[pt] Neste trabalho é apresentado um estudo sobre nanopartículas metálicas, passando brevemente pela Teoria de Maxwell-Garnett do meio efetivo além de ter sido feita uma pequena pesquisa acerca dos trabalhos já existentes nessa área. É apresentada ainda uma proposta de um sensor à fibra óptica baseado no fenômeno da Ressonância Plasmonica de Superfície Localizada, que utiliza essas nanopartículas cujas propriedades ópticas são sensíveis às mudanças das características do meio onde estão imersas. Esse tipo de sensor é uma ferramenta simples e muito eficiente, além de ser de baixo custo financeiro. A descrição deste sensor mostra ainda três processos distintos de fabricação dessas nanopartículas, as configurações utilizadas para a aquisição dos dados experimentais, e a análise dos mesmos, incluindo a simulação computacional feita para o melhor entendimento dos resultados obtidos. / [en] In this work a study about metallic nanoparticles is presented. A brief revision of the Maxwell-Garnett Theory for the effective medium is made, in addition to a bibliographical research concerning the existing works on the topic. A proposal of a fiber optic sensor based in the Localized Surface Plasmon Resonance phenomena using these metallic nanoparticles, whose optic properties are sensible to changes in the medium in which they are immersed, is also made. This kind of sensor is a simple and efficient tool, in addition to also having low financial cost. Three distinct processes for fabrication of these nanoparticles are discussed. The setups used for the acquisition of the experimental data and the analysis of this data, including the computational simulation made to improve the understanding of the obtained results, are also discussed.

The content of this thesis is based upon the interaction of light with metallic nanoparticles arranged in different array geometries. An incident electric field (light) can force the conduction electrons of a metallic nanoparticle to oscillate. At particular frequencies, in the optical regime for gold and silver particles, absorption and scattering of the light by the particle is enhanced, corresponding to the particle plasmon resonance. The spectral position and width of the particle plasmon resonance of an isolated single particle may be tuned by adjusting its size and shape, thus changing the surface charge distribution. Periodic arrays of particles offer additional control over the frequency and width of the resonance attributed to the re-radiating (scattering) property of plasmonic particles. By fabricating arrays with a pitch comparable to the wavelength of an isolated single particle plasmon resonance, a coherent interaction between particles may be produced, known as surface lattice resonances (SLRs). The electromagnetic coupling between in-plane particle plasmon modes for different particle array geometries is explored through experiment and theory. Firstly, SLRs in square, hexagonal and honeycomb arrays are investigated by normal-incidence extinction measurements and compared to a simple-coupled dipole model. Secondly, to verify the nature of the coupling between the scattered electric field associated with particle resonances, the incident electric field polarization-dependence of the extinction of rectangular arrays and chains is studied. Thirdly, the optical response of square arrays with a symmetric two-particle basis is investigated, particularly the retardation of the scattered electric field between particles in a pair. Fourthly, square arrays with an asymmetric two-particle basis are fabricated to explore the symmetric (dipole moments of both particles are parallel) and anti-symmetric (dipole moment of both particles anti-parallel) SLRs, excited by normal-incidence light.

<p>The aims of this study are to first immobilize positively charged gold nanorods to negatively charged cell culture surfaces. Second, to use polyelectrolytes for controlling the distance between gold nanorods and fluorophores. This is used to optimally determine the distance, of which maximum fluorescence enhancement is achieved, between gold nanorods and fluorophores. In order to approach these aims, we use UV/VIS absorption spectroscopy, fluorescence spectroscopy, atomic force microscopy, and ellipsometry. The results show that we could control the immobilization of gold nanorods on plastic microwell plates and create reproducible polyelectrolyte layers, in order to control the distance between the gold nanorods and fluorophores. In addition, the localized surface plasmon resonance wavelength red shifted as the PELs increased. In conclusion, we found that the maximum fluorescence enhancement of the fluorophores (Cy7) is about 2.3 times at a fluorophores-nanoparticles separation of approximately 9-12 nm. This work contributes some research information towards the design of optical biochip platforms based on plasmon-enhanced fluorescence.</p>

The aims of this study are to first immobilize positively charged gold nanorods to negatively charged cell culture surfaces. Second, to use polyelectrolytes for controlling the distance between gold nanorods and fluorophores. This is used to optimally determine the distance, of which maximum fluorescence enhancement is achieved, between gold nanorods and fluorophores. In order to approach these aims, we use UV/VIS absorption spectroscopy, fluorescence spectroscopy, atomic force microscopy, and ellipsometry. The results show that we could control the immobilization of gold nanorods on plastic microwell plates and create reproducible polyelectrolyte layers, in order to control the distance between the gold nanorods and fluorophores. In addition, the localized surface plasmon resonance wavelength red shifted as the PELs increased. In conclusion, we found that the maximum fluorescence enhancement of the fluorophores (Cy7) is about 2.3 times at a fluorophores-nanoparticles separation of approximately 9-12 nm. This work contributes some research information towards the design of optical biochip platforms based on plasmon-enhanced fluorescence.

Noble metal nanoparticles supporting localized surface plasmon resonances (LSPR) have been extensively investigated for label free detection of various biological and chemical interactions. When compared to other optical sensing techniques, LSPR sensors offer label-free detection of biomolecular interactions in localized sensing volume solutions. However, these sensors also suffer from a major disadvantage – LSPR sensors remain highly susceptible to interference because they respond to both solution refractive index change and non-specific binding as well as specific binding of the target analyte. These interactions can severely compromise the measurement of the target analyte in a complex unknown media and hence limit the applicability and impact of the sensor. In spite of the extensive amount of work done in this field, there has been a clear absence of efforts to make LSPR sensors immune to interfering effects. The work presented in this document investigates, both experimentally and numerically, dual- and tri-mode LSPR sensors that utilize the multiple surface plasmon modes of gold nanostructures to distinguish target analyte from interfering bulk and non-specific binding effects. Finally, a series of biosensing experiments are performed to examine various regeneration assays for LSPR sensors built on indium tin oxide coated glass substrate.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第19959号 / 理博第4226号 / 新制||理||1607(附属図書館) / 33055 / 京都大学大学院理学研究科化学専攻 / (主査)教授 寺西 利治, 教授 倉田 博基, 教授 島川 祐一 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

No description available.

The first thermal cycling experiments of ionic self-assembled multilayer (ISAM) films have been reported examining their survivability through repeated thermal cycles from -20° C to 120° C in ambient atmospheric conditions. The films were constructed from alternating layers of Nile Blue A and gold nanoparticles which provided a strong absorbance in the optical wavelength range. No degradation of the optical characteristics of the ISAM films was observed [1]. Techniques for measuring the capacitance and resistivity of various ISAM films have also been developed allowing for a more complete electrical characterization of ISAM films. Capacitance measurements enabled a calculation of the dielectric function and breakdown field strength of the ISAM films. The capacitance measurement technique was verified by measuring the dielectric function of a spin-coated thin film PMMA, which has a well characterized dielectric function [2]. Surface-enhanced Raman spectroscopy (SERS) has been studied as a possible detection method for malignant melanoma revealing spectral differences in blood sera from healthy horses and horses with malignant melanoma. A SERS microscope system was constructed with the capability of resolving the Raman signal from biologically important molecules such as beta-carotene and blood sera. The resulting Raman signals from sera collected from horses with malignant melanoma were found to have additional peaks not found in the Raman signals obtained from sera collected from healthy horses. A systematic analysis of the combination of absorbance and fluorescence signals of blood sera collected from populations of healthy dogs and dogs with cancer has resulted in a rapid and cost-effective method for monitoring protein concentrations that could possibly be used as part of a cancer screening process. This method was developed using the absorbance and fluorescence signals from known serum proteins, the combinations of which were used to match the absorbance and fluorescence signals of blood sera allowing for an accurate determination of protein concentrations in blood sera [3]. Finally, a novel method for measuring the melting point of DNA in solution using capacitance measurements is presented. This method allows for the determination of the melting temperature as well as the melting entropy and melting enthalpy of DNA strands. Two different short strands of DNA, 5'-CAAAATAGACGCTTACGCAACGAAAAC-3' along with its complement and 5'-GGAAGAGACGGAGGA-3' along with its complement were used to validate the technique as the characteristics of these strands could be modeled using theoretical methods. This experimental technique allows for the precise determination of the melting characteristics of DNA strands and can be used to evaluate the usefulness of theoretical models in calculating the melting point for particular strands of DNA. Additionally, a micro-fluidic device has been proposed that will allow for a rapid and cost-effective determination of the melting characteristics of DNA [4]. / Ph. D.

<p>Gold nanoparticles exhibit remarkable optical properties and could prove useful in sensitive biosensing applications. Upon illumination gold nanoparticles produce localized surface plasmons, which influence nearby fluorophores and an enhancement in their fluorescence intensity can be observed. This property makes gold nanoparticles attractive for enhancing optical signals.</p><p>In this project gold nanoparticles were functionalized with an antibody and immobilized to the surface of an existing biochip platform based on fluorescence. The aim was to investigate the possibility of obtaining an increased fluorescence signal from the gold nanoparticles. Two different conjugation procedures were investigated, direct physisorption and covalent attachment of the antibodies to the particles. Activity of bound antibodies was confirmed in both cases.</p><p>The on-chip fluorescence intensity produced by the different conjugates was monitored by use a specialized fluorescence reader designed for point-of-care use. AFM and SEM were used to determine the surface concentration of particles. A correlation between the produced fluorescence intensity and the surface concentration could be seen.</p>

Gold nanoparticles exhibit remarkable optical properties and could prove useful in sensitive biosensing applications. Upon illumination gold nanoparticles produce localized surface plasmons, which influence nearby fluorophores and an enhancement in their fluorescence intensity can be observed. This property makes gold nanoparticles attractive for enhancing optical signals. In this project gold nanoparticles were functionalized with an antibody and immobilized to the surface of an existing biochip platform based on fluorescence. The aim was to investigate the possibility of obtaining an increased fluorescence signal from the gold nanoparticles. Two different conjugation procedures were investigated, direct physisorption and covalent attachment of the antibodies to the particles. Activity of bound antibodies was confirmed in both cases. The on-chip fluorescence intensity produced by the different conjugates was monitored by use a specialized fluorescence reader designed for point-of-care use. AFM and SEM were used to determine the surface concentration of particles. A correlation between the produced fluorescence intensity and the surface concentration could be seen.