Nowadays plasmonics is rapidly developing areas from fundamental studies to more application driven research. This dissertation contains three different research topics on plasmonics. In the first research topic, by modulating the zone width of a plasmonic zone plate, we demonstrate that a beam focused by a proposed plasmonic zone plate lens can be achieved with higher intensity and smaller spot size than the diffraction-limited conventional zone plate lens. This sub-diffraction focusing capability is attributed to extraordinary optical transmission, which is explained by the complex propagation constant in the zone regions afforded by higher refractive index dielectric layer and surface plasmons. On the other hand, the resulted diffraction efficiency of this device is relatively low. By introducing a metal/dielectric multilayered zone plate, we present higher field enhancement at the focal point. This higher field enhancement originates not only from surface plasmon polaritons-assisted diffraction process along the propagation direction of the incident light (longitude mode), but also from multiple scattering and coupling of surface plasmons along the metal/dielectric interface (transverse mode). In the second research topic, we suggest a novel concept of SERS-active substrate applications. The surface-enhanced Raman scattering enhancement factor supported by gap surface plasmon polaritons is introduced. Due to higher effective refractive index induced by gap surface plasmon polaritons in the spacer region between two metal plates, incident light tends to localize itself mostly in the medium with higher refractive index than its adjacent ones and thereby the lights can confine with larger field enhancement. In the last research topic, we offer a simple structure in which a gold dipole antenna is formed on the SiC substrate. Surface phonon polaritons, counterparts of surface plasmon polaritons in the mid-infrared frequencies, are developed. Due to the synergistic action between the conventional dipole antenna coupling and the resonant excitation of surface phonon polaritons, strong field enhancement in the gap region of dipole antenna is attained. Most of research topics above are expected to find promising applications such as maskless nanolithography, high resolution scanning optical microscopy, optical data storage, optical antenna, SERS-active substrate, bio-molecular sensing and highly sensitive photo-detectors.

In this study, optical behavior of metal nanoparticles having dimensions smaller than the wavelength of visible light is studied experimentally and numerically. Gold (Au) and silver (Ag) nanoparticles are studied due to their superior optical properties when compared to other metals. A compact code based on Discrete Dipole Approximation (DDA) is developed to compute extinction efficiencies of nanoparticles with various different properties such as material, dimension and geometry. To obtain self consistent nanoparticle arrays with well defined geometries and dimensions, Electron Beam Lithography (EBL) technique is mainly used as the manufacturing method. Dose parameters required to produce nanoparticles with dimensions down to 50 nm over substrates with different electrical conductivities are determined. Beam current is found to affect the doseV size relation. The use of thin Au films as antistatic layer for e-beam patterning over insulating substrates is considered and production steps, involving instabilities due to contaminants introduced to the system during additional removal steps, are clarified. 4 nm thick Au layer is found to provide sufficient conductivity for e-beam patterning over insulating substrates. An optical setup capable of performing transmittance and reflectance measurements of samples having small areas patterned with EBL is designed. Sizes of the metal nanoparticles are determined by scanning electron microscope (SEM) and spectral data obtained using the optical setup is analyzed to find out the parameters affecting the localized surface plasmon resonances (LSPR). Arrays of particles with diameters between 50 &ndash / 200 nm are produced and optically analyzed. Size and shape of the nanoparticles are found to affect the resonance behavior. Furthermore, lattice constants of the particle arrays and surrounding medium are also shown to influence the reflectance spectra. Axes with different lengths in ellipsoidal nanoparticles are observed to cause distinguishable resonance peaks when illuminated with polarized light. Peak intensities obtained from both polarizations are observed to decrease under unpolarized illumination. Binary systems consisting of nanosized particles and holes provided better contrast for transmitted light.

The literature on nanomaterials has been flooded with new shapes, sizes, and compositions of nanostructures. The process of developing and characterizing these particles has been broadly accomplished and many interesting and promising properties have been revealed for application in current and developing technologies. In particular, the phenomenon of surface plasmon resonance seen in metallic gold and silver nanoparticles has drawn substantial interest. It has been established that the electromagnetic fields surrounding plasmonic particle surfaces can influence the properties of nearby systems, causing them to experience effects such as enhanced absorption and emission of light or drastically increased conductivity. For this reason, plasmonic nanoparticles are being applied to an endless number of applications for new materials. This thesis investigated the effects of silver nanocube (AgNC) arrays on the photophysical properties of poly(paraphenyleneethynylene) (PPE) fluorescent polymers, a particularly relevant material to the applications of organic-electronics. AgNCs were selected because of their particularly strong plasmonic field, which is enhanced at the sharp features of the cubes. The PPE polymer is an exceptionally fluorescent conjugated polymer that often serves as a building block for polymer-based sensing applications. By monitoring the absorption and emission of the PPE polymer, a better understanding of plasmonic effects on this polymer system was obtained. Compression of the monolayer of AgNCs on the surface of a Langmuir-Blodgett trough can be used for control of interparticle distance and, thus, the plasmon field intensity felt by an adsorbed layer of PPE polymer. In the Chapter 4, PPE (n = 15) emission was monitored as a function of the AgNC plasmonic field. A two-photon process was found to explain the unusual increase then decrease of the fluorescence intensity. This observation was attributed to exciton-exciton annihilation processes within the polymer. The annihilation process is initiated by large enhancements of the polymer absorption rate when plasmonic fields are at their highest (when the AgNCs are compressed to short interparticle distances). In chapter 5, the optical properties of PPE polymers as a function of their chain length and the AgNC density were examined. A simple study was conducted to consider the conformational/geometrical effects on PPE that were caused by the deposition of PPE onto the AgNC topography. In this study, the structure of the absorption and emission profiles were evaluated and used as evidence of polymer interchain interactions, planarization, and even the potential generation of oligomeric species through breaking of conjugation. Fundamental interactions between materials must be evaluated and optimized prior to their use in devices. This thesis serves to shed a little bit of light on the interaction of a well-defined plasmonic particle with a conjugated polymer. The Langmuir-Blodgett technique serves as a critical tool in applying these colloidally produced nanoparticles to 2D arrays in practical applications. The observation of exciton-exciton annihilation at low-energy excitation is an entirely new phenomenon that was initiated by the plasmonic properties of metal nanoparticles. It is the hope of the author that the results contained herein can aide in the use of plasmonic nanoparticles in future devices.

<p>All conducting polymers are potentially electrochromic, owing to the injection of charge carriers that changes their electronic structure and results in a shift of their optical absorption towards higher wavelengths. PEDOT-PSS and PEDOT-S are very promising materials in terms of electrochromic properties, due to the good contrast existing between their doped and undoped forms. However this contrast has to be enhanced in order to design more efficient electrochromic devices, and new solutions should thus be found in order to solve this issue.</p><p>Surface plasmons are described as electromagnetic waves propagating along the surface between a dielectric and a metal. Coupled to an incident radiation, they create an energy loss in the light transmitted and reflected by the interface. When the metallic surface is periodically corrugated, this absorption phenomenon due to plasmonic resonance occurs at a specific wavelength that depends on several parameters, such as the incidence angle, the dielectric constants of the two media and the grating period. By coating metallic gratings with electrochromic polymers, we may thus be able to trigger a plasmonic absorption at a given wavelength and shift it upon reduction or oxidation of the material.</p><p>Electrochromic devices consisting of PEDOT-PSS or PEDOT-S spin-deposited on gold and silver gratings were investigated by UV-visible reflectance measurements. The periodically corrugated structures were reproduced from commercial gratings by soft nanolithography and were analyzed by AFM. Some electrochromic cells exhibited new colors or a high shift of the plasmonic resonance upon redox switching of the polymer film. Depending on the step and the nature of the grating employed, this shift could reach 20 nm in the case of PEDOT-PSS and more than 100 nm for PEDOT-S. A theoretical model was found to predict the wavelength of plasmonic excitation and the orientation of the shift.</p>

Ce travail de thèse porte sur l'étude des propriétés de guidage des polaritons-plasmons de surface (vitesse de groupe, couplage radiatif, absorption) dans des cristaux plasmoniques 1D et 2D constitués de films métalliques percés d'ouvertures nanométriques périodiques (fentes ou trous). Nous avons développé un banc de mesures optiques (transmission et réflexion) sur un large domaine angulaire (0 − 60°) et spectral (1-16 μm). Il permet d'obtenir les diagrammes de dispersion des modes de surface avec une haute résolution (±0.3°, 0.5 cm−1). <br /><br />Dans les cristaux plasmoniques 1D, nous montrons une modulation des pertes radiatives due au couplage des plasmons de surface se propageant le long des interfaces air/métal et substrat/métal. Il en résulte deux régimes de propagation : un régime radiatif présentant une absorption négligeable, et un régime faible perte très peu couplé à l'espace libre. De plus nous montrons qu'une faible variation de l'indice du substrat (1%) permet de passer d'un régime de propagation à un autre et ouvre la voie à un contrôle externe des couplages radiatifs et non radiatifs des modes guidés.<br /><br />Nous présentons également les propriétés dispersives des plasmons de surface excités sur les interfaces de cristaux plasmoniques 2D anisotropes ayant des périodes différentes selon ses deux axes de symétrie. Nous montrons l'existence d'une bande interdite loin des bords de la zone de Brillouin, et mettant en jeu un couplage entre trois plasmons de surface se propageant dans des directions quasi-orthogonales. Un des modes couplés présente un fort couplage radiatif et une faible vitesse de groupe.

Les puces à ADN, dont la détection est réalisée par fluorescence, ont démontré leur efficacité pour l'identification du génome depuis plusieurs années. Cependant, si on s'intéresse à l'analyse fine des interactions mises en jeu, c'est à dire visualiser en temps réel la cinétique de l'interaction, le marquage est susceptible de changer la distribution de charges et par la même de modifier l'affinité des sites de reconnaissance. Parmi les approches s'affranchissant du marquage fluorescent, notre choix s'est porté sur une détection optique, par ellipsométrie spectroscopique et / ou par la lecture de la résonance des plasmons de surface (RPS), des interactions, présentant le compromis le plus intéressant entre sensibilité et capacité de miniaturisation. <br /><br />Ces techniques optiques reposant sur la mesure couplée de l'épaisseur et des indices optiques de la couche adsorbée. Dans une première étape, la détermination statistique par Microscopie à Force Atomique de microstructures lithographiées et fonctionnées par des monocouches biomimétiques a permis d'estimer les variations d'épaisseurs nanométriques induites par l'adsorption des molécules étudiées. Si l'ellipsométrie spectroscopique présente une très grande sensibilité ex situ à l'indice optique, l'étude angulaire de réflectivité RPS s'avère être la technique optique la plus sensible en milieu liquide. Nous avons montré, par ailleurs que la lecture spectroscopique du déphasage de la réflectivité RPS est 100 x plus sensible que l'étude angulaire et permet de déterminer séparément les épaisseurs, le modèle d'indices optiques (gradient, fraction volumique) de la couche biologique.<br /><br /> Le passage d'une analyse monocapteur à une lecture multicapteurs a été étudié par deux modes de microscopies RPS : <br />- l'imagerie en champ lointain par CCD permet outre la rapidité d'acquisition, d'intégrer 1 000 capteurs / cm2 <br />- la microscopie spectroscopique ellipsométrique à balayage, compte de tenu de la convolution du faisceau incident avec la surface microstructurée est limitée à 256 capteurs / cm2 mais présente l'avantage d'acquérir localement un spectre qui servira à une analyse paramétrique (indices optiques, fraction volumique, épaisseur).

Molecular optical imaging enables the ability to non-invasively image biological function. When used in conjunction with optical contrast agents, molecular imaging can provide biomarker-specific information with subcellular spatial resolution. Plasmonic nanoparticles are unique optical contrast agents due to the fact that the intensity and peak wavelength of scattering is dependant on interparticle spacing. This distance dependance puts these nanosensors in a position to probe molecular interactions by exploiting contrast between isolated and closely spaced nanoparticles. This dissertation presents the first intracellular molecular imaging platform using multifunctional gold nanoparticles which incorporate both cytosolic delivery and targeting moieties on the same particle. In order to produce robust nanosensors, a novel conjugation strategy was developed involving a heterofunctional linker capable of rigidly attaching various components to the nanoparticle surface. Since most biomarkers of interest are localized intracellularly, the delivery functionality was a key focus. It was achieved using the TAT-HA2 fusion peptide which has been previously shown to enhance both endosomal uptake and subsequent release into the cytosol. The feasibility of these nanoparticles as intracellular sensors was proposed by attempting to image actin rearrangement in live fibroblasts. The assembly of nanoparticles at the leading of motile cells was which was potentially due to actin targeting resulted in a red shift in scattering maxima due to plasmon resonance coupling between particles as well as a dramatic increase in scattering intensity. Although several challenges still exist, the potential for these contrast agents as nanosensors for the presence of proteins implicated in viral carcinogenesis is also introduced. / text

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Σε αυτή την διπλωματική στο ΠΜΣ Επιστημής Υλικών, έγινε προσπάθεια δημιουργίας νέων πλασμονικών δομών, μέσω της οξείδωσης μεταβατικών μετάλλων από τα στερεά τους διαλλύματα που αναπτύχθηκαν μέσω της τεχνικής της ιοντοβολής. Ελέγχοντας, την διεθνή βιβλιογραφία δεν βρέθηκε τρόπος παρεμφερής της πειραματικής διαδικασίας που ακολουθήθηκε, για την επίτευξη πλασμονικών δομών. Τα συστήματα που μελετήθηκαν είναι υμένια CuO / Au και Cu2O / Au, όπου η διηλεκτρική μήτρα είναι το ημιαγώγιμο οξείδιο και το πλασμονικό μέταλλο είναι το ευγενές μέταλλο του Au. Επίσης, να σημειωθεί ότι έλαβαν χώρα προκαταρκτικά πειράματα με χρήση NiO, όπου και αποδεικνύεται η γενικότητα της μεθοδολογίας, που ακολουθείται. Συνολικά, υπήρξαν τρεις διαφορετικές συγκεντρώσεις σε Au στα υμένια, οι οποίες πιστοποιήθηκαν μέσω της τεχνικής EDS. Πέραν, του επηρεασμού που δέχτηκαν τα ημιαγώγιμα οξείδια του χαλκού στο ενεργειακό διάκενο (υπολογισμός μέσω φασματοσκοπίας απορρόφησης ορατού / υπεριώδους UV / VIS), εξαιτίας της δημιουργίας διαφορετικών παχών υμενίου (φαινόμενα κβαντικού περιορισμού) και της παρουσίας του ευγενούς μετάλλου (Au), το σημαντικότερο σημείο είναι αυτό που αφορά την μελέτη και παρατήρηση εντοπισμένων επιφανειακών πλασμονικών συντονισμών (υπολογισμός μέσω τεχνικής UV / VIS), των λεγόμενων Localized Surface Plasmon Resonances – LSPR, τα οποία σχετίζονται με την απόκριση των ηλεκτρονίων αγωγιμότητας των μεταλλικών νανοσωματίδίων (< 100 nm) με μέγεθος μικρότερο από το μήκος κύματος της προσπίπτουσας ακτινοβολίας. Επιπρόσθετα, παρουσιάζονται κάποια διαγράμματα που αφορούν επιφανειακούς πλασμονικούς συντονισμούς σε μεταλλικά υμένια Au – Cu. Οι συντονισμοί LSPR μελετήθηκαν για διάφορους ρυθμούς ανόπτησης και για διάφορες συγκεντρώσεις. / In this thesis, an attempt was made to create new plasmonic structures, through the technique of sputtering. Going through the literature we could not find way similar experimental procedure followed to achieve plasmonic structures. The systems that have been studied are films CuO / Au and Cu2O / Au, wherein the dielectric matrix is semiconductor oxide and the plasmon metal is a noble metal of Au. Overall, there were three different concentrations of Au in the films, which were identified through EDS. In addition, the influence of thin film thickness on the energy gap due to quantum confinement was studied. The most important point is the observation of localized surface plasmon resonances (calculation through UV / VIS), the so-called LSPR, which are related to the response of the free electrons of metal nanoparticles (<100 nm) to the electric field of light. Resonances LSPR studied for various annealing rates and different concentrations of gold. We have to say that, after the appropriate annealing, we observed the creation of solid solutions (XRD).

Depuis plusieurs ann??es, une attention toute particuli??re a ??t?? port??e ?? la conception de biocapteurs. Divers types ont ??t?? d??velopp??s (ex. optiques, ??lectriques) et ont men?? ?? une multitude d???applications. On en retrouve d??sormais dans des champs d???applications aussi vari??s que la d??tection d???explosifs et de toxines, la s??curit?? alimentaire, la d??tection et le dosage de polluants environnementaux ou la sant??. Le d??veloppement de telles technologies se base sur l???union de deux domaines scientifiques tr??s diff??rents. D???un c??t??, la partie ?? capteur ?? est con??ue en utilisant des m??thodes de microfabrication. Ces derni??res font appel ?? l???emploi de compos??s inorganiques (ex. m??taux, mat??riaux semi-conducteurs, verre et autres). De l???autre c??t??, on retrouve un assemblage de mol??cules organiques, prot??ines, enzymes ou r??cepteurs issus du domaine biologique. L???un des grands d??fis est d???unir la portion biologique au capteur (c.-??-d. substrat) sans alt??rer les propri??t??s de ces deux composants. Plusieurs m??thodes sont envisageables pour arriver ?? coupler le mat??riel biologique au substrat. L???objectif de la recherche de cette th??se est d?????tudier la liaison de mol??cules sur un substrat et de cr??er un syst??me biologique servant comme syst??me de d??tection pour un biocapteur. Le mod??le choisi pour ??tablir le concept de base est l???affinit?? variable entre l???avidine et la 2-iminobiotine. Il est connu que l???affinit?? de l???avidine ?? l???iminobiotine peut ??tre modifi??e en changeant les conditions de pH. La liaison form??e en milieu basique sera affaiblie en milieu acide menant ?? la s??paration de la prot??ine et du ligand. Contrairement ?? l???iminobiotine, la biotine poss??de un lien fort et stable avec l???avidine impossible ?? briser dans des conditions non d??naturantes. L???avidine ??tant une prot??ine t??tram??rique, quatre ligands peuvent s???y lier. On profite donc de cette propri??t?? pour lier l???avidine ?? un bras polym??rique, une chaine de poly??thyl??ne glycol (PEG) comprenant une biotine, lui-m??me attach?? ?? la surface. Ce bras, maintenant fonctionnalis??, devra permettre de garder pr??s de la surface une avidine, lui permettant de se lier ?? des iminobiotine aussi attach??es en surface ou s???en d??lier selon les conditions de pH. La premi??re partie de cette th??se est consacr??e ?? la fonctionnalisation des surfaces. La premi??re ??tape de la construction a ??t?? de faire un attachement pour cr??er une couche de mol??cules qui serviront de support et d???ancrage au m??canisme mol??culaire du biocapteur. L???attachement de mol??cules ??tant r??alisable sur les surfaces d??sign??es, une construction a ??t?? test??e. La strat??gie propos??e consistait en l???utilisation d???une mol??cule bifonctionnelle en forme de ?? Y ??. Cette mol??cule a ??t?? synth??tis??e sp??cifiquement pour l???attachement en deux ??tapes successives des deux composantes du syst??me mol??culaire modulable en pH. Sur la premi??re branche se trouve une iminobiotine. La seconde a ??t?? pr??vue afin d???y attacher le bras polym??rique. Cette construction a ??t?? faite et test??e par SPR. Enfin, une seconde strat??gie de construction a ??t?? ??tudi??e. Celle-ci impliquait l???utilisation d???une prot??ine (albumine de s??rum bovin, BSA) modifi??e comme base de la construction. Une premi??re BSA a ??t?? modifi??e avec de l???iminobiotine tandis qu???une seconde avec le PEG. Ces deux prot??ines modifi??es ont ??t?? mises ensemble en solution et d??pos??es sur un substrat SPR. Elles constituent ensemble les deux morceaux du syst??me pr??c??demment mentionn??. L???objectif de cette strat??gie ??tait de contr??ler la quantit?? relative des esp??ces n??cessaires en surface de fa??on ?? obtenir un signal SPR optimal. De plus, la pr??sence de ces prot??ines en surface devait bloquer l???adsorption non sp??cifique sur cette derni??re d???esp??ces non d??sir??es.