Designing novel nanostructures which exploit the self-assembly capabilities of biomolecules yields a promising approach to control matter at the nanoscale. Here, the homochiral molecular self-assemblies of the methionine and tyrosine amino acids on the monocrystalline Ag(111) and Cu(111) surfaces are characterized by means of scanning tunneling microscopy (STM) and spectroscopy (STS), helium atom scattering (HAS), x-ray photoelectron spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) in ultrahigh vacuum (UHV). On Ag(111), methionine self-assembles into supramolecular chains following the <110> substrate axis, forming regular nanogratings with tunable periodicity. Within the nanowires, a zwitterionic dimerization scheme is revealed. STS shows that the biomolecular nanostructures act as tunable one-dimensional quantum resonators for the surface state electrons. Zero-dimensional electronic confinement is achieved by positioning single iron atoms in the molecular trenches. This shows a novel approach to control the dimensionality of surface state electrons. The nanogratings were exploited to steer the spontaneous one-dimensional ordering of cobalt and iron atoms. For T > 15 K, the metal species self-align into homogeneously distributed chains in between the biomolecular trenches with ~25 Å interatomic distace. For Co, the dynamics of the self-alignment was monitored, revealing a reduced mobility in comparison with isolated Co atoms on bare Ag(111). On Cu(111), the self-assembly of methionine is influenced by the substrate reactivity and its temperature during molecular deposition. For T < 273 K, the biomolecules assemble in anisotropic extended clusters oriented with a -10° rotation off the <110> substrate orientations, whereas above 283 K a regularly ordered 1D phase arises with a +10° rotation off these high-symmetry axis. XPS reveals a structural transformation triggered by a thermally activated deprotonation of the zwitterionic ammonium group. On Ag(111), tyrosine self-assembles above a critical temperature into linear structures primarily following the substrate crystalline symmetry. A zwitterionic non-covalent molecular dimerization is demonstrated, NEXAFS data providing evidence of a non-flat adsorption of the phenyl ring. This recalls the geometrical pattern of methionine on Ag(111) and supports a universal self-assembling scheme for amino acids on close-packed noble metal surfaces, the different mesoscopic ordering being determined by the side chain reactivity.

The main focus of this thesis is ab initio modeling of core level spectra with a high-level quantum chemical description both of the chemical interactions and of local atomic multiplet effects. In particular, the combination of calculations and synchrotron-based core-level spectroscopy aims at understanding the local structure of the electronic valence in transition metal complexes, and the details of the solvation mechanisms of electrolyte solutions, systems relevant for the dye-sensitized solar cell. Configurational sampling in solution is included through molecular dynamics simulations. Transition metal complexes are studied with x-ray absorption (XA) and resonant inelastic scattering (RIXS) spectroscopy, characterizing excited states with atomic site specificity. The theoretical multiconfigurational method, applying an active-space partitioning of the molecular orbitals (RASSCF), is used to assign the transitions observed in spectra of hydrated Ni2+ explicitly, including charge transfer and multiplet effects. Furthermore, the solvent-induced binding energy properties of the I- and I3- anions in aqueous, ethanol, and acetonitrile solutions are analyzed using photoelectron spectroscopy (XPS). The study shows that specific ion–solvent interactions are important for the core-level binding energy shifts in solution. The special case with I3- dissolved in water, where hydrogen bonding causes breaking of the molecular symmetry, is treated and proves that the geometry changes influence the photoelectron spectrum of aqueous I3- directly.

This thesis describes and develops two experimental techniques, Time Resolved Photoelectron Spectroscopy (TRPES), and Time Resolved Coincidence Imaging Spectroscopy (TRCIS), to study ultrafast gas phase chemical dynamics. We use TRPES to investigate the effects of methyl substitution on the electronic dynamics of the simple alpha, beta-enones acrolein, crotonaldehyde, methylvinylketone, and methacrolein following excitation to the S2 state. We determine that following excitation, the molecules move rapidly away from the Franck-Condon region reaching a conical intersection promoting relaxation to the S1 state. Once on the S1 surface, the trajectories access another conical intersection leading them to the ground state. Only small variations between molecules are seen in their S2 decay times. However, the position of methyl group substitution greatly affects the relaxation rate from the S1 surface. Ab initio calculations used to compare the geometries, energies, and topographies of the S1/S0 conical intersections of the molecules are not able to explain the variations in relaxation behaviour. We propose a model that uses dynamical factors of specific motions in the molecules to explain the differing nonadiabatic S1/S0 crossing rates. The second part of this thesis examines the issues involved with design and construction of a Coincidence Imaging Spectrometer. This type of spectrometer measures the 3-dimensional velocities of both photoelectrons and photoions generated from probing of laser induced photodissociation reactions. Importantly, the photoelectrons and photoions are measured in coincidence from single molecules, enabling measurements such as recoil frame photoelectron angular distributions and correlated photoelectron/photoion energy maps, inaccessible using existing techniques. How to optimize the spectrometer resolution through design, tuning, and calibration is discussed. The power of TRCIS is demonstrated with the investigation of the photodissociation dynamics of the NO dimer. TRPES experiments first identified a sequential kinetic model following 209nm excitation resulting in NO(X) (ground state) and NO(A) (excited state) products. Using TRCIS, it was possible to measure time resolved vibrational energy distributions of the products, indicating the extent of vibrational energy redistribution within the dimers prior to dissociation. Recoil frame photoelectron angular distributions and theoretical support allow identification of a previously disputed intermediate on the dissociation pathway. / Thesis (Ph.D, Chemistry) -- Queen's University, 2007-04-01 10:12:39.968

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This talk was presented in the 14th International Conference on Atomic Layer Deposition (ALD 2014) in Kyoto, Japan on 18th June 2014. Abstract Atomic Layer Deposition (ALD) is emerging as a ubiquitous method for the deposition of conformal and homogeneous ultra-thin films on complex topographies and large substrates in microelectronics. Electrochemical deposition (ECD) is the first choice for the deposition of copper (Cu) into the trenches and vias of the interconnect system for ULSI circuits. The ECD of Cu necessitates an electrically conductive seed layer for filling the interconnect structures. ALD is now considered as a solution for conformal deposition of Cu seed layers on very high aspect ratio (AR) structures also for technology nodes below 20 nm, since physical vapor deposition is not applicable for structures with high AR. Cu seed layer deposition by the reduction of Cu2O, which has been deposited from the Cu(I) β-diketonate [(nBu3P)2Cu(acac)] (1) used as Cu precursor, has been successfully carried out on different substrates like Ta, TaN, SiO2, and Ru [1, 2]. It was found that the subsequent gas-phase reduction of the Cu2O films can be aided by introducing catalytic amounts of a Ru precursor into the Cu precursor, so that metallic copper films could potentially obtained also on non-catalytic substrates [3, 4]. In this work, in situ X-ray photoelectron spectroscopy (XPS) investigation of the surface chemistry during Cu2O ALD from the mixture of 99 mol % of 1 and 1 mol % of [Ru(η5 C5H4SiMe3)(η5-C7H11)] (2) as ruthenium precursor, and the reduction of Cu2O to metallic Cu by formic acid carried out on SiO2 substrate are demonstrated. Oxidation states of the Cu in the film are identified by comparing the Cu Auger parameter (α) [5] with literature data. α calculated after ALD equals 362.2 eV and after reduction equals 363.8 eV, comparable to the Cu2O and metallic Cu in thin-films [6] respectively. In addition, <10 % of Cu(I), Cu(II), and Cu(OH)2 species are identified from the Cu 2p3/2 and Cu L3VV Auger spectrum after reduction. Consequently, the ALD Cu2O is successfully reduced to metallic copper by in-situ thermal reduction using formic acid. [1] T. Waechtler et al., J. Electrochem. Soc., 156 (6), H453 (2009). [2] T. Waechtler et al., Microelectron. Eng., 88, 684 (2011). [3] S. Mueller et al., Conference Proceedings SCD 2011, Semiconductor Conference Dresden, pp. 1-4. [4] T. Waechtler et al., US Patent Application Publication, US 2013/0062768. [5] C. D. Wagner, Faraday Discuss. Chem. Soc., 60, 291 (1975). [6] J. P. Espinós et al., J. Phys. Chem. B, 106, 6921 (2002).

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Sodium borohydride is stable in alkaline solution, however, it hydrolyses and generates hydrogen gas in the presence of suitable catalyst. By this way hydrogen can be generated safely for the fuel cells. All of the catalyst having been used in the hydrolysis of sodium borohydride, with one exception, are heterogeneous. The limited surface area of the heterogeneous and therefore, have limited activity because of the surface area. Thus, the use of metal nanoclusters as catalyst with large surface area is expected to provide a potential route to increase the catalytic activity. In this dissertation we report for the first time the use of ruthenium(0) nanoparticles as catalyst in the hydrolysis of sodium borohydride. The water dispersible ruthenium(0) nanoparticles were prepared by the reduction of RuCl3.xH2O with sodium borohydride and were stabilized by three different ligands dodecanethiol, ethylenediamine and acetate. Among these three colloidal materials the acetate stabilized ruthenium(0) nanoparticles were found to have the highest catalytic activity in catalyzing the hydrolysis of sodium borohydride. The acetate stabilized ruthenium(0) nanoparticles were characterized by tranmission electron microscopy (TEM), X-ray photoelectron spectroscopy and FT-IR spectroscopy. The particle size of the acetate stabilized ruthenium(0) nanoparticles was determined to be 2.62&plusmn / 1.18 nm from the TEM analysis. The kinetic of the ruthenium(0) nanoparticles catalyzed hydrolysis of sodium borohydride was studied depending on the catalyst concentration, substrate concentration and temperature. The activation parameters of this reaction were also determined from the evaluation of the kinetic data. This catalyst provides the lowest activation energy ever found for the hydrolysis of sodium borohydride.

ABSTRACT CARBON SUPPORTED AND SURFACTANT STABILIZED METAL NANOPARTICLE CATALYSTS FOR DIRECT METHANOL FUEL CELLS &Ccedil / elik, &Ccedil / aglar M.S., Department of Chemistry Supervisor: Assoc. Prof. Dr. G&uuml / ls&uuml / n G&ouml / kaga&ccedil / August 2005, 72 pages Carbon supported surfactant, such as 1-decanethiol and octadecanethiol, stabilized platinum and platinum/ruthenium species have been prepared recently. In this thesis, for the first time, 1-hexanethiol has been used as an organic stabilizer for the preparation of carbon supported platinum and platinum/ruthenium nanoparticle catalysts. These new catalysts were employed for methanol oxidation reaction, which were used for direct methanol fuel cells. Cyclic voltammetry, X-ray photoelectron spectroscopy and transmission electron microscopy have been used in order to determine the nature of the catalysts. The effect of temperature and time on catalytic activity of catalysts were examined and the maximum catalytic activity was observed for carbon supported 1-hexanethiol stabilized platinum nanoparticle catalyst (with 1:1 thiol/platinum molar ratio) which was heated up at 200oC for 5 hours. The particle size of platinum nanoparticles was determined to be ~ 10 nm in diameter. The size and distribution of metal nanoparticles on carbon support, the Pt/Ru surface composition, the relative amount of Pt(0), Pt(II) and Pt(IV) and the removal of organic surfactant molecules around the metal nanoparticles were found to be important in determining the catalytic activity of electrodes towards methanol oxidation reaction. A significant decrease in catalytic activity was observed for carbon supported 1-hexanethiol stabilized Pt75Ru25 and Pt97Ru3 (with 1:1 thiol/PtRu molar ratio) with respect to carbon supported 1-hexanethiol stabilized Pt (with 1:1 thiol/platinum molar ratio). This result might be due to unremoved stabilizer shell around platinum/ruthenium nanoparticles and increase in amount of Pt(II) and Pt(IV) compared to Pt(0) where the methanol oxidation occured.

The development of new storage materials will facilitate the use of hydrogen as a major energy carrier in near future. In hydrogen economy, chemical hydrides such as NaBH4, KBH4, LiH, NaH have been tested as hydrogen storage materials for supplying hydrogen at ambient temperature. Among these chemical hydrides, sodium borohydride seems to be an ideal hydrogen storage material because it is stable under ordinary conditions and liberates hydrogen gas in a safe and controllable way in aqueous solutions. However, self hydrolysis of sodium borohydride is so slow that it requires a suitable catalyst. All of the prior catalysts tested for the hydrolysis of sodium borohydride are heterogeneous and, therefore, have limited activity because of the small surface area. Here, we report for the first time the employment of water dispersible metal(0) nanoclusters having a large portion of atoms on the surface as a catalyst for the hydrolysis of sodium borohydride. In-situ formation of nickel(0) nanoclusters and catalytic hydrolysis of sodium borohydride were performed in the same medium. Nickel(0) nanoclusters are prepared from the reduction of nickel(II) acetylacetonate by sodium borohydride in aqueous solution and stabilized with hydrogenphosphate anions. The nickel(0) nanoclusters were characterized by using XPS, Powder XRD, FT-IR, UV-Vis and NMR spectroscopic methods. The kinetics of the nickel(0) nanoclusters catalyzed hydrolysis of sodium borohydride was studied depending on the catalyst concentration, substrate concentration, stabilizing agent concentration and temperature. Tha kinetic study shows that the nickel(0) nanocluster-catalyzed hydrolysis of sodium borohydride is first order with respect to catalyst concentration and zero order with respect to substrate concentration The activation parameters of this reaction were also determined from the evaluation of the kinetic data. The hydrogenphosphate-stabilized nickel(0) nanoclusters provide a lower activation energy (Ea= 55 kJ/mol) than bulk nickel (Ea=73 kJ/mol) for the hydrolysis of sodium borohydride.

Thin-film solar cells based on Cu(In,Ga)Se2 contain a thin buffer layer of CdS in their standard configuration. In order to avoid cadmium in the device for environmental reasons, Cd-free alternatives are investigated. In this thesis, ZnO-based films, containing Mg or S, grown by atomic layer deposition (ALD), are shown to be viable alternatives to CdS. The CdS is an n-type semiconductor, which together with the n-type ZnO top-contact layers form the pn-junction with the p-type Cu(In,Ga)Se2. From device modeling it is known that a buffer layer conduction band (CB) position of 0-0.4 eV above that of the Cu(In,Ga)Se2 layer is consistent with high photovoltaic performance. For the Cu(In,Ga)Se2/ZnO interface this position is measured by photoelectron spectroscopy and optical methods to –0.2 eV, resulting in increased interface recombination. By including sulfur into ZnO, a favorable CB position to Cu(In,Ga)Se2 can be obtained for appropriate sulfur contents, and device efficiencies of up to 16.4% are demonstrated in this work. From theoretical calculations and photoelectron spectroscopy measurements, the shift in the valence and conduction bands of Zn(O,S) are shown to be non-linear with respect to the sulfur content, resulting in a large band gap bowing. ALD is a suitable technique for buffer layer deposition since conformal coverage can be obtained even for very thin films and at low deposition temperatures. However, deposition of Zn(O,S) is shown to deviate from an ideal ALD process with much larger sulfur content in the films than expected from the precursor pulsing ratios and with a clear increase of sulfur towards the Cu(In,Ga)Se2 layer. For (Zn,Mg)O, single-phase ZnO-type films are obtained for Mg/(Zn+Mg) &lt; 0.2. In this region, the band gap increases almost linearly with the Mg content resulting in an improved CB alignment at the heterojunction interface with Cu(In,Ga)Se2 and high device efficiencies of up to 14.1%.