Thesis (M.S.)--Boise State University, 2009. / Title from t.p. of PDF file (viewed Apr. 30, 2010). Includes abstract. Includes bibliographical references (leaves 85-86).

Chalcogenide glasses (ChG) have shown very promising properties for integrated optical applications at the 1.3 and 1.55 µm optical communication wavelengths due to their transparency in the near-infrared region and high nonlinear Kerr effect. Recent experiments on the ChG system have demonstrated the vast flexibility and potential of these materials in applications as optical memories, switches, and diffractive elements, as well as couplers and self-written planar waveguides. However, to advance these novel applications, it is crucial to identify the structure-property relationship in the glass, in both bulk and film materials. Throughout this research work we used conventional near-infrared (NIR) Raman spectroscopy (e.g. backscattering and 90° geometry) to investigate structure-property relationships in chalcogenide materials. Initially, we conducted a homogeneity study of the bulk glass to analyze the elaboration and processing conditions of these glasses. Furthermore, we investigated the compositional variation of the bulk glass and established a relationship between the Raman spectra, and hence their molecular structure, with the optical properties of the material. When the analysis of the bulk glass was completed, we sent the bulk samples to Laval University in Canada, where the fabrication of the thin films and waveguide structures took place. Right after the film and waveguide samples were created, they were sent back to us, where, once again, we conducted a Raman study to investigate any differences between the films and the bulk glass. In this case, the Raman analysis was conducted using Micro-Raman (backscattering geometry) and Waveguide Raman spectroscopy (90° scattering geometry). Here we demonstrate, for the first time to our knowledge, the use of near-infrared (NIR) waveguide Raman spectroscopy to investigate the microstructure of chalcogenide thin films. This integrated optical technique is extremely powerful in the microstructural analysis of thin film devices due to the combination of good molecular specificity and high sensitivity. The Raman spectra depict microstructural differences between As2S3 films, fibers, and bulk glasses. In the ternary compounds, these microstructural differences are less observable. In chalcogen-rich glasses, the vibrational spectra reveal the preferential formation of homopolar Se-Se and S-S bonds. In those compositions, where Se-Se bonds are observed, high nonlinear optical coefficients have been measured. Near-infrared Raman spectroscopy of photoinduced and annealed structures also allows to identify specific bonding changes which accompany the aging process.

Abstract Chalcogenide glasses and films are excellent candidates for near-infrared guiding configurations in opto-e]ectronics due to the ir high transmission. Their photosensitivity allows waveguide creation by standard lithography or one- and two-photon writing. The near-infrared Raman spectra of a series of As-S(Se) glasses are analyzed using spectral deconvolution and correlated with the molecular structure. Contributions due to As­ (S,Se)3 pyramjdal subunits as well as homopolar Se-Se and S-S bonds are determined. Photoinduced molecular changes in waveguide structures are probed by Raman scattering employing guided mode excitation. A new approach is demonstrated to optically interrogate composite layers where a chalocogenide waveguide provides the substrate and the guiding layer for a biomolecular film whose Raman spectrum is desired. Hydrophilic chalcogenide surfaces were prepared by exposure to 0 ₂ plasma and characterized by XPS spectroscopy. Thin layers of the photo-active protein bacteriorhodopsin were deposited on As₂S3 waveguides and observed by scanning electron and atomic force microscopy. The evanescent wave excited near-infrared Raman spectrum is measured in-situ providing a molecular probe of the chromophore and the light-adaptedstate. This novel technique offers potential for protein monolayer characterization and bio-sensors.

This dissertation focuses on the synthetic exploratory synthesis of molybdenum chalcogenides and rare earth metal-rich ternary tellurides as a part of an effort to produce molecular building blocks of molybdenum chalcogenide clusters and to explore their structural relationships with solid state cluster networks. The tightly cross-linked Mo3nSe3n+2(n = 2, 3, ...∞) clusters and chain compounds react with alkali metal cyanide or cyanide salt mixtures at temperatures of 450-675 °C to yield reduced, cyanide-terminated molybdenum chalcogenide clusters that are thermodynamically stable. At temperatures of 650-675 °C, linear chain compounds I6[Mo6Se8(CN)4(CN)2/2] (MI = K, Cs) were prepared from reactions of Mo6Se8 or elemental starting materials, Mo and Se with excess molten cyanide (KCN, CsCN). These are the first known compounds to feature linking of Mo6Se8 clusters via cyanide bridges. Magnetic susceptibility and EPR measurements indicate that there is one unpaired electron per cluster. A new reduced molecular octahedral complex, Na8[Mo6Se8(CN)6]•20H2O was prepared by the reduction of [Mo6Se8(CN)6]7-with Zn in an aqueous NaCN solution. Single crystal structure was determined. Cyclic voltammetric measurements in basic aqueous media show multiple reversible redox waves corresponding to [Mo6Se8(CN)6]6-/7-, [Mo6Se8(CN)6]7-/8-, [Mo6Se8(CN)6]8-/9-redox couples with half-wave potentials of E1/2 = -0.442 V, -0.876 V, and 11.369 V respectively versus the standard hydrogen electrode (SHE). UV-Vis studies support the presence of the reduced cluster compound. New reduced molecular tetrahedral complexes, K7Na[Mo4Se4(CN)12]•5H2O•MeOH, Na4Cs7[Mo4Se4(CN)12]Cl3, Na8[Mo4Se4(CN)12], and Na4K4[Mo4Se4(CN)12]•12H2O were prepared. Preparation of Na8[Mo4Se4(CN)12] is an improved method for the synthesis of the Mo4Se4 core. Half-wave potentials of E1/2 for the [Mo4Se4(CN)12]6-/7-and [Mo4Se4(CN)12]7-/8-couples are 0.233 V, and -0.422 V respectively versus SHE. The molecular cubane clusters [Mo4Se4(CN)12]7-/8-play an essential role in the process by which the discrete [Mo6Se8(CN)6]6-and [Mo6Se8(CN)6]are excised from the CN-linked chain compound, K6Mo6Se8(CN)5. A new rare-earth telluride compound with the empirical composition of Gd4NiTe2 was synthesized from a high-temperature solid-state reaction. Gd4MTe2 (M = Ni) crystallizes in the orthorhombic space group Pnma. This unprecedented structure consists of a cluster condensation of Ni-centered gadolinium tricapped trigonal prisms along the rectangular faces of the trigonal prism such that the Ni atoms act as two of the caps to the trigonal prisms.

This dissertation focuses on the synthetic exploratory synthesis of molybdenum chalcogenides and rare earth metal-rich ternary tellurides as a part of an effort to produce molecular building blocks of molybdenum chalcogenide clusters and to explore their structural relationships with solid state cluster networks. The tightly cross-linked Mo3nSe3n+2(n = 2, 3, ...∞) clusters and chain compounds react with alkali metal cyanide or cyanide salt mixtures at temperatures of 450-675 °C to yield reduced, cyanide-terminated molybdenum chalcogenide clusters that are thermodynamically stable. At temperatures of 650-675 °C, linear chain compounds I6[Mo6Se8(CN)4(CN)2/2] (MI = K, Cs) were prepared from reactions of Mo6Se8 or elemental starting materials, Mo and Se with excess molten cyanide (KCN, CsCN). These are the first known compounds to feature linking of Mo6Se8 clusters via cyanide bridges. Magnetic susceptibility and EPR measurements indicate that there is one unpaired electron per cluster. A new reduced molecular octahedral complex, Na8[Mo6Se8(CN)6]•20H2O was prepared by the reduction of [Mo6Se8(CN)6]7-with Zn in an aqueous NaCN solution. Single crystal structure was determined. Cyclic voltammetric measurements in basic aqueous media show multiple reversible redox waves corresponding to [Mo6Se8(CN)6]6-/7-, [Mo6Se8(CN)6]7-/8-, [Mo6Se8(CN)6]8-/9-redox couples with half-wave potentials of E1/2 = -0.442 V, -0.876 V, and 11.369 V respectively versus the standard hydrogen electrode (SHE). UV-Vis studies support the presence of the reduced cluster compound. New reduced molecular tetrahedral complexes, K7Na[Mo4Se4(CN)12]•5H2O•MeOH, Na4Cs7[Mo4Se4(CN)12]Cl3, Na8[Mo4Se4(CN)12], and Na4K4[Mo4Se4(CN)12]•12H2O were prepared. Preparation of Na8[Mo4Se4(CN)12] is an improved method for the synthesis of the Mo4Se4 core. Half-wave potentials of E1/2 for the [Mo4Se4(CN)12]6-/7-and [Mo4Se4(CN)12]7-/8-couples are 0.233 V, and -0.422 V respectively versus SHE. The molecular cubane clusters [Mo4Se4(CN)12]7-/8-play an essential role in the process by which the discrete [Mo6Se8(CN)6]6-and [Mo6Se8(CN)6]are excised from the CN-linked chain compound, K6Mo6Se8(CN)5. A new rare-earth telluride compound with the empirical composition of Gd4NiTe2 was synthesized from a high-temperature solid-state reaction. Gd4MTe2 (M = Ni) crystallizes in the orthorhombic space group Pnma. This unprecedented structure consists of a cluster condensation of Ni-centered gadolinium tricapped trigonal prisms along the rectangular faces of the trigonal prism such that the Ni atoms act as two of the caps to the trigonal prisms.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

This dissertation describes and summarizes the research I performed as a member of the Roy group. The Roy group uses molecular clusters as nanoscale building blocks for new materials, in addition to several other topics of related interest including the design and synthesis of molecular wires to study the movement of electrons (conductance) at the molecular level. Chapter 1 introduces molecular clusters as superatomic nanoscale building blocks and describes how superatomic crystals, analogous to ionic crystals, can be controllably assembled from these building blocks. Next, Chapter 2 examines how the atomic properties of ionization energy and electron affinity can be extended to superatoms by investigating the Co6S8(PEt3)6(CO)6-x family of clusters. As the degree of cabonylation increases, the superatom moves from alkali-like to halogen-like behavior; i.e., it becomes harder to ionize and easier to add an electron to the superatom as PEt3 ligands are replaced with CO ligands while still maintaining the overall electron count of the cluster. Chapter 3 then moves to discuss how the related building blocks, Co6Te8(PEt3)6 and its derivatives, can be assembled into superatomic crystals using the electron-accepting Fe8O4pz12Cl4 cluster. Chapter 4 then uses this same Fe8O4pz12Cl4 cluster as a probe for singlet fission triplet dynamics by functionalizing this cluster with a singlet fission chromophore. Chapter 5 continues the idea of ligand design by exploring a series of oligophenylenediamine molecules capable of binding to gold (and presumably other metals), and it is observed that the conductance dramatically increases by applying a high positive bias to the molecules when they are bound to the tips of two gold electrodes. This dissertation concludes with Chapter 6, which discusses how new cobalt chalcogenide materials prepared from superatomic precursors can be deployed as new battery electrode materials for lithium and sodium ion batteries. Each of these chapters help illustrate how synthetic chemistry can be used to both elucidate interesting chemical phenomena and to design new materials with tailored properties.

Thesis (Ph.D.)--University of Hong Kong, 1997. / Includes bibliographical references (leaf 389-411). Also available in print.

Thesis (Ph. D.)--University of Hong Kong, 1997. / Includes bibliographical references (leaf 389-411).

Thesis (Ph. D.)--Rutgers University, 2008. / "Graduate Program in Chemistry and Chemical Biology." Includes bibliographical references (p. 78-80).