The application of nanowires (NWs) in solar cells (SCs) is of great interest due to their new promising aspects established in nanoelectronics. Semiconductors associated with plasmonic metal nanoparticles (NPs) such as Silver (Ag), Gold (Au) and Copper (Cu), show enhanced performance in solid state light absorbing SCs owing to plasmonic characteristic of noble metal NPs. Plasmonic NPs presented a significant role in development of visible light harvesting for many applications such as photocatalytic materials, photodynamic in Surface Enhanced Raman Spectroscopy (SERS) and photovoltaics (PVs). Integration of plasmonic NPs in semiconductor materials have opened the routes to expand new PV systems with high efficiency light absorption. In this project, we introduce the synthesis ZnO and TiO2 NWs used as N-type semiconducting substrates and various methods for isolating plasmonic metal NPs, which are later deposited on the semiconducting substrates. Vertically aligned ZnO and TiO2 NWs arrays were grown on the fluorine-doped tin oxide (FTO) conductive glass substrates via hydrothermal method at low temperature and the plasmonic NPs were synthesized by wet chemistry procedures and finally decorated on the NW films by using electrophoretic deposition.  The impact of metal NPs loaded on the ZnO and TiO2 NWs substrates was studied by means of UV-vis spectroscopy and Photoluminescence (PL) spectroscopy. The absorbance spectra of individual NPs were recorded. Remarkably, the reflectance spectra of produced samples presented an enhancement in light absorption of the substrates after uptake of NPs on the ZnO and TiO2 NWs. The optical properties of the as grown ZnO NWs films decorated with Ag NPs (I) in direct contact with substrate and (II) in presence of an Al2O3 insulating spacer layer have been investigated. Both systems exhibited an enhancement in the UV band-edge emission from the ZnO when excited at 325 nm. In contrast, the broad bend defect emission of the samples did not have a significant change compare to bare ZnO substrates. The observed results suggested that the ZnO and TiO2 NWs decorated with plasmonic nanoparticles can boost the optical properties of MOs NWs substrates and hence effectively enhance the separation of photoexcited electron-hole pairs and photo-conversion applications.

Cette thèse s'inscrit dans un projet plus vaste, utilisant les propriétés plasmoniques de systèmes colloïdaux pour développer des guides d’onde à l'échelle submicrométrique. La plasmonique exploite les oscillations collectives des électrons libres à la surface des métaux nobles, excités par une lumière incidente. Les guides d’onde plasmoniques fabriqués par lithographie ont montré un potentiel pour le confinement et le guidage de l'énergie. En revanche, leur polycristallinité induit une dissipation optique. Notre approche consiste à exploiter les plasmons localisés à la surface de nano-objets colloïdaux et monocristallins. Les simulations, au même titre que les expériences, ont confirmé que la structure et l'organisation de ces objets engendraient un confinement et une exaltation du champ proche optique dans leur voisinage. Contrairement aux études en champ lointain, la caractérisation du confinement du champ proche produit par ce type de structures, de faibles tailles, présente plusieurs défis. Dans un premier temps, il est nécessaire de synthétiser les objets. Nous avons choisi d'étudier des particules sphériques d'or assemblées en réseaux de chaînes, puis des nanobâtonnets et des nanoprismes d'or. Le second défi a résidé dans l'organisation et le dépôt des réseaux de chaînes sur un substrat adéquat. Des réseaux étendus monocouches de chaînes monoparticulaires ont été obtenus après dépôt sur un substrat préalablement immergé dans une solution alcaline. Enfin nous avons caractérisé le champ proche optique au voisinage de ces colloïdes. Nous avons appliqué une méthode indirecte : la photomigration moléculaire, pour imager le champ proche optique avec une résolution spatiale latérale d'environ 50 nm. Celle-ci repose sur les propriétés d'un photochrome, qui se déplace sous l'effet d'une excitation lumineuse. Une caractérisation topographique par AFM, avant et après excitation, permet alors de cartographier l'intensité du champ proche. Un déplacement du film, uniquement au niveau des structures et suivant le gradient du champ, a été observé. Nous avons complété cette étude en utilisant deux techniques en "champ lointain", basées sur le balayage "pixel par pixel" d'une "sonde optique virtuelle". La photoluminescence à deux photons (TPL) a mis en évidence la possibilité de confiner ou d'étendre le signal suivant l'organisation des objets. Par ailleurs, l'enregistrement de cartes de température par la technique d'anisotropie de polarisation de fluorescence a démontré l'intérêt des réseaux réticulés de particules, comme sources de chaleur localisées en surface / This thesis is part of a larger project which uses plasmonic properties of colloidal systems to develop and conceive new submicron scale waveguides. Plasmonics exploits the collective oscillations of free electrons on noble metal surfaces, excited by incident light. Plasmonic waveguides made by lithography have shown potential for the confinement and guiding of light energy. On the other hand, their polycristallinity induces an optical dissipation that limits the propagation length. Our approach consists in using localized plasmons on colloidal and monocrystalline nano-object deposited on dielectric surfaces. Simulations, as well as experiments, have confirmed that the structure and organization of such objects generate both a confinement and an enhancement of the optical near field intensity in their vicinity. The characterization of the near field confinement near tiny plasmonic self-assembled structures presents several difficulties. First, it was necessary to synthesize objects and assemble them into networks, in coplanar geometry. Extended monolayer networks of monoparticle chains were obtained after deposition on a substrate previously immersed in an alkaline solution. In a second step, we have characterized the optical near-field around the colloids. We have applied molecular photomigration to image the near-field with a 50nm spatial resolution. This phenomenon relies on the molecular movement of photochromic films induced under light excitation. An AFM topographic characterization, before and after illumination, allows then to map the near-field intensity. A film migration, only around the object and along the field gradient, has been observed. Finally, we completed this study by using two "far field" techniques, based on "pixel by pixel" scanning of an "optical virtual probe". The two photons photoluminescence (TPL) has shown the possibility to confine or expand the signal, depending on object organization. The recording of map temperature by fluorescence polarisation anisotropy has demonstrated the interest of particle networks as localised heat sources

Cette thèse a pour sujet la modélisation mathématique de nouvelles méthodes expérimentales d'imagerie. Elle est divisée en deux parties. La première porte sur l'étude de techniques dites hybrides basées sur des interactions entre différents types d'ondes. La deuxième parte est consacrée à l'étude du comportement des nano-particules métalliques soumises à des champs électro-magnétiques. La première partie contient trois chapitres dans lesquels sont étudiés trois techniques d'imagerie différentes : - la tomographie magnéto-acoustique par force de Lorentz ; - la tomographie magnéto-acoustique par induction magnétique ; - l'élastographie par tomographie cohérente optique. Dans les deux premiers chapitres nous donnons un modèle mathématique explicite pour les expériences étudiées, ainsi que des formules explicites pour résoudre les problèmes inverses associés. Nous introduisons une méthode de reconstruction directe dite de « viscosité » permettant de reconstruire la conductivité électrique du milieu étudié. Dans le troisième chapitre nous proposons une méthode d'optimisation pour récupérer le module de cisaillement du milieu à partir de mesures d'un champs de déplacement. La deuxième partie contient deux chapitres dans lesquels sont étudiés la diffraction par de petites particules. Les phénomènes suivant sont abordés : - les résonances plasmoniques ; - la génération de seconde harmonique. Nous étudions les résonances plasmoniques dans le cadre d'une approximation petit volume. / In this thesis we study the mathematical modelling of new experimental imaging techniques. It is divided in two parts. The first one contains work on hybrid imaging techniques based on the interactions betwenn different types of waves. The second part is devoted to the study of the behavior of metallic nanoparticles embedded in electromagnetic fields. The first part contains three chapters in which three different imaging techniques are studied : - magneto-acoustic tomography by Lorentz force, - magneto-acoustic tomography with magnetic induction, - optical coherence tomography based elastography. In the first two chapters we give a mathematical model for the experiments studied as well as explicit reconstruction formulas for the associated inverse problems. We introduce a new direct reconstruction method ("viscosity method") allowing the recovery of the electrical conductivity of the medium. In the third chapter we give an optimisation method to reconstruct the shear modulus of the medium from a displacement field. The second part contains two chapters in which are studied the diffraction of light by small metallic nanoparticles. We study: - plasmonic resonances, - second harmonic generation. The plasmonic resonances are studied within the Maxwell frame. We give an asymptotic formula for the electromagnetic fields within a small volume approximation.

Different types of plasmonic nanostructures are proposed and examined experimentally and theoretically, with a view towards sensing applications. First, a self-assembly approach was developed to create arrays of well-ordered glass-supported gold nanoparticles (AuNPs) with controllable particle size and inter-particle spacing. Then, a periodic array of gold nano-disks (AuNDs) supported by a Bragg reflector was proposed and examined in a search for Fano resonances in its optical response. Arrays of heptamer-arranged nanoholes (HNH) in a thin gold film were also proposed and explored theoretically and experimentally, revealing a very rich spectrum of resonances, several exhibiting a Fano lineshape. A commercial implementation of the vectorial finite element method (FEM) was used to model our plasmonic structures. Taking advantage of the periodic nature of the structures, a unit cell containing a single element was modelled. The transmittance, reflectance or absorbance spectra were computed, and the associated electromagnetic fields were obtained by solving the vector wave equations for the electromagnetic field vectors throughout the structures, subject to the applicable boundary conditions, and the applied source fields. The sensing performance of the structures, based on the bulk sensitivity, surface sensitivity and figure of merit (FOM) was calculated. First, a novel bottom-up fabrication approach was applied (by our collaborators) to form a periodic array of AuNPs with controllable size over large areas on SiO2 substrates. In this method, self-assembly of block copolymer micelles loaded with metal precursors was combined with a seeding growth route to create ordered AuNPs of desired size. It was shown that this new fabrication method offers a new approach to tune the AuNP size and edge-to-edge inter-particle spacing while preserving the AuNP ordering. The optical characteristics of the AuNP arrays, such as their size, interparticle spacing, localized surface plasmon resonance (LSPR) wavelength, and bulk sensitivity, were examined, numerically and experimentally. This proposed novel fabrication method is applicable for low-cost mass-production of large-area arrays of high-quality AuNPs on a substrate for sensing applications. Then, we proposed and examined the formation of Fano resonances in a plasmonic-dielectric system consisting of uncoupled gold nano-disk (AuND) arrays on a quarter-wave dielectric stack. The mechanism behind the creation of Fano resonances was explained based on the coherent interference between the reflection of the Bragg stack and the LSPPs of the AuNDs. Fano parameters were obtained by fitting the computational data to the Fano formula. The bulk sensitivities and figure of merit of the Fano resonances were calculated. This plasmonic structure supports Fano resonances with a linewidth around 9 nm which is much narrower than the individual AuND LSPP bandwidth ( 80 nm) and the Bragg stack bandwidth ( 100 nm). Supporting Fano resonances with such a narrow linewidth, the structure has a great potential to be used for sensing applications. Also, this metallic-dielectric nanostructure requires no near-field coupling between AuNDs to generate the Fano resonances. So, the AuNDs can be located far enough from each other to simplify the potential fabrication process. The optical properties of HNH arrays on an SiO2 substrate were investigated, numerically and experimentally. Helium focused ion beam (HeFIB) milling was applied (by Dr. Choloong Hahn) to fabricate well-ordered and well-defined arrays of HNHs. Transmittance spectra of the structures were obtained as the optical response, which exhibits several Fano resonances. Then, the mechanism behind the formation of the Fano resonances was explained, and the sensing performance of the structure was inspected by measuring the bulk sensitivities. This array of nanohole cluster is exciting because it supports propagating SPPs and LSPPs, and also Wood’s anomaly waves, which makes the optical response very rich in excitations and spectral features. Also, as a periodic array of sub-wavelength metallic nanoholes, the system produces extraordinary optical transmission - highly enhanced transmission through (otherwise) opaque metallic films at specific wavelengths, facilitating measurement acquisition in transmission.

This diploma thesis deals with study of resonance modes of plasmonic structures. First part provides an overview of theoretical models, which explain the resonanace modes in plasmonic structures. Next part describes technology of electron beam lithography. First section of experimental part deas with technological processes leading to an improvement of resulting structures made by electron beam lithography that is followed by lift-off process. Last part focuses on a study of reflectance spactra of plasmonic antenas and the identification of resonance modes.

Les travaux de cette thèse portent sur la conception et la réalisation de nanopinces optiques intégrées basées sur l’utilisation du champ proche pour piéger des nanoparticules de taille inférieure à 1 µm.Le dispositif proposé exploite l’existence d’un couplage fort entre un guide d'onde SOI et une chaîne d’ellipses d’or afin d’exciter efficacement des plasmons de surface localisés et ainsi créer une énergie potentielle suffisamment intense pour piéger des billes de polystyrène.Des simulations par la méthode FDTD permettent d’optimiser la géométrie de la structure et d’extraire des valeurs de constante de raideur et de potentiel d’énergie de piégeage. L’efficacité ainsi que la stabilité de piégeage du système sont évaluées en présence de particules de taille comprise entre 20 nm et 1 µm. Les travaux mettent en évidence qu’avec une simple ou une double chaîne plasmonique, des billes de polystyrène sont piégées de manière efficace lorsqu’elles ont une dimension comprise entre 50 et 250 nm de rayon avec une puissance incidente de 10 mW. Utiliser seulement deux ellipses d’or au-dessus d’un guide d’onde SOI localise mieux le champ électrique entre elle. Cette structure peut alors être utilisée comme capteurs et détecter le changement d’indice optique du milieu environnant ou encore la variation de la taille de la bille à piéger. Le piégeage de billes métalliques de dimension supérieure à 15 nm de rayon est également présenté. Il est aussi possible de concevoir des dispositifs permettant de contrôler la position d’une particule piégée le long d’une chaîne d’ellipses d’or en faisant varier la longueur d’onde de la lumière injectée dans le guide.Des dispositifs de piégeage sont fabriqués en salle blanche en exploitant les résultats obtenus par simulation et sont caractérisés sur un banc d'optique guidée. Des mesures de transmission optique détermine la longueur d'onde de résonance de la chaîne plasmonique, qui se traduit par une forte diminution de la transmission. Des expériences de piégeage optique mettent en évidence la possibilité de piéger de manière stable des nanoparticules diélectriques. Le suivi de la trajectoire des particules en fonction du temps permet de tracer des histogrammes de position et ainsi d’extraire les valeurs de l'énergie potentielle et de la constante de raideur du piège. Ces valeurs, déterminées expérimentalement, sont plus faibles que celles attendues par simulation. Cet écart peut être expliqué par la présence de vibrations mécaniques du banc de caractérisation optique.Ce dispositif de piégeage ouvre des perspectives d’applications dans le domaine des capteurs tout intégrés de taille nanométrique à faible puissance incidente. / This work is focused on the conception and the realisation of an integrated nano-tweezers based on the near field effect to trap nanoparticles smaller than 1 µm.The proposed device exploits the strong coupling between a SOI waveguide and a gold elliptic chain to excite the localized surface plasmon and to create a deep energy potential well to trap polystyrene beads.FDTD simulations are used to optimize the geometry of the structure and to extract the stiffness values and the potential energy. The efficiency and the trapping stability are evaluated with particles having size between 20 nm and 1 $upmu$m. This work shows that polystyrene beads with a radius between 50 and 250 nm are efficiently trapped thanks to single and double plasmonic chain with an injected power of 10 mW. The electric field is more localized when two gold elliptic nanocylinders on top of a SOI waveguide are considered. This structure can be used as a sensor to detect the shift of the optical index or the variation of the bead size. The tweezing of metallic beads having radius higher than 15 nm is also presented. It is also possible to control the position of the trap particle along a gold elliptic chain by varying the injected wavelength into the waveguide.Trapping device are fabricated in clean-room based on the simulations results of the geometry optimisation and are characterized on an optical bench. Optical measurements of transmission enable to determine the resonance wavelength of the plasmonic chain. Optical trapping experiment highlight the efficient tweezing of dielectric nanoparticles. With time resolved tracking method of the particle, position histograms can be plotted to extract potential energy and stiffness value. These experimentals results are not as good as the simulations results which can be explain by mechanic vibrations of the optical bench.This trapping device opens news applications in all integrated nanometric sensors with a small injected power.

Ma thèse a été centrée sur l’étude par luminescence à deux photons (TPL) de nanostructures d’or uniques, éventuellement couplées, dans le but d’en déterminer les propriétés de nano-antennes optiques. Les différentes expériences réalisées ont permis de mettre en évidence les paramètres clés à l’origine de la luminescence à deux photons (TPL) permettant de mettre en évidence le rôle du plasmon transverse. Ce résultat a été confirmé par l’étude de nanobipyramides présentant des caractéristiques plasmoniques légèrement différentes. Ce modèle a été approfondi via l’étude des propriétés TPL de nanobâtonnets présentant des volumes différents mais des résonances plasmoniques identiques. Enfin, en confrontant les résultats expérimentaux à des simulations obtenues par BEM (Boundary Element Method), nous avons montré que le signal provenait a priori des atomes du volume de la NP. Des problèmes de photo-dégradations ont par ailleurs été constatés et analysés. Au-delà des nano-bâtonnets, nous avons quantifié les effets dits de pointes de nanobipyramides présentant des caractéristiques plasmoniques proches de celles des bâtonnets. Nous avons également pu mettre en évidence de très fortes intensités TPL sur les points chauds issus d’échantillons d’or semi-continu. Un second volet de mes travaux a concerné la mise en œuvre et la caractérisation des propriétés optiques linéaires et non-linéaires de nano-émetteurs hybrides individuels couplant une nano-antenne à des fluorophores. Différentes techniques ont été testées : la mise en œuvre de dépôts multicouches (méthode dite « layer-by-layer »), ou la nanophotopolymérisation localisée. Dans les deux cas, outre la complexité de mise en œuvre de ces techniques, nous avons été confrontés à la difficulté d’extraire le signal des molécules du très fort signal de luminescence à deux photons des nanostructures d’or. / My PhD work has been dealing with the two-photon luminescence (TPL) study of single gold nanostructures, possibly coupled in order to determine their nano-antenna optical properties. Key parameters to explain the origin of the TPL were provided from the two-photon luminescence study of single small 10 nm x 40 nm colloidal gold nanorods (GNR) which highlight the transverse plasmon influence. This origin was confirmed by the results obtained after the characterization of nanobipyramid exhibiting plasmonic properties closed to nanorods. A deeper insight in this model was further developed after investigating the properties of gold nanorods having closed aspect ratio and plasmonic resonances but increasing volume. Experimental data were correlated with BEM (Boundary Elements Method) simulations. It was shown that the TPL signal was coming from the bulk atoms. Photodegradations problems have moreover been observed and analyzed. Above the analysis of gold nanorods, the lightning rod effect of nanobipyramid was also investigated. Finally very high TPL intensity spots were recorded in semi-continuous gold films close to percolation. A second part of my study was related to the fabrication and the characterization of the optical properties of hybrid nano-emitters. They were fabricated by coupling a nano-antenna with fluorophores. Two different techniques were tested: the so-called layer-by-layer method and localized nanophotopolymerization. In both cases, together with the difficulty to accurately control both methods, retrieving the molecules signal from the huge TPL signal of the gold nanostructures was shown to be rather difficult.

Two types of 3-dimensional (3D) Ag nanosponge aggregates were prepared and tested as samples for surface-enhanced Raman scattering (SERS) and as active surfaces for surface- enhanced luminescence. 3D Ag nanosponge aggregates were assembled from 2D fused fractal aggregates (D = 1.87 ± 0.02) prepared by modification of Ag nanoparticle (NP) hydrosol resulting from the reduction of AgNO3 by NH2OH·HCl. For SERS measurements, 3D Ag nanosponge aggregates with incorporated [Ru(bpy)3]2+ cations and chloride anions were prepared and overlayed by a thin layer of aqueous phase. For SEL measurements, the 3D Ag nanosponge aggregates were assembled from fused fractal aggregates of chloride- modified Ag NPs. After preparation the active surface was overlayed by a 1×10-5 M aqueous solution of [Ru(bpy)3]2+ . The SERRS (1×10-15 M) and SER(R)S (1×10-14 M) limits of detection of [Ru(bpy)3]2+ determined at 445 and 532 nm excitations, respectively, correspond to the single molecule level of the complex detection. Its achievement is attributed to a large electromagnetic mechanism enhancement experienced by [Ru(bpy)3]2+ incorporated in "hot spots", an efficient localization of "hot spots" in the 3D aggregate to the focus of the laser beam in micro-Raman spectral measurements and to a molecular resonance contribution to the...

Plasmonic nanocrystals have a unique ability to support localized surface plasmon resonances and exhibit rich and intriguing optical properties. Engineering plasmonic nanocrystals can maximize their potentials for specific applications. In this dissertation, we developed three unprecedented Au nanorod-based plasmonic nanocrystals through rational design of the crystal shape and/or composition, and successfully demonstrated their applications in light condensation, photothermal conversion, and surface-enhanced Raman spectroscopy (SERS). The “Au nanorod-Au nanosphere dimer” nanocrystal was synthesized via the ligand-induced asymmetric growth of a Au nanosphere on a Au nanorod. This dimeric nanostructure features an extraordinary broadband optical absorption in the range of 400‒1400nm, and it proved to be an ideal black-body material for light condensation and an efficient solar-light harvester for photothermal conversion. The “Au nanorod (core) @ AuAg alloy (shell)” nanocrystal was built through the epitaxial growth of homogeneously alloyed AuAg shells on Au nanorods by precisely controlled synthesis. The resulting core-shell structured, bimetallic nanorods integrate the merits of the AuAg alloy with the advantages of anisotropic nanorods, exhibiting strong, stable and tunable surface plasmon resonances that are essential for SERS applications in a corrosive environment. The “high-index faceted Au nanorod (core) @ AuPd alloy (shell)” nanocrystal was produced via site-specific epitaxial growth of AuPd alloyed horns at the ends of Au nanorods. The AuPd alloyed horns are bound with high-index side facets, while the Au nanorod concentrates an intensive electric field at each end. This unique configuration unites highly active catalytic sites with strong SERS sites into a single entity and was demonstrated to be ideal for in situ monitoring of Pd-catalyzed reactions by SERS. The synthetic strategies developed here are promising towards the fabrication of novel plasmonic nanocrystals with fascinating properties for nanoplasmonics and nanophotonics.

Infectious pathogens are a prominent threat to human health in the world. There is a ubiquitous need for safe and reliable pathogen inactivation in the entire health care sector and pharmaceutical industry. Unfortunately, existing chemical treatment methods for virus inactivation have shortcomings as they introduce toxic chemicals or alter the structure of the products, which often pose significant side effects. Furthermore, considering the alarming growth of antibiotic resistances and hospital associated microbial infections, there is an urgent need for alternative pathogen inactivation strategies. Femtosecond (fs) pulsed laser irradiation technique is a promising solution free of added toxic chemicals and does not require the invention of new antibiotics for inactivation of virus contaminations in biological samples. Conventional pulsed laser techniques require relatively long irradiation times to achieve a significant viral inactivation. This thesis is focused on developing a novel photonic inactivation approach that is selective to pathogens, doesn’t compromise the protein-based pharmaceuticals, and is obtained without specific targeting to the pathogens. In our study, we report comparative studies using femtosecond laser pulses generated using Chirped Pulse Amplification (CPA) centered at either 800 nm or frequency-doubled 400 nm wavelengths, on the model bacteriophage φX174. We show that photonic inactivation is wavelength dependent and a Log Reduction Value (LRV) of > 6 in a 2 ml bacteriophage sample volume is achieved with less than 1 min of 400 nm laser exposure. Traditional methods for assaying viral inactivation require cell culture studies that can take up to 48–72 hours. We describe a solid-state nanopore technique that can monitor the effect of this optical viral therapy in under 10 minutes. By developing a statistical model based on the probability distribution function obtained from nanopore data, we monitor the survival fraction of viruses with low sample volume, high precision and fast assay time. Lastly, the purely photonic virus inactivation requires UV fs laser irradiation, which can risk photodamage to biologics. In our research, we introduce a novel inactivation approach that takes advantage of the strong light-matter interactions provided by noble metal nanoparticle (NP) structures that sustain plasmons. We report a plasmonically enhanced virus inactivation of Murine Leukemia Virus (MLV) via 10 s laser exposure with 800 nm fs pulses through gold nanorods, with LRV>3.7. We demonstrate that this NP-enhanced, physical inactivation approach is effective against a diverse group of pathogens, including both enveloped and non-enveloped viruses, and a variety of bacteria and mycoplasma. Importantly, the fs-pulse induced inactivation was selective to the pathogens and did not induce any measurable damage to co-incubated antibodies, or to large mammalian cells. Based on the observations, a model of selective pathogen inactivation based on plasmon enhanced cavitation is proposed.