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Browsing by Author "Kale, Amanda R., author"

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    Exploring phase selectivity and morphological control in Cu-Sb-Se nanoparticle synthesis
    (Colorado State University. Libraries, 2023) Kale, Amanda R., author; Prieto, Amy L., advisor; Sambur, Justin, committee member; Krummel, Amber, committee member; Ma, Kaka, committee member
    Nanoparticles are used in a variety of applications, such as optoelectronics, medicine, and energy generation and storage. Different applications necessitate different nanoparticle compositions and morphologies. Thus, developing fine synthetic control over composition, phase, and morphology is of interest to the field. Solution-phase nanoparticle synthesis allows control over particle shape and size, though phase purity is often an issue in ternary syntheses. Often precursor reactivity must be balanced to avoid binary sinks; however, in the Cu-Sb-Se system, the ternaries compete with one another. In this dissertation we explore the knobs of a hot-injection synthesis in oleylamine that can be tuned to favor different Cu-Sb-Se ternary phases and control particle morphologies. In Chapter I we begin with a discussion of the term precursor reactivity and how we define it here. We also address the common frameworks used to explain reactivity, and the specific challenges of balancing reactivity in multinary chalcogenide syntheses. We also discuss how these challenges manifest in the Cu-Sb-Se system, and why the structures and phase space of this material are interesting to study. In Chapter II we discuss a guide for fitting X-ray diffraction data for complex nanomaterial systems, outlining important considerations when working on the nanoscale as well as our sequential approach to refinements and recommended best practices. We also discuss a case study on the refinements of anisotropic, multiphase systems, which we use for the following chapter. The main synthetic work follows in the next two chapters, focusing first in Chapter III on the decomposition of metastable Cu3SbSe3 to thermodynamic CuSbSe2. We investigate how this can be manipulated through the addition of an amide base. In Chapter IV, we explore tuning morphology and specifically nanosheet branching in CuSbSe2, in which we show that we can induce twinning in CuSbSe2 and initial characterization suggests that this occurs in a different manner than in the very similar sulfide system. Finally, in Chapter V we reflect on the considerations and next steps for this work, including preliminary results on the use of soft base ligands to complex Cu, as well as on promising directions of field of nanoparticle synthesis as a whole.