Controlling Gold Nanoparticles With Atomic Precision

Author : Zachary Rhoden
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (138 download)

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Download or read book Surface Chemistry Characterization and Control of the Electronic Structure of Gold Nanosystems written by Zachary Rhoden and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Metal nanoparticles (NPs) are valued in fields including biomedical imaging, chemical sensing, catalysis, and fundamental physics. Their utility often stems from their unique optical and electronic properties, but their broad applicability is due to their robust surface chemistry that allows a wide variety of ligands to be bound to them to tune stability, solubility, and reactivity. However, there has been little work focusing on linking these two aspects of nanoparticles, despite their importance. The lack of work, in part, stems from the significant challenges arising from the inherent dispersity within nanoparticle populations and complicated characterization techniques in which sample measurement can be difficult or provide limited information. The focus of this thesis is to refine the understanding of the structure-property relationship in gold nanosystems by improving the characterization of gold surfaces and by controlling gold nanoparticle properties through surface chemistry. This thesis reports the characterization of the gold-thiol surface, where thermal treatment of gold nanoparticles (AuNPs) volatilized gold and sulfur, which was collected and subsequently quantified by inductively coupled plasma mass spectrometry and atomic emission spectroscopy. It was found that the mass loss in these samples ranged from 0-30\% gold by mass, rather than purely from the thiol ligands, and that the level of gold desorption is related to the Au--S bond strength.This study calls into question the usefulness of thermogravimetric analysis as a characterization technique of gold nanosytems. Additionally, the influence of surface chemistry on the electronic structure of gold nanosystems has been probed using magnetic spectroscopies. First, electron spin resonance has been used to examine the perturbation to the superatomic structure of Au$_{25}$(SR)$_#x18;$ nanoclusters (NCs) by a series of alkanethiolate ligands in hexane and tetrahydrofuran solvents. It has been found that the nanocluster electronic is sensitive to surface chemistry, with the $g_x$ component of the electronic \textit{g}-factor shifting linearly towards the free electron \textit{g}-value, $g_e$, and the perturbation is large, given the minute changes in ligand identity. The changes are dissimilar to those seen in gold nanoparticles with similar surface chemistry, indicating that use of AuNCs as model systems for larger, metallic AuNPs should be reevaluated. Finally, Evans Method nuclear magnetic resonance spectroscopy has been used to probe the density of states (DOS) of gold nanoparticles protected by aromatic thiolate ligands. Aromatic ligands are a common tool for tuning the electronic structure of inorganic complexes, and this thesis reports their capability to alter the electronic structure of gold nanoparticles. The DOS of these nanoparticles increases with increasing electron withdrawing character of the aromatic ligands, and it has been found that trends in controlling the gold nanoparticle's DOS found with aromatic thiols cannot necessarily be compared to those found with aliphatic thiols. This work examines not only how surface chemistry influences the properties of nanosystems, but also the usefulness of model systems and naive assumptions about characterization techniques.