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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Novel Photonic Crystal Architectures for Optoelectronics

Puzzo, Daniel 22 February 2011 (has links)
The discovery of photonic crystals made over two decades ago sparked great excitement in the scientific community as this breakthrough brought with it the promise of novel and highly advanced photonic devices for a broad range of new technologies. Surprisingly, for a myriad of reasons, a few of which will be discussed in this thesis, little headway has been made in the development of commercial devices based on photonic crystals. Indeed, a disproportionate amount of research has been devoted to more fundamental studies and thus confined to the academic arena. In this thesis, we demonstrate the fabrication of novel bottom-up or combined bottom-up and top-down photonic crystals and demonstrate their integration into viable optoelectronic technologies. In particular, we highlight the fabrication of colloidal one-dimensional and three-dimensional photonic crystals with color reflectivity that is electrically tunable throughout the entire visible spectrum. In our methodology, a requisite material for the preparation of an electrically tunable one-dimensional photonic crystal, was a porous one-dimensional photonic crystal fabricated entirely from nanoparticles. We thus fabricated and highlight here the preparation of one-dimensional photonic crystals from various combinations of SiO2, TiO2, SnO2, and Sb:SnO2 (ATO) nanoparticles. We also demonstrate that these nanoparticle one-dimensional photonic crystals are also capable of serving as the resonator structure in organic dye and polymer based distributed feedback lasers. Finally, we also describe the fabrication of the first example of electrically conductive one-dimensional photonic crystals for optical wavelengths based entirely on conducting and optically transparent metal oxides. Owing to the conductivity and optical transparency of such materials, they are particularly well suited for serving simultaneously as the anode and mirror of a Light Emitting Diode microcavity for enhanced color purity.
2

Synthesis, Characterization, and Hydrogenation Activity of Group 10 Metal Complexes Featuring Bulky Phosphine Ligands

Gwynne, Erin 26 July 2010 (has links)
Bulky, electron-rich phosphine ligands facilitate unique reactivity in various chemical systems and can stabilize metal species in unusual oxidation states or environments. Routes to bulky bis(phosphine) chelating ligands that mimic the sterics of the exceptionally bulky tri-tert-buylphosphine are explored with the ultimate goal of preparing novel catalyst systems of group 10 metals capable of hydrogenation. Attempts to target bulky phosphines from phosphinimine precursors highlight some interesting phosphinimine reactivity, however attempts to reduce the phosphinimine bond revealed limitations. Bis(aminophosphine) ligands present an alternate route to bulky bis(phosphines) and allow for tunability of the environment around phosphorus. The coordination of these ligands with palladium and nickel exhibit a novel bonding mode in which C-H or N-H activation of the ligand occurs to form strained metallacycles. Prepared compounds showed some activity as catalysts under hydrogen and isomerized 1-hexene to 2-hexene, offering support for their potential use as hydrogenation catalysts.
3

Synthesis, Characterization, and Hydrogenation Activity of Group 10 Metal Complexes Featuring Bulky Phosphine Ligands

Gwynne, Erin 26 July 2010 (has links)
Bulky, electron-rich phosphine ligands facilitate unique reactivity in various chemical systems and can stabilize metal species in unusual oxidation states or environments. Routes to bulky bis(phosphine) chelating ligands that mimic the sterics of the exceptionally bulky tri-tert-buylphosphine are explored with the ultimate goal of preparing novel catalyst systems of group 10 metals capable of hydrogenation. Attempts to target bulky phosphines from phosphinimine precursors highlight some interesting phosphinimine reactivity, however attempts to reduce the phosphinimine bond revealed limitations. Bis(aminophosphine) ligands present an alternate route to bulky bis(phosphines) and allow for tunability of the environment around phosphorus. The coordination of these ligands with palladium and nickel exhibit a novel bonding mode in which C-H or N-H activation of the ligand occurs to form strained metallacycles. Prepared compounds showed some activity as catalysts under hydrogen and isomerized 1-hexene to 2-hexene, offering support for their potential use as hydrogenation catalysts.
4

Ligand Development Directed Towards Applications in Late Metal Catalysis

Brown, Christopher 02 August 2013 (has links)
Olefin metathesis is a powerful tool in organic chemistry and in the last 20 years has seen prolific expansion. Olefin metathesis has allowed the expedient and concise preparation of otherwise extremely difficult or impossible molecules. The vast majority of research has recently focused on the use of ruthenium olefin metathesis catalysts and relatively simple variations of Grubbs style catalysts. This research was focused on the preparation and investigation of new ruthenium chemistry and its potential application towards olefin metathesis catalysis. The research hub was the development of new ligand sets and their application. Furthermore, established ligand sets were applied to new applications of ruthenium chemistry and interesting reactivity investigated. Hitherto, the N-heterocyclic carbenes and phosphines have formed the basis of auxiliary ligands for ruthenium catalysts which most significantly promote catalytic olefin metathesis. The first strategy employed herein was the development of a new class of monodentate ligands. A new class of monodentate heterocyclic phosphinimines is prepared, characterized, and applied. Subsequently, the successful coordination to silver and gold is described. An interesting reaction is also noted with palladium. In the development of heterocyclic phosphinimines, phosphino-imines were prepared and applied to ruthenium chemistry. Coordination analogues of second generation Grubbs catalyst were prepared. Additionally, investigation into the coordination chemistry to general ruthenium starting materials was investigated and a unique template reaction was observed. The reaction involved the scission of a P N bond and subsequent formation of a new P,N bidentate ligand. The final main focus of research was the application of tridentate ligands towards catalytic olefin metathesis. First, bis(imino)pyridine ligands were applied to Grubbs style catalysts and unique reactivity was observed. Second, tridentate phosphinimine ruthenium complexes were prepared and screened for activity in catalytic olefin metathesis.
5

Novel Photonic Crystal Architectures for Optoelectronics

Puzzo, Daniel 22 February 2011 (has links)
The discovery of photonic crystals made over two decades ago sparked great excitement in the scientific community as this breakthrough brought with it the promise of novel and highly advanced photonic devices for a broad range of new technologies. Surprisingly, for a myriad of reasons, a few of which will be discussed in this thesis, little headway has been made in the development of commercial devices based on photonic crystals. Indeed, a disproportionate amount of research has been devoted to more fundamental studies and thus confined to the academic arena. In this thesis, we demonstrate the fabrication of novel bottom-up or combined bottom-up and top-down photonic crystals and demonstrate their integration into viable optoelectronic technologies. In particular, we highlight the fabrication of colloidal one-dimensional and three-dimensional photonic crystals with color reflectivity that is electrically tunable throughout the entire visible spectrum. In our methodology, a requisite material for the preparation of an electrically tunable one-dimensional photonic crystal, was a porous one-dimensional photonic crystal fabricated entirely from nanoparticles. We thus fabricated and highlight here the preparation of one-dimensional photonic crystals from various combinations of SiO2, TiO2, SnO2, and Sb:SnO2 (ATO) nanoparticles. We also demonstrate that these nanoparticle one-dimensional photonic crystals are also capable of serving as the resonator structure in organic dye and polymer based distributed feedback lasers. Finally, we also describe the fabrication of the first example of electrically conductive one-dimensional photonic crystals for optical wavelengths based entirely on conducting and optically transparent metal oxides. Owing to the conductivity and optical transparency of such materials, they are particularly well suited for serving simultaneously as the anode and mirror of a Light Emitting Diode microcavity for enhanced color purity.
6

Ligand Development Directed Towards Applications in Late Metal Catalysis

Brown, Christopher 02 August 2013 (has links)
Olefin metathesis is a powerful tool in organic chemistry and in the last 20 years has seen prolific expansion. Olefin metathesis has allowed the expedient and concise preparation of otherwise extremely difficult or impossible molecules. The vast majority of research has recently focused on the use of ruthenium olefin metathesis catalysts and relatively simple variations of Grubbs style catalysts. This research was focused on the preparation and investigation of new ruthenium chemistry and its potential application towards olefin metathesis catalysis. The research hub was the development of new ligand sets and their application. Furthermore, established ligand sets were applied to new applications of ruthenium chemistry and interesting reactivity investigated. Hitherto, the N-heterocyclic carbenes and phosphines have formed the basis of auxiliary ligands for ruthenium catalysts which most significantly promote catalytic olefin metathesis. The first strategy employed herein was the development of a new class of monodentate ligands. A new class of monodentate heterocyclic phosphinimines is prepared, characterized, and applied. Subsequently, the successful coordination to silver and gold is described. An interesting reaction is also noted with palladium. In the development of heterocyclic phosphinimines, phosphino-imines were prepared and applied to ruthenium chemistry. Coordination analogues of second generation Grubbs catalyst were prepared. Additionally, investigation into the coordination chemistry to general ruthenium starting materials was investigated and a unique template reaction was observed. The reaction involved the scission of a P N bond and subsequent formation of a new P,N bidentate ligand. The final main focus of research was the application of tridentate ligands towards catalytic olefin metathesis. First, bis(imino)pyridine ligands were applied to Grubbs style catalysts and unique reactivity was observed. Second, tridentate phosphinimine ruthenium complexes were prepared and screened for activity in catalytic olefin metathesis.
7

Ruthenium 4,5-diazafluorene Complexes and their Reactivity

Stepowska, Elzbieta 15 February 2010 (has links)
The reaction between RuCl2(PPh3)3 and 4,5-diazafluorene (LH) produced the orange, air sensitive RuCl2(LH)(PPh3)2 (1). Exposing this complex to air led to the oxidation of the CH2 group on the central ring of LH to a carbonyl group. RuCl2(LH)(dppb) (3) was synthesized but did not show the same reactivity as complex 1. The reaction between RuHCl(LH)(PPh3)2 (4) and KOtBu produced the purple complex RuH(N2)(L)(PPh3)2 (5), L = deprotonateed 4,5-diazafluorene. Complex 5 heterolytically splits H2 to form RuH2(LH)(PPh3)2 (6), quantitatively. Complex 5 shows C-D bond activation of C6D6 and is air sensitive in the solid state and in solution. Both 1 and 6 were shown to catalyze the hydrogenation of acetophenone. Bis(4,5-diazafluoren-9-yl)methane has been synthesized and fully characterized by 1H NMR, 13C NMR and X-ray crystallography.
8

Towards 'S4' Molybdenum with Two Labile Sites: New Ligands for Molybdenum Bisdithiolenes

Gapinska, Agata 04 December 2012 (has links)
Molybdenum disulfide (MoS2) catalysts are used for hydrodesulfurization processes, needed for the removal of sulfur from oil feedstocks. The commonly accepted active site of MoS2 is believed to have a S4 pyramidal geometry with molybdenum (IV) at the apex. This work is interested in small molecules as models. Recent work has shown that one ligand can be removed from a molybdenum trisdithiolene by reacting the metal complex with an olefin creates a labile chelate cap. The resulting structure resembles the active site of interest. The present contribution will show approaches to molybdenum bisdithiolenes with one or two labile solvent molecules. The use of acetonitrile, adiponitrile, isobutyronitrile, and oxalate has been investigated. A complex containing two different labile moieties (tetrahydrothiophene, acetonitrile) was crystallographically characterized. Other nitrile molybdenum complexes were monitored using NMR spectroscopy. Two complexes have been characterized with an oxalato ligand; a single unit, and a dimer.
9

Towards 'S4' Molybdenum with Two Labile Sites: New Ligands for Molybdenum Bisdithiolenes

Gapinska, Agata 04 December 2012 (has links)
Molybdenum disulfide (MoS2) catalysts are used for hydrodesulfurization processes, needed for the removal of sulfur from oil feedstocks. The commonly accepted active site of MoS2 is believed to have a S4 pyramidal geometry with molybdenum (IV) at the apex. This work is interested in small molecules as models. Recent work has shown that one ligand can be removed from a molybdenum trisdithiolene by reacting the metal complex with an olefin creates a labile chelate cap. The resulting structure resembles the active site of interest. The present contribution will show approaches to molybdenum bisdithiolenes with one or two labile solvent molecules. The use of acetonitrile, adiponitrile, isobutyronitrile, and oxalate has been investigated. A complex containing two different labile moieties (tetrahydrothiophene, acetonitrile) was crystallographically characterized. Other nitrile molybdenum complexes were monitored using NMR spectroscopy. Two complexes have been characterized with an oxalato ligand; a single unit, and a dimer.
10

Ruthenium 4,5-diazafluorene Complexes and their Reactivity

Stepowska, Elzbieta 15 February 2010 (has links)
The reaction between RuCl2(PPh3)3 and 4,5-diazafluorene (LH) produced the orange, air sensitive RuCl2(LH)(PPh3)2 (1). Exposing this complex to air led to the oxidation of the CH2 group on the central ring of LH to a carbonyl group. RuCl2(LH)(dppb) (3) was synthesized but did not show the same reactivity as complex 1. The reaction between RuHCl(LH)(PPh3)2 (4) and KOtBu produced the purple complex RuH(N2)(L)(PPh3)2 (5), L = deprotonateed 4,5-diazafluorene. Complex 5 heterolytically splits H2 to form RuH2(LH)(PPh3)2 (6), quantitatively. Complex 5 shows C-D bond activation of C6D6 and is air sensitive in the solid state and in solution. Both 1 and 6 were shown to catalyze the hydrogenation of acetophenone. Bis(4,5-diazafluoren-9-yl)methane has been synthesized and fully characterized by 1H NMR, 13C NMR and X-ray crystallography.

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