| Nanostructured materials (nanofibers, nanoparticles, nanotubes etc.) with high surface to volume ratio have potential applications in biosensing, tissue engineering, energy conversion, catalysis etc., if the composition and arrangement of matter are adequately controlled. Electrospinning enables rapid production of nanofibers from a variety of polymers but yields randomly oriented fibers if additional controls are not imposed when the fibers are deposited onto a support. In the first part of this two-part dissertation, we studied the effects of different salts on the electrospinning of organic and aqueous solutions of polymers to manipulate the diameter of the nanofiber and we studied the effect of using a secondary electric field to increase control over fiber alignment. We found that the addition of small amounts of conductive salts to organic solutions decreased the nanofiber diameter but at higher loadings or in more conductive aqueous solutions fibers "back built" forming fiber bundles and in some cases fused to form larger and more polydisperse fibers. The use of a secondary electric field increased the alignment of fiber on dual electrodes but not on a rotating collector at the rotation rates we could achieve. In the second part of this dissertation TiO2 nanofiber and nanotube arrays were prepared for use in quantum-dot sensitized solar cells. Only poor quality unaligned TiO2 nanofibers were produced that adhered poorly to the Indium Tin Oxide electrode and gave very low photocurrent. Two-Dimensional TiO2 nanotube arrays, prepared by anodization of titanium foils, gave a maximum photocurrent generated in TiO2--CdSe electrodes of 6.0 mA/cm2 and a photo voltage of -1.24 V. These devices exhibit a fill factor of up to 56% and an overall efficiency of 0.76 %. The effect of including gold nanoparticles in the cell design was tested on the performance of the TiO2--CdSe electrodes under identical conditions as the original TiO2--CdSe electrodes. Inclusion of the gold nanoparticles resulted in a significant decrease in the photocurrent, and a moderate decrease in the photo voltage which is attributed to decreased electron transfer from CdSe to TiO2 in the presence of gold nanoparticles. |
