Strategies for metal colloidal nancrystal synthesis in sustainable media
[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Over the past decades, the Green Chemistry and Sustainability concept has aroused researchers to denounce their traditional ways of thinking regarding chemical processes to address the challenges relevant to global environmental concerns. The concept has demonstrated how fundamental scientific methodologies can protect human health and the environment in an economically beneficial manner. In academia and industry, the use of green solvents, such as water, supercritical fluids, ionic liquids (ILs) and deep eutectic solvents (DESs), has then become desirable in chemical processes. In the field of green nanochemistry, ILs and DESs have acquired courtesy as sustainable media for nanomaterials synthesis. There have been attempts to employ such eco-friendly fluids to synthesize, and additionally, control size and shapes of nanomaterials, where the field has been gaining intense interests as the morphology dictates the properties and functionalities of such nanomaterials. This dissertation reports strategies for metal colloidal nanocrystal synthesis in sustainable media and aims to build a foundation for understanding how to tailor eco-friendly IL and DES fluids to control the growth of metal nanocrystals. Chapter 1 explores research reporting strategies used for metal colloid synthesis in ILs and DESs. In Chapter 2, we have developed a strategy to replace a common organic solvent with an IL to prepare monodisperse gold nanoparticles (AuNPs) by a very fast microwave method. The pyrrolidinium IL used in the work demonstrates its capability to be efficiently recovered and reused for carrying out nanoscale synthesis iteratively. The work highlights the incompatibility of imidazolium ILs for the select nanoscale synthetic strategy. For Chapter 3, we have demonstrated a control over nanoparticle size and shape generated at an aqueous-organic interface. We have shown that an interfacial photoreduction leads to the production of spherical and wire-like nanostructures, respectively, when the IL employed involves a coordinated and non-coordinated IL anion, respectively. Next, Chapter 4 has focused on exploitation of a purposefully designed IL-inspired surfactant, acting dually as a reducing and stabilizing agent, for facile and controllable AuNP formation. The reported synthetic method is simple and rapid, using only a gold precursor and the surfactant. Coinage AuNPs can be obtained very fast, while predominantly triangular-shaped AuNPs can also be achieved by tuning parameters, such as the ratio of surfactant to the gold precursor, temperature, implementing a time delay before heating, and an addition of a directing agent. Finally, Chapter 5 outlines zwitterionic deep eutectic solvents (ZDESs) as novel media for metal nanocrystal synthesis, to expand portfolio of available DESs as the field is relatively new compared to that of IL.
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