Dissertation/Thesis Abstract

Silicon Nanocrystals: Optical Properties and Self-assembly
by Brown, Samuel Lynn, Ph.D., North Dakota State University, 2018, 183; 10790537
Abstract (Summary)

Silicon nanocrystal’s (SiNCs) size dependent optical properties and nontoxic nature portend potential applications across a broad range of industries. With any of these applications, a thorough understanding of SiNC photophysics is desirable to tune their optical properties while optimizing quantum yield. However, a detailed understanding of the photoluminescence (PL) from SiNCs is convoluted by the complexity of the decay mechanisms, including a stretched-exponential relaxation and the presence of both nanosecond and microsecond decays.

In this dissertation, a brief history of semiconductor nanocrystals is given, leading up to the first discovery of room temperature PL in SiNCs. This is then followed by an introduction to the various nanocrystal synthetic schemes and a discussion of quantum dot photophysics in general. Three different studies on the PL from SiNCs are then presented. In the first study, the stretched nature of the time dependent PL is analyzed via chromatically-resolved and full-spectrum PL decay measurements. The second study analyzes the size dependence of the bimodal PL decay, where the amplitude of the nanosecond and microsecond decay are related to nanocrystal size, while the third project analyzes the temperature and microstructure dependencies of the PL from SiNC solids.

After an indepth look at the PL from SiNCs, this report examines preliminary results of SiNC and silver nanocrystal self-assembly. When compared to metal and metal chalcogenide nanoparticles, there is a dearth of literature on the self-assembly of SiNCs. To understand these phenomena, we analyze the size dependent ability of SiNCs to form a ‘superlattice’ and compare this with silver nanocrystals. Although the results on self-assembly are still somewhat preliminary, it appears that factors such as SiNC concentration and size dispersity play a key role in SiNC self-assembly, while suggesting intrinsic differences between the self-assembly of SiNCs and silver nanocrystals.

Finally, at the end of this dissertation, a corollary project is presented on the computational analysis of fluorescent silver nanoclusters (AgNCs). Due to their small size and non-toxic nature, AgNCs are an ideal fluorophore for biological systems, yet there is a limited understanding of their photophysics, which is the focus of this part of the dissertation.

Indexing (document details)
Advisor: Hobbie, Erik
Commitee: Choi, Yongki, Denton, Alan, Kilina, Svetlana, Rasmussen, Seth
School: North Dakota State University
Department: Materials and Nanotechnology
School Location: United States -- North Dakota
Source: DAI-B 79/10(E), Dissertation Abstracts International
Source Type: DISSERTATION
Subjects: Chemistry, Physics, Nanotechnology
Keywords: Fluorescence, Radiative recombination, Self-assembly, Silicon nanocrystals
Publication Number: 10790537
ISBN: 9780438002388
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