Study of Semiconducting Nanomaterials: Photoelectrochemistry and Dynamic Light Scattering
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This dissertation discusses photoelectrochemical studies on zinc oxide (ZnO) nanomaterials and stochastic collision studies of bare and sensitized titanium dioxide (TiO2) nanoparticles (NPs). A detailed study of NP colloidal behavior has been described with respect to dynamic light scattering (DLS) measurements. In our system, we studied electron transfer across the semiconductor (SC) electrode and electrolyte interface. The application of ZnO and TiO2 nanomaterials in dye-sensitized solar cells is the motivation behind the study of the fundamentals of electron transfer phenomena across interfaces. We studied how to control surface recombination on ZnO nanomaterials (specifically, nanowires) for efficient charge carrier collection. We concluded that the presence of iodide in the solution stabilizes ZnO nanowires due to the faster rate of iodide oxidation for hole (h+) removal. In addition, we studied the stochastic collision and detection of bare TiO2 NPs on fluorine-doped tin oxide microelectrodes (FTO µE). We observed peak current transients with magnitudes of a few nA to 100 nA. The variation in the peak current magnitude is attributed to the detection of single NPs and of agglomerates of 100 nm to 1-2 µm diameter as supported by DLS measurements. Interestingly, agglomeration is the function of time for colloid prepared with and without supporting electrolyte. Illumination time as well as the full history of colloid also has effect on agglomeration for both bare TiO2 and the DSTiO2 NPs suspended in the methanol.