published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

by Leung, Kwok Kong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 67). / Text in English; abstracts in English and Chinese. / by Leung, Kwok Kong. / Abstract --- p.ii / Acknowledgement --- p.iii / Contents --- p.iv / List of Figures --- p.vi / Chapter Chapter 1. --- Introduction --- p.1 / Chapter Chapter 2. --- Transmittance in Metal-Dielectric Multilayers --- p.4 / Chapter 2.1 --- Introduction --- p.4 / Chapter 2.2 --- Transfer matrix approach --- p.5 / Chapter 2.3 --- Transfer matrix simulation --- p.7 / Chapter 2.4 --- Physical explanation --- p.14 / Chapter Chapter 3. --- Optical Nonlinear Response of Composite Layer --- p.17 / Chapter 3.1 --- Transfer matrix formalism for oblique incidence --- p.18 / Chapter 3.1.1 --- Transfer matrix method in nonlinear region --- p.18 / Chapter 3.1.2 --- S-polarization --- p.19 / Chapter 3.1.3 --- P-polarization --- p.19 / Chapter 3.1.4 --- Backward propagation technique --- p.22 / Chapter 3.2 --- Nonlinear phase shift --- p.22 / Chapter 3.3 --- Transfer matrix method approach --- p.24 / Chapter 3.4 --- Analytic solution formalism --- p.26 / Chapter Chapter 4. --- Study of Photonic Band Gap of Nonlinear Dielectrics --- p.33 / Chapter 4.1 --- Introduction --- p.33 / Chapter 4.2 --- Nonlinear response of single thin nonlinear layer --- p.34 / Chapter 4.3 --- Nonlinear response of δ-function between two linear dielectric --- p.37 / Chapter 4.4 --- Photonic band structure --- p.41 / Chapter 4.4.1 --- Photonic band structure of linear thin films --- p.41 / Chapter 4.4.2 --- Photonic band structure of linear layers --- p.42 / Chapter 4.5 --- Photonic band gap of nonlinear dielectric multilayers --- p.46 / Chapter Chapter 5. --- Optical Limiting of Composite Material --- p.49 / Chapter 5.1 --- Transmittance of periodic multilayer structures --- p.50 / Chapter 5.1.1 --- Transmittance properties at low intensity --- p.50 / Chapter 5.1.2 --- Transmittance at high intensity: optical limiting effect --- p.52 / Chapter 5.2 --- The effect of layer thickness on optical limiting --- p.53 / Chapter 5.3 --- Optical limiting property of PBG materials --- p.55 / Chapter Chapter 6. --- Conclusion --- p.63 / Chapter Appendix A. --- Effective dielectric function --- p.64 / Bibliography --- p.67

"Self-assembled monolayers (SAMs) are organized molecular assemblies that are formed by spontaneous adsorption of a compound in solution to a surface (e.g. alkanethiols on gold). The design, preparation, and characterization of several self-assembled monolayers and multilayers on surfaces (gold, indium tin oxide and quartz) are described. The systems were chosen based on their ability to form ordered films and to perform a given device function. SAMs were fabricated with selected functional groups at the air-monolayer interface, capable of complexing metal ions (e.g. dicarboxypyridine, dicarboxybenzene, imidazole, 4-hydroxypyridine) with the purpose of using these SAMs to construct multilayered films. Deposition of a second layer consisting of metal ions (e.g. Cu(II), Co(II) and Fe(III)), occurs by non-covalent metal ligand binding interactions between the metal ion layer and the different organic ligands on the surface. Deposition of subsequent layers was achieved by the incorporation of the appropriate organic ligands and metal ions. These monolayers and multilayered films were characterized by contact angle measurements, ellipsometry, grazing angle FT-IR, cyclic voltammetry and impedance spectroscopy following deposition of each layer on the film. Electrochemical analysis of the multilayered films shows alternating insulating/conducting behavior (cyclic voltammetry) and alternating changes in films capacitance (impedance spectroscopy) depending on the outermost layer of the film. Films capped with an organic layer show low conductivity, while films capped with a metal layer show conducting behavior. The electrochemical behavior of the films is related to the degree of “leakiness” or electrolyte solution permeation through the film, which is high for films with metal layers as the top layer and decreases once the film is capped with an organic layer. The alternating conducting/insulating behavior of the films allows for fabrication of multilayered thin films of variable thickness and tunable conducting properties. Ordered films were fabricated with up to seven layers of dicarboxypyridine and Cu(II), and 4-hydroxypyridine and Fe(III) metal-ligand units. The construction of these films provides an example of molecular films that could function as molecular wires or junctions due to their controllable electrochemical properties. Photocurrent generating films were fabricated by incorporation of chromophore groups (e.g. pyrene, porphyrins) into the multilayered structures. These films generate cathodic or anodic current upon photoexcitation of the chromophores. The monolayers functionalized with different organic ligands were also used to study lanthanide complexation on the surfaces. Successful deposition of different lanthanide ions was achieved from DMSO solutions. Monolayers of a bicyclic structure, 4, 7, 13, 16-tetraoxa-1,10,21-triaza-bicycle[8.8.5] tricosane-19,23-dione, attached to a hexadecanethiol molecule were used to study the ability of metal ion detection on the surface using electrochemical (cyclic voltammetry and impedance spectroscopy) techniques. The SAMs show higher complexation affinity for Li+ than for Na+ or K+. Preliminary studies were also carried out to investigate the ability of different SAMs to cell adhesion interactions. Future experiments will help elucidate a systematic relation of cell adherence and the bulk and molecular-level properties of the functionalized surfaces. The different multilayered films described in this dissertation served as preliminary models for different molecular scale device applications. Current work is focused in the design and preparation of more efficient photocurrent generating films, highly selective sensors for different types of ions, surfaces for cell adhesion and microbial interactions, and the study of other potential applications such as the design of micro and nanofluidic devices. "

Orientador: Carlos José Leopoldo Constantino / Banca: Luis Vicente de Andrade Scalvi / Banca: Eloi da Silva Feitosa / Banca: Paola Corio / O programa de Pós graduação em Ciência e Tecnologia de Materiais, POSMAT, tem carater institucional e integra as atividades de pesquisa em materiais de diversos campi da UNESP / Resumo: A presente dissertação de mestrado trata da fabricação de filmes ultrafinos (nanômetros de espessura) de fosfolipídios aniônicos (DPPG e CLP) e zwiteriônicos (DPPC e DOPC) utilizando as técnicas layer-by-layer (LbL) e Langmuir-Blodgett (LB), possibilitando assim a obtenção de filmes com diferentes arquiteturas moleculares. O objetivo principal foi explorar a aplicação destas diferentes arquiteturas moleculares na detecção do fármaco fenotiazínico azul de metileno (AM) em soluções diluídas. O crescimento linear, camada por camada, desses filmes foi verificado e monitorado por espectroscopia de absorção no UV-Vis. Verificou-se por FTIR que o crescimento dos filmes LbL e LB é determinado por interações eletrostáticas entre os fosfolipídios e o polieletrólito catiônico PAH utilizado como camada de suporte, favorecendo o crescimento dos filmes com fosfolipídios aniônicos. A morfologia foi analisada através de microscopias ópticas, AFM e MEV, revelando que os fosfolipídios estruturam-se como vesículas nos filmes LbL e monocamadas nos filmes LB. Filmes LbL e LB de fosfolipídios com diferentes espessuras foram então depositados sobre eletrodos interdigitados de Pt formando unidades sensoriais que foram aplicadas na detecção de AM via espectroscopia de impedância. Os resultados mostraram que as diferentes arquiteturas moleculares dos filmes LbL e LB levam a respostas elétricas distintas e permitem a detecção de AM em concentrações de nanomolar. A técnica SERS foi utilizada para obter informações estruturais do sistema AM/fosfolipídios nos níveis de diluição alcançados via espectroscopia de impedância. Para tanto, monocamadas LB foram depositados sobre filmes evaporados com 6 nm de Ag e nanopartículas de Ag foram dispersas no interior dos filmes LbL. A presença da Ag na forma de nanopartículas em ambos os casos permitiu a obtenção... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Thin films of anionic (DPPG and CLP) and zwiterionic (DPPC and DOPC) phospholipids with different molecular architectures were fabricated using the layer-by-layer (LbL) and Langmuir-Blodgett (LB) techniques. The main goal of this work was to explore the Application of these distinct molecular architectures in the detection of high diluted solutions of methylene blue (MB), a phenothiazine derivative drug. The linear growth, layer by layer, of these films was verified and monitored by UV-Vis absorption spectroscopy. It was found by FTIR that electrostatic interactions among the phosholipids and the supporting layer of PAH (cationic electrolyte) are the main driving force allowing the growth of the LbL and LB films, which favors the growth of the cationic phospholipids. The morphology was analyzed through optical microscopy, AFM and SEM, revealing that the phospholipids are structured as vesicles in the LbL films and as monolayers in the LB films. Different thickness of LbL and as monolayers in the LB filma containing phospholipids were deposited onto Pt interdigitated electrodes forming sensingn units applied in the detection of MB using impedance spectroscopy. The results showed that the different molecular architectures of the LbL and LB films take to different eletrical responses and allow the MP detection in concentrations of nanomolar. The SERS technique was applied to obtain structural information of the system MP/phospholipids at the dilution levels reached via impedance spectroscopy at the dilution levels reached via impedance spectroscopy. Then, LB monolayers were deposited onto 6nm of Ag evaporated films with and Ag evaporated films with and Ag nanoparticles were dispersed within the LbL films. The presence of Ag forming nanoparticles in both cases played a key role in achieving the MB SERRS signal allowing obtaining the detection in high dilution levels, approaching... (Complete abstract click electronic access below) / Mestre

The structural and stress changes in molybdenum/amorphous silicon (Mo/a-Si) EUV reflecting multilayers during annealing at 316��C were studied. The amorphous interlayers, with an Mo:Si stoichiometry of 1:2, grew during annealing. The residual stresses in each component of the multilayer also changed significantly. Through high resolution electron microscopy, selected area electron diffraction, and x-ray diffraction of the crystalline Mo, the biaxial tensile stresses were shown to increase from approximately two to about ten GPa in the lateral direction, parallel to the interface plane. The compressive strains developed in the vertical direction, perpendicular the interface plane, are consistent with a Poisson contraction calculated from bulk elastic properties. Laser deflectometry measurements of thicker (non-EUV, 0.1��m) amorphous silicon showed compressive stress relaxation in the amorphous silicon with annealing, which may also take place in the thin (EUV) silicon. The residual stress in a 40 bilayer EUV film changes from about -0.5 GPa to about +1.5 GPa. / Graduation date: 1996

Multilayered structures have many application in industry and society: they have peculiar properties and serve a variety of purposes, like structural support, thermal insulation, vibrational and acoustic isolation. This thesis concerns the prediction of sound transmission in multilayered structures. Two problems are herein investigated: the transmission of energy through structures and the transmission of energy along structures. The focus of the analysis is on the mid to high frequency range. To predict sound transmission in these structures, statistical energy analysis (SEA) is used.SEA models are devised for the prediction of the sound reduction index for two kinds of multilayered structures, double-walls used in buildings and trim-panels in vehicles; the double-walls comprise an air cavity in between flat plasterboard or glass plates, whereas the trim-panels a porous layer in between curved aluminium and rubber layers. The SEA models are based upon the wave-types carrying energy. The novelty in these SEAs is an element describing the waves in the air cavity, or in the porous layer, fully coupled to the mass-impeded external layers. Compared to measurements, the proposed SEA performs well: for double-walls, it performs better than previous models; for trim-panels, it is an original result. The parameters of the new SEA element, such as modal density, are derived from the coupling equations describing the fully coupled waves. For double-walls, these equations are derived via Newton's laws. For trim-panels, a variational approach based upon a modified Hamilton's principle valid for non-conservative systems is preferred, because it is a powerful machinery for deriving equations of motion and coupling conditions of a medium as complex as the porous layer. The modified Hamilton's principle for non-conservative systems is based upon a self-adjoint functional analogous to the Lagrangian, inspired by Morse and Feshbach's construction. A self-adjoint variational principle for Biot's equations in the displacement formulation is devised. An equivalent mixed formulation is obtained changing the coordinates of the displacement formulation via Lagrange multipliers. From this mixed formulation, the Lagrangian for a porous material with a limp frame is derived, which yields the continuity of the total displacement of the porous layer. Lagrange multipliers help to obtain the correct coupling functionals between a porous material and a solid. The Lagrange multipliers introducing the continuity of the frame and the solid displacements equal the traction of the in-vacuo frame, thus disappearing if the latter is limp. Measurements to gather material parameters for a Biot model of the porous layer have been conducted.The effects of spatial energy decay in the transmission along structures predicted by SEA is studied: a major effect is the increased relevance of indirect coupling loss factors between SEA elements. This may jeopardize the usefulness of SEA at higher frequencies. / <p>QC 20130218</p>

Graduation date: 1993

In this research, the amorphous/nanocrystalline ZrCu/Cu multilayered thin films with various conditions such as individual layer thickness, total layer thickness, and interface type have been successfully fabricated by the multi-gun sputtering processes. To investigate the mechanical properties and deformation behaviors of substrate-supported ZrCu/Cu multilayered thin films, these films deposited on the Cu or polyimide foils were prepared for tensile testing. Firstly, the tensile behaviors of the monolithic ZrCu thin film metallic glass and the ZrCu/Cu multilayered thin films deposited on the pure Cu foils are systematically examined. The extracted tensile modulus and strength of the 1-£gm-thick multilayered thin films are in good agreement with the theoretical iso-strain rule of mixture prediction. The extracted 2-£gm-thick multilayered film data are lower, but can be corrected back by considering the actual intact cross-sectional area during the tensile loading. Moreover, the current results reveal that the ZrCu/Cu multilayered coating exhibit much better tensile performance than the monolithic ZrCu coating. It indicates that the amorphous/nanocrystalline multilayered thin film structure can certainly enhance the mechanical properties of monolithic thin film metallic glasses under tension. Secondly, for the further investigation of tensile response, the polyimide-supported amorphous/nanocrystalline ZrCu/Cu multilayered thin films with various individual layer thicknesses from 10 to 100 nm were prepared. The relatively soft, smooth, and flexible polyimide foils as the substrates in this experiment can undergo sufficient deformation under In this research, the amorphous/nanocrystalline ZrCu/Cu multilayered thin films with various conditions such as individual layer thickness, total layer thickness, and interface type have been successfully fabricated by the multi-gun sputtering processes. To investigate the mechanical properties and deformation behaviors of substrate-supported ZrCu/Cu multilayered thin films, these films deposited on the Cu or polyimide foils were prepared for tensile testing. Firstly, the tensile behaviors of the monolithic ZrCu thin film metallic glass and the ZrCu/Cu multilayered thin films deposited on the pure Cu foils are systematically examined. The extracted tensile modulus and strength of the 1-£gm-thick multilayered thin films are in good agreement with the theoretical iso-strain rule of mixture prediction. The extracted 2-£gm-thick multilayered film data are lower, but can be corrected back by considering the actual intact cross-sectional area during the tensile loading. Moreover, the current results reveal that the ZrCu/Cu multilayered coating exhibit much better tensile performance than the monolithic ZrCu coating. It indicates that the amorphous/nanocrystalline multilayered thin film structure can certainly enhance the mechanical properties of monolithic thin film metallic glasses under tension. Secondly, for the further investigation of tensile response, the polyimide-supported amorphous/nanocrystalline ZrCu/Cu multilayered thin films with various individual layer thicknesses from 10 to 100 nm were prepared. The relatively soft, smooth, and flexible polyimide foils as the substrates in this experiment can undergo sufficient deformation under tension. The modulus and strength of the multilayered thin film are again demonstrated to be consistent with the theoretical iso-strain rule of mixture values. As the individual layer thickness decreases from 100 to 10 nm, the Young¡¦s moduli are only varied slightly. However, the maximum tensile stress exhibits a highest value for the 25 nm layer thickness. The higher crack spacing, or the lower crack density, of this 25 nm multilayer film leads to the highest strength. Thirdly, to avoid the stress and strain incompatibility owing to the mismatch of elastic modulus and strength levels from the connected amorphous/nanocrystalline layers, the Cu-supported amorphous/nanocrystalline ZrCu/Cu multilayered thin films with sharp and graded interfaces were successfully sputtered and examined by tensile testing. The extracted tensile properties of the multilayered films can be compared with the predicted values based on the two-phase and three-phase iso-strain rule of mixture model. The multilayered films with graded interfaces, each about 50 nm thick, consistently exhibit higher tensile strength and elongation. This can be rationalized by the reduced stress and strain incompatibility along the interfaces.

This thesis presents a critical reading of the multilayeredness in contemporary cities through the case of Divanyolu, main road of the historical istanbul. The ground in this case displays the fragmented character, so in order to follow the discontinuities in the morphological, economical, cultural and also hypothetic structures / this study will concentrate on the confrontation of layers within the framework of modernization process in the city. Beyond many possible discussions questioning the multiplicity of Istanbul, this study aims to encompass the specific character of the modernization process observed in Divanyolu. Furthermore, the information derived from the evaluation can suggest an exemplary framework for the new grounds in the multilayered sites, which is actually the other aim of the study. Within this framework, Divanyolu is chosen as a major urban case to discuss the complexity of the stratified ground. It was an example of a stratified ground being the main thoroughfare of the Ottoman Capital, which formed the important network from the Topkapi Palace to the Edirne Gate. The road has been the stage for the modernization process beginning from the 19th century to the present. With the different stage modernization process, the ground displayed the fragmented character. In this thesis, the main dynamics of this partial transformation will be evaluated.

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references. Also available in electronic version. Access restricted to campus users.