs (ZnO-MNPs) and aged ZnO-MNPs, including phosphatated (pZnO-MNPs) and sulfidized (sZnO-MNPs), as well as ZnSO4 have on C. elegans using a toxicogenomic approach. Aging of ZnO-MNPs reduced toxicity nearly 10-fold. Toxicity of pristine ZnO-MNPs was similar to the toxicity caused by ZnSO4 but less than 30% of responding genes was shared between these two treatments. This suggests that some of the effects of pristine ZnO-MNPs are also particle-specific. The genomic results showed that based on Gene Ontology and induced biological pathways all MNP treatments shared more similarities than any MNP treatment did with ZnSO4. This dissertation demonstrates that the toxicity of Ag- and ZnO-MNPs to C. elegans is reduced and operates through different mechanisms after transformation during the wastewater treatment process.

<p>Renewable energy technologies and the development of cleaner and more environmentally friendly power have been at the forefront of research for the past few decades. Photovoltaic systems – systems that convert photon energy to electrical energy – are at the center of these research efforts. Decreasing the cost of energy production, through increasing the power conversion efficiency or decreasing the device cost, is a key factor in widespread use of these energy production systems. To increase the energy conversion efficiency, ideally, all useful photons should be absorbed by the solar cell; however, due to the large discontinuity in the refractive index at the solar cell/air interface, a large fraction of incidence light is lost due to reflection (30% loss in crystalline silicon cells). The currently used single and double layer anti-reflection coatings reduce the reflection losses, but their optimal performance is limited to a narrow range of wavelengths and angles of incidence. Moth-eye anti-reflection coatings are composed of patterned single layer films having a gradual decrease in refractive index from the solar cell surface to air. This study is focused on developing an inexpensive method for direct deposition of patterned films – in the form of moth-eye anti-reflection coatings – on solar cell surface.</p> <p>In this research, the creation of moth-eye anti-reflection coatings has been attempted through the process of electrodeposition. ZnO was chosen for the thin film material, and the ability to develop the required moth-eye structure by changing the electrodeposition parameters including temperature, applied potential, type and concentration of solution-borne species, and type of substrate was investigated. Using this method, pyramidal and hemispherical structures with a 100-200 nm diameter and 100-200 nm height were created directly on ITO substrates. Similar structures were also developed on silicon substrates. The anti-reflection properties of ZnO-coated silicon substrates were investigated by comparing their broadband and broad angle reflection-mode UV-VIS spectrum with uncoated silicon. The optimized ZnO-coated silicon substrate showed a reflectance of at most 20% for wavelengths between 400-1500 nm at angles of incidence less than 50^O.</p> / Master of Applied Science (MASc)