Atomically Precise Metal Clusters: Synthesis, Excited State Dynamics, and Unique Optical Properties
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Authors
Yousefalizadeh, Goonay
Date
Type
thesis
Language
eng
Keyword
Metal Clusters , Optical Properties , Solar Cells , Photochemistry , Photocatalysis , Two Photon Absorbance , Transient Absorption Spectroscopy , Atomic Precision , Bbimetallic Metal Clusters
Alternative Title
Abstract
Metal clusters are small particles with the exact number of metal atoms and the number/type of ligand molecules bound to the surface. The optical and electronic properties of these materials can be tuned and controlled with precise synthesis. These materials exhibit phenomena such as fluorescence and molecule-like light absorbance. Owing to the unique optical properties of clusters, this new class of materials is finding applications in solar energy harvesting, chemical sensing, biomedical imaging and catalysis. Partly due to their extremely small size, properties like absorbance, HOMO-LUMO energy gap, and fluorescence lifetimes/quantum yield can be tuned through minor changes in either the metal or the coordinating ligands. The electronic properties of clusters can be characterized using spectroscopic techniques that provide valuable information on the ability to absorb light, fluorescence capabilities, and excited state behavior, and so on. All of these factors are critical in dictating photocatalytic activity. These clusters can be functionalized with peptides, which makes them ideal for use in biomedicine as well. The nonlinear optical properties of these clusters make them excellent candidates for use in next generation biomedical imaging and therapy.
In this thesis:
• A photochemical route for producing atomically precise gold clusters is reported.
• Electronic properties (i.e., HOMO energy) and the wavelength-dependent photocatalytic activity of glutathione protected clusters have been investigated with photovoltaic experiments.
• The excited-state properties of Au18(SR)14 clusters are studied in-depth by ultrafast pump/probe spectroscopy and a single model describing the optical characteristics of thiol protected Au18(SR)14 and Au25(SR)18 clusters is offered.
• Au-Ag alloy clusters and their photophysical and photocatalytic activity have been studied and compared to monoatomic Au and Ag clusters.
• Using pump/probe femtosecond transient absorption spectroscopy, we have probed the two-photon absorbance of 11 different Au and Ag clusters which allows us to draw conclusions on the role of the particular metal, cluster size/structure, and the effects of the 2PA behavior of clusters. The dramatic effect of excitation wavelength and how double resonance mechanism leads to different non-linear responses has been investigated.
Overall, the content of this thesis describes the importance of precise synthesis of metal clusters and how different clusters with unique optical and electronic properties can be advantageous in various research areas.
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Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada
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Attribution-NonCommercial-NoDerivs 3.0 United States
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
Attribution-NonCommercial-NoDerivs 3.0 United States