No description available.

Metal nanostructures, with their extraordinary optical properties, have attracted great attention in recent years. Subwavelength-scaled metal elements, without involving array effects, have the unique ability to confine or route light at the nano-scale. In this thesis, we provide three topics relating to the manipulation of light using metal nanostructures. We first present a theory to solve the end-face reflection of a subwavelength metal stripe, which is beneficial to the design of optical resonator antennas. Subsequently, we take the advantage of the destructive interference among triple nano-slits to sharpen the focus beam in the near-field at near-infrared wavelengths, which is of interest to the study of near-field optical phase imaging and lithography. Lastly, we demonstrate a rectangular subwavelength aperture quad to convert linearly polarized radiation to a radially polarized beam, which is useful to create a deep-subwavelength focus and for optical trapping. / Graduate

Thesis (Ph. D.)--University of Canterbury, 2006. / Typescript (photocopy). "1st of February 2006." Includes bibliographical references (p. [217]-230). Also available via the World Wide Web.

Surface plasmons have been attracted extensive interests in recent decades due to the novel properties in nanometer sized dimensions. My work focused on the novel optical properties of metal nanostructures based on surface plasmons using theoretical simulation methods. In the first part, we investigated metal nanofilms and nanorods and demonstrated that extremely low scattering efficiency, high absorption efficiency and propagation with long distance could be obtained by different metal nanostructures. With a perforated silver film, we demonstrated that an extremely low scattering cross section with an efficiency of less than 1% can be achieved at tunable wavelengths with tunable widths. The resonance wavelength, width, and intensity are influenced by the shape, size and arrangement pattern of the holes, as well as the distance separating the holes along the polarization direction. The extremely low scattering could be used to obtain high absorption efficiency of a two-layer silver nanofilm. Using the discrete dipole approximation method, we achieved enhanced absorption efficiencies, which are close to 100%, at tunable wavelengths in a two-layer silver thin film. The film is composed of a 100 nm thick perforated layer facing the incident light and a 100 nm thick solid layer. Resonance wavelengths are determined by the distances between perforated holes in the first layer as well as the separation between two layers. The resonance wavelengths shift to red with increasing separation distance between two layers or the periodic distance of the hole arrays. Geometries of conical frustum shaped holes in the first layer are critical for the improved absorption efficiencies. When the hole bottom diameter equals the periodic distance and the upper diameter iv is about one-third of the bottom diameter, close to unit absorption efficiency can be obtained. We examined the electromagnetic wave propagation along a hollow silver nanorod with subwavelength dimensions. The calculations show that light may propagate along the hollow nanorod with growing intensities. The influences of the shape, dimension, and length of the rod on the resonance wavelength and the enhanced local electric field, |E|2 , along the rod were investigated. In the second part, a generalized electrodynamics model is proposed to describe the enhancement and quenching of fluorescence signal of a dye molecule placed near a metal nanoparticle (NP). Both the size of the Au NPs and quantum yield of the dye molecule are crucial in determining the emission intensity of the molecule. Changing the size of the metal NP will alter the ratio of the scattering and absorption efficiencies of the metal NP and consequently result in different enhancement or quenching effect to the dye molecule. A dye molecule with a reduced quantum yield indicates that the non-radiative channel is dominant in the decay of the excited dye molecules and the amplification of the radiative decay rate will be easier. In general, the emission intensity will be quenched when the size of metal NP is small and the quantum yield of dye molecule is about unity. A significant enhancement factor will be obtained when the quantum yield of the molecule is small and the particle size is large. When the quantum yield of the dye molecule is less than 10-5 , the model is simplified to the surface enhanced Raman scattering equation

Type 2 diabetes or adult onset diabetes, has been a global epidemic for the past two decades, and the number of new cases accelerates every year. Insulin resistance is one of the major factors behind this, wherein the insulin receptor, which signals to regulate glucose levels, based on the hormone insulin, loses its sensitivity. Obesity is one other major concern which is caused due to the improper balance between the caloric intake and the energy utilized. Gastric bypass surgeries (GBP) are performed to avert obesity. However, a beneficial side-effect is that the state of insulin resistance is reset to near baseline levels within a few days after the procedure. The reason behind this remains unexplained, with possible humoral effects, hypothesized to occur after the bariatric procedure. In this work, high-five insect cell line was utilized to recombinantly produce full length insulin receptors (IR). However commercially sourced IR ectodomains (eIR – soluble version of the full length IR with the completely extracellular α subunits along with extracellular and transmembrane regions of the β subunit), were used to study the interaction. Measuring the kinetics of IR-insulin interactions is critical to improving our understanding of this disease. In this study, a multiplex surface plasmon resonance (SPR) assay was developed for studying the interaction between insulin and the eIR. A scaffold approach was used in which anti-insulin receptor monoclonal antibody 83–7 (Abcam, Cambridge, UK) was first immobilized on the SPR sensorchip by amine coupling, followed by eIR capture. The multiplex SPR system (ProteOn XPR36TM, Bio-Rad Laboratories, Hercules, CA) enabled measurement of replicate interactions with a single, parallel set of analyte injections, whereas repeated regeneration of the scaffold between measurements caused variable loss of antibody activity. The main approach was to replicate the physiological IR-insulin interaction using this assay. It was also observed that insulin at higher concentrations tend to form dimers and hexamers in solution. This was tested using size exclusion chromatography analysis and proved to be true. Therefore an alternative analyte with the similar binding properties and affinity of insulin and at the same time with reduced self- association characteristics was explored. Lispro, the analogue of insulin with reduced self-association properties (generated by swapping of residue 28 and 29 with Lys and Pro respectively) was finally used to study the interaction with eIR. Interactions between recombinant human insulin with eIR-A (A isoform of the insulin receptor ectodomain) followed a two-site binding pattern (consistent with the literature), with a high-affinity site (dissociation constant KD1 = 38.1 ± 0.9 nM) and a low-affinity site (KD2 = 166.3 ± 7.3 nM). The predominantly monomeric insulin analogue Lispro had corresponding dissociation constants KD1 =73.2 ± 1.8 nM and KD2 =148.9 ± 6.1 nM, but the fit to kinetic data was improved when conformational change factor was included in which the high-affinity site was converted to the low-affinity site. Kinetics of interaction of insulin with eIR-A and eIR-B isoforms were then compared. eIR-A bound insulin with apparently higher affinity (with both the binding sites) when compared with eIR-B. This was again consistent with literature that IR-A had two-fold higher affinity for binding insulin than IR-B. The assay was further extended to study the effect of external factors such as glucose, visfatin on this interaction. Glucose (the main biomolecule which is regulated by the IR-insulin interaction) was tested, if it had any direct effect on the interaction. It was observed that glucose did not have any effect on eIR-insulin interactions. Visfatin, an adipocytokine which has been highly debated in literature for its insulin mimetic effects and IR binding properties, was then tested. The standard assay did not provide much insights as the reference channel immobilized with 83-7 monoclonal antibody to the receptor had much affinity for visfatin, leading to non-specific binding and negative responses. Therefore, in an alternative methodology was used - visfatin, Lispro and insulin were immobilized on separate channels along with bovine serum albumin immobilized on reference channel and eIR isoforms used as analyte to study the effect of visfatin on IR. This study showed that visfatin, a higher molecular weight protein compared to insulin, bound both the eIR isoforms. This is consistent with literature that visfatin binds IR at a site distinct from insulin, but the assay described here could not confirm the fact that it mimicked the signalling carried out by IR-insulin binding. Further studies are required to interpret the kinetics of visfatin-eIR interaction. To my knowledge, this is the first SPR assay developed to study eIR-insulin interactions in real-time. This could potentially be extended to study the interaction of insulin with full length insulin receptors and the effect of humoral and other external factors on the interaction, without the need for insulin labelling.

No description available.

The production of an efficient and low cost device has been the ultimate goal in the photovoltaic cell development. The fabrication and application of nanostructured materials in the field of energy conversion has been attracting a lot of attention. In this work, applications of surface plasmons (SPs) and photonic nanostructures to the field of energy conversion, specifically in the area of silicon solar cells and lanthanide energy upconversion (UC) luminescence applications were studied. Enhanced power conversion efficiency in bulk (single crystalline) silicon solar cells was demonstrated using an optimized mixture of the silver and gold nanoparticles (NPs) on the front of the cell to tackle the negative effect in the Au NPs plasmonic application. Then, a comparison of identically shaped metallic (Al, Au and Ag) and nonmetallic (SiO2) NPs integrated to the back contact of amorphous thin film silicon solar cells were investigated to solve a controversy issue in literature. The result indicates that parasitic absorption from metallic NPs might be a drawback to the SPs enhancement. A cost-effective fabrication of large area (5x5 cm2) honeycomb patterned transparent electrode for “folded” thin film solar cell application by combining the nanosphere lithography and electrodeposition were realized. Furthermore, the SPs enhanced tunable energy upconversion from NaYF4:Yb3+/Er3+ NPs in nanoslits were also demonstrated, our results shows that the relative red/green emission can be controlled by different plasmonic mode coupling. / Graduate / phwang@uvic.ca

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