The Quantitative Analysis and Modification of Colloidal Nanoparticle Surfaces and Structures
出版項
2020
說明
1 online resource (132 pages)
文字
text
無媒介
computer
成冊
online resource
附註
Source: Dissertations Abstracts International, Volume: 82-05, Section: B
Advisor: Cossairt, Brandi
Thesis (Ph.D.)--University of Washington, 2020
Includes bibliographical references
Nanoparticles have consumed the attention of inorganic and materials chemists for decades owing to both their tremendous breadth in composition, size, and shape, as well as the many exceptional physical and chemical properties which derive therefrom. Organic and metallic nanoparticles are exceptional classes of materials, but of particular interest to us are nanoparticles produced from semiconducting compositions. Nanoparticles derived from combinations of group II and VI or III and V elements on the sub 10 nm scale are commonly referred to as quantum dots (QDs). Quantum dots have attracted a great deal of attention as the result of potent emergent properties arising from their quantum scale as well as the many benefits and applications of solution processability. Quantum dot research has led to a generational advance in numerous technologies and real-world applications including bio-sensing, catalysis, light harvesting, solid- state lighting, and displays. Continued development of the physicochemical properties of QDs promises a more technologically advanced and a greener future. One of the most poorly understood and yet functionally-critical properties of nanomaterials is their surface. Surfaces of bulk materials do not appreciably contribute to most of the material's physical properties such as the band gap, absorptivity, or charge mobility. By contrast the surface of a nanoparticle is paramount to its physical as well as chemical properties. While size predominantly dictates the bandgap via the quantum confinement effect in QDs, the surface speciation ultimately decides charge trapping, transfer, solubility, and all manner of chemical reactivity. These varied implications of the surface represent both a responsibility and an opportunity to the chemist. The responsibility lies in identifying and characterizing the surface even though such measurements are often exceptionally difficult. However, if the surface can be well understood and controlled it holds the invaluable opportunity to tune the desired properties of the nanomaterial in ways not available through other means. Post-synthetic surface modification represents one of the most readily accessible and tractable methods for producing high-quality quantum dots with specific, engineered applications in mind. Our work in the Cossairt Lab has been exceptionally well poised to tackle this problem using atomistic and precise synthetic methodology. Understanding the surface properties of quantum dots is also a critical step towards extending synthesis across length scales through the formation of mesocrystalline assemblies. Mesocrystals can be described as macroscopic pseudo-crystals and assemblies of nanomaterial units. Such assemblies offer not only another method of tuning the material properties, but a handle with which to create products for real-world problems that cannot be adequately solved by solution or amorphous film phases of matter. Just as the cytoplasm of a light harvesting plant cell contains a delicate assembly of countless microscopic components, future applications of quantum dots too must be built up from the nanoscale and incorporated into greater structures to extract their usefulness. By transcending the nanoscopic scale and engineering these structures across scales researchers can begin to tackle more problems with a greater degree of control and rational design. In order to achieve this though, one must simultaneously understand and control the critical interface of every nanoparticle: the surface. In Chapter One of this thesis conceptualizations of nanoparticle surfaces will be reviewed in a greater detail. The discussion will be focused on II-VI and III-V materials, especially InP as it is the predominant focus of this body of work. An overview of mesocrystals and across length scale design will also be examined here. Chapter Two will focus on a quantitative investigation of ligand speciation and exchange at the surface of InP nanoparticles. This topic was thoroughly examined using atomically precise InP clusters and a combination of 1H NMR and 31P NMR spectroscopy as well in-situ SAXS via synchrotron. The controlled manipulation of InP surfaces is further examined in Chapter Three where manipulation of the nanoparticle surface is shown to give rise to control over nanoparticle crystal phase and growth profiles. Finally, Chapter Four will continue manipulations of the quantum dot surface towards the formation of mesocrystalline assemblies. Mechanisms of mesocrystalline material formation as well as preliminary applications towards photocatalysis will be discussed
Electronic reproduction. Ann Arbor, Mich. : ProQuest, 2021
