Date of Award
2019
Document Type
Dissertation
Degree Name
Ph.D. in Chemistry
Department
Chemistry and Biochemistry
First Advisor
Amala Dass
Second Advisor
James Cizdziel
Third Advisor
Jared H. Delcamp
Relational Format
dissertation/thesis
Abstract
Atomically precise thiolate protected gold nanoparticles (AuNPs) known as gold nanomolecules (AuNMs) are intensely pursued owing to their feasibility to elucidate their structure by single crystal X-ray crystallography. They have distinct number of Au atoms (n) and thiolate (-SR, R-hydrocarbon chain) ligands (m) with molecular formula of the form [Aun(SR)m]. AuNMs are made of a gold core protected by a thiolate-monolayer and possess size-dependent properties conferred by quantum confinement. Atomic precision has been achieved in the 1-3 nm range and crystal structures of several AuNMs ranging from 18 to 279gold atoms have been studied. They provide significant insights into the structural assembly of AuNMs and surface protection motifs. Also, AuNMs in the range of 1-3 nm are the most ideal form of AuNPs and they can be predictably manipulated at the atomic level. Therefore, this dissertation will focus on addressing the factors governing the formation of unique atomic structure, composition, metal-ligand interface and their properties have been addressed in detail. In this dissertation, the thiolate ligands are categorized into three main classes, namely; aliphatic, aromatic and bulky thiolate ligands. These distinct classes of thiolate ligands exclusively form a unique series of AuNMs and unique size-dependent properties. Thiolate monolayer protecting the gold core of AuNMs have been shown to greatly influence the atomic structure, surface chemistry, composition and physicochemical properties of AuNMs. Therefore, investigation of ligand effect on atomic structure of AuNMs would provide insights into designing the atomic structure and surface assembly architecture of AuNMs and atomically precise nanomaterials beyond 3 nm as well. Numerous synthesis, molecular conversions and interconversions, crystal structures and various applications of AuNMs have been reported over the past 5-10 years. The idea of ligand effect to tune the atomic structure and properties of materials which has not been reviecomprehensively and critically to date, would be highly beneficial and relevant to this field as well as other fields of metal cluster research. Tailoring chemical structure of metal nanoparticles is of paramount importance to utilize them effectively in related applications. This dissertation comprehensively and critically describes, a fundamental criterion, namely, the ligand effect on nanoparticles’ atomic structure, metal-ligand interface and properties of thiolate-protected AuNPs, which must be focused to enable nanoengineering at atomic level. Overall, the work presented in this dissertation discuss; 1. The influence of thiolate-ligands on atomic structure and formation of AuNMs, and their physicochemical properties will be established based on experimental and computational studies. 2. The ligand effect on atomic structure of AuNMs to reveal that ligand engineering is a promising means to enable us to achieve atomically precise next generation nanomaterials and impart novel properties. 3. The influence of ligand-ligand interactions of the three classes of thiolate ligands on thermodynamic stability of AuNMs. 4. Understandings of ligand effect on atomic structure and properties of AuNMs will improve the predictability of the designed synthetic protocols and can be extended to metal nanoparticles, quantum dots, magnetic nanoparticles and self-assembled monolayers.
Recommended Citation
Rambukwella, Milan, "Ligand Effect on Gold Nanomolecules Demonstrated Using Aliphatic, Aromatic and Bulky Thiolate Ligands" (2019). Electronic Theses and Dissertations. 1547.
https://egrove.olemiss.edu/etd/1547