Flame-driven aerosol synthesis of copper sulfide nanoparticles
Miller, Christopher L.
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This thesis focuses on the synthesis of copper sulfide (Cu x S) nanoparticles and film coatings in a flame-based high temperature reducing jet (HTRJ) reactor. The system, which is powered by a hydrogen flame, is the first reactor of its kind that successfully separates the combustion and particle formation steps that are normally coupled in traditional flame-based aerosol reactors. Water-soluble precursors are injected into a converging-diverging nozzle where they undergo atomization and thermal decomposition in a hot turbulent jet. The continuous operation of this process and the absence of harmful organic solvents make this a promising first step to producing metal and semiconductor nanomaterials on an industrial scale. Cu x S nanoparticles could play in important role in photocatalytic and photovoltaic applications, with Cu 2 S in particular offering an abundant and low-cost alternative to silicon, the most widely used semiconductor in the photovoltaic industry. This material's optical properties (band gap and high absorption coefficient) and p-type semiconductor behavior are well-suited for applications ranging from flexible solar cells to photocatalysis, and production in nanoparticulate form opens the possibility of low cost roll-to-roll manufacturing using colloidal inks. A brief review of vapor-phase nanoparticle synthesis methods is provided, and the HTRJ process is described in greater detail. The latter half of this thesis presents the materials characterization results. The nanoparticles and films were characterized with techniques including scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and ultraviolet-visible (UV-Vis) spectroscopy. The thesis closes with concluding remarks about the work on Cu x S nanoparticles, including some more general suggestions for future research on the HTRJ system.