Material Type  

 학위논문

 

0017160139

Date and Time of Latest Transaction  

20250211150917

ISBN  

9798382840642

DDC  

620.11

Author  

Yao, Yuan.

Title/Author  

Optoelectronic Properties of Metal Chalcogenide Nanoparticles: Inter-band Transition Resonance and Chiroptical Effect.

Publish Info  

[S.l.] : Cornell University., 2024

Publish Info  

Ann Arbor : ProQuest Dissertations & Theses, 2024

Material Info  

312 p.

General Note  

Source: Dissertations Abstracts International, Volume: 85-12, Section: B.

General Note  

Advisor: Robinson, Richard.

학위논문주기  

Thesis (Ph.D.)--Cornell University, 2024.

Abstracts/Etc  

요약The emergence of nanomaterials, driven by the size-dependent quantum confinement effect, has opened new possibilities for researchers to manipulate material properties by simply adjusting particle sizes. It continues to captivate us that by controlling the size and morphology of nanoparticles, a vast range of novel material properties and applications can be achieved. Among various classes of nanomaterials, optoelectronic nanomaterials have gained significant attention due to their immense potential in industries such as semiconductors. This thesis focuses on investigating two types of innovative semiconductor nanomaterials with distinct optoelectronic properties. The first material of interest is CuFeS2 nanoparticle, which belongs to the category of intermediate-band semiconductor nanomaterials. The second material is CdS magic size cluster hierarchical thin film, representing an intriguing inorganic/organic hybrid hierarchical chiral material. By utilizing these two materials as model systems, the primary objective of this thesis is to establish fundamental knowledge that will facilitate future advancements in similar materials. Each study is accompanied by a summary of the background, motivation, and summary, as outlined below.Part 1: CuFeS2 (chalcopyrite) exhibits a yellowish color and metallic luster in its natural bulk form, often leading to confusion with gold. However, CuFeS2 nanoparticles display entirely different optical properties. Upon dispersion in a solvent, they exhibit a deep red/purple color, characterized by a visible absorption band centered around 500 nm. The optical absorption characteristics of CuFeS2 nanoparticles have garnered significant research attention, as they resemble those of precious metal plasmonic nanoparticles like gold and silver. Furthermore, as CuFeS2 is a semiconductor, its absorption properties can be adjusted through post-synthetic modifications of chemical composition and crystal structure. However, previous literature presents conflicting accounts regarding the existence of the 500 nm absorption band, the underlying mechanism behind it, and the oxidation states of the cations involved. In this study, we establish our synthesis method for CuFeS2 nanoparticles and address these unresolved questions through a combination of advanced ex-situ and in-situ material characterization techniques. These include x-ray absorption spectroscopy (XAS) and x-ray emission spectroscopy (XES), along with material properties simulations such as density functional theory (DFT) and linear optical Lorentzian modeling.Part 2: Historically, chiral materials have garnered significant attention in the pharmaceutical industry due to the human body's stereoselective chemical reactions, where drugs with opposite chirality can have distinct effects. Apart from their stereoselective chemical properties, optically active chiral materials exhibit differential absorption of left-handed and right-handed light, which is characterized by circular dichroism (CD). However, it's important to note that achiral materials with linear anisotropic contributions, such as linear dichroism (LD) and linear birefringence (LB), can also result in a CD signal. This linear anisotropy-induced CD signal becomes more pronounced in complex material systems, particularly in hierarchically structured nanomaterials that encompass a wide range of length scales, from molecular-scale nanoclusters to micron-sized assemblies. Our recent research has demonstrated the self-assembly of CdS magic-sized clusters (MSCs) into ordered films with a hierarchical structure spanning seven orders of length scales. These films exhibit a strong circular dichroism (CD) response, but the chiral origins are obscured by the hierarchical architecture and contributions from linear anisotropy (linear dichroism, linear birefringence). Using first principle analysis, we have derived and validated a four-scan averaging method for extracting the "pure" CD signal, which specifically arises from structural dissymmetry, from hierarchical MSCs films. Using four-scan averaging method, we successfully characterized the true CD signal of our films, and identified the chiral assembly of our film as the chiral origin. To test the limit of the four-scan averaging method, we simulated the higher order linear anisotropy pairwise interaction and found the threshold at which our four scan method is no longer applicable. Additionally, to study MSCs with difference chemical composition, we conducted a mechanistic study on CdS MSC cation exchange reaction and found an interesting two steps reaction mechanism.

Subject Added Entry-Topical Term  

Materials science.

Subject Added Entry-Topical Term  

Nanoscience.

Subject Added Entry-Topical Term  

Optometry.

Index Term-Uncontrolled  

Chirality

Index Term-Uncontrolled  

Optoelectronic material

Index Term-Uncontrolled  

Pharmaceutical industry

Index Term-Uncontrolled  

Density functional theory

Index Term-Uncontrolled  

X-ray emission spectroscopy

Added Entry-Corporate Name  

Cornell University Materials Science and Engineering

Host Item Entry  

Dissertations Abstracts International. 85-12B.

Electronic Location and Access  

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Control Number  

joongbu:658045