Master of Science / Department of Chemistry / Jun Li / With the worldly consumption of energy continually increasing and the main source of this energy, fossil fuels, slowly being depleted, the need for alternate sources of energy is becoming more and more pertinent. One promising approach for an alternate method of producing energy is using solar cells to convert sunlight into electrical energy through photovoltaic processes. Currently, the most widely commercialized solar cell is based on a single p-n junction with silicon. Silicon solar cells are able to obtain high efficiencies but the downfall is, in order to achieve this performance, expensive fabrication techniques and high purity materials must be employed. An encouraging cheaper alternative to silicon solar cells is the dye-sensitized solar cell (DSSC) which is based on a wide band gap semiconductor sensitized with a visible light absorbing species. While DSSCs are less expensive, their efficiencies are still quite low compared to silicon. In this thesis, Grätzel cells (DSSCs based on TiO2 NPs) were fabricated and optimized to establish a reliable standard for further improvement. Optimized single layer GSCs and double layer GSCs showing efficiencies >4% and efficiencies of ~6%, respectively, were obtained. Recently, the incorporation of metallic nanoparticles into silicon solar cells has shown improved efficiency and lowered material cost. By utilizing their plasmonic properties, incident light can be scattered, concentrated, or trapped thereby increasing the effective path length of the cell and allowing the physical thickness of the cell to be reduced. This concept can also be applied to DSSCs, which are cheaper and easier to fabricate than Si based solar cells but are limited by lower efficiency. By incorporating 20 nm diameter Au nanoparticles (Au NPs) into DSSCs at the FTO/TiO2 interface as sub wavelength antennae, average photocurrent enhancements of 14% (maximum up to ~32%) and average efficiency enhancements of 13% (maximum up to ~23% ) were achieved with well dispersed, low surface coverages of nanoparticles. However the Au nanoparticle solar cell (AuNPSC) performance is very sensitive to the surface coverage, the extent of nanoparticle aggregation, and the electrolyte employed, all of which can lead to detrimental effects (decreased performances) on the devices.

Doctor of Philosophy / Biochemistry and Molecular Biophysics Interdepartmental Program / Timothy P. Durrett / The direct use of vegetable oils as a biofuel suffers from problems such as high viscosity, low volatility and poor cold temperature properties. 3-acetyl-1,2-diacyl-sn-glycerols (acetyl-TAGs) have lower viscosity and freezing temperature than regular vegetable oils. However, by modifying their fatty acid composition, further improvement in their fuel properties is possible. Our goal was to develop plants that synthesize seed oils with further improved fuel properties. Euonymus alatus diacylglycerol acetyltransferase (EaDAcT) synthesizes acetyl-TAGs by the acetyl-CoA dependent acylation of diacylglycerol (DAG). Knowledge of the substrate specificity of EaDAcT for its acetyl-CoA donor and DAG acceptor substrates is important to generate the required acetyl-TAG composition in seed oil. A rapid method to quantify acetyl-TAGs was developed based on electrospray ionization mass spectrometry to gain information about the substrate specificity of EaDAcT. This method is as accurate and more rapid than the traditional radiolabeled substrate based assay and additionally provides information on acetyl-TAG molecular species present. Using this assay, EaDAcT specificity for different chain length acyl-CoA and DAGs was tested. It was found that although EaDAcT can use other short chain length acyl-CoAs as acyl donors, it has high preference for acetyl-CoA. Further, EaDAcT can acetylate a variety of DAGs with short, medium and long chain length fatty acids with high preference for DAGs containing unsaturated fatty acids. To generate acetyl-TAGs with lower molecular mass, EaDAcT was transformed into transgenic Camelina sativa lines producing high amounts of medium chain fatty acids (MCFAs). EaDAcT expression was also combined with the knockdown of DGAT1 and PDAT enzymes, which compete with EaDAcT for their common DAG substrate. High acetyl-TAG yielding homozygous T3 transgenic lines were generated but the incorporation of MCFAs into acetyl-TAGs was inefficient. A small increase in the viscosity of acetyl-TAGs from these lines was observed compared to acetyl-TAGs produced in wild type Camelina plant. The combined effect of insufficient lowering of molecular mass and increased fatty acid saturation levels of acetyl-TAGs might be responsible for this increased viscosity. Overall, it was concluded that the molecular mass and the saturation levels of fatty acids of acetyl-TAGs need to be considered at the same time in future attempts to further decrease their viscosity.