Plasmonic polymer nanocomposites contain plasmonic nanoparticles that are dispersed within a polymer. The polymer matrix strongly influences the optical properties of plasmonic nanoparticles. It is imperative to understand the interaction between plasmonic nanoparticles and polymers so that one can develop functional devices using nanocomposites. The utilization of plasmonic nanoparticles as fillers has great potential to transform critical nanotechnologies where light management is crucial, such as refractive index based nanosensors, optical coatings, and light actuated devices. Despite the great potential, effective integration of plasmonic nanoparticles with polymers remains challenging. This dissertation presents i) the effects of dielectric media on the optical properties of plasmonic nanoparticles, ii) the sensing of polymer brush formation on nanoparticles, iii) the fabrication of plasmonic nanocomposite thin-films with controlled optical properties, and iv) the development of electrically conductive membranes for electrostatic speakers. The optical response of plasmonic nanoparticles (referred to as wavelength of localized surface plasmon resonance, λLSPR) is sensitive to changes in refractive index of the medium. The sensitivity (S) plays a critical role in determining the performance of nanoparticles in sensing applications. In this dissertation, I have conducted a systematic study on the sensitivity of plasmonic nanoparticles as a function of various parameters: shape, size, composition, initial plasmonic resonance wavelength, cross-sectional area, and aspect ratio. Among the parameters investigated, aspect ratio (R) is determined to be the key parameter that controls S, following an empirical equation, S = 46.87 R + 109.37. This relationship provides a guideline for selecting fillers in plasmonic polymer nanocomposites, and it predicts the final effect of plasmonic nanoparticles on the optical properties of polymer nanocomposites. Plasmonic nanoparticles are employed to probe polymer grafting on the surfaces of metal nanoparticles. Using ultraviolet-visible (UV-vis) spectroscopy, I have demonstrated the quantification of polymer grafting density on the surface of plasmonic nanoparticles. The λLSPR of plasmonic nanoparticles red-shifts as the polymer concentration near the nanoparticle surface increases. I have investigated the formation of polymer brush by grafting the nanoparticles with thiolated polyethylene glycol (PEG-SH) and revealed the three–regime kinetics in situ. Importantly, this study suggests that a latent regime arises due to fast polymer adsorption and prolonged chain rearrangement on nanoparticle surfaces. When the polymer chains rearrange and chemically tether to the surface, they contract and allow more polymer chains to graft onto the particle surface until saturation. This analytical method provides a new surface probing technique for polymer brush analysis, complementary to conventional methods such as quartz crystal microbalance, atomic force microscope, and microcantilivers. Commercial tinted glass employs expensive metalized films to reduce light transmittance but has limited spectral selectivity. To reduce the cost of metalized films and to improve the spectral selectivity, I have employed plasmonic nanoparticles in polymers to fabricate spectral-selective tinted films. First, I have synthesized two-dimensional (2D) plasmonic silver nanoparticles (AgNPs) using multi-step growth. The nanoparticles have a tunable plasmon resonance and provide spectral selectivity. The multi-step growth forgoes polymeric ligands such as poly(vinylpyrrolidone) (PVP) and solely relies on a small molecule sodium citrate. Briefly, small citrate-capped Ag seeds are first grown into small 2D AgNPs. The small 2D AgNPs are then used to grow large 2D AgNPs via multiple growth steps. The PVP-free method allows for fast synthesis of 2D AgNPs with large sizes and tunable plasmon resonance across the visible and NIR region. The 2D AgNPs are integrated with polymers to produce thin-film plasmonic nanocomposites. By controlling the planar orientation of the 2D AgNPs through layer-by-layer assembly, the polymer nancomposites have achieved reduced light transmittance and enhanced reflectance across the visible and NIR range. In contrast to conventional polymer nanocomposites where the AgNPs are randomly oriented, the thin-film polymer nanocomposites exhibit excellent control over nanoparticle density and hence the optical properties, that is, tunable light transmittance and reflectance across the visible and NIR. Lastly, graphene is used to prepare conductive free-standing polymer thin-films. Graphene, an ultralight weight 2D material with excellent electrical and mechanical properties, has potential for use in thin-film composites essential for photovoltaics, electrostatic speakers, sensors, and touch displays. Current graphene-based composite films contain graphene flakes randomly mixed in a polymer matrix and usually possess poor mechanical and electrical properties. In this dissertation, I have developed thin-film nanocomposites comprised of chemical vapor deposited (CVD) graphene and high-performance polyetherimide (PI). The CVD-grown graphene is polycrystalline, and it cannot be used as a free-standing film. By enforcing the polycrystalline graphene with a thin layer of PI, I have prepared free-standing thin-film composites with a high aspect ratio of 105. Mechanical and electrical property characterization reveals a Young's modulus of 3.33 GPa and a resistance of 200 - 500 Ω across the membrane. A typical spring constant of the membrane is ~387 N/m. Dynamic electromechanical actuation shows that the membrane vibrates at various input frequencies. The polymer/graphene film has excellent acoustic properties, and when used as a speaker membrane, it reduces the electrical power consumption by a factor of 10-100 over the frequency range of 600–10,000 Hz. / Doctor of Philosophy / Nanomaterials such as plasmonic nanoparticles and graphene have optical, electrical, and mechanical properties that are important for light filters, sensors, printing, photovoltaics, touch screens, speakers, and biomedical devices. To fully employ the nanomaterials, a support such as polymer is often required. However, when the nanomaterials and polymers are combined, their optical, electrical, and mechanical properties drastically change. Therefore, it is imperative to understand the interactions between nanomaterials and polymers, as well as the resulting properties. Towards this goal, I have studied the sensitivity of plasmonic nanoparticles in a dielectric media and then utilized the sensitivity to investigate polymer brush formation on nanoparticle surfaces. In addition, I have investigated the integration of plasmonic nanoparticles and graphene with polymers to develop thin-film nanocomposites for window coatings and audio speakers, respectively. Plasmonic nanoparticles can detect trace amounts of chemicals, biomolecules, toxics, warfare agents, and environmental pollutants. Sensitivity is the key criterion that determines the performance of nanoparticles for such applications. Firstly, I have conducted a detailed and comprehensive study of the plasmonic sensitivity as a function of various nanoparticle parameters including shape, size, composition, cross-sectional area, initial plasmonic resonance wavelength, and aspect ratio. I have found that the sensitivity scaled linearly with aspect ratio. The strong dependence of sensitivity on aspect ratio provides insight into designing effective plasmonic sensors. Based on the sensitivity study, I have used plasmonic nanoparticles as sensors to probe and understand the mechanism of polymer brush formation in situ. When the concentration of polymer increases on the nanoparticle surfaces, the optical response of the nanoparticle changes. Through functionalizing the plasmonic nanoparticles with polymers, I have confirmed the three different regimes of polymer brush formation. Plasmonic nanoparticles resonating in the visible and near infrared have a great potential in designing polymer nanocomposites for window coatings. Among different exotic shapes, two-dimensional nanoplates are the most important as their optical properties can be easily tuned across a wide range of wavelengths. However, most of the current methods require polymers, long hours of reaction time, and multiple purification steps. I have developed a new multi-step strategy to synthesize Ag nanoplates which absorb in the range of 500–1660 nm. Utilizing the plasmonic nanoparticles, the spectral-selective plasmonic nanocomposites comprised of polymers and planarly oriented Ag nanoparticles of judiciously selected sizes and compositions were prepared. The plasmonic polymer nanocomposites spectral-selectively reflect, scatter, and filter light of any desired wavelength. The nanocomposites will impact on the tinted glass in modern energy-efficient buildings. The outstanding electrical and mechanical properties of graphene have stirred a large volume of research in the last 15 years. Most graphene-based technologies focus on graphene at the nano or micro scale. To further the practicality of graphene in large devices like audio speakers, large areas and thin films are needed to reduce energy consumption. Graphene on its own cannot be used over large areas due to the inherent defects arising during the growth. Here I present results on combining suspended sheets of single layer graphene with a mechanically strong polymer thin film. The acoustic properties of speakers made of polymer/graphene thin films are similar to those of conventional electrodynamic speakers in modern cellphones. The energy consumption, however, reduces sharply by a factor of 10-100 for the polymer/graphene based speakers. This sharp decrease in energy is attributed to the lightweight, flexibility, and excellent electrical conductivity. Apart from speakers, the membrane designed here also has huge potential in other devices like touch panels, capacitive sensors, and photovoltaics.

Anisotropic plasmonic noble metallic nanoparticles (APMNs) have received enormous attention due to their distinct geometric features and fascinating physicochemical properties. Owing in large part to their tailored localized surface plasmon resonance (LSPR) and the intensive electromagnetic field at the sharp corners and edges, APMNs are exceptionally well suited for biomedical applications such as biosensing, bioimaging, diagnostics and therapeutics. Although a rich variety of surfactant-assisted colloidal routes have been developed to prepare well-defined APMNs, biomedical applications necessitate tedious and rigorous purification processes for the complete removal of toxic surfactants. In this dissertation, we aim to develop generic bioenabled green synthetic methodologies towards APMNs. By applying a series of thermodynamic, kinetic and seed quality control, a series of APMNs with varied morphologies such as branched nanostars and triangular nanoprisms have been successfully prepared. We first presented the preparation of gold nanostars (Au NSTs) through a two-step approach utilizing a common Good's buffer, HEPES, as a weak reducing agent. Single crystalline Au NSTs with tunable branches up to 30 nm in length were produced and the halide ions rather than the ionic strength played a significant roles on the length of the branches of Au NSTs. Then consensus sequence tetratricopetide repeat (CTPR) proteins with increasing number of repeats were used as model proteins to probe the effects of concentration as well as the protein shape on the morphology and resulting physicochemical properties of plasmonic gold nanoparticles. Since the underlying growth mechanism for the biomimetic synthesis of APMNs remains elusive and controversial, the other objective is to elucidate the molecular interactions between inorganic species and biopolymers during the course of NP evolution. Fluorescent quenching and 2D NMR experiments have confirmed the moderate binding affinity of CTPR to the Au(0) and Au(III). We observed that the initial complexation step between gold ions and CTPR3 is ionic strength dependent. Furthermore, we also found that NPs preferentially interact with the negatively charged face of CTPR3 as observed in 2D NMR. Knowledge of binding behavior between biospecies and metal ions/NPs will facilitate rational deign of proteins for biomimetic synthesis of metallic NPs. A modified seed-mediated synthetic strategy was also developed for the growth of silver nanoprisms with low shape polydispersity, narrow size distribution and tailored plasmonic absorbance. During the seed nucleation step, CTPR proteins are utilized as potent stabilizers to facilitate the formation of planar-twinned Ag seeds. Ag nanoprisms were produced in high yield in a growth solution containing ascorbic acid and CTPR-stabilized Ag seeds. From the time-course UV-Vis and transmission electron microscopy (TEM) studies, we postulate that the growth mechanism is the combination of facet selective lateral growth and thermodynamically driven Ostwald ripening. By incorporation of seeded growth and biomimetic synthesis, gold nanotriangles (Au NTs) with tunable edge length were synthesized via a green chemical route in the presence of the designed CTPR protein, halide anions (Br⁻) and CTPR-stabilized Ag seeds. The well-defined morphologies, tailored plasmonic absorbance from visible-light to the near infrared (NIR) region, colloidal stability and biocompatibility are attributed to the synergistic action of CTPR, halide ions, and CTPR-stabilized Ag seeds. We also ascertained that a vast array of biosustainable materials including negatively charged lignin and cellulose derivatives can serve as both a potent stabilizers and an efficient nanocrystal modifiers to regulate the growth of well-defined Ag nanoprisms using a one-pot or seeded growth strategy. The influential effects of reactants and additives including the concentration of sodium lignosulfonate, H2O2 and NaBH4 were studied in great detail. It implies that appropriate physicochemical properties rather than the specific binding sequence of biomaterials are critical for the shaped-controlled growth of Ag NTs and new synthetic paradigms could be proposed based on these findings. Last but not the least, we have demonstrated the resulting APMNs, particularly, Au NSTs and Ag NTs exhibit remarkable colloidal stability, enhanced SERS performance, making them promising materials for biosensing and photothermal therapy. Since the Ag nanoprisms are susceptible to morphological deformation in the presence of strong oxidant, they also hold great potential for the colorimetric sensing of oxidative metal cation species such as Fe3+, Cr3+, etc. / Ph. D. / When a beam of light impinges on the surface of noble metallic nanoparticle (NP), particularly gold (Au) and silver (Ag), the conduction electrons are excited which induces a collective oscillatory motion, resulting in an intense localized surface plasmon resonance (LSPR) absorbance as well as the amplified localized electromagnetic filed. Owing in large part to the tailored LSPR and the intensive electromagnetic field at the sharp corners and edges, anisotropic plasmonic noble metallic nanoparticles (APMNs) can be utilized to span an array of applications such as biosensing, bioimaging, diagnostics and therapeutics. Although great advancement has been made to prepare well-defined APMNs through versatile surfactant-assisted colloidal methodologies, biomedical applications necessitate tedious and rigorous purification processes for the complete removal of toxic surfactants. To address this ubiquitous challenge, biomimetic and bioinspired green synthesis have been extensively explored to fabricate APMNs under mild and ambient conditions. In this dissertation, we aim to develop generic bioenabled synthetic strategies towards APMNs, particularly, Au nanostars and Au/Ag nanoprisms. Herein, protein mediated shape-selective synthesis of APMNs were presented, in which consensus sequence tetratricopetide repeat (CTPR) proteins and biological Good’s buffers were employed as nanocrystal growth modifiers and mild reducing agents, respectively. The dramatic implications of repeat proteins on the morphological and optical properties of the Au NPs were explicitly discussed. The other objective of this dissertation is to elucidate the molecular interactions between inorganic species and biopolymers to further unravel the underlying growth mechanism during the course of APMNs evolution. By incorporation of seeded growth and biomimetic synthesis, Ag/Au nanotriangles (Au NTs) with tunable edge length were synthesized in the presence of the designed CTPR protein, halide anions (Br⁻) and CTPR-stabilized Ag seeds. The well-defined morphologies, tailored plasmonic absorbance from visible-light to the near infrared (NIR) region, colloidal stability and biocompatibility are attributed to the synergistic action of each components in the synthetic system. Last but not the least, we have demonstrated the resulting NPs exhibit remarkable colloidal stability, mitigated cytotoxicity and surface enhanced Raman spectroscopy (SERS) performance, making them good candidates for biosensing and photothermal therapy. This work might shed light on the roles biomolecules play in green synthesis of APMNs, along with rationalizing the design of biomimetic systems to bridge the gap between the bioenabled technique and traditional colloidal synthesis.

Monitoring biological systems is crucial in healthcare, driving the need for reliable and noninvasive solutions. The proliferation of unverified drugs in the market necessitates reliable methods for their detection and identification, especially amidst advancements in pharmaceuticals. Plasmonic biosensors emerge as a great platform for ultra-sensitive detection, identification, and manipulation of biomolecular systems. This dissertation report addresses the critical need for precise detection and monitoring of biomolecules and drugs, presenting innovative solutions through the design of a plasmonic biosensor to tackle challenges in sensitivity, selectivity, and label-free detection and identification. We introduce a robust and tunable, cavity-integrated plasmonic nanopatterned sensor that exhibits superchiral light in the infrared domain for ultrasensitive detection of chiral molecular concentrations and enantiomeric excesses. The multispectral capability of this system is further harnessed to generate unique chiral fingerprint-based barcodes for the identification of diverse chiral drugs and biomolecules. We further discuss and demonstrate results for a surface-modified plasmonic biosensor operating in the visible-near-infrared realm in detecting viral biomarkers and neurotransmitters directly from complex physiological environments. The system, on coupling with a microfluidic flow setup allows sensitive, selective and rapid detection without requiring complex pre-processing or sample preparation steps. We discuss additional applications of the unique plasmonic sensor, utilizing the property of tunable superchirality to create a dynamic chirality tracking system operating in the near infrared for real-time monitoring of protein dynamics. These techniques aim to revolutionize bio-detection, chiral differentiation, and sorting processes, having extensive applications in medical research and pharmaceutical industries.

Cette thèse porte sur l’étude mathématique des interactions entre la lumière et certains types de nanoparticules.À l’échelle du nanomètre, des particules métalliques comme l’or ou l’argent subissent un phénomène de résonance lorsque leurs électrons libres interagissent avec un champ électromagnétique. Cette interaction produit une augmentation du champs électrique proche et lointain, leur permettant d’améliorer la luminosité et la directivité de la lumière, confinant des champs électromagnétiques dans des directions avantageuses. Ce phénomène, appelé "résonances plasmoniques pour des nanoparticules" ouvre une porte sur une large gamme d’applications, des nouvelles techniques d’imagerie médicale à des panneaux solaires efficaces. En utilisant des techniques issues des potentiels de couches et de la théorie de la perturbation,nous proposons une étude de la dispersion d’ondes électromagnétiques par une et plusieurs nanoparticules plasmoniques, dans le cadre quasi-statique, Helmholtz et Maxwell. Nous étudions ensuite certaines applications tel que la génération de chaleur, les métasurfaces et l’imagerie super-résolue. / This thesis deals with the mathematical study of the interactions between light and certain types of nanoparticles. At the nanometer scale, metal particles such as gold or silver undergo a resonance phenomenon when their free electrons interact with an electromagnetic field. This interaction results in an enhancement of the near and far electric field, enabling them to improve the brightness and the directivity of the light, confining electromagnetic fields in advantageous directions. This phenomenon, called "plasmonic resonances for nanoparticles", opens a door to a wide range of applications, from new medical imaging techniques to efficient solar panels. Using layer potentials techniques and perturbation theory, we proposea study of the scattering of electromagnetic waves by one and several plasmonic nanoparticles in the quasi-static, Helmholtz and Maxwell framework. We then study some applications such as heat generation, metasurfaces and super-resolution.

Doctor of Philosophy / Department of Chemistry / Viktor Chikan / This dissertation reports the colloidal synthesis of iron silicide, hafnium oxide core-gold shell and water soluble iron-gold alloy for the first time. As the first part of the experimentation, plasmonic and superparamagnetic nanoparticles of gold and iron are synthesized in the form of core-shell and alloy. The purpose of making these nanoparticles is that the core-shell and alloy nanoparticles exhibit enhanced properties and new functionality due to close proximity of two functionally different components. The synthesis of core-shell and alloy nanoparticles is of special interest for possible application towards magnetic hyperthermia, catalysis and drug delivery. The iron-gold core-shell nanoparticles prepared in the reverse micelles reflux in high boiling point solvent (diphenyl ether) in presence of oleic acid and oleyl amine results in the formation of monodisperse core-shell nanoparticles. The second part of the experimentation includes the preparation of water soluble iron-gold alloy nanoparticles. The alloy nanoparticles are prepared for the first time at relatively low temperature (110 oC). The use of hydrophilic ligand 3-mercapto-1-propane sulphonic acid ensures the aqueous solubility of the alloy nanoparticles. Next, hafnium oxide core-gold shell nanoparticles are prepared for the first time using high temperature reduction method. These nanoparticles are potentially important as a high κ material in semiconductor industry. Fourth, a new type of material called iron silicide is prepared in solution phase. The material has been prepared before but not in a colloidal solution. The Fe3Si obtained is superparamagnetic. Another phase β-FeSi2 is a low band gap (0.85 eV) semiconductor and is sustainable and environmentally friendly. At last, the iron monosilicide (FeSi) and β-FeSi2 are also prepared by heating iron-gold core-shell and alloy nanoparticles on silicon (111) substrate. The nucleation of gaseous silicon precursor on the melted nanoparticles results the formation of nanodomains of FeSi and β-FeSi2. A practical application of these nanoparticles is an important next step of this research. Further improvement in the synthesis of β-FeSi2 nanoparticles by colloidal synthetic approach and its application in solar cell is a future goal.

Le domaine du spectre électromagnétique correspondant aux fréquences térahertz est encore peu exploité, pourtant, les applications nécessitant la génération, l’amplification ou la détection d’un signal térahertz sont nombreuses et intéressantes. Dans ce travail, nous nous intéressons tout particulièrement au détecteurs plasmoniques, qui constituent une alternative prometteuse à la montée en fréquence des capteurs électroniques et à l’utilisation de capteurs thermiques pour les photons de faible énergie. Les capteurs plasmoniques fonctionnent grâce au couplage entre le photon térahertz et un plasmon au sein d’un gaz d’électrons bidimensionnel (2DEG). Le plasmon-polariton est ensuite transformé en un signal continu et détectable. Nous utilisons pour cela le 2DEG présent dans l’hétérostructure AlGaN/GaN. Le couplage entre le photon et le plasmon-polariton est réalisé par un réseau métallique déposé sur la structure semi-conductrice. Tout d’abord, l’étude du couplage photon/plasmon par des simulations électromagnétiques nous a permis de connaître les fréquences de résonance des plasmons-polaritons en fonction des dimensions du réseau. Le motif de réseau composé de deux bandes de métal de largeurs différentes a été plus particulièrement étudié. Ce motif permettant aux détecteurs d’atteindre une très haute sensibilité [Coquillat et al., 2010] et n’avait pas encore été étudié du point de vue de son efficacité de couplage. Des détecteurs, dimensionnés pour notre montage de test à 0,65 THz, ont ensuite été fabriqués puis mesurés avec un réseau non-polarisé, à température ambiante et refroidis à l’azote. La correspondance entre la variation de la sensibilité en fonction de la fréquence et les spectres d’absorption mesurés au spectromètre infrarouge à transformée de Fourier (FTIR) montre l’importance de l’étape de couplage dans le processus de détection. Contrôler la densité électronique dans le 2DEG permet de modifier la fréquence de résonance des plasmons-polaritons et d’augmenter la sensibilité des détecteurs. Nous avons mené des développements technologiques de manière à pouvoir contrôler la densité électronique du 2DEG en appliquant une tension sur le réseau. Cette étape constitue un défi technologique compte tenu de la surface très étendue des réseaux (plusieurs mm²). Nous avons finalement fabriqué des détecteurs pour lesquels la fréquence de résonance de couplage peut être contrôlée grâce à la tension appliquée sur le réseau. / Abstract: The objectives of this thesis were the fabrication, the measurement and the study of gallium nitride THz detectors. These detectors are working as follows : first the incident THz photon is coupled to a plasmon in the quantum well at the interface AlGaN/GaN. This plasmon is then turned into a continuous measurable current. One of the key-components in this type of detectors is the grating coupling the incident photon and the plasmon. Electromagnetic simulations have been made to determine the dimensions of the grating depending on the detection frequency. Detectors were then fabricated using the precendently calculated grating patterns. Their working frequency depending on their dimensions were measured with a good agreement with the previously led simulations. The grating is not used only as coupling element, but can be used to monitor the electron density in the quatum well as well, what should allow an exaltation of the rectification phenomenon and a frequency tunability. A technological development was needed to achieve grating actually monitoring the electron density over a wide range. It was a real challenge to fabricate such wide grating (36 mm²) with such small periods (about one micrometer) using epitaxies developped for devices with a much smaller area.

Master of Science / Department of Chemistry / Jun Li / With the worldly consumption of energy continually increasing and the main source of this energy, fossil fuels, slowly being depleted, the need for alternate sources of energy is becoming more and more pertinent. One promising approach for an alternate method of producing energy is using solar cells to convert sunlight into electrical energy through photovoltaic processes. Currently, the most widely commercialized solar cell is based on a single p-n junction with silicon. Silicon solar cells are able to obtain high efficiencies but the downfall is, in order to achieve this performance, expensive fabrication techniques and high purity materials must be employed. An encouraging cheaper alternative to silicon solar cells is the dye-sensitized solar cell (DSSC) which is based on a wide band gap semiconductor sensitized with a visible light absorbing species. While DSSCs are less expensive, their efficiencies are still quite low compared to silicon. In this thesis, Grätzel cells (DSSCs based on TiO2 NPs) were fabricated and optimized to establish a reliable standard for further improvement. Optimized single layer GSCs and double layer GSCs showing efficiencies >4% and efficiencies of ~6%, respectively, were obtained. Recently, the incorporation of metallic nanoparticles into silicon solar cells has shown improved efficiency and lowered material cost. By utilizing their plasmonic properties, incident light can be scattered, concentrated, or trapped thereby increasing the effective path length of the cell and allowing the physical thickness of the cell to be reduced. This concept can also be applied to DSSCs, which are cheaper and easier to fabricate than Si based solar cells but are limited by lower efficiency. By incorporating 20 nm diameter Au nanoparticles (Au NPs) into DSSCs at the FTO/TiO2 interface as sub wavelength antennae, average photocurrent enhancements of 14% (maximum up to ~32%) and average efficiency enhancements of 13% (maximum up to ~23% ) were achieved with well dispersed, low surface coverages of nanoparticles. However the Au nanoparticle solar cell (AuNPSC) performance is very sensitive to the surface coverage, the extent of nanoparticle aggregation, and the electrolyte employed, all of which can lead to detrimental effects (decreased performances) on the devices.

Nanopartículas (NPs) que apresentam ressonância plasmon de superfície localizada (RPSL) são aplicáveis em diversas áreas como, por exemplo, em terapia e diagnóstico na área biomédica. Estudos e aplicações in vivo requerem que a banda plasmon (BP) ocorra na mesma região da janela terapêutica, entre 600 e 1000 nm. Esta condição pode ser atingida com a modulação da BP pelo controle da morfologia e da composição química das NPs. Os objetivos principais deste trabalho foram estudar métodos de síntese que permitissem obter maiores quantidades de materiais quando comparados aos métodos convencionais em meio aquoso, e conjuntamente avaliar os parâmetros de síntese para obter NPs com diferentes morfologias e composições almejando modular a BP para região de interesse. Obteve-se nanoesferas (NEs) de Au monodispersas com diâmetro médio de 9 nm por redução com oleilamina em solução concentrada de sais de ouro. Dispersibilidade em água com elevada estabilidade coloidal foi alcançada via um procedimento de troca de ligantes, substituindo as moléculas de oleilamina, presentes na superfície das NPs assim como sintetizadas, por moléculas de ácido 11-mecaptoundecanóico. Nanobastões (NBs) de Au (largura de 12 nm) com diferentes comprimentos (30-300 nm) foram obtidos em misturas incomuns das fases cristalinas fcc e hcp. Estes NBs apresentam duas BP no espectro UV-Vis-NIR, uma em 520 nm e outra banda alargada a partir de 800 nm atribuídas à RPSL transversal e longitudinal, respectivamente. Inicialmente, os NBs foram sintetizados utilizando oleilamina como agente redutor e surfactante, sendo posteriormente avaliado que a presença de álcool oleico ou trietilamina no meio mantiveram uma condição de crescimento-1D mantendo a forma dos nanomateriais. NEs de Ag foram obtidas em condições semelhantes às NEs de Au com a BP em torno de 420 nm. Obteve-se misturas de NEs e NBs de AuCu3 (NBs, com razão de aspecto de 3) em todas as condições estudadas, sendo posteriormente separadas. Duas BP foram observadas para os NBs de AuCu3 em 560 e 766 nm, atribuídas à ressonância transversal e longitudinal, respectivamente. NPs monodispersas de Cu1,8S com 10 nm e BP centradas em 1150 nm foram sintetizadas por injeção a quente. Uma tentativa de recobrimento com Au das NPs de Cu1,8S resultou em uma reação de substituição, formando NPs de Au2S, a qual não apresentou BP. Investigou-se sínteses de NPs Cu1,8S dopado com M (M = Fe, Al e Zn) e alguns resultados foram: i) todas amostras foram obtidas na fase digenita e com baixa dispersão de tamanho; ii) Al e Fe incorporaram na estrutura cristalina, mas aparentemente o Zn não incorporou; iii) a BP foi deslocada para maiores comprimentos de ondas em todas amostras. Em resumo, obteve-se NPs com BP na região de interesse, em quantidades maiores que as sínteses convencionais. Este trabalho contribui para a compreensão da ação de reagentes/condições experimentais sobre a composição e o controle morfológico das NPs (principalmente crescimento-1D). Ressalta-se, entre os estudos, a formação de NBs de Au na fase hcp, possibilitando futuros estudos de propriedades; o redshift da BP das NPs de Cu1,8S dopados que não eram esperados, sendo um resultado instigante para futuros estudos; e a efetiva modificação de superfície das NPs de Au que resultou em elevada estabilidade coloidal na faixa de pH entre 6 e 10, possibilitando futuras aplicações. / Nanoparticles (NPs) that present localized surface plasmon resonance (LSPR) enables several applications, for example, therapy and diagnosis in the biomedical area. In vivo studies and applications require that plasmon band occurs in the same region of the therapeutic window, between 600 and 1000 nm. This condition can be achieved with the plasmon band (PB) modulation by morphological and chemical composition control of the NPs. The main purpose of this work concerning to evaluate of the syntheses parameters to obtain NPs with different morphologies and compositions by using experimental procedures, which to enable reach larger NPs amounts than the conventional aqueous medium methods. Monodisperse Au nanospheres (NSs) with average diameter of 9 nm were obtained by reduction of gold salts in concentrated solutions by oleylamine. As-synthesized Au-NSs present oleylamine molecules onto the surface that it was replaced by 11-mercaptoundecanoic acid by using a ligand exchange procedure, resulting in the water-dispersible system with high colloidal stability. Au nanorods (NRs, 12 nm-width) with different lengths (30-300 nm) were synthesized. These NRs are an expressive result, because its present an unusual fcc and hcp crystalline phases mixtures. There is only one paper in the literature that reports the direct synthesis of Au-hcp nanostructure. The NRs dispersion show two PB in the UV-Vis-NIR spectrum at 520 nm and another large band starting in 800 nm attributed to transversal and longitudinal LSPR, respectively. Initially, the NRs were synthetized by using oleylamine as reducing agent and surfactant, and NPs with same shape were obtained in presence of oleyl alcohol or triethylamine as surfactant in the medium. Ag NSs were obtained in similar conditions of Au NSs with shape control, and LSPR band in 420 nm. Mixtures of NSs and NRs (aspect ratio of 3) of AuCu3 were obtained for all studied conditions, and separated by using a selective separation process. Two PB were observed for AuCu3 NRs at 560 and 766 nm, assigned to transversal and longitudinal resonance, respectively. Monodisperse Cu1,8S semiconductor NSs with 10 nm and PB centered in 1150 nm were synthetized via hot-injection, and attempts to cover them with Au resulted in a substitution reaction that lead the formation of Au2S NPs, which did not present PB. Syntheses of M-doped Cu1,8S NPs (M = Fe, Al e Zn) were investigated and some results were: i) all samples are digenite phase and presented low dispersivity of size; ii) Al and Fe were incorporate more effective into the crystal structure than Zn; iii) were observed redshift of PB for all samples. In summary, NPs with PB in the region of interest were obtained in greater amounts than the conventional syntheses. This thesis presents contributions to the understanding of experimental parameters that act on the compositional and morphological control of NPs (mainly 1D growth). It is emphasized among the studies: the formation of Au NRs in the hcp phase, enabling future studies of properties; the PB redshift of the doped Cu1,8S NPs that were not expected, however, this is a stimulating result for future studies; and an effective surface modification of the Au NPs that result in high colloidal stability in the pH range between 6 and 10, allowing for future applications.

Nanopartículas (NPs) que apresentam ressonância plasmon de superfície localizada (RPSL) são aplicáveis em diversas áreas como, por exemplo, em terapia e diagnóstico na área biomédica. Estudos e aplicações in vivo requerem que a banda plasmon (BP) ocorra na mesma região da janela terapêutica, entre 600 e 1000 nm. Esta condição pode ser atingida com a modulação da BP pelo controle da morfologia e da composição química das NPs. Os objetivos principais deste trabalho foram estudar métodos de síntese que permitissem obter maiores quantidades de materiais quando comparados aos métodos convencionais em meio aquoso, e conjuntamente avaliar os parâmetros de síntese para obter NPs com diferentes morfologias e composições almejando modular a BP para região de interesse. Obteve-se nanoesferas (NEs) de Au monodispersas com diâmetro médio de 9 nm por redução com oleilamina em solução concentrada de sais de ouro. Dispersibilidade em água com elevada estabilidade coloidal foi alcançada via um procedimento de troca de ligantes, substituindo as moléculas de oleilamina, presentes na superfície das NPs assim como sintetizadas, por moléculas de ácido 11-mecaptoundecanóico. Nanobastões (NBs) de Au (largura de 12 nm) com diferentes comprimentos (30-300 nm) foram obtidos em misturas incomuns das fases cristalinas fcc e hcp. Estes NBs apresentam duas BP no espectro UV-Vis-NIR, uma em 520 nm e outra banda alargada a partir de 800 nm atribuídas à RPSL transversal e longitudinal, respectivamente. Inicialmente, os NBs foram sintetizados utilizando oleilamina como agente redutor e surfactante, sendo posteriormente avaliado que a presença de álcool oleico ou trietilamina no meio mantiveram uma condição de crescimento-1D mantendo a forma dos nanomateriais. NEs de Ag foram obtidas em condições semelhantes às NEs de Au com a BP em torno de 420 nm. Obteve-se misturas de NEs e NBs de AuCu3 (NBs, com razão de aspecto de 3) em todas as condições estudadas, sendo posteriormente separadas. Duas BP foram observadas para os NBs de AuCu3 em 560 e 766 nm, atribuídas à ressonância transversal e longitudinal, respectivamente. NPs monodispersas de Cu1,8S com 10 nm e BP centradas em 1150 nm foram sintetizadas por injeção a quente. Uma tentativa de recobrimento com Au das NPs de Cu1,8S resultou em uma reação de substituição, formando NPs de Au2S, a qual não apresentou BP. Investigou-se sínteses de NPs Cu1,8S dopado com M (M = Fe, Al e Zn) e alguns resultados foram: i) todas amostras foram obtidas na fase digenita e com baixa dispersão de tamanho; ii) Al e Fe incorporaram na estrutura cristalina, mas aparentemente o Zn não incorporou; iii) a BP foi deslocada para maiores comprimentos de ondas em todas amostras. Em resumo, obteve-se NPs com BP na região de interesse, em quantidades maiores que as sínteses convencionais. Este trabalho contribui para a compreensão da ação de reagentes/condições experimentais sobre a composição e o controle morfológico das NPs (principalmente crescimento-1D). Ressalta-se, entre os estudos, a formação de NBs de Au na fase hcp, possibilitando futuros estudos de propriedades; o redshift da BP das NPs de Cu1,8S dopados que não eram esperados, sendo um resultado instigante para futuros estudos; e a efetiva modificação de superfície das NPs de Au que resultou em elevada estabilidade coloidal na faixa de pH entre 6 e 10, possibilitando futuras aplicações. / Nanoparticles (NPs) that present localized surface plasmon resonance (LSPR) enables several applications, for example, therapy and diagnosis in the biomedical area. In vivo studies and applications require that plasmon band occurs in the same region of the therapeutic window, between 600 and 1000 nm. This condition can be achieved with the plasmon band (PB) modulation by morphological and chemical composition control of the NPs. The main purpose of this work concerning to evaluate of the syntheses parameters to obtain NPs with different morphologies and compositions by using experimental procedures, which to enable reach larger NPs amounts than the conventional aqueous medium methods. Monodisperse Au nanospheres (NSs) with average diameter of 9 nm were obtained by reduction of gold salts in concentrated solutions by oleylamine. As-synthesized Au-NSs present oleylamine molecules onto the surface that it was replaced by 11-mercaptoundecanoic acid by using a ligand exchange procedure, resulting in the water-dispersible system with high colloidal stability. Au nanorods (NRs, 12 nm-width) with different lengths (30-300 nm) were synthesized. These NRs are an expressive result, because its present an unusual fcc and hcp crystalline phases mixtures. There is only one paper in the literature that reports the direct synthesis of Au-hcp nanostructure. The NRs dispersion show two PB in the UV-Vis-NIR spectrum at 520 nm and another large band starting in 800 nm attributed to transversal and longitudinal LSPR, respectively. Initially, the NRs were synthetized by using oleylamine as reducing agent and surfactant, and NPs with same shape were obtained in presence of oleyl alcohol or triethylamine as surfactant in the medium. Ag NSs were obtained in similar conditions of Au NSs with shape control, and LSPR band in 420 nm. Mixtures of NSs and NRs (aspect ratio of 3) of AuCu3 were obtained for all studied conditions, and separated by using a selective separation process. Two PB were observed for AuCu3 NRs at 560 and 766 nm, assigned to transversal and longitudinal resonance, respectively. Monodisperse Cu1,8S semiconductor NSs with 10 nm and PB centered in 1150 nm were synthetized via hot-injection, and attempts to cover them with Au resulted in a substitution reaction that lead the formation of Au2S NPs, which did not present PB. Syntheses of M-doped Cu1,8S NPs (M = Fe, Al e Zn) were investigated and some results were: i) all samples are digenite phase and presented low dispersivity of size; ii) Al and Fe were incorporate more effective into the crystal structure than Zn; iii) were observed redshift of PB for all samples. In summary, NPs with PB in the region of interest were obtained in greater amounts than the conventional syntheses. This thesis presents contributions to the understanding of experimental parameters that act on the compositional and morphological control of NPs (mainly 1D growth). It is emphasized among the studies: the formation of Au NRs in the hcp phase, enabling future studies of properties; the PB redshift of the doped Cu1,8S NPs that were not expected, however, this is a stimulating result for future studies; and an effective surface modification of the Au NPs that result in high colloidal stability in the pH range between 6 and 10, allowing for future applications.

Dans ce travail de these, nous étudions comment des nano-structures métalliques modifient le processus d'émission spontannée d'objets fluorescents et jouent ainsi un rôle d'antenne. Ces structures supportent des modes optiques confinés aux interfaces metal-diélectrique: ce sont des modes plasmoniques.De par leur fort confinement, ces modes modifient la densité locale d'états optiques et permettent notamment d'accélérer le processus d'émission spontannée (facteur de Purcell). Nous étudions le cas d'une structure planaire metal-isolant-métal de type patch couplée à un ensemble de nanocristaux colloïdaux fluorescents. Nos mesures, soutenues par des calculs numériques, montrent une acceleration de l'émission fluorescente d'un facteur 80 ainsi qu'une augmentation de la directivité de l'émission. Nous décrivons ensuite le procedé de fabrication d'une structure patch metal-semiconducteur-métal pour laquelle la source fluorescente est un puits quantique émettant dans le proche infra-rouge. Nous montrons que l'antenne permet d'augmenter l'extraction fluorescente d'un facteur 8. Enfin, nous considérons le cas d'une structure sphérique composée d'un unique nanocristal fluorescent au centre d'une bille de silice entourée par une fine coquille métallique. Cette structure plasmonique accélère l'émission d'une facteur 10 et permet de supprimer le scintillement caractéristique de l'émission des nanocristaux. La coquille métallique permet également d'isoler chimiquement le nanocristal de l'environnement, assurant ainsi une grande photostabilité et une toxicité réduite. L'émetteur ainsi obtenu est donc un candidat prometteur pour des applications de marquage de fluorescence in-vivo. / The present work focuses on the modification of spontaneous emission of fluorescent emitters using metallic nano-structures. These structures support confined plasmonic modes that strongly increase the local density of optical states. Consequently, the plasmonic structure enhances the spontaneous decay rate of the emitter. We use both numerical simulations and experimental results to demonstrate the potential of plasmonic antennas as tools to control spontaneous emission. First, we study a metal-dielectric-metal planar structure called patch antenna. This structure is coupled to an ensemble of quantumdots emitting visible light. We show that, in the presence of the patch antenna, the fluorescent emission is accelerated by a factor 80 and that its directivity is increased. Then, we use a similar plasmonic structure coupled to a quantum well emitting in the near infrared. Using an ad hoc hyperspectral imaging setup, we show that the antenna increases the extracted light by a factor 8. Finally, we study a spherical geometry composed of a single fluorescent quantum dot at the center of a silica bead coated with a thin gold shell. This plasmonic structure