Browsing by Author "Elliott, C. Michael, committee member"
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Item Open Access Development of a microchip electrophoresis system for online monitoring of atmospheric aerosol composition(Colorado State University. Libraries, 2011) Noblitt, Scott Douglas, author; Henry, Charles S., 1972-, advisor; Collett, Jeffrey L., committee member; Elliott, C. Michael, committee member; Strauss, Steven H., committee member; Rickey, Dawn, committee memberAtmospheric aerosols are solid or liquid particles that remain suspended in the environment for an extended time because of their size. Due to their high number concentration, low mass concentration, unique size range, and high temporal and spatial variability, atmospheric aerosols represent a significant unknown in both environmental impact and human health. Despite the importance of aerosols, current instrumentation for monitoring their chemical composition is often limited by poor temporal resolution, inadequate detection limits, lack of chemical speciation, and/or high cost. To help address these shortcomings, microchip electrophoresis (MCE) has been introduced for the semi-continuous monitoring of water-soluble aerosol composition. The MCE instrument was coupled to a water condensation particle collector (growth tube), and the integrated system is termed Aerosol Chip Electrophoresis (ACE). ACE is capable of measuring particle composition with temporal resolution of 1 min and detection limits of ~100 ng m-3. This dissertation covers the development process of the prototype ACE instrument, including the novel separation chemistry, necessary modifications to traditional microfluidic devices, and the interface between the growth tube and the microchip.Item Open Access Direct fluorination of K2B12H12 and synthesis and characterization of metal salts of B12F122-(Colorado State University. Libraries, 2011) Peryshkov, Dmitry V., author; Strauss, Steven H., advisor; Rappe, Anthony K., committee member; Elliott, C. Michael, committee member; Bernstein, Elliot R., committee member; Ridley, John R., committee memberA significantly improved large-scale (10 g) perfluorination of K2B12H12 is described. The advantages of the new procedure are: (i) a ten-fold increase in the scale of the reaction with no sacrifice in yield or product purity; (ii) acetonitrile is used as the solvent instead of anhydrous HF; and (iii) a glass reaction vessel is used instead of a Monel reactor. DFT calculations and experimental data are reported that suggest that the absence of acidity significantly increased the rate and improved the efficiency of the reaction. Number of salts of Li+; Na+; K+; Rb+; Cs+; NH4+, Ag+; Mg2+; Ca2+; Ba2+; Co2+; Ni2+; and Zn2+ and the B12F122- anion were prepared and 24 crystal structures (some compounds were prepared by others) were determined. The thermal stabilities of the Mm(L)nB12F12 salts were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). It was found that Cs2B12F12 is stable up to 600 °C under an inert atmosphere, which is the highest temperature among weakly coordinating fluoroanions. The compounds K2B12F12, Rb2B12F12, Cs2B12F12, and Ag2B12F12 were prepared as ligand-free solids. It was found that the K2(H2O)0,2,4B12F12 system of compounds can undergo rapid interconversion among the three crystalline phases, two of them reversibly in presence of water vapor. The reversible interconversion was found to be a reconstructive (i.e., topotactic) solid-state reaction and, when carried out very slowly, a single-crystal-to-single-crystal transformation. The exchange of H2O(g) with either D2O or H218O in crystalline K2(D2O)2B12F12 or K2(H218O)2B12F12 at 25 °C was also rapid. The new concept of latent porosity, as ligands rapidly enter a lattice and displace some of the weak and non-directional M•••F(B) bonds in salts of the large, highly-symmetric, superweak anion B12F122-, is presented and discussed.Item Open Access Distinguishing homogeneous and heterogeneous water oxidation catalysis when beginning with cobalt polyoxometalates(Colorado State University. Libraries, 2013) Stracke, Jordan J., author; Finke, Richard G., advisor; Chen, Eugene Y.-X., committee member; Elliott, C. Michael, committee member; Ferreira, Eric M., committee member; Sites, James R., committee memberDevelopment of energy storage technologies is required prior to broad implementation of renewable energy sources such as wind or solar power. One of the leading proposals is to store this energy by splitting water into hydrogen and oxygen--that is, to store energy in chemical bonds. A major obstacle en route to this overall goal is the development of efficient, cost-effective water oxidation catalysts (WOCs). Due to the highly oxidizing environment needed to drive this reaction, one question which has arisen when dealing with homogeneous precatalysts is whether these precursors remain as intact, homogeneous WOCs, or whether they are transformed into heterogeneous metal-oxide catalysts. This problem, reviewed in Chapter II, addresses the methods and literature studies related to distinguishing homogeneous and heterogeneous water oxidation catalysts. Chapters III through V further develop the methodology for distinguishing homogeneous and heterogeneous water oxidation catalysis when beginning with the cobalt polyoxometalate [Co4(H2O)2(PW9O34)2]10- (Co4POM). In Chapter III, the investigation of Co4POM using electrochemical oxidation at a glassy carbon electrode reveals that under the conditions therein, an in-situ formed, heterogeneous cobalt-oxo-hydroxo (CoOx) material is the dominant catalyst and is formed from Co2+ leached from the Co4POM. In Chapter IV, investigation of whether the intact Co4POM could be a catalyst under other, more forcing conditions of higher electrochemical potentials and lower Co4POM concentrations is reported. Although the Co4POM shows different electrochemical properties relative to CoOx controls, the possibility that the Co4POM is being transformed into a meta-stable heterogeneous catalyst cannot be ruled out since the Co4POM degrades during the experiment. Lastly, Chapter V presents a kinetic and mechanistic study of the Co4POM when using a ruthenium(III)tris(2,2'-bipyridine) (Ru(III)(bpy)33+) chemical oxidant to drive the water oxidation reaction (i.e., rather than electrochemically driven oxidation). In this study, it was found that Co4POM catalyzes the oxidation of water as well as oxidation of the 2,2'-bipyridine ligand. In contrast, controls with in-situ formed CoOx catalysts more selectively promote the catalytic oxidation of water. The difference in reactivity and kinetics between the Co4POM and CoOx systems indicates that the active catalysts are fundamentally different when a chemical oxidant is employed. Overall, these studies demonstrate the need for careful experimental controls and highlight the importance which reaction conditions--in particular the source and electrochemical potential of the oxidant--can play in determining the active oxidation catalyst in water oxidation reactions.Item Open Access Electrodeposition and speciation study of different transition metal antimonides for application into lithium ion batteries(Colorado State University. Libraries, 2010) Kershman, Jacob Ray, author; Prieto, Amy L., advisor; Elliott, C. Michael, committee member; Kipper, Matthew J., committee memberSeveral new deposition setups were designed and tested to increase the uniformity of depositions of Cu2Sb. It was shown that the jacketed beaker setup produces the most uniform films compared to other setups used. This setup was used to obtain the average thickness and mass measurements of a triplicate set of films deposited at deposition times of 1, 2.5, 5, 7, and 10 minutes. The thickness (determined by AFM) and weight were both linear and corresponded to a growth rate of 300 nm per minute or 0.2 mg of Cu2Sb per minute. Preliminary battery testing revealed that the thinner films cycled much better than thicker films. Films thicker than ~1 µm did not cycle well at all, and cleaved completely off the surface of the electrode during cycling. Cu2Sb was successfully electrodeposited into commercial alumina filters. The Cu2Sb wires were ordered in a different direction compared to the electrodeposition on planar substrates ([101] versus [001] direction). A two step anodization process was shown to produce self-ordered AAO templates with pore sizes between 30 and 40 nm. It was shown that the mechanical and electrochemical polishing steps are not necessary to obtain the self-ordered templates. Promising results have been shown with multiple methods to break through the barrier layer of these alumina templates. Even when the barrier layer is removed a native oxide is formed within a few seconds on the surface of the aluminum which blocks the electrodeposition of copper. The backside of the template indicated that the breakthrough was only in localized spots. Previously, crystalline Cu2Sb was electrodeposited at single potential through the complexation of the metals in aqueous solution using citric acid at pH 6. This direct electrodeposition is unusual for intermetallic materials and the reason for the Cu2Sb case is not well understood. In order to determine why this material deposits under these solution conditions, a deeper understanding of the speciation in solution must be obtained. To study what metal-ligand complexes are present in the Cu-Sb-Citrate deposition, solution electrospray ionization mass spectrometry (ESI-MS) was employed. ESI-MS results were shown to be a qualitative technique to study the solution chemistry of the Cu2Sb system. These results have been compared to speciation calculations, UV-Vis, titrations, and literature results. The heterometallic species [CuSb(HCit)(Cit)], previously only reported in solids that had been crystallized out of solution, was discovered in solution through ESI-MS. In addition, ESI-MS data pointed to [Sb(HCit)2]- as the most abundant antimony citrate species over previously reported [SbH-1Cit]-. The additional species from ESI-MS gave rise to the development of two new balanced reactions for the deposition of Cu2Sb, in hope of the realization of understanding why Cu2Sb deposits. By understanding the solution chemistry, other transition metal antimonides were electrodeposited from aqueous citrate solutions. It is shown that through the co-deposition reaction, which is dependent on the solution chemistry and the fast interstitial diffusion of metals through antimony diffusion in the solid state, many different intermetallic antimonides can be deposited including: crystalline NiSb, the co-deposition of FeSb, and several copper-rich copper antimonide phases including Cu11Sb3, Cu4Sb, Cu0.95Sb0.05, and possibly other mixed copper antimonide phases. This leads to a better understanding of the electrodeposition of the Cu2Sb system, which can lead to further improvement of the electrodeposition other transition metal antimonides and intermetallics.Item Open Access Investigating plasma modifications and gas-surface reactions of TiO2-based materials for photoconversion(Colorado State University. Libraries, 2012) Pulsipher, Daniel J. V., author; Fisher, Ellen R., advisor; Elliott, C. Michael, committee member; Van Orden, Alan, committee member; Strauss, Steven H., committee member; Yalin, Azer, committee memberPlasmas offer added flexibility for chemists in creating materials with ideal properties. Normally unreactive precursors can be used to etch, deposit and modify surfaces. Plasma treatments of porous and compact TiO2 substrates were explored as a function of plasma precursor, substrate location in the plasma, applied rf power, and plasma pulsing parameters. Continuous wave O2 plasma treatments were found to reduce carbon content and increase oxygen content in the films. Experiments also reveal that Si was deposited throughout the mesoporous network and by pulsing the plasma, Si content and film damage could be eliminated. Nitrogen doping of TiO2 films (N:TiO2) was accomplished by pulsed plasmas containing a range of nitrogen precursors. N:TiO2 films were anatase-phased with up to 34% nitrogen content. Four different nitrogen binding environments were controlled and characterized. The produced N:TiO2 films displayed various colors and three possible mechanisms to explain the color changes are presented. Both O2 treated and N:TiO2 materials were tested in photocatalytic devices. Preliminary results from photocatalytic activities of plasma treated P25 TiO2 powders showed that nitrogen doping treatments hinder photocatalytic activity under UV light irradiation, but silicon deposition can improve it. N:TiO2 materials were tested in photovoltaic devices to reveal improved short-circuit current densities for some plasma-modified films. To understand the gas-phase and surface chemistry involved in producing the N:TiO2 films, NH and NH2 species in pulsed NH3 plasmas were explored by systematically varying peak plasma power and pulsing duty cycle. Results from these studies using gas phase spectroscopy techniques reveal interconnected trends of gas-phase densities and surface reactions. Gas-phase data from pulsed plasmas with two different types of plasma pulsing reveal diminished or increased densities at short pulses that are explained by plasma pulse initiation and afterglow effects. Overall this work reveals characteristics of the plasma systems explored, knowledge of the resulting materials, and control over plasma etching, deposition, and modification of TiO2 surfaces.Item Open Access Mitomycin alkaloids: synthetic studies(Colorado State University. Libraries, 2009) Gubler, Daniel Alan, author; Williams, Robert M., advisor; Rovis, Tomislav, committee member; Kennan, Alan J., committee member; Elliott, C. Michael, committee member; Luger, Karolin, committee memberDocumented herein are efforts towards the first asymmetric total synthesis of the mitomycin family of natural products. Methods have been developed that efficiently construct eight-membered ring precursors of the natural products. Additionally, a tetracyclic mitosane compound containing all the core features of the mitomycins except the C9a methyl aminal has been constructed. The above-mentioned synthetic efforts help set the stage for future completion of the asymmetric total synthesis of this family of compounds. The studies mentioned herein, while not totally successful, shed new light on the reactivity of the mitomycins as well as the remarkable electronic effect of the electron-rich arene ring.Item Open Access Novel polynuclear copper compounds of halides and pseudo-halides(Colorado State University. Libraries, 1987) Reibenspies, Joseph Henry, author; Anderson, Oren, advisor; Elliott, C. Michael, committee memberMixed-valence compounds (one trinuclear (4) and two polymeric (5,6)) of copper(I,II) containing bridging cyano ligands and the ligands 1 (Pre-H) and 2 (cyclops) have been synthesized and characterized by single crystal X-ray diffraction. For 4, [Cu(1)(μ-NC)]2Cu(CN) · H2O, a= 9.723(2) Å, b = 10.908(2) A, c = 16.184(3) A, ɑ = 97.82(1) ᵒ, β = 103.64(2)ᵒ, γ= 92.21(2)ᵒ. Compound 5 ([Cu(1)(μ-NC)Cu(μ-CN)]n) occurs in three structural modifications. For 5a, a= 7 .755(2) Å, b = 13.179(3) Å, c = 16.508(5) A. For 5b, a= 7.878(2) Å, b = 8.418(2) Å, c = 25.874(4) Å, ~= 94.15(2)ᵒ. For 5c, a= 8.85(1) Å, b = 20.755(8) Å, c = 23.081(8) Å. For 6, [Cu(2)(μ-NC)Cu(μ- CN)·(l/2C6H6)]n, a= 11.667(2) Å, b = 8.962(2) Å, c = 19.895(5) Å,~= 97.58(2)ᵒ. The discrete molecules of 4 contain a trigonal planar [Cu(CN)3]^2- unit, which bridges between two [Cu(l)]+ complexes through two cyano ligands. Each of the polymeric species 5a, 5b, 5c, and 6 consists of a chain of [Cu(CN)2]- units joined by bridging cyano ligands. A cyano ligand also bridges between the copper(I) atoms of the chain and [Cu(1)]+ or [Cu(2)]+ complexes. The structures of three dinuclear copper(II) complexes, in which the Cu(II) atoms are bridged by azido and hydroxo ligands and by either the phenolate oxygen atom of N6OH or N6'OH have been determined by single crystal X-ray diffraction. The compound [Cu2(μ-l,3-N3)(N6O)](ClO4)2·THF (7) crystallized in the orthorhombic space group P 212121, with a= 12.977(2) Å, b = 13.188(3) Å, c = 22.033(6) Å. The compound [Cu2(μ-1,1-N3)(N6'O)](BF4)2·THF (8) crystallized in the orthorhombic space group P21cn, with a= 10.222(2) Å, b = 16.683(4) Å, c = 23.517(7) Å. The compound [Cu2(μ- OH)(N6'O)](BF4)i · THF (9a) crystallized in the monoclinic space group ?21/n, with a= 12.457(3) Å, b = 10.222(3) Å, c = 30.397(10) Å, β= 91.63(2). In these complexes each copper(II) atom is five-coordinate and is bound to three nitrogen atoms and the bridging phenoxo oxygen atom of either N60- or N6'0-. The fifth coordination site on each copper(II) atom is occupied by an atom of the bridging azido or hydroxo ligand. A dinuclear copper(II) complex which contains a bridging iodo ligand and two [Cu(2)]+ moieties has been characterized by X-ray crystallography. [Cu2(2)2I](ClO4) · 2MeOH (10) crystallized in the monoclinic system, space group C2/c, with Z = 4 and a= 21.564(3) Å, b = 11.920(2) Å, c = 14.831(2) Å, β = 96.83(1)ᵒ. Each of the copper(II) atoms in the dimer is coordinated to four nitrogen atoms of ligand 2 and to the bridging iodo ligand. The structures of two phases of the perchlorate salt of the copper(II) complex of 1 and methanol have been characterized by X-ray crystallography. For the room temperature phase {[Cu(1)]C1O4 · 1/2 MeOH}n (11a), a= 23.018(3) Å, b = 6.903(1) Å, c = 22.511(3) Å, β= 105.48(1)ᵒ. For the low temperature phase { [Cu(l)]ClO4 · 1/2 MeOH}i ((llb), a= 6.850(2) A, b = 11.886(3) A, c = 22.303(5) A, a= 75.26(2)0 , β= 88.97(2)ᵒ, γ= 73.38(2)ᵒ. When cooled, the crystalline solid 11 undergoes a reversible structural change. 11a is polymeric in nature, with bridging between copper atoms accomplished by an oxime oxygen atom of ligand 1. 11b is best described as dimeric.Item Open Access Part 1: Synthesis and characterization of magnetic Cr5Te8 nanoparticles. Part 2: Local atomic structure studies using theory to simulate polarons in superconducting cuprates and experiment to analyze alternative energy nanomaterials(Colorado State University. Libraries, 2012) Martucci, Mary B., author; Prieto, Amy L., advisor; Elliott, C. Michael, committee member; Fisher, Ellen R., committee member; Rickey, Dawn, committee member; Patton, Carl E., committee memberThe field of spintronics, the development of spin-based devices that utilize the spin degree of freedom to increase memory capacity, has emerged as a solution to faster more efficient memory storage for electronic devices. One class of materials that has been extensively studied is the half-metallic ferromagnets, compounds that are 100% spin-polarized at the Fermi level. One material in this group that has been investigated is chromium telluride (Cr1-xTe), whose family of compounds is known to exhibit a wide range of interesting magnetic and electronic properties. We have developed a hot injection solution synthesis of Cr5Te8 nanoplatlets which show similar magnetic behavior to the bulk material. It has also been shown that selenium and sulfur analogues can be obtained without changing the reaction conditions, making progress toward a better understanding of the reaction as well as an interesting family of compounds. Using real-space simulations, the effect of polarons in the high-Tc superconducting cuprates has been studied. The simulations demonstrate energetically favorable sites for the defects and show evidence of longer-range pairing interactions. Variations of the stripe show similar energetic results. X-ray absorption fine structure spectroscopy and neutron scattering have been utilized to examine the local structure of Ni-doped Mg nanoparticles, a hydrogen storage material as well as Cu2ZnSnS4 (CZTS) nanoparticles, a photovoltaic material. The Mg-Ni material shows much local disorder upon hydrogen cycling. The CZTS data demonstrate a loss of sulfur from around the copper sites upon annealing, helping to explain the changes observed in the optical absorption properties resulting from the annealing process.Item Open Access Quantum dot and polymer sensitization of single crystal titanium dioxide electrodes(Colorado State University. Libraries, 2011) Sambur, Justin, author; Parkinson, Bruce A., advisor; Maciel, Gary E., committee member; Elliott, C. Michael, committee member; Van Orden, Alan K., committee member; Marconi, Mario C., committee memberThe morphology of semiconductor nanocrystals or quantum dots (QDs) and conjugated polymers at the interface of TiO2 is expected to play an important role in the electron injection efficiency of mesoporous sensitized solar cells (SSCs). Atomic force microscopy (AFM) and photocurrent spectroscopy were employed to correlate the interfacial morphology of QDs and polymers with the sensitized photocurrent yields on planar TiO2 single crystal electrodes. QDs prepared by the ex situ ligand exchange method, whereby 3-mercaptopropionic acid (MPA)-capped QDs were synthesized and directly adsorbed onto bare TiO2 single crystals, resulted in both reproducible sensitized photocurrents and predominantly single layer surface coverages. Photoluminescence (PL) and photocurrent measurement techniques were simultaneously employed to detect electron injection from QDs to TiO2 for a variety of long and short alkyl chain capping ligands. Quenching of the PL lifetime, often interpreted as a spectroscopic signature for electron transfer, was observed for QDs capped with long chain ligands that do not produce sensitized photocurrent. The ex situ ligand exchange procedure was also utilized to adsorb single layers of MPA-capped CdSe/ZnS core/shell (CS) and PbS QDs onto single crystal TiO2 electrodes. Despite a potential energy barrier for photo-excited carriers in the CdSe core imposed by the wide band gap ZnS shell, type-I CS QDs effectively sensitized single crystal TiO2 electrodes and continued to operate in a regenerative mode in an aerated, corrosive iodide electrolyte for more than 20 h. PbS quantum dots adsorbed on TiO2 single crystals exhibited for the first time hot electron injection from higher QD excited states and absorbed photon-to-current efficiencies greater than 100% due to multiple exciton collection. The nanoscale morphology and photoactivity of conjugated polyelectrolytes (CPEs) deposited from different solvents onto single crystal TiO2 was investigated with atomic force microscopy (AFM) and photocurrent spectroscopy. Absorbed photon-to-current efficiencies approaching 50% were measured for CPE layers as thick as 4 nm on TiO2. The research herein suggests that controlling surface morphology of QD and polymer sensitizers may lead to the development of inexpensive, high-efficiency sensitized solar cells.Item Open Access Structural variations in metal ion complexes of the ligand EGTA⁴-(Colorado State University. Libraries, 1985) Schauer, Cynthia Karen, author; Anderson, Oren, advisor; Elliott, C. Michael, committee memberStructural studies of several metal ion complexes with the tetraanion of the octadentate ligand, H^4EGTA (3,12-bis(carboxymethyl)-6, 9-dioxa-3, 12-diazatetradecanedioic acid), as well as the structure of H^4EGTA, have been performed by single crystal X-ray diffraction. Of particular interest was the structural basis for the large preference for EGTA^4- to bind calcium ion rather than (K(CaL^2-) ~= 10^6 magnesium ion = 10^6 (K(MgL^2-)), a preference which is similar to that exhibited by intracellular calcium binding proteins. The alkaline earth compounds, Ca[Ca(EGTA)]·(22/3)H2o, Sr[Ca(EGTA)] ·6H2O, Mg[Sr(EGTA)(OH2 )]·7H2o, Mg(Ba-(EGTA)]·(8/3)H2O·(1/3) (CH3) 2CO, and (Mg2(EGTA)(OH2 )6]·5H2O, have been structurally characterized. [Ca(EGTA)]2- is eight-coordinate and utilizes the full octadentate chelating capability of the EGTA^4- ligand. The ether oxygen atoms are bound at a shorter distance than the amine nitrogen atoms. EGTA^4 - is octadentate toward both the strontium and barium ions, which are nine- and ten-coordinate, respectively. The magnesium complex is dinuclear, utilizing each end of the EGTA^4- ligand as a tridentate iminodiacetate ligand; the ether oxygen atoms are not involved in coordination to the metal ion. Structures of EGTA^4 - chelates of metal ions that are commonly used as spectroscopic probes for calcium ion binding sites have also been determined. The cadmium chelate in Sr[Cd(EGTA)]·7H2 o is eight-coordinate, li k e [Ca(EGTA)]^2 -, but the amine nitrogen atoms are bound at shorter distances than the ether oxygen atoms. The metal ions in the structures of tripositive lanthanide ion complexes, Ca[Er(EGTA)(OH2)]2·12H2O and Ca[Nd(EGTA)- (OH 2 )]2·9H2O, are nine- and ten-coordinate, respectively. To further explore coordination modes of the EGTA^4 - ligand with smaller metal ions, where the ligand is not likely to be octadentate, structures of manganese and copper complexes of were determined. Sr[Mn(EGTA)] ·7H2O is isomorphous with the cadmium compound. As a result, the Mn(II) ion is eight-coordinate. The copper complex crystallizes as a dinuclear species, [CU2(EGTA)(OH2)2] ·2H2O, in which each end of the EGTA^4- ligand binds a copper(II) ion in a tetradentate fashion; the ether oxygen atom is bound in the apical position of the square pyramidal coordination sphere.Item Open Access Studies on the biosynthesis of prenylated indole secondary metabolites from Aspergillus versicolor and Aspergillus sp.; and A novel approach to tumor specific drug delivery: use of a naphthyridine drug linker with a DNA hairpin(Colorado State University. Libraries, 2011) Finefield, Jennifer M., author; Williams, Robert Michael, advisor; Rovis, Tomislav, 1968-, committee member; Kennan, Alan J., committee member; Elliott, C. Michael, committee member; Thamm, Douglas H., committee memberHerein are documented our efforts in two projects, beginning with studies toward elucidating the biosynthesis of prenylated indole alkaloids from two different Aspergillus species. Marine-derived Aspergillus sp. and terrestrial-derived Aspergillus versicolor were found to produce antipodal metabolites, in which we have developed several putative biosynthetic pathways to determine the enantio-diverging point of these fungal cultures. Through the synthesis of several potential intermediates, both with and without isotopic labeling, as well as through bioinformatics analysis of both the (-)- and (+)-notoamide biosynthetic gene clusters, significant progress has been made toward identifying a single biosynthetic precursor that serves as an intermediate to the postulated enantio-diverging event, the intramolecular hetero Diels-Alder cycloaddition. In the second project discussed, through collaboration with Dr. James Berenson at the University of California, Los Angeles, we have developed a novel tumor specific drug delivery system. Two naphthyridine-drug derivatives were synthesized and conjugated to a modified DNA oligonucleotide specifically targeted for multiple myeloma cells. The oligonucleotide-drug conjugate was successfully delivered and activated specifically within RMI8226 multiple myeloma cells.Item Open Access Synthesis and characterization of iridium model, and cobalt and nickel, industrial Ziegler-type hydrogenation catalysts and their precursors(Colorado State University. Libraries, 2011) Alley, William Morgan, author; Finke, Richard G., advisor; Chen, Eugene Y.-X., committee member; Elliott, C. Michael, committee member; Levinger, Nancy E., committee member; Kipper, Matthew J., committee memberFollowing a comprehensive critical review of the pertinent literature, the research presented herein is focused on the synthesis of an Ir precursor used to model industrial Ziegler-type hydrogenation catalysts, and on catalyst characterization using both the Ir model, and genuine Co and Ni, industrial catalyst materials. The studies include: (i) the synthesis, characterization, and initial catalytic investigation of Ir (and Rh) compounds for use as models for the industrial Co and Ni Ziegler-type hydrogenation catalysts; (ii) characterization of the Ziegler-type hydrogenation catalyst made from the Ir precursor; and (iii) characterization of the authentic industrial Co and Ni Ziegler-type hydrogenation catalysts. The synthesis and definitive characterization of Ir (and Rh) precatalysts designed to facilitate investigation into the homogeneous versus heterogeneous nature of Ziegler-type hydrogenation catalysts is described herein. Additionally, the ability of these Ir (and Rh) precatalysts to form active Ziegler-type hydrogenation catalysts upon combination with AlEt3 is demonstrated. The homogeneous versus heterogeneous nature of the Ir Ziegler-type hydrogenation catalyst is investigated using several complementary analytical methods plus kinetic studies. Initial active catalyst solutions contain a variety of Ir species ranging from mono-Ir compounds to nanometer-scale Irn clusters, but on average are subnanometer, Ir~4-15 species. However, crystalline Ir(0)~40-150 nanoclusters are rapidly formed when the solutions are put under pressurized H2 gas, and these larger, "Ziegler nanoclusters" are shown to be the most active catalysts, an important result in comparison to all the prior, extensive literature of these important industrial catalysts. The homogeneous versus heterogeneous nature of the authentic industrial Co- and Ni-based Ziegler-type hydrogenation catalysts are investigated using an approach parallel to that used for the Ir system, and are compared to the results from the Ir model system. The metal cluster species are essentially the same pre- and posthydrogenation; they comprise a broad distribution of Mn cluster sizes from subnanometer to nanometer in scale, with average diameters of about one nanometer, and with some amount of unreduced mono-metallic complexes also present dependent on the Al/M ratio. These findings support the primary working hypothesis present in the most recent literature, namely that Ziegler-type hydrogenation catalysis is enacted by "Ziegler nanoclusters" (as defined herein), nanoclusters of size M4 in the case of the industrial Co and Ni system.Item Open Access Synthesis, characterization and catalytic evaluation of a Ziegler-type model iridium hydrogenation catalyst plus a novel tetrairidium tetrahydride complex(Colorado State University. Libraries, 2013) Hamdemir, Isil Kayiran, author; Finke, Richard G., advisor; Bernstein, Elliot R., committee member; Chen, Eugene Y.-X., committee member; Elliott, C. Michael, committee member; Wang, David, committee memberFollowing a critical review of the pertinent literature of Ziegler-type hydrogenation catalysts, the research presented herein is primarily focused on the synthesis, characterization and catalytic properties of a model Ziegler-type hydrogenation catalyst system made from [Ir(1,5-COD)(μ-O2C8H15)]2 plus AlEt3. The studies include: (i) a critical review of the relevant literature, (ii) ranking the activity, lifetime and thermal stability of the resulting Ir(0)n Ziegler nanoparticles; (iii) characterization of the true stabilizer species for Ir(0)n Ziegler nanoparticles as a function of the initial Al/Ir ratio; and (iv) the synthesis and characterization of a novel [Ir(1,5-COD)(μ-H)]4 complex considered as a plausible intermediate en route to Ir(0)n Ziegler nanoparticles. Studies evaluating and ranking the catalytic properties of Ziegler-type catalysts in the test reaction of cyclohexene hydrogenation reveal that the catalyst made with [Ir(1,5-COD)(μ-O2C8H15)]2 plus AlEt3 is a highly catalytically active, long-lived and thermally unusually stable nanoparticle catalyst. The catalytic lifetimes of the Ir(0)n Ziegler nanoparticles are higher than any known Ir(0)n nanoparticles in the extant literature. The nature of the stabilizer species in the Ziegler-type catalyst system made with [Ir(1,5-COD)(μ-O2C8H15)]2 plus AlEt3 at Al/Ir ratios 1-3 is then investigated by comparing 1H, 13C, 27Al NMR and IR data of the catalysts with those of individually-synthesized standards such as AlEt2(O2C8H15), [(n-Bu)4N][AlEt3(O2C8H15)] and [(n-Bu)2Al(µ-OH)]3. The results of the study shows that (i) AlEt2(O2C8H15) (Al/Ir=1, 2 and 3) and (iii) free AlEt3 (Al/Ir=3) are present in the catalyst solution in this model Ziegler-type hydrogenation catalyst system made from [Ir(1,5-COD)(μ-O2C8H15)]2 plus AlEt3. The spectroscopic and catalytic evidence provided in this study helps to rule out the initial hypotheses (iii) that anionic [AlEt3(O2C8H15)]- stabilizer exists and provides DLVO-type, Coulombic-repulsion stabilization. Also ruled out is (iv) that the AlEt3-derived stabilizers are Al-O-Al containing alumoxanes. In a separate study, a novel [Ir(1,5-COD)(μ-H)]4 complex is synthesized and characterized with the goal of (i) obtaining information on formation and stabilization mechanisms of Ziegler-type industrial hydrogenation model catalysts prepared from [Ir(1,5-COD)(μ-O2C8H15)]2 plus AlEt3; and with the goal of (ii) understanding the stabilization efficacies of various Al-based cocatalysts in the absence of any added carboxylate.Item Open Access The formation and reactivity of α,β-unsaturated platinum carbenes: new approaches to heterocycle synthesis(Colorado State University. Libraries, 2014) Allegretti, Paul Andrew, author; Ferreira, Eric, advisor; Rovis, Tomislav, committee member; Kennan, Alan, committee member; Elliott, C. Michael, committee member; Crick, Dean, committee memberThe use of transition metal carbenes in organic synthesis has enabled chemists to promote an incredible variety of bond-forming reactions. These intermediates are traditionally accessed via the decomposition of diazo species. Alternative methods for accessing metal carbene intermediates from functional groups beyond diazo species could present many practical advantages and would complement the existing methods. Presented herein are our efforts to develop a novel method of carbene generation from the reactions of alkynes and π-acidic transition metals, and their use in the synthesis of different heterocycles. Our initial investigations focused on the ability to generate substituted furan products from the intramolecular addition of alcohols into alkynes containing propargylic methyl ethers. We then extended this reaction manifold to the synthesis of complementary positional isomers of isoxazoles, adding both propargylic N-hydroxycarbamates and propargylic N-Boc amino ethers into the activated alkyne. Key to this transformation was the inclusion of Brønsted acids to facilitate activation and elimination of the methyl ether leaving group. While studying the synthesis of furans and isoxazoles it was observed that the nature of the carbene could be modulated, leading to selective silicon or hydrogen migration. Also observed was the addition of nucleophiles into the β-position of the carbene species. This last mode of reactivity led to the discovery of a new way to synthesize vicinal bisheterocycles using alkyne activation conditions.Item Open Access Tuning optoelectronic properties and understanding charge transport in nanocrystal thin films of earth abundant semiconducting materials(Colorado State University. Libraries, 2011) Riha, Shannon C., author; Parkinson, Bruce A., advisor; Prieto, Amy L., advisor; Elliott, C. Michael, committee member; Field, Stuart, committee member; Henry, Charles, committee member; Rappe, Anthony, committee memberWith the capability of producing nearly 600 TW annually, solar power is one renewable energy source with the potential to meet a large fraction of the world's burgeoning energy demand. To make solar technology cost-competitive with carbon-based fuels, cheaper devices need to be realized. Solution-processed solar cells from nanocrystal inks of earth abundant materials satisfy this requirement. Nonetheless, a major hurdle in commercializing such devices is poor charge transport through nanocrystal thin films. The efficiency of charge transport through nanocrystal thin films is strongly dependent on the quality of the nanocrystals, as well as their optoelectronic properties. Therefore, the first part of this dissertation is focused on synthesizing high quality nanocrystals of Cu2ZnSnS4, a promising earth abundant photovoltaic absorber material. The optoelectronic properties of the nanocrystals were tuned by altering the copper to zinc ratio, as well as by introducing selenium to create Cu2ZnSn(S1-xSex)4 solid solutions. Photoelectrochemical characterization was used to test the Cu2ZnSnS4 and Cu2ZnSn(S1-xSex)4 nanocrystal thin films. The results identify minority carrier diffusion and recombination via the redox shuttle as the major loss mechanisms hindering efficient charge transport through the nanocrystal thin films. One way to solve this issue is to sinter the nanocrystals together, creating large grains for efficient charge transport. Although this may be quick and effective, it can lead to the formation of structural defects, among other issues. To this end, using a different copper-based material, namely Cu2Se, and simple surface chemistry treatments, an alternative route to enhance charge transport through nanocrystals thin films is proposed.Item Open Access Understanding the molecular-level chemistry of H2O plasmas and the effects of surface modification and deposition on a selection of oxide substrates(Colorado State University. Libraries, 2011) Trevino, Kristina J., author; Fisher, Ellen R., advisor; Elliott, C. Michael, committee member; Henry, Charles S., committee member; Prieto, Amy L., committee member; Bailey, Travis S., committee memberThis dissertation first examines electrical discharges used to study wastewater samples for contaminant detection and abatement. The abatement process of contaminants in liquid discharges is relatively unstable; thus, to help elucidate the sources of instability, the gas phase constituents of plasmas formed from artificially-contaminated water samples were examined using optical emission spectroscopy (OES) and mass spectrometry (MS). Two different water samples contaminated with differing concentrations of either methanol (MeOH) or methyl tert-butyl ether (MTBE) were used to follow breakdown mechanisms. Emission from CO* was used to monitor the contaminant and for molecular breakdown confirmation through actinometric OES as it can only arise from the carbon-based contaminant in either system. Detection limits for each compound were as low as 0.01 ppm at a range of varying plasma parameters. MS data revealed plasma molecular breakdown and little evidence for fragment recombination to form larger molecules. MS data for the two contaminated H2O samples suggest the primary plasma species are CHx, C2Hx, CH2O, CO, C4Hx, and C3HxO and their corresponding ions. From this study, the detection and decomposition of organic molecules in water was accomplished for the first time with an ICP system. Detection was achieved at concentrations as low as 0.01 ppm, and molecular decomposition was seen at a variety of plasma parameters. This dissertation also explores the vibrational (θV), rotational (θR) and translational (θT) temperatures for a range of diatomic species in different plasma systems. Specifically we have investigated four molecules; OH in plasmas formed from H2O (g), tetraethyl orthosilicate (TEOS), NH3/O2 mixtures, and CH3OH; NH formed in plasmas created from NH3 and NH3/O2 mixtures; SiH radicals in SiH4, SiH4/Ar, Si2H6 and Si2H6/Ar plasmas; and CH in plasmas formed from mixtures of CH4/Ar. These species were probed with both laser induced fluorescence (LIF) and OES. For the majority of the plasma species studied, θV are much higher than θR and θT. This suggests that more energy is partitioned into the vibrational degrees of freedom in our plasmas. The θR reported are significantly lower in all the plasma systems studied and this is a result of radical equilibration to the plasma gas temperature. θT values show two characteristics; (1) they are less than the θV and higher than the θR and (2) show varying trends with plasma parameters. Radical energetics were examined through comparison of θR, θT, and θV, yielding significant insight on the partitioning of internal and kinetic energies in plasmas. Correlations between energy partitioning results and corresponding radical surface scattering coefficients obtained using our imaging of radicals interacting with surfaces (IRIS) technique are also presented. Another aspect of plasma process chemistry, namely surface modification via plasma treatment, was investigated through characterization of metal oxides (SiOxNy, nat-SiO2, and dep-SiO2) following their exposure to a range of plasma discharges. Here, emphasis was placed on the surface wettability, surface charge, and isoelectric point (IEP). The results demonstrate that 100% Ar, H2O, and NH3 plasma treatments cause changes in surface charge, wettability, and IEP values for all treated surfaces. Observed variations in these values depend primarily on the specific mechanism for surface functionalization with each plasma treatment. Ar plasmas tend to create surface radical sites, H2O plasmas yield surface-bound OH, and NH3 plasmas lead to the incorporation of nitrate functional groups. The wettability, surface charge, IEP values, chemical composition, and surface damage of the substrates were analyzed using contact angle goniometry (CA), x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Although the permanence of these modifications varied with substrate, lasting between one week and one month, these results highlight the utility of IEP measurements for characterizing plasma treated surfaces and suggest the possibility that plasmas may provide a valuable means of controlling surface charge and wettability of metal oxides. The incorporation of functional groups on the surface of Zeolite X was also examined as an additional form of plasma surface modification. The intention of these studies was to (1) alter the surface functionality by simple plasmas treatments, as characterized by XPS data; (2) change the hydrophilic nature of the zeolite to be more hydrophobic with flurocarbon plasmas; (3) gain total surface area functionality with our new rotating drum reactor; and (4) ensure that damage was not occurring to the zeolite structure, as evidenced by SEM images. Results showed the incorporation of different surface functionality was accomplished with all plasma systems studied (CF4, C2F6, C3F8), the zeolite structure was not damaged by the plasma, and the potential for altering the entire surface area of these porous materials exists. The final portion of this dissertation addresses aspects of work designed to understand the adhesion behavior of amorphous carbon nitride (a-CNx) films deposited from a CH3CN and BrCN plasmas. In particular, films obtained from CH3CH plasmas stayed intact whereas BrCN plasmas produced films that delaminated upon their exposure to atmosphere. These results have been attributed to humidity, film stress, hydrocarbon species, and the Br content in the film. The major contributions to this work made here center on the chemical composition and binding environments of the deposited films as measured by XPS, which are shown to be critical in understanding the mechanical properties of a-CNx films.