Physical Sciences and Mathematics Commons^™

The Design And Characterization Of Gold Nanoclusters As Elementary Building Blocks, Heather Gaebler

Theses and Dissertations (Comprehensive)

Gold nanoclusters with diameters in the quantum size regime (< ~2 nm) are promising building blocks for the design of novel nanomaterials as they exhibit unique size-dependent properties that can be altered and fine-tuned. The research outlined in this PhD thesis employs density functional theory to construct and analyze small ligand-protected cage and rod-shaped nanoclusters. Chapter 2 reports stable halide-protected gold nanocages that were engineered to have a closed-shell valence electron count of 18. This study finds that nanocages comprised of 19 and 20 gold atoms can be converted into stable magic number species containing 18 valence electrons by modifying their charged states via adsorption of halide ligands to the cage’s surface. Chapter 3 reports stable ligand-protected gold nanoclusters with a tetrahedral Au₄ core that were engineered to have a closed-shell valence electron count of 2. This study investigates the structural and electronic effects of halide and alkoxy ligands on the tetrahedral nanocluster and concludes that the results support the broader conclusion that it’s possible to fine-tune the stability and electronic properties of small gold nanoclusters using appropriate ligands. Chapter 4 reports stable gold nanorods that have diameters in the quantum regime that were constructed from elementary building blocks that contain “halide-staples”. This study presents different orientations of the “halide-staple” motifs on …

Cerberus-Type Trisanionic Trisnhc And Its Zwitterionic Gold And Silver Complexes, Maleek Montgomery, Daniela Tapu

Master of Science in Chemical Sciences Theses

While early efforts have been made to explore the chemistry of neutral multitopic nonchelating N-heterocyclic carbenes (NHCs), limited progress has been made in the development of their anionic counterparts. This thesis describes the synthesis and characterization of a novel trianionic NHC. The corresponding thione was generated through an NMR experiment of the free carbenes with an excess of sulfur. The utility of this novel triscarbene as a ligand in organometallic chemistry has been proven by the construction of homotrimetallic systems. The resulting zwitterionic metal complexes of type [(MPPh)₃(NHC)] (M = Au or Ag) have been fully characterized by …

Coinage Metal Chalcogenide Clusters With N-Heterocyclic Carbene Ancillary Ligands, Alex Polgar

Electronic Thesis and Dissertation Repository

This thesis describes the synthesis and characterization of homo- and heterometallic group 11 – group 16 clusters with N-heterocyclic carbene (NHC) ligands. The clusters were prepared from reactive group 11 trimethylsilylchalcogenolate reagents (NHC-M-ESiMe3; M = Cu, Au; E = S, Se, Te) by silane deprotection reactions with phosphine- or phosphite-solubilized group 11 acetates (R3P-M-OAc; M = Cu, Ag, Au). Clusters were characterized by combustion analysis and spectroscopic methods in solution and the solid state. The clusters were phosphorescent at low temperatures with emission energies that depend on the metal/chalcogen composition, ancillary NHC ligand, cluster geometry and nuclearity, and local environment. …

Electronic Structure And Stability Of Ligated Superatoms And Bimetallic Clusters, William H. Blades

Theses and Dissertations

Quantum confinement in small metal clusters leads to a bunching of states into electronic shells reminiscent of shells in atoms. The addition of ligands can tune the valence electron count and electron distribution in metal clusters. A combined experimental and theoretical study of the reactivity of methanol with Al_nI_m⁻ clusters reveals that ligands can enhance the stability of clusters. In some cases the electronegative ligand may perturb the charge density of the metallic core generating active sites that can lead to the etching of the cluster. Also, an investigation is conducted to understand how the bonding …

Coinage Metal Silylphosphido Complexes Stabilized By N-Heterocyclic Carbene Ligands, Bahareh Khalili Najafabadi

Electronic Thesis and Dissertation Repository

N-Heterocyclic carbenes (NHCs) are strong σ-donating ligands and thus, promising candidates for decorating and stabilizing metal-phosphide nanoclusters. While much research has been focused on the coordination of NHC ligands to different coinage metal centers in order to synthesize mononuclear organometallic complexes, their application in nanocluster chemistry has been relatively unexplored. The work described in this thesis involves employment of NHC ligands for stabilizing coinage metal t-butylthiolate and silylphosphido complexes. These complexes are promising molecular precursors for formation of larger NHC-stabilized nanoclusters.

In particular, the ligation of NHCs to [CuS^tBu] and [AgS^tBu] was developed as an …

Electrochemistry Of Pani/Metal Composites In Basic Solutions, Tamthinhan Quy

UNLV Theses, Dissertations, Professional Papers, and Capstones

Polyaniline (PANI) has been extensively investigated due to its unique conductivity, which is primarily dependent on the oxidation state of the material and the solution pH. PANI is an insulator when it is oxidized, and the solution pH exceeds four. Numerous attempts to extend PANI's conductivity to neutral and alkaline environments have been unsuccessful. However, our previous study has demonstrated that PANI/Pd composite is conductive and catalytically active in a basic solution, pH ∼ 12. Therefore, the conductivity and the electrochemical properties of PANI composites including PANI/Au, PANI/Pd and PANI/Pt were evaluated in basic solutions. The fundamental studies of PANI/metal …

Supramolecular Organization Of Nanoparticles, Brenda M. Porta Linnell

Open Access Theses & Dissertations

The study of supramolecular structures with nano-architectures has become an active area of research in recent years. They have the potential to generate functional materials with applications in medicine and emerging technologies. In this dissertation, the supramolecular organization of gold nanoparticles (AuNP) and other nano-scale structures such as discrete styrene-based polymers was investigated. The synthesis and characterization of metal-mediated AuNPs systems using pendant ligands on the AuNP such as 11-diethylenetriamine-undecane-1-thiol, 11-Mercapto-undecanoic acid [2-(2-amino-ethylamino)-ethyl]-amide, Bis(11-oxo-nicotinic acid, undecine)disulfide, and 11-mercaptoundecanoic acid, and using Cu(II) to mediate the formation of supramolecular AuNP systems with sizes of 200 nm ¡V 3 fÃ?m, are …

Oxidation Of Dibenzothiophene To Dibenzothiophene Using Metal Nanoparticles Supported On Silica, Karina Castillo

Open Access Theses & Dissertations

Silica and nanoparticles of Pt, Au, and Ag supported on silica were tested for the ability to oxidize dibenzothiophene (DBT) to sulfone. High performance liquid chromatography was used to study the removal of DBT from solution. In addition, X- ray diffraction, infrared spectroscopy and Raman Spectroscopy were used to characterize the product of the oxidation reaction. Further studies involved the use X-ray absorption spectroscopy to characterize the nanoparticle catalysts before and after the oxidation reaction.

To better understand the reaction, silica was synthesized at different pHs using three different acids. The acids used to synthesize the silica were HCl, HNO3, …

Distance-Dependent Electron Hopping Conductivity And Nanoscale Lithography Of Chemically-Linked Gold Monolayer Protected Cluster Films, Francis P. Zamborini, Laura E. Smart, Michael C. Leopold, Royce W. Murray

Chemistry Faculty Publications

Films of monolayer protected Au clusters (MPCs) with mixed alkanethiolate and ω-carboxylate alkanethiolate monolayers, linked together by carboxylate–Cu2+–carboxylate bridges, exhibit average edge-to-edge cluster spacings that vary with the numbers of methylene segments in the alkanethiolate ligand as determined by a combined atomic force microscopy (AFM)/UV-Vis spectroscopy method. The electronic conductivity (σEL) of dry films is exponentially dependent on the cluster spacing, consistent with electron tunneling through the alkanethiolate chains and non-bonded contacts between those chains on individual, adjacent MPCs. The calculated electronic coupling factor (β) for tunneling between MPCs is 1.2 Å−1, which is similar to …