No description available.

Gold used to be regarded as catalytically inert until about 20 years ago when it was shown that supported gold clusters < 5 nm in diameter exhibited some unique catalytic properties. Based on this revelation, several studies have demonstrated the feasibility of reactions previously thought of as impossible on gold. The ability of gold to oxidize CO below ambient temperatures at rates higher than conventional CO oxidation catalysts (Pd and Pt) has been shown to hold potentials for technological applications. Extensive past and on-going research are geared towards elucidating the mechanistic details of this reaction. The nature of the active sites, the effect of the supports and the effect of moisture are still debated in literature. I therefore present some experimental results supported with density functional theory calculations to shed additional light on some of the issues concerning gold catalysis in general, and low temperature CO oxidation in particular. Previous studies of the effect of moisture on oxide-supported gold reported that although water promotes CO oxidation on this surface by as much as two orders of magnitude, it is only a spectator molecule on the surface. I present here evidence for strong water-oxygen interactions when water is co-adsorbed with atomic oxygen on Au(111). Impinging a CO beam on the surface co-adsorbed with oxygen and water produces water-enhanced CO oxidation. Based on these results, I propose that CO reacts with hydroxyls formed from water-oxygen interactions to form CO₂, similar to a previous observation on Pt(111). Exposing a Au(111) surface pre-covered with ¹⁶O to isotopically labeled carbon dioxide (C¹⁸O₂) showed that ¹⁶O¹⁸O (m/e = 34) was produced from carbonate formation and decomposition. Estimates of reaction probability and activation energy gave ~ 10⁻⁴ - 10⁻⁵ and -0.15 eV respectively. The effect of annealing on the reactivity of oxygen pre-covered Au(111) was investigated using water, carbon monoxide and carbon dioxide as probe molecules. Precovering Au(111) with atomic oxygen followed by annealing resulted in surfaces that were less reactive towards water, CO and CO₂. Annealing is believed to stabilize the reactive metastable oxygen thereby increasing the barrier to reaction similar to what is reported on other surfaces. / text

No description available.

This text describes the synthesis of surface-oriented multilayers based on novel monomeric species. The impetus of this study is to incorporate atypical species and techniques in order to prepare well-ordered assemblies on gold surfaces. These thin films were characterized by one or more of following techniques: grazing angle FT-IR; optical ellipsometry and x-ray photoelectron spectroscopy. First, chemical vapor deposition polymerization was used to prepare surface-oriented monolayers on amine functionalized gold from 4-aminobenzaldehyde and 5-phenyl-1, 3-dioxolane-2, 4-dione. The 4-aminobenzaldehyde showed regular increases in the intensity of characteristic IR absorptions with number of deposition cycles while the dioxolane showed no regularity in this respect. We infer from our data that this technique is a practical way to synthesize highly conjugated polymers. Secondly, we investigated the preparation of surface oriented materials based on host-guest assemblies. Cyclodextrin functionalized gold surfaces could serve as orientational templates for multilayered well-ordered host-guest materials. However, in our study, thiol modified cyclodextrin showed no ability to organize surface multilayers via surface crystallization in the presence of the appropriate host; nor did it show an ability to pre-organize in solution via polyethylene glycol rotaxane formation followed by surface attachment. Finally, surface-oriented organometallic monolayers and multilayers were prepared from alkyne functionalized gold surfaces. Using bis-orthodimethylaminomethyl (NCN) ligands we synthesized two unique surface-oriented organometallic assemblies. Palladium NCN hydrosulfides formed monolayers on gold. Characterization by FT-IR, XPS and ellipsometry show that these species similar to their thiol counterparts. In addition, organometallic polymers were grown from alkyne functionalized surfaces. The thickness of these films, which reached 40 Å by ellipsometry was dependent upon the nature of the alkyne initiator. / text

Self-assembled monolayers (SAMs) of organosulfur precursors on gold have been extensively used since they offer a wide range of technological applications such as corrosion inhibition, lubrication, adhesion promotion/inhibition, nanofabrication, chemical and biosensors, catalysis, and molecular electronics. Furthermore, the electronic and optical properties of aromatic SAMs make them a potential candidate for molecular electronics. However, these practical applications are limited by the short-range ordering, low packing density, irreproducibility, and inferior quality of SAMs, which are more critical for aromatic SAMs. Therefore, the discovery of alternative precursors is essential. This thesis reports for the first time, the use of organic sulfenyl chlorides as precursors for the modification of gold surfaces. These precursors may help to overcome some practical limitations of the traditional organosulfur precursors. The modification is done in a non-aqueous medium. Characterization of the modified surfaces is performed by X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), and scanning tunnelling microscopy (STM). Through the use of 4-nitrophenyl sulfenyl chloride, evidence for the formation of well-ordered aromatic SAMs formation on gold is provided. XPS data shows that the modification involves the scission of the S-Cl bond. PM-IRRAS studies further indicate that the adsorbed molecules are nearly vertically oriented on the surface. Both short and long-range well-ordered aromatic SAMs (a 4 x √3 rectangular and √3 x √3 hexagonal unit cells) are obtained from the STM images using two different modification conditions. This molecular density is usually only observed for aliphatic SAMs using the traditional precursors. Along with the main hexagonal lattice, the reversible distinct superstructures including hexagons, partial hexagons, parallelograms, and zigzags resulting from specific arrangements of adsorbed molecules provide submolecular details. This is the first direct experimental example, where the STM has shown its effectiveness to provide physical structure information of standing-up aromatic SAMs at room temperature. This work also provides some insight into a heavily debated issue regarding the origin of the various features and contrasts obtained in STM images of SAMs. The use of 2-nitrophenyl sulfenyl chloride and 2,4-dinitrophenyl sulfenyl chloride for the formation of aromatic SAMs on Au provides some insight regarding the modification extent and the effect of a nitro substituent (at ortho position ) on the quality of nitrophenyl thiolate SAMs on gold. XPS, PM-IRRAS, electrochemistry and STM provide evidence for the formation of less ordered, low density and less stable SAMs that may decompose to sulfur at longer modification times. The efficient deposition of sulfur on gold is observed using a series of substituted methane sulfenyl chlorides (triphenylmethane sulfenyl chloride, trichloromethane sulfenyl chloride and chlorocarbonyl sulfenyl chloride). The XPS, STM and electrochemical data show the formation of high density sulfur phases. These include rhombus, rectangular, and zig-zag sulfur structures. A mechanism is suggested involving the cleavage of the S-Cl bond and the ejection of the molecular backbone. This study also suggests that substituted methane sulfenyl chlorides do not form long-range ordered SAMs.

No description available.

Luk, Wai Chun = / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 101-108). / Abstracts in English and Chinese. / Luk, Wai Chun = / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Theoretical Background --- p.5 / Chapter 2.1 --- Maxwell´ةs equations in matter --- p.5 / Chapter 2.2 --- Dielectric constant of materials --- p.8 / Chapter 2.3 --- Dispersion relation of surface plasmon polaritons --- p.10 / Chapter 2.4 --- Excitation of surface plasmon polaritons --- p.16 / Chapter 2.4.1 --- Prism coupling --- p.17 / Chapter 2.4.2 --- Grating coupling --- p.21 / Chapter 2.5 --- Diffraction of light in gratings --- p.26 / Chapter 2.6 --- Applications --- p.27 / Chapter 3 --- Analysis Methods --- p.29 / Experimental Section --- p.29 / Chapter 3.1 --- Interference Lithography --- p.29 / Chapter 3.2 --- Gold grating fabrication --- p.32 / Chapter 3.2.1 --- Substrate preparation --- p.33 / Chapter 3.2.2 --- Photoresist preparation --- p.34 / Chapter 3.2.3 --- Spin coating of omnicoat and photoresist --- p.35 / Chapter 3.2.4 --- Interference lithography set-up and procedures --- p.35 / Chapter 3.2.5 --- The post-exposed treatments --- p.37 / Chapter 3.2.6 --- The optimal exposure time calibration --- p.37 / Chapter 3.2.7 --- Gold thin film deposition --- p.39 / Chapter 3.2.8 --- Typical gold grating sample --- p.41 / Chapter 3.3 --- Measurement system --- p.41 / Chapter 3.3.1 --- The angle dependent reflectivity measurement --- p.42 / Chapter 3.3.2 --- Data presentation of a typical band structure --- p.45 / Chapter 3.3.3 --- Periodicity measurement of the grating samples --- p.48 / Chapter 3.3.4 --- Diffracted intensity measurement of gratings --- p.52 / Chapter 3.3.5 --- Data presentation of the angle dependent diffracted intensity measurement --- p.53 / Calculation Section --- p.54 / Chapter 3.4 --- RCWA simulations --- p.54 / Chapter 3.4.1 --- The dispersion relation --- p.56 / Chapter 3.4.2 --- The diffracted intensity --- p.56 / Chapter 3.4.3 --- The field pattern graphs --- p.57 / Chapter 4 --- Resonance modes in one-dimensional gold gratings --- p.60 / Chapter 4.1 --- Structure of the gold grating samples --- p.61 / Chapter 4.2 --- Results of angle dependent reflectivity --- p.63 / Chapter 4.2.1 --- Surface Plasmon Polaritons (SPPs) --- p.65 / Chapter 4.2.2 --- Wood´ةs anomaly --- p.65 / Chapter 4.2.3 --- Waveguide Resonance (WG) --- p.67 / Chapter 4.2.4 --- Coupling of SPPs and WG --- p.67 / Chapter 4.3 --- Results of angle dependent diffracted intensity measurement --- p.68 / Chapter 4.4 --- Basic properties of SPPs and WG modes by RCWA --- p.73 / Chapter 4.4.1 --- Sample 1 (D = 40 nm) --- p.74 / Chapter 4.4.1(a) --- λ = 980 nm of Sample 1 --- p.75 / Chapter 4.4.1(b) --- λ = 633 nm of Sample 1 --- p.81 / Chapter 4.4.2 --- Sample 2 (D = 390 nm) --- p.83 / Chapter 4.4.2(a) --- λ = 980 nm of Sample 2 --- p.85 / Chapter 4.4.2(b) --- λ = 725 nm of Sample 2 --- p.87 / Chapter 4.4.2(c) --- λ = 633 nm of Sample 2 --- p.92 / Chapter 4.5 --- Summary --- p.97 / Chapter 5 --- Conclusions --- p.99 / Bibliography --- p.101

Sham, Chun Hong = 金屬光栅光學特性的實驗和理論研究 / 沈鎮康. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 109-111). / Abstract also in Chinese. / Sham, Chun Hong = Jin shu guang shan guang xue te xing de shi yan he li lun yan jiu / Shen Zhenkang. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.2 --- Overview of the Thesis --- p.2 / Chapter 2 --- Basic Theory --- p.4 / Chapter 2.1 --- Dielectric Constant of Metals --- p.5 / Chapter 2.2 --- The Maxwell´ةs Equations --- p.7 / Chapter 2.3 --- Scaling Properties of the Maxwell´ةs Equations --- p.9 / Chapter 2.4 --- Translational Symmetry and the Bloch´ةs Theorem --- p.10 / Chapter 2.4.1 --- Continuous Translational Symmetry --- p.11 / Chapter 2.4.2 --- Discrete Translational Symmetry --- p.12 / Chapter 2.4.3 --- Photonic Bloch´ةs Theorem --- p.13 / Chapter 3 --- Principles of Rigorous Coupled Wave Analysis --- p.14 / Chapter 3.1 --- Mathematical Formulation --- p.15 / Chapter 3.2 --- One-layer systems --- p.15 / Chapter 3.3 --- Layered Systems --- p.19 / Chapter 3.3.1 --- Matching Boundary Conditions --- p.19 / Chapter 3.3.2 --- The Transfer Matrices --- p.21 / Chapter 3.3.3 --- Scattering Matrices --- p.22 / Chapter 3.4 --- Calculation of Reflection and Transmission --- p.24 / Chapter 3.5 --- Calculation of Field Pattern --- p.26 / Chapter 3.5.1 --- Finding the Coefficients --- p.26 / Chapter 3.5.2 --- Summing to Get the Field --- p.27 / Chapter 3.6 --- 5-polarization --- p.27 / Chapter 3.7 --- Analogy to mechanics --- p.29 / Chapter 3.8 --- Conclusion --- p.30 / Chapter 4 --- Numerical Implementation of Rigorous Coupled Wave Analysis --- p.31 / Chapter 4.1 --- Finite Number of Terms --- p.31 / Chapter 4.2 --- Fourier Factorization Rule --- p.32 / Chapter 4.3 --- Calculation of Field Pattern --- p.34 / Chapter 4.4 --- Transfer Matrix for Forward Deduction --- p.36 / Chapter 4.5 --- Calculation of Time-Averaged Poynting Vector --- p.36 / Chapter 4.6 --- Convergence of RCWA --- p.37 / Chapter 4.7 --- Simple Examples --- p.40 / Chapter 4.7.1 --- Oblique Incidence on Vacuum --- p.40 / Chapter 4.7.2 --- Oblique Incidence on Semi-Infinite Glass --- p.41 / Chapter 4.7.3 --- Normal Incidence on a Thin Gold Film --- p.41 / Chapter 5 --- A Tunable All-Direction Light Absorber --- p.43 / Chapter 5.1 --- Description of the Absorber --- p.44 / Chapter 5.2 --- Tunability --- p.45 / Chapter 5.3 --- Theoretical Understanding on the Results --- p.46 / Chapter 5.4 --- Other EM modes Involved --- p.49 / Chapter 5.5 --- Structural Flexibility --- p.54 / Chapter 6 --- Sample Preparation Techniques --- p.57 / Chapter 6.1 --- Interference Lithography --- p.57 / Chapter 6.1.1 --- Basic Principle of IL --- p.58 / Chapter 6.1.2 --- Experimental Setup for IL --- p.59 / Chapter 6.1.3 --- Experimental Procedures for IL --- p.60 / Chapter 6.1.4 --- Tuning the Period --- p.61 / Chapter 6.1.5 --- Tuning Grating Width --- p.62 / Chapter 6.1.6 --- Tuning the grating height --- p.64 / Chapter 6.2 --- Sputtering --- p.65 / Chapter 6.2.1 --- Description of Sputtering System --- p.65 / Chapter 6.2.2 --- Effect of Varying the Position on Sample Holder --- p.66 / Chapter 6.3 --- Chemical deposition of silver --- p.69 / Chapter 7 --- Sample Characterization Techniques --- p.72 / Chapter 7.1 --- Scanning Electron Microscope --- p.72 / Chapter 7.1.1 --- Grating width measurement --- p.72 / Chapter 7.1.2 --- Sidewall Coverage Measurement --- p.73 / Chapter 7.2 --- Thickness Measurement --- p.74 / Chapter 7.3 --- Reflectance Measurement --- p.75 / Chapter 7.3.1 --- Experimental Setup --- p.76 / Chapter 7.3.2 --- Use of Prism --- p.79 / Chapter 8 --- Experimental Realization of All-Direction Light Absorber --- p.82 / Chapter 8.1 --- Reflectance of Glass Substrate --- p.82 / Chapter 8.2 --- Planar Metal-SU8-Metal Systems --- p.87 / Chapter 8.3 --- SU8 Grating on Glass Substrate --- p.89 / Chapter 8.4 --- SU8 Grating on Gold Substrate --- p.92 / Chapter 8.4.1 --- Grating on a Thick Layer of Gold --- p.93 / Chapter 8.4.2 --- Grating on a Thin Layer of Gold --- p.93 / Chapter 8.5 --- Cavities-Embedded Systems and Future Work --- p.96 / Chapter 8.6 --- Summary and Future Experimental Work --- p.100 / Chapter 9 --- Conclusion --- p.102 / Chapter A --- Notes on Glass Cleaning --- p.104 / Chapter B --- An Experiment on Sidewall Coverage --- p.107 / Bibliography --- p.109