Ce travail de thèse porte sur la modélisation des propriétés optiques de diélectriques nanostructurés par des particules métalliques. Nous nous sommes intéressés à deux aspects du problème : la détermination de l’indice effectif et la distribution du champ du plasmon de nanoparticules métalliques dispersées dans de tels milieux. Nous avons développé deux approches numériques. La première étude a été consacrée à la modélisation des parties réelle et imaginaire de l’indice effectif d’un milieu hétérogène. Pour comparer nos résultats de simulations d’indice à l’expérience, nous avons proposé une méthode expérimentale pour la mesure de l'indice de réfraction effectif de solutions colloïdales comportant des nanosphères métalliques ou semiconductrices. La seconde étude traite de la méthode d’extraction de la distribution du champ du plasmon sur la surface d’une nanosphère métallique excitée par une onde électromagnétique plane. Pour l’ensemble de ce travail nous avons tenu compte des paramètres caractéristiques de la matrice hôte et des nanoparticules sur l’indice effectif et le champ du plasmon calculés / This thesis is devoted to modeling of the optical properties of nanostructured dielectrics by metal particles. We interested in two aspects of the problem: the determination of effective index and field distribution of plasmon nanoparticles dispersed in such media. We have developed two numerical approaches. The first is devoted to the simulation of real and imaginary parts of the effective index of heterogeneous medium. In order to compare experience and theory, we have proposed an experimental approach to measure the effective refractive index of colloidal solutions containing metal or semiconductor nanospheres. The second aspect deals with the method of extraction of the field plasmon on the surface of metal nanosphere when it is excited by electromagnetic plane wave. The calculated effective index and field plasmon are done in function of characteristic parameters of nanoparticles and host matrix

Nanopartículas de Fe3O4 e Fe2O3 foram sintetizadas a partir da rota de coprecipitação, em atmosfera de N2, mantendo-se o pH entre 9 e 14 na temperatura ambiente e utilizando como precursores o FeCl2 e FeCl3. Após a síntese, as nanopartículas foram tratadas termicamente a 250, 500 e 800 oC. Para obtenção de um sistema híbrido, foram sintetizadas nanopartículas de ouro sobre as nanopartículas de óxido previamente tratadas em diferentes temperaturas. As amostras foram caracterizadas por UV-Vis, difratometria de Raios-X (DRX), microscopia eletrônica de transmissão (MET), microscopia eletrônica de transmissão de alta resolução (MET-AR), espectroscopia no na região do infravermelho (FTIR), magnometria de amostra vibrante (VSM) e espectroscopia Mossbauer (EM), e aplicadas para produção de hidrogênio promovendo a decomposição da hidrazina. Os resultados mostram a síntese de nanopartículas de óxido de ferro com diâmetro médio de cerca de 7 nm. Quando aquecidas a 250 oC o tamanho médio aumentou para ca. de 11 nm e foi observado uma pequena mudança no comportamento óptico e estrutural, mantendo o comportamento superparamagnetico. Quando aquecidas a 500 oC o tamanho médio aumenta para ca. de 50nm e são observadas mudanças significativas nas propriedades ópticas, morfológicas, estruturais. Adicionalmente observa-se transição de comportamento superparamagnetico para paramagnético. Quando aquecidas a 800 oC os efeitos nas propriedades dos materiais são ainda mais significativos; as partículas apresentam tamanho médio de 200 nm, o espectro de absorção no UV-Vis muda significativamente e as partículas passam a ter comportamento pagamagnético. Os resultados obtidos pelas diferentes técnicas e somadas ao Mossbauer sugerem que as amostras sintetizadas são uma mistura de Fe3O4 e -Fe2O3, quando aquecido a 250 e 500 oC uma mistura de -Fe2O3 e -Fe2O3 e a 800 oC somente -Fe2O3. As nanopartículas de ouro sintetizadas sobre as amostras de oxido de ferro apresentaram tamanho médio de 6,0 nm e não afetaram as propriedades magnéticas dos oxidos. As amostras de óxido com nanopartículas de ouro promoveram a decomposição da hidrazina por rota completa, levando a formação de hidrogênio com seletividade de até 33%. / Fe3O4 and Fe2O3 nanoparticles were synthesized by coprecipitation route carried out under N2 atmosphere, maintaining the pH between 9 and 14 at room temperature and using FeCl2 and FeCl3 as precursors. After synthesis the iron oxide nanoparticles were thermally treated at 250, 500 and 800 oC. To obtain a hybrid system, gold nanoparticles were synthesized on the thermally treated oxide nanoparticles. The samples were analyzed by UV-Vis, X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (MET-AR), spectroscopy in the region of Infrared (FTIR), vibrating sample magnitude (VSM) and Mossbauer, and applied to produce H2 through hydrazine decomposition. The results show the synthesis of Fe3O4 nanoparticles with average diameter of about 7 nm. When heated to 250 oC the average size increased to about 11 nm and a small change in the optical and structural behavior was observed, while the superparamegnetic behaviour was maintained. When heated to 500 °C, the average particle size increase to ca 51nm, significant changes in the optical, morphological and structural properties are observed, in addition to a transition from superparamegnetic to paramagnetic behaviour. When heated to 800 oC the effects on the properties are even more significant; the nanoparticles increase to ca. 200 nm, the absorption spectrum in UV-Vis changes significantly and the particles present paramagnetic behaviour. The results suggest that when heated to 250 and 500 oC a mixture of -Fe2O3 e -Fe2O3 is obtained, after heating at 800 oC only -Fe2O3 is observed. The gold nanoparticles synthesized on the iron oxides present average size of 6.0 nm, and did not affect the magnetic properties of the oxides. The iron oxides/gold nanoparticle samples were efficiently applied to produce hydrogen, promoting the decomposition of hydrazin. The selectivity to hydrogen reached up to 33%.

Surface plasmon resonance (SPR) biosensors have attracted great attention in scientific research in the past three decades. Extensive studies on the immobilisation of biorecognition elements have been conducted in pursuit of higher sensitivity, but trialled formats have focussed on a thin layer modification next to the plasmon film, which usually requires in situ derivatization. This thesis investigates an 'off-chip' immobilisation strategy for SPR biosensing using silica particles and considers the implications of a particle-modified evanescent field on the signal amplitude and kinetics, for an exemplar affinity binding between immobilised IgG and its anti-IgG complement. Submicron silica particles were synthesized as carriers for the bio-recognition elements. They were then immobilised to form a sub-monolayer on the gold film of an SPR biosensor using two methods: thiolsilane coupling and physical adsorption aided by mechanical pressure. The bio-sensitivity towards an antigen/antibody interaction was lower than an SPR biosensor with an alkanethiolate SAM due to the difference in ligand capacity and position in the evanescent field. The binding kinetics of antigen/antibody pair was found to follow the Langmuir model closely in a continuous flow configuration but was heavily limited by the mass transport from the bulk to the sensor surface in a stop-flow configuration. A packed channel configuration was designed with larger gel particles as ligand carriers, packed on top of a gold film to create a column-modified SPR biosensor. This sensor has comparable bio-sensitivity to the previous sub-monolayer particle-modified systems, but the binding and dissociation of the analyte was heavily dependent on mass transport and binding equilibria across the column. A bi-directional diffusion mechanism was proposed based on a two-compartment mass transport model and the expanded model fitted well with the experimental data. The column-modified sensor was also studied by SPR imaging and analyte band formation was observed and analysed. Using the lateral resolution, a multiplexing particle column configuration was explored, and its potential in distinguishing a multicomponent analyte.

In this thesis study, the surface/interface plasmon excitations in different Si nanostructures were revealed through the EELS study in TEM/STEM. In the case of the planar boundary such as the wedge-like specimen, the spatially resolved EELS results disclose the dependence of the intensity and the position of the interface plasmon peak on the sample thickness. In the case of the Si-core/ SiO2-shell nanoparticles, we found that the SP/IP peak will firstly red-shifts with the increase of the SiO2 shell thickness and eventually levels off . As the aspect ratio of the Si nanoparticles increases, (from spherical particle to nanorod and nanowire), the SP/IP will split into two branches: transverse and longitudinal modes. We also found the intensity ratio of the transverse/longitudinal mode excitations depends on the diameter of the Si core size in the nanostructures. In the one-dimensional interacting Si nanoparticle chains, the Si nanoparticles were embedded in the SiO 2 shell, the splitting of the SP excitation into transverse and longitudinal modes was also observed. As the inter-particle distance reduces to several nanometers, the coupling of the IP excitation between the adjacent particles becomes significant, and results in the local field enhancement in-between the two particles. This is directly visualized using EFTEM imaging in TEM/STEM. / Surface/interface plasmons (SP/IP) are the plasmons confined at specific boundaries, describing the surface/interface charge density oscillation. They are generated when the scattered electromagnetic wave with its scattering vector component parallel to the boundary propagates along the surface/interface. Study of surface plasmon resonance in noble metals such as gold and silver nanoparticles have started decades ago, and recent interests are focused on the plasmonic properties of individual nanoparticles, as enabled by the size/shape control in the nanostructure growth and advances made in the characterization methodologies. Besides the noble metals, semiconductor such as silicon also attracts much attention for its plasmonic behavior. The surface/interface plasmon resonance frequency of Si-based nanostructures occurs at relatively higher energies (compared to Au and Ag), making it a perfect system to be studied using electron energy loss spectroscopy (EELS) based techniques. When performed in a scanning transmission electron microscope (STEM), such a technique enjoys excellent spatial resolution, and can map the local plasmonic properties of individual nanostructures. / The plasmon excitation depends sensitively on not only the material dielectric properties but also the geometrical configurations of the material. In the present thesis work, silicon-based nanostructures with planar, spherical, and cylindrical boundaries were investigated using both experimental and theoretical approaches, with focus on the plasmon oscillation originating from the Si/SiO 2 interface. The specimens employed include silicon/silica thin films, Si-core/SiO2-shell nanoparticles with different aspect ratios and spherical-shaped nanoparticle chains, as well as Si-core/SiO2-shell nanocables. / Wang, Xiaojing = 低維硅納米結構表界面等離激元之研究 / 王笑靜. / Adviser: Li Quan. / Source: Dissertation Abstracts International, Volume: 73-01, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 118-122). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Wang, Xiaojing = Di wei gui na mi jie gou biao jie mian deng li ji yuan zhi yan jiu / Wang Xiaojing.

Shao, Lei = 金顆粒納米晶中角度、能量和空間位置分辨的表面等離子共振耦合 / 邵磊. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references. / Abstracts in English and Chinese. / Shao, Lei = Jin ke li na mi jing zhong jiao du, neng liang he kong jian wei zhi fen bian de biao mian deng li zi gong zhen ou he / Shaolei. / Abstract --- p.1 / 摘要 --- p.iii / Acknowledgement --- p.v / Table of Contents --- p.vii / List of Figures --- p.ix / List of Tables --- p.xiv / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Localized Surface Plasmon Resonances of Noble Metal Nanocrystals --- p.3 / Chapter 1.1.1 --- Dielectric Functions of Noble Metal Nanocrystals --- p.3 / Chapter 1.1.2 --- Absorption and Scattering of Light by Noble Metal Nanoparticles --- p.7 / Chapter 1.2 --- Coupling between Localized Surface Plasmons --- p.14 / Chapter 1.2.1 --- Theoretical Treatments for Plasmon Coupling --- p.14 / Chapter 1.2.2 --- Unique Properties Resulting from Plasmon Coupling --- p.15 / Chapter 1.2.3 --- Applications Based on Plasmon Coupling --- p.17 / Chapter 1.3 --- Outline of Thesis --- p.18 / Chapter 2. --- Growth of Gold Nanocrystals and Characterization Techniques --- p.26 / Chapter 2.1 --- Growth of Gold Nanocrystals --- p.26 / Chapter 2.2 --- Characterization Techniques --- p.29 / Chapter 3. --- Surface Plasmon Coupling in Homodimers of Elongated Gold Nanocrystals --- p.34 / Chapter 3.1 --- Formation of Homodimers of Elongated Gold Nanocrystals --- p.35 / Chapter 3.2 --- Angle-Resolved Plasmon Coupling in Gold Nanorod Dimers --- p.37 / Chapter 3.2.1 --- Experimental Results --- p.39 / Chapter 3.2.2 --- FDTD Calculations --- p.43 / Chapter 3.2.3 --- Dipolar Modeling --- p.49 / Chapter 3.3 --- Effect of the Head Shape on the Plasmon Coupling --- p.57 / Chapter 3.4 --- Summary --- p.60 / Chapter 4. --- Surface Plasmon Coupling in Heterodimers of Gold Nanocrystals --- p.64 / Chapter 4.1 --- Formation of Heterodimers of Gold Nanocrystals --- p.65 / Chapter 4.2 --- Energy-Resolved Plasmon Coupling in Gold Nanorod Heterodimers --- p.67 / Chapter 4.3 --- Position-Resolved Plasmon Coupling in Gold Nanorod-Nanosphere Heterodimers --- p.70 / Chapter 4.3.1 --- Experimental Results --- p.71 / Chapter 4.3.2 --- FDTD Calculations --- p.75 / Chapter 4.4 --- Summary --- p.83 / Chapter 5. --- Summary and Conclusion --- p.87

Yu, Tsz Tat. / "December 2010." / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 143-147). / Abstracts in English and Chinese. / Abstract --- p.2 / 摘要 --- p.4 / Acknowledgements --- p.5 / List of Figures --- p.6 / List of Tables --- p.12 / List of Abbreviations --- p.13 / Table of Contents --- p.14 / Chapter Chapter 1 --- Introduction --- p.17 / Chapter Chapter 2 --- Literature Review / Chapter 2.1 --- Surface Plasmon Wave --- p.19 / Chapter 2.2 --- Excitation of Surface Plasmon --- p.23 / Chapter 2.3 --- Surface Plasmon Coupling --- p.24 / Chapter 2.4 --- Surface Plasmon Resonance Detection Techniques --- p.33 / Chapter 2.5 --- Applications of SPR biosensors --- p.39 / Chapter Chapter 3 --- Theory of irradiance modulator / Chapter 3.1 --- Polarization --- p.44 / Chapter 3.2 --- Optical polarizer --- p.45 / Chapter 3.3 --- Liquid Crystal Modulator --- p.49 / Chapter 3.4 --- Irradiance Modulator --- p.52 / Chapter Chapter 4 --- LCM characterization / Chapter 4.1 --- Single LCM Transmittance driven by pure square wave --- p.66 / Chapter 4.2 --- Single LCM Reflectance driven by 50:50 STAM wave --- p.70 / Chapter 4.3 --- Multiple LCMs Reflectance driven by 90:10 STAM wave --- p.73 / Chapter Chapter 5 --- Background of phase measurement / Chapter 5.1 --- From holography to shearography --- p.77 / Chapter 5.2 --- From static Mach-Zehnder interferometer to differential-phase Mach-ZehnderZ interferometer --- p.81 / Chapter 5.3 --- From differential-phase imaging to pixel-referencing imaging --- p.86 / Chapter Chapter 6 --- Pixel-referencing data processing / Chapter 6.1 --- Background --- p.89 / Chapter 6.2 --- Procedures --- p.94 / Chapter 6.3 --- Experimental results --- p.98 / Chapter 6.4 --- Sensor resolution --- p.116 / Chapter 6.5 --- Performance comparison between single-beam LCM and Mach Zehnder configuration --- p.119 / Chapter Chapter 7 --- Discussions / Chapter 7.1 --- Experiment precautions --- p.136 / Chapter 7.2 --- Linear curve fitting --- p.137 / Chapter 7.3 --- Hardware limitation: Low frame rate --- p.138 / Chapter 7.4 --- Matching oil and glass slide --- p.139 / Chapter Chapter 8. --- Conclusions --- p.141 / References --- p.143 / Appendix / Chapter A1 --- "Concentration, Refractive Index and Dielectric constant of Sodium Chloride Solution (20°C)" --- p.148 / Chapter A2 --- Liquid Crystal Modulator Specification --- p.149 / Chapter A3 --- "Digital-to-analogue Converter Device (NI, PCI6036E) Datasheet" --- p.150 / Chapter A4 --- "CCD Camera (Lumenera, Infinity) Datasheet" --- p.151 / Chapter A5 --- Flow chart of SPR phase extraction --- p.152 / Chapter A6 --- Codes of SPR phase extraction in modules --- p.153

At the heart of the field of photonics is the control of the reflection and transmission of light. Plasmonics looks at this problem of control of electromagnetic radiation in the context of surface plasmon polaritons (SPP). SPPs are propagating electromagnetic modes localized at the interfaces between media with positive and negative permittivities. Their excitation can accompany the enhancement of transmission, reflection, or absorption of EM radiation. There are a number of ways to excite SPPs and this work looks at several geometries and analyzes the transmission and reflection characteristics using a numerical approach based on the finite element method.<p> The first method of excitation is by incident evanescent wave that was totally internally reflected from an earlier interface. It is shown that an evanescent wave can excite SPPs and create resonant transmisison. It is also found that high values of dissipation limit transmission and instead create resonant absorption. The second method involves the modulation of the negative permittivity of the plasma slab itself. Numerical results are compared to analytical ones and are in good agreement because harmonics of the solution above the first are negligible. An investigation of transmission through a plasma slab with a single thin diffraction grating placed nearby follows. Analytical and numerical calculations show that a single thin grating is sufficient to create transmission resonance. It is found that for large values of diffraction grating modulation parameter, higher harmonics, usually not accounted for in analytical solutions, results in discrepancies between analytical and numerical results. The next geometry considered is of a plasma layer with only part of it having modulated permittivity. The presence of modulation of only part of the plasma layer is shown to create transmission and reflection resonances. By tailoring parameters of the system, it is shown how the resonant frequencies can be shifted. The final geometry considers a copper grating beside a plasma and transmission of a radio frequency wave. Even though the copper used here in this simulation is very absorbing, there are ranges of frequencies when transmission or reflection are enhanced.

Nobel metal nanoparticles that exhibit plasmon resonances in the visible and near infrared have been of great interest in recent years. Strong light-matter interactions on the nanoscale have a range of interesting properties that may be useful in applications in medicine, sensing, solar energy harvesting and information processing. Depending on the application, particle materials and geometries can be optimized for performance. A novel method of quantifying individual nanoparticle scattering cross-sections by comparing experiments with analytical theory for gold nanospheres is proposed and utilized. Results show that elongated particles scatter very brightly for their volumes. This brightness is due to a strong longitudinal plasmon resonance that occurs in the near infrared – where gold has minimal loss. Elongated particles, such as nanorods, are therefore, ideal for applications that rely on particles scattering brightly in small spaces, such as biological imaging. Next, gold nanobelts are discussed and characterized. These novel structures are akin to nanowires, but with a small, rectangular cross-sectional geometry. Gold nanobelts are shown to exhibit a strong transverse resonance that has never been reported previously in nanowires. The transverse resonance is shown to shift linearly with crosssectional aspect ratio. Other interesting products from the nanobelt synthesis, tapered and split nanobelts, are discussed. Gold nanobelts also support longitudinal propagating plasmons, and have the smallest cross-sectional area of any elongated plasmonic structure that has been reported to do so. By analyzing the output tip signal of propagating plasmons for nanobelts of different lengths, the decay length is measured. Finite Difference Time Domain simulations and polarization measurements show the fundamental, azimuthally symmetric mode is very strong for thin structures such as these, but decays much more quickly than a higher-order mode, which begins to dominate at longer lengths. The cross-sectional mode area is given, illustrating the high confinement of plasmons in these structures. A figure of merit that takes into account both confinement and propagation length is calculated to be 1300 for the higher-order mode, the highest reported for nanoscale plasmonic waveguides. The high figure of merit makes gold nanobelts excellent candidates for studying strong coupling between plasmonic structures and objects that exhibit quantum behavior.

At the heart of the field of photonics is the control of the reflection and transmission of light. Plasmonics looks at this problem of control of electromagnetic radiation in the context of surface plasmon polaritons (SPP). SPPs are propagating electromagnetic modes localized at the interfaces between media with positive and negative permittivities. Their excitation can accompany the enhancement of transmission, reflection, or absorption of EM radiation. There are a number of ways to excite SPPs and this work looks at several geometries and analyzes the transmission and reflection characteristics using a numerical approach based on the finite element method.<p> The first method of excitation is by incident evanescent wave that was totally internally reflected from an earlier interface. It is shown that an evanescent wave can excite SPPs and create resonant transmisison. It is also found that high values of dissipation limit transmission and instead create resonant absorption. The second method involves the modulation of the negative permittivity of the plasma slab itself. Numerical results are compared to analytical ones and are in good agreement because harmonics of the solution above the first are negligible. An investigation of transmission through a plasma slab with a single thin diffraction grating placed nearby follows. Analytical and numerical calculations show that a single thin grating is sufficient to create transmission resonance. It is found that for large values of diffraction grating modulation parameter, higher harmonics, usually not accounted for in analytical solutions, results in discrepancies between analytical and numerical results. The next geometry considered is of a plasma layer with only part of it having modulated permittivity. The presence of modulation of only part of the plasma layer is shown to create transmission and reflection resonances. By tailoring parameters of the system, it is shown how the resonant frequencies can be shifted. The final geometry considers a copper grating beside a plasma and transmission of a radio frequency wave. Even though the copper used here in this simulation is very absorbing, there are ranges of frequencies when transmission or reflection are enhanced.

A new method is developed referred to as Gold Nanorod Optical Modeling Equations (GNOME) for determining the average aspect ratio of gold nanorods in solution. In this method, the observed inhomogeneously broadened optical spectrum is fitted to a number of calculated homogeneously broadened spectra with different aspect ratios having different contributions. From this method, the average aspect ratio is determined. This is a more accurate than the presently used method of TEM. The surface plasmon enhanced fluorescence spectra of gold nanorods are calculated as a function of the aspect ratio and compared to experimental spectra. In this calculation, the inclusion of both the aspect ratio distribution calculated from the GNOME method as well as the incorporation of the intrinsic fluorescence of bulk gold are found necessary to model the enhanced fluorescence spectrum of gold nanorods using previously published equations. The enhanced spectrum decreases rapidly as the aspect ratio increases and the surface plasmon band shift away from the gold interband absorption. Photochemical methods are used to synthesize silver nanoparticles on silica surfaces and gold nanoparticles in solution. The formation silver nanoparticles utilizes benzophenone as a photosensitizing agent to initiate the reaction. The effects of the light source and irradiation time are investigated. The presence of different forms of silica are investigated in the formation of metal nanoparticles. This method produced silver nanoparticles on silica that can be in the form of film or powder that are useful in heterogeneous catalysis. Direct photochemical methods are applied to generate gold nanoparticles from chloroauoroic acid in ethylene glycol in the presence of polyvinylpyrrolidone as a capping material. A detailed mechanism of the formation of the gold nanoparticle is determined. This is done by following the kinetics of formation of the gold nanoparticles after irradiation under different conditions. The disproportionation of the gold ions as well as their reduction by ethylene glycol is found to be important in the formation of the nanoparticles. Photochemical synthesis provides room temperature techniques to generate metal nanoparticles in a variety of environments.