[ES] La irradiación de nanopartículas de oro (AuNPs) esféricas en una suspensión coloidal con pulsos láser de nanosegundos puede inducir su metamorfosis, dando lugar a la aparición de esferas con cavidades internas. La concentración del surfactante estabilizador de las partículas, el uso de fluencias de láser moderadas y el tamaño de las partículas, determinan la eficiencia y características del proceso. Las partículas huecas resultantes se obtienen cuando las moléculas del medio circundante (ej., agua, materia orgánica del surfactante) quedan atrapadas durante la irradiación láser. Estas observaciones experimentales sugieren la existencia de un balance sutil entre los procesos de calentamiento y enfriamiento. El primero induce la expansión y paso a un estado amorfo y, el segundo, la subsecuente recristalización manteniendo en su interior el material atrapado. Estas observaciones experimentales han sido explicadas satisfactoriamente con las simulaciones de dinámica molecular clásica desarrolladas en el marco de esta tesis. Específicamente, la dinámica molecular confirma que es necesaria la existencia de moléculas en el interior de las cavidades que se forman dentro de las AuNPs para que se produzca su estabilización. En la segunda parte de esta tesis, se detallan las simulaciones de dinámica molecular clásica y los cálculos de propiedades ópticas de la irradiación de nanopartículas esféricas de oro con pulsos láser de femtosegundos, para predecir los cambios de forma que se producen en las mismas, bajo una exploración de los diferentes parámetros involucrados, es decir, la fluencia y duración del láser, el tamaño de las nanopartículas cristalinas esféricas y la capacidad de enfriamiento del medio circundante. El objetivo fundamental de las simulaciones es brindar una guía para la síntesis de nanopartículas con morfologías determinadas. Los resultados de las simulaciones indican que, para la formación de nanopartículas huecas, las mismas deben ser calentadas hasta una temperatura entre 2500 y 3500 K, seguido por un enfriamiento exponencial rápido, con una constante de tiempo menor de 120 ps. Por lo tanto, se describen las condiciones experimentales para la producción eficiente de nanopartículas huecas, lo que abre un amplio rango de posibilidades de aplicación en áreas fundamentales, tales como el almacenamiento de energía y la catálisis. En la última parte de esta memoria se exponen las simulaciones de dinámica molecular clásica implementadas para profundizar en los experimentos pumpprobe con nanoesferas plasmónicas de oro, desarrollados en la referencia [R.Fuentes-Domínguez et al. Appl. Sci. 2017, 7(8), 819.]. Tras la irradiación láser y consecuente deposición de energía, las partículas vibran, lo que se puede medir mediante la fuerte modulación producida en la sección eficaz de dispersión. La vibración mecánica de las AuNPs esféricas, tras ser irradiadas con láseres ultracortos, las convierte en generadores termoelásticos eficientes de ultrasonido y, por tanto, en excelentes candidatos para transductores luz-sonido en diversas aplicaciones. / [CA] La irradiació de nanopartícules d'or (AuNPs) esfèriques en una suspensiócolloidal amb polsos làser de nanosegons pot induir la seua metamorfosi, donant lloc a l'aparició d'esferes amb cavitats internes. La concentració del surfactante estabilitzador de les partícules, l'ús de fluencias de làser moderades i la grandària de les partícules, determinen l'eficiència i característiques del procés. Les partícules buides resultants s'obtenen quan les molècules del mitjà circumdant (ex., aigua, matèria orgànica del surfactante) queden atrapades durant la irradiació làser. Aquestes observacions experimentals suggereixen l'existència d'un balanç subtil entre els processos de calfament i refredament. El primer indueix l'expansió i passe a un estat amorf i, el segon, la subseqüent recristalización mantenint en el seu interior el material atrapat. Aquestes observacions experimentals han sigut explicades satisfactòriament amb les simulacions de dinàmica molecular clàssica desenvolupades en el marc d'aquesta tesi. Específicament, la dinàmica molecular confirma que és necessària l'existència de molècules a l'interior de les cavitats que es formen dins de les AuNPs perquè es produïsca la seua estabilització. En la segona part d'aquesta tesi, es detallen les simulacions de dinàmica molecular clàssica i els càlculs de propietats òptiques de la irradiació de nanopartícules esfèriques d'or amb polsos làser de femtosegundos, per a predir els canvis de manera que es produeixen en aquestes, sota una exploració dels diferents paràmetres involucrats, és a dir, la fluencia i duració del làser, la grandària de les nanopartícules cristal·lines esfèriques i la capacitat de refredament del mitjà circumdant. L'objectiu fonamental de les simulacions és brindar una guia per a la síntesi de nanopartícules amb morfologies determinades. Els resultats de les simulacions indiquen que, per a la formació de nanopartícules buides, les mateixes han de ser calfades fins a una temperatura entre 2500 i 3500 K, seguit per un refredament exponencial ràpid, amb una constant de temps menor de 120 pg. Per tant, es descriuen les condicions experimentals per a la producció eficient de nanopartícules buides, la qual cosa obri un ampli rang de possibilitats d'aplicació en àrees fonamentals, tals com l'emmagatzematge d'energia i la catàlisi. En l'última part d'aquesta memòria s'exposen les simulacions de dinàmica molecular clàssica implementades per a aprofundir en els experiments pumpprobe amb nanoesferas plasmónicas d'or, desenvolupats en la referència [R. Fuentes-Domínguez et al. Appl. Sci. 2017, 7(8), 819.]. Després de la irradiació làser i conseqüent deposició d'energia, les partícules vibren, la qual cosa es pot mesurar mitjançant la forta modulació produïda en la secció eficaç de dispersió. La vibració mecànica de les AuNPs esfèriques, després de ser irradiades amb làsers ultracortos, les converteix en generadors termoelásticos eficients d'ultrasò i, per tant, en excel·lents candidats per a transductors llum-so en diverses aplicacions. / [EN] The irradiation of gold nanoparticles (AuNPs) in a colloid with nanosecond laser pulses can give rise to the formation of cavities. The concentration of the surfactant used to stabilize the particles, the laser fluency, and the size of the nanoparticles, determine the efficiency and features of the process. The resulting hollow particles are obtained when the right balance between the heating and cooling processes is given. The first process induces an expansion and the melting of the particle, while the second, leads to the recrystallization, keeping the extraneous matter trapped in the inside. These experimental observations have been satisfactorily explained by the molecular dynamics simulations carried out in this thesis. Specifically, the simulations have confirmed that it is necessary the existence of trapped molecules in the inside of the cavities to stabilize the cavities. In the second part of this thesis, the molecular dynamics simulations and calculation of optical properties when gold nanoparticles (in a colloid) are irradiated with femtosecond laser pulses. The simulations allowed to predict the the shape changes under different conditions for the laser fluency and duration, the size of the nanoparticles and the cooling rate, which is driven by the properties of the solvent and the surfactant. These simulations provide a guidance for the synthesis of nanoparticles with specific morphological features. The results show that the nanospheres should be heated up to 2500 y 3500 K, followed by a fast cooling (time constant of 120 ps). Therefore, the experimental conditions for the efficient production of hollow nanoparticles are described what opens a broad range of possibilities for applications in areas such as energy storage and catalysis. MD simulations are carried out in the last part of this thesis to gain insights into the pump-probe experiments using AuNPs in reference [R. Fuentes-Domínguez et al. Appl. Sci. 2017, 7(8), 819.]. Upon femtosecond laser irradiation and deposition of energy, the nanospheres vibrate which can be measured by means of the scattering cross section. This fact becomes the AuNPs in ideal thermoelastic ultrasound generators and therefore in excellent candidates for light-sound transducers in different applications. / Castro Palacio, JC. (2021). Modelación físico-matemática y simulaciones computacionales para guiar el diseño y fabricación de nanoestructuras plasmónicas optimizadas para aplicaciones energéticas [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/175557

Lysosomen spielen entscheidende Rolle bei der zellulären Homöostase. Die Überwachung von Lysosomen, die Lipide ansammeln, ist eine erhebliche Herausforderung. Diese Arbeit konzentriert sich auf die Entwicklung der oberflächenverstärkten Raman-Streuung (SERS) als Methode zur Überwachung intakter Lysosomen, insbesondere hinsichtlich des Einflusses von Arzneimitteln, die den Lipidstoffwechsel stören. Um das Potenzial von SERS zur Untersuchung von Lysosomen in lebenden Zellen zu bewerten, wurden die Wechselwirkungen zwischen trizyklischen Antidepressiva und saurer Sphingomyelinase untersucht. Zunächst wurden Modellsysteme untersucht. Die Wechselwirkungen zwischen den Antidepressiva und Goldnanopartikeln wurden durch SERS charakterisiert. Die Daten zeigten, dass Moleküle mit den Nanopartikeln interagieren. Als Modellsystem der lipidreichen Umgebung wurden Komposite aus Liposomen und Goldnanopartikeln von SERS und Cryo-EM untersucht. Die SERS-Spektren sind charakteristisch für die Lipidzusammensetzung der Vesikel. Die Wechselwirkungen zwischen den Antidepressiva und den Lysosomen wurden in der Fibroblastenzelllinie 3T3 durch SERS und komplementäre Methoden untersucht. In Übereinstimmung mit den SERS-Spektren von Modellsystemen zeigen die SERS-Spektren lebender Zellen Signaturen sowohl der Antidepressiva als auch der Lipide. Um die Unterschiede in den Lysosomen zwischen behandelten und nicht behandelten Zellen aufzudecken, wurde ein zufälliger Waldansatz verwendet. Darüber hinaus wurde SERS verwendet, um die Lipidverteilung in Leishmania-infizierten Makrophagen zu untersuchen, von denen bekannt ist, dass sie Lipide akkumulieren. Die Ergebnisse zeigen, dass SERS verwendet werden kann, um die Lipidzusammensetzung in lebenden Zellen verschiedener Zelltypen zu untersuchen. Als neue methodische Entwicklung zeigt die Random-Forest-Analyse von SERS-Daten, dass Ansätze des maschinellen Lernens für ein besseres Verständnis von Daten aus biologischen Systemen nützlich sein können. / Lysosomes play a crucial role in cellular homeostasis. Monitoring lysosomes that accumulate lipids represents a considerable challenge. This thesis focuses on the development of surface-enhanced Raman scattering (SERS) as a method to monitor intact lysosomes, in particular regarding the influence of drugs that interfere with lipid metabolism. To evaluate the potential of SERS for studying lysosomes in live cells, the interactions between tricyclic antidepressants and acid sphingomyelinase were studied. First, model systems were investigated. The interactions between the antidepressants and gold nanoparticles were characterized by SERS. The data showed that molecules interact with the nanoparticles. As a model system of the lipid-rich environment, composites of liposome and gold nanoparticles were studied by SERS and cryo-EM. The SERS spectra are characteristic of the vesicles’ lipid composition. The interactions between the antidepressants and the lysosomes were studied in the fibroblast cell line 3T3 by SERS and complementary methods. In agreement with the SERS spectra of model systems, the SERS spectra of live cells show signatures of both, the antidepressants and the lipids. To reveal the differences in the lysosomes between treated and non-treated cells, a random forest approach was used. Moreover, SERS was used to study the lipid distribution in Leishmania-infected macrophages known to accumulate lipids. The results show that SERS can be used to investigate lipid composition in live cells of different cell types. As a new methodological development, the random forest analysis of SERS data shows that machine learning approaches can be useful for a better understanding of data from biological systems.

Noble metal nanoparticles such as gold and silver are of interest because of the unique electro-optical properties (e.g., localized surface plasmon resonance [LSPR]) that originate from the collective behavior of their surface electrons. These nanoparticles are commonly developed and used for biomedical and industrial application. A recent report has predicted that the global market for gold nanoparticles will be over 12.7 tons by year 2020. However, these surface-functionalized nanoparticles can be potential environmental persistent contaminants post-use due to their high colloidal stability in the aquatic systems. Despite, the environmental risks associated with these nanoparticles, just a few studies have investigated the effect of nanofeature factors such as size and shape on the overall fate/transport and organismal uptake of these nanomaterials in the aquatic matrices. This study presents a comprehensive approach to evaluate the colloidal stability, fate/transport, and organismal uptake of these nanoparticles while factoring in the size and shape related properties. We demonstrate the importance and effect of anisotropicity of a gold nanoparticle on the colloidal behavior and interaction with ecologically susceptible aquatic biota. We also show how readily available characterization techniques can be utilized to monitor and assess the fate/transport of this class of nanoparticles. We further describe and investigate the relationship between the aspect ratio (AR) of these elongated gold nanoparticles with clearance mechanisms and rates from the aquatic suspension columns including aggregation, deposition, and biopurification. We illustrate how a fresh water filter-feeder bivalve, Corbicula fluminea, can be used as a model organism to study the size and shape-selective biofiltration and nanotoxicity of elongated gold nanoparticles. The results suggest that biofiltration by C. fluminea increases with an increase in the size and AR of gold nanoparticle. We develop a simple nanotoxicity assay to investigate the short-term exposure nanotoxicity of gold nanoparticles to C. fluminea. The toxicity results indicate that for the tested concentration and exposure period that gold nanoparticles were not acutely toxic (i.e., not lethal). However, gold nanoparticles significantly inhibited the activities of some antioxidant enzymes in gill and digestive gland tissues. These inhibitions could directly affect the resistance of these organisms to a secondary stressor (temperature, pathogens, hypoxia etc.) and threaten organismal health. / Ph. D. / Nanoparticles are fine particles that cannot be seen with naked eye and possess unique chemical and physical properties. Gold and silver nanoparticles are specifically of interest due to tunable optical properties and are commonly developed and used for biomedical and industrial applications. Unfortunately, these metallic nanoparticles can be potential environmental persistent contaminants post-use in the soil and aquatic systems. Despite, the environmental risks associated with these metallic nanoparticles, just a few studies have investigated the effect of size and shape of these nanoparticles on their interaction and transportation in the surrounding environment and with existing organisms. This study presents a comprehensive approach to evaluate the stability, transportation, and organismal uptake of these nanoparticles while factoring in the size and shape related properties. We also show how readily available detection techniques can be utilized to monitor and assess the presence and transport of this class of nanoparticles. We illustrate how a fresh water bivalve, Corbicula fluminea, can be used as a model organism to study the size and shape-selective uptake and toxicity of gold nanoparticles. The results suggest that nanoparticles uptake by C. fluminea increases with an increase in the size of gold nanoparticle. We develop a simple toxicity assay to investigate the short-term exposure toxicity of gold nanoparticles to C. fluminea. The toxicity results suggest that for the tested concentration and exposure period that gold nanoparticles were not acutely toxic (i.e., not lethal) but affect the resistance of these organisms to an environmental change (temperature, pathogens, hypoxia etc.) and threaten organismal health.

Increased proliferation of nanotechnology has led to concerns regarding its implication to the water environment. Gold nanoparticles (AuNP) were used as a model nanomaterial to investigate the fate and dynamics of nanoparticles in the complex water environment. A column study was performed to examine the fate and transport of gold nanoparticles with two different coatings in porous media. The resulting data suggested that gold nanoparticles aggregate significantly in the porespace of the column interior, a finding that is not predicted by traditional colloidal filtration theory or Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Surface-enhanced Raman spectroscopy (SERS) was developed as a new technique to investigate AuNP aggregation in water with varying salt levels. The SERS technique proved valuable as an analytical technique, elucidating information about aggregation as well as AuNP surface interactions with dissolved halides in water. A thorough investigation examining Aunt aggregation with monovalent and divalent salts utilizing SERS, ultraviolet-visible light (UV-Vis) spectroscopy, and dynamic light scattering (DLS) was conducted. Each technique provided data describing different aspects of the dynamic behavior of AuNPs in complex water environments. Results suggest that in addition to attractive and repulsive interactions described by DLVO theory, chemical interactions between the AuNP surface and dissolved halides were also a significant driving force for aggregation and other transformative behaviors of AuNPs in water. The SERS technique developed in this work was shown to be a viable tool to help unveil the vastly complex dynamics of nanomaterial in the water environment. / Ph. D. / Nanotechnology is everywhere. It is in our smartphones, in our food, in our clothes, even if we do not recognize it is there. And this is a good thing, because nanotechnology – that is, technology that utilizes nanomaterials – can provide things that traditional technology often cannot. This is all because many nanomaterials have “superpowers” due to their size range: they are generally larger than what we may think of when we think of chemical molecules, but much smaller than macroscopic materials whose behaviors can be approximated by classic physics and chemistry. For example, we all know that gold has a shiny yellow metallic appearance. However, if we make little particles of gold – and these are going to be very tiny, with diameters about 10,000 times smaller than that of a strand of human hair (but about 100 times larger than what we would typically think of as molecules of chemicals) – and put them in water, the resulting mixture will be ruby-red like wine. One of the “superpowers” these gold nanoparticles possess is that they interact with light in a very different way than bulk gold. Currently, researchers in the biomedical field are producing promising work employing these particles in nextgeneration imaging, and much more. In this study, we were interested in what happens to these materials once they are released to the water environment. Because of the “superpowers” these gold nanoparticles possess, we really do not know how they will behave once they are released to either surface or groundwater because the physics and chemistry of those environments can be quite variable and complex. In this work, we have shown that traditional assumptions about particulate contaminants in water systems do not necessarily hold for gold nanoparticles. Laboratory simulations show that interactions between these particles and the surrounding environment that were once thought to be negligible, are in fact highly significant. As our title suggests, we are developing new and advanced “photonics” methods to help us discover the dynamic complexity dictating the fate of these gold nanoparticles once they are in the water environment. Photonics methods are techniques that employ light as a probing tool. These techniques use a well understood laser light source that is directed towards the particles in a water environment, and we then measure changes in the scattered light after it has interacted with the particles. The technique we have employed here (called surface-enhanced Raman spectroscopy, or SERS) simultaneously provides us information about different behaviors of gold nanoparticles in water, including how they may aggregate (that is, stick to one another and form big clumps) and how they interact with existing dissolved chemicals that may be present in the natural water environment. By pairing this method with other existing methods, we were able to paint a more complete picture of how these nanoparticles behave in the water environment, and we can answer some questions as to why they do not follow some previously held assumptions. In the end, the work in this dissertation will help future scientists continue to unlock the complexity of nanomaterial fate and dynamics in the water environment.

Optical properties of nanoscopic materials have been intensively perused over last couple of decades due to their tunable optical properties. Recent interests in this field have been mainly focused on the preparation of ordered arrays of nanoscopic materials and study of their optical properties. These interests have been motivated by the usability of such systems for nano photonic devices. Theoretical predictions from such systems reveal complex absorption and emission properties, different from individual ones mainly because of energy transfer between them. These properties can be controlled further by preparing hybrid arrays of nanostructures, including nano crystals of different types. Hybrid arrays with semiconducting quantum dots and metallic nanoparticles are an example of such system. Optical properties of such a system can be tuned by controlling the interaction between excitons and plasmons. This the-sis presents the experimental studies on optical properties of polymer capped polymer nanoparticles, quantum dot arrays and hybrid arrays with semiconducting quantum dot and metal nanoparticles. A brief summary of the experi-mental methods and results have been highlighted below. First chapter deals with the theoretical aspects of confined nanoscopic materials, especially describing the physics of zero dimensional systems and its optical properties. The discussions are mostly focused on two types of nano materials cadmium selenide (CdSe) quantum dot (QDs) and gold nano particles (Au NPs), used for the experimental study. Variation of energy levels of CdSe QDs and its absorption and emission properties under strong confinement regime has been discussed with respect to effective mass approximation (EMA) model. This is followed by the discussion on optical properties of Au NPs, describing absorption properties, based on Mie theory. Size dependent variation of absorption spectra of Au NPs and the modifications based on different models has been discussed. Second part of the chapter describes the physics of QD arrays and theory of exciton plasmon interactions based on the recent literatures. Energy transfer mechanism between semiconducting QDs and metal nanoparticles has been discussed based on numerical method and dipole approximation. Second chapter deals with the discussion on experimental techniques used for the study. Chapter 2 starts with the discussion on the synthesis method for CdSe QDs and Au NPs with different capping ligands. Preparation of QD ar-rays and hybrid arrays using self assembly technique has been discussed in this chapter. Preparation CdSe QD arrays and hybrid arrays with CdSe QDs and Au NPs using block copolymer (BCP) template and Langmuir Blodgett (LB) technique has been the main focus in the discussion. This is followed by the discussion on optical microscopy techniques, confocal, near field scanning microscopy (NSOM), Brewster angle microscopy and electron microscopy techniques, transmission electron microscopy and scanning electron microscopy. Studies on variation of band structure of small polymer capped Au NPs, with respect to the size and grafting density of the capping polymer is discussed in chapter 3. Polymer capped Au NPs with sizes 2-5 nm was used for the study. Dielectric constants of Au NPs were extracted from the absorption spectra by fitting the data using modified Mie theory. Dielectric constants of Au NPs were reproduced using an analytical expression, describing the contribution from different transitions in the optical regions. Results indicate systematic variations of the band structure with respect to the particle size and grafting density. The observations have been interpreted in terms of variation of co ordination number and chemical interaction of capping polymer with the surface atoms. Our new method analysis points to the importance of both quantum and surface effects in determining optical and electronic properties of polymer capped gold nanoparticles. Chapter 4 describes the study on morphology of the CdSe QD arrays prepared using different BCP templates and its correlation with optical properties. Spatially resolved spectra from the thin films of QD arrays were collected in near field and the compared with the spectra collected in far field. Spectra collected in near field mode shows sharp features in the emission spectra, possibly indicating the interaction of optical near field with QD excitation. It has been suggested that such fine structure could be induced by coupling between optical near filed and excitons and this coupling seems to be determined by local heterogeneity in QD density and disorder. Variation of exciton life time with respect to QD density and absorption spectra from the QD -BCP system is also described in chapter 4. Chapter 5 and 6 deals with the experimental studies on exciton -plasmon interaction in hybrid arrays of CdSe QDs and Au NPs. Emission properties hybrid arrays prepared using BCP templates has been the focus of chapter 5. Photoluminescence (PL) and lifetime measurements were performed on hybrid arrays and their variation with respect to the density and dispersion of Au NPs has been described. Optical measurements were performed on two sets of films using two different sizes of CdSe QDs, with the smaller QD emission overlapping with the plasmon resonance of Au NPs, while a red shifted emission peak for larger QDs. PL emission from hybrid arrays with smaller QDs shows en-hancement/quenching with respect to the dispersion of Au NPs, also showing systematic reduction of life time of CdSe QDs with Au NP density. Even though enhancement/quenching of emission properties of hybrid film with large QD shows similar behavior, PL decay measurements from such films shows non monotonic variation of exciton life time with respect to Au NP density. The enhancement/quenching behavior of the PL emission has been explained in terms of two competing mechanism, electromagnetic field enhancement and non radiative energy transfer. However to explain the energy transfer mechanism in hybrid arrays requires more systematic calculations. Chapter 6 describes the optical properties of highly compact hybrid arrays prepared using LB techniques. Hybrid arrays prepared at the air water inter-face were transferred to a glass substrates. The main focus on chapter 6 is to study the emission properties of highly compact hybrid arrays with respect to the spectral overlap between exciton energy of CdSe QDs and plasmon band of Au NPs with respect to their surface density (inter particle distance). Hybrid arrays were prepared with three types of QDs, with smaller QDs emission peak overlapping with plasmon band of Au NPs and clearly separated exciton and plasmon band for largest QDs. The PL emission from hybrid arrays with smaller QDs shows quenching, compared to strong enhancement in the emission from hybrid films with larger QDs. The disagreement of the observed results with respect to the theoretical calculations based on dipole approximation has been highlighted in the chapter. Chapter 7 includes the summary of the experimental results and the future works to be carried out as a continuation of the work presented in this thesis.

<p>We have studied fundamental aspects of time-resolved two-photon excited fluorescence depolarisation. The thesis presents experimental as well as theoretical progress. We show that a multi-photon induced instrumental response function obtained from a suspension of gold nanoparticles is appropriate for the analysis of two-photon excited fluorescence decays obtained using time-correlated single photon counting detection. Theoretical expressions have been derived for the fluorescence anisotropy decay obtained upon two-photon excitation of various molecular systems in liquid solutions: a) an anisotropic rigid rotor that undergoes rotational diffusion in the presence of ultrafast unresolved restricted reorientations, e.g. librations. b) a molecular group covalently attached to a stationary macromolecule, and undergoing local reorientation in a uniaxial ordering potential. A new approach to the analysis of two-photon excited fluorescence depolarisation experiments was developed, which combines data obtained by using linearly and circularly polarised excitation light, in a global manner. In the analysis, knowledge about unresolved reorientations was obtained from one-photon excitation studies of the corresponding systems. By means of this procedure it has been possible to obtain quantitative information about the molecular two-photon absorption tensor for perylene and two of its derivatives. Thereby the symmetry of the final excited and intermediate vibronic states could be assigned. The analysis reveals that the two-photon transition studied with the 800 nm laser exhibits mixed character. An important finding from the experiments was that the two-photon absorption tensor appears to be solvent dependent. Furthermore, the thesis presents the first theoretical treatment of two-photon excited donor-donor energy migration in the presence of molecular reorientation and which applies the extended Förster theory. Explicit expressions for molecules that belong to the point groups D_2h, D₂ and C_2v are given. Preliminary experiments are finally also reported on a two-photon excited donor-donor energy migration system consisting of a bisanthryl-bisteroid. </p>

La concentration locale des messagers chimiques sécrétés par les cellules peut être mesurée afin de mieux comprendre les mécanismes moléculaires liés à diverses maladies, dont les métastases du cancer. De nouvelles techniques analytiques sont requises pour effectuer ces mesures locales de marqueurs biologiques à proximité des cellules. Ce mémoire présentera le développement d’une nouvelle technique basée sur la réponse plasmonique sur des leviers AFM, permettant d’étudier les réactions chimiques et biologiques à la surface des leviers grâce au phénomène de résonance des plasmons de surface (SPR), ainsi qu’à la diffusion Raman exaltée par effet de pointe (TERS). En effet, il est possible de localiser l’amplification du signal Raman à la pointe d’un levier AFM, tout comme le principe de la diffusion Raman exaltée par effet de surface (SERS) basée sur la diffusion de la lumière par des nanoparticules métalliques, et permettant une large amplification du signal Raman. La surface du levier est recouverte d’une nano-couche métallique d’or, suivi par des réactions biologiques pour l’immobilisation d’un récepteur moléculaire, créant ainsi un biocapteur sur la pointe du levier. Une détection secondaire utilisant des nanoparticules d’or conjuguées à un anticorps secondaire permet également une amplification du signal SPR et Raman lors de la détection d’antigène. Ce mémoire démontrera le développement et la validation de la détection de l’immunoglobuline G (IgG) sur la pointe du levier AFM.Dans des projets futurs, cette nouvelle technique d’instrumentation et d’imagerie sera optimisée grâce à la création d’un micro-détecteur protéique généralement adapté pour l’étude de la communication cellulaire. En intégrant le signal SPR à la microscopie AFM, il sera alors possible de développer des biocapteurs SPR couplés à une sonde à balayage, ce qui permettra d’effectuer une analyse topographique et de l’environnement chimique d’échantillons cellulaires en temps réel, pour la mesure des messagers moléculaires sécrétés dans la matrice extracellulaire, lors de la communication cellulaire. / Measurement of the local concentration of chemical messengers secreted by cells may give a better understanding of molecular mechanisms related to different diseases, such as cancer metastasis. Current techniques are not suited to perform such measurements and thus, new analytical techniques must be developed. This Master’s thesis reports the development of a new technique based on the plasmonic response of atomic force microscopy (AFM) tips, which will ultimately allow monitoring of chemical and biological molecules on the surface of a cantilever by use of surface plasmon resonance (SPR) and tip-enhanced Raman scattering (TERS). Indeed, it is possible to localize the enhancement of the Raman signal on the AFM tip using principles associated to surface-enhanced Raman spectroscopy (SERS), based on the absorption of light by nanometer-sized metal particles, resulting in a large enhancement of the Raman signal. The AFM tip was constructed by the deposition of a nanometer-size gold layer, followed by the assembly of a biosensor with a biomolecular receptor. Gold nanoparticles (AuNPs) conjugated with a secondary antibody served as the secondary detection step. In addition, the use of the gold nanoparticles for antigen detection allows an amplification of the SPR and Raman signals. This Master’s thesis will demonstrate the development and validation of a biosensor for immunoglobuline G (IgG) at the tip of an AFM cantilever.This thesis sets the basis for future projects, where this new imaging technique will be developed for monitoring cellular communication by exploiting the plasmonic signal at the AFM tip. Different biosensors will then be developed and coupled to an AFM probe for scanning the chemical environment and detect in real-time chemical messengers secreted in the extracellular matrix in cellular communication.

Généralement, un bon conducteur thermique est aussi bon conducteur électrique (Wiedemann-Franz). Pour de nombreuses applications, il est impératif de pouvoir découpler ces deux propriétés. La nanostructuration permet de modeler les propriétés thermiques sans affecter les propriétés électriques. Lors de cette thèse, nous nous sommes intéressés à la synthèse et à la caractérisation d'un matériau initialement isolant dans lequel est insérée une assemblée de nanoparticules métalliques. Le nanocomposite élaboré est constitué de nanoparticules cœur@écorce (Au@SiO2 ou Au@Thiol) structurées en opale par méthode de type "Langmuir". Lorsque la concentration en nanoparticules est suffisante, une amplification du transfert thermique dans le nanocomposite est prédite par certains auteurs. Le couplage par rayonnement en champ proche, majoritairement plasmonique, constitue un nouveau mécanisme de transport de chaleur. Dans ce travail, nous avons étudié le transfert d'énergie au sein de nanoparticules isolées et sous forme de réseau. Dans un premier temps, nous présentons les techniques de synthèse chimique mises en œuvre pour la conception des nanocomposites et détaillons leurs propriétés optiques. Puis, nous présentons la conception du banc de mesure, il s'agit d'un banc d'imagerie pompe-sonde femtoseconde accordable en longueur d'onde permettant des études en réflexion et transmission. Les expériences que nous avons menées nous ont permis d'étudier la dynamique thermique électronique de nanoparticules d'or pour différents environnements et de mettre en évidence expérimentalement des modes de vibration acoustiques de systèmes cœur-écorce lorsqu'ils sont soumis à une excitation laser femtoseconde. / Typically, a good thermal conductor is also a good electrical conductor (Wiedemann-Franz). For several applications, it is imperative to be able to decouple these two properties. Nanostructuration allows for the modification of thermal properties without affecting electrical properties. This thesis is concerned with the synthesis and characterization of nanocomposites made from an insulating matrix impregnated with metallic nanoparticles. The elaborated nanocomposite is assembled from core@shell nanoparticles (Au@SiO2 or Au@Thiol) structured in an artificial opal by the "Langmuir" method. When the nanoparticle concentration is sufficiently high, certain authors predict an amplification of thermal transport in the nanocomposite. The radiative near-field coupling, largely plasmonic, constitutes a new mechanism for heat transport. In this work, we have studied the energy transfer within isolated nanoparticles and in arrays. First, we present chemical synthesis techniques used for the nanocomposites conception and detailed their optical properties. Then, we present the conception of the experimental set-up; a multicolor femtosecond pump-probe Imaging system permitting studies in reflection or transmission. These experiments permit us to study the electronic temperature dynamics of gold nanoparticles in different environments and to measure core@shell system's acoustic vibrational modes femtosecond laser excitation.

Le procédé sol-gel permet la réalisation de matériaux optiquement performants et la possibilité d’intégrer diverses molécules dans ces systèmes ouvre les portes à des applications dans de nombreux domaines. Nous nous sommes intéressés en particulier à la réalisation de matériaux sol-gel monolithiques, fortement dopés avec des molécules actives, dans le cadre de la réalisation de limiteurs optiques performants dans le visible et dans l’infrarouge.La mise au point de procédés et de matrices sol-gel compatibles avec divers types de chromophores a tout d’abord été effectuée. Une investigation des paramètres expérimentaux et de la nature des précurseurs influençant la microstructure des matériaux a été réalisée, ainsi que la mise au point de méthodes de gélification accélérée capables de piéger efficacement les chromophores dans les matrices sol-gel même à de très hautes concentrations.Le dopage des matrices obtenues avec différents chromophores pour la limitation optique dans le visible et dans l’infrarouge s’en est suivi, avec une étude de l’impact des matrices sur les propriétés optiques des dopants. L’évaluation des performances en limitation a révélé les performances exceptionnelles des systèmes étudiés dans le visible, et des résultats prometteurs pour l’infrarouge.Enfin, la synthèse de nanoparticules d’or isotropes et anisotropes et leur incorporation dans les matériaux préparés a permis de mettre en évidence des effets d’exaltation importants sur les propriétés non-linéaires des chromophores au sein des matrices sol-gel et permettent d’améliorer les performances en limitation de manière considérable. / Sol-gel chemistry is a potent approach for the realization of optical materials, and enables chromophores incorporation in materials making the soft process a gateway for many applications. In this work, we focused on monolithic sol-gel materials, heavily doped with optically active chromophores for the realization of solid-sate optical power limiting devices in the visible and near-infrared range.The elaboration and optimization of compatibles sol-gel matrices with those chromophores was the first step. An investigation of the different synthesis parameters and the nature of the precursors on the materials nanostructure were done, together with the creation of high speed gelation processes to enable the incorporation of very high chromophores contents.Using these approaches, the preparation of highly doped materials for optical power limiting in the visible and the near infrared range was successful, and the impact of the matrices on chromophores properties was studied. Evaluation of optical limiting properties of these materials revealed exceptional performance in the visible range and promising results for the NIR range.Finally, isotropic and anisotropic gold spheres were prepared and incorporated inside the materials. The resulting composites showed enhancements of the non-linear properties of the chromophores inside the matrix, and dramatic improvement of the optical power limiting efficiency was achieved.

Les matériaux méso-structurés sont des matériaux à porosité contrôlée, issus de synthèses de chimie sol/gel entre micelles de tensioactifs et précurseur inorganique, le plus souvent de silice. Parmi ces matériaux, le SBA-15, formé en milieu super-acide à partir de P123 (un copolymère tribloc) comme tensioactif et de TEOS comme précurseur inorganique de silice, est un des plus étudiés. La synthèse de ce matériau a été étudiée par diffusion des rayons X à petits angles (SAXS) in situ, et a permis de décrire qualitativement et quantitativement les mécanismes d’auto-assemblages entre micelles de tensioactifs et particules silicatées. Spécifiquement, nos résultats ont montré que l’hydrolyse-condensation du TEOS en solution a permis la formation d’oligomères de silice, qui interagissent avec la couronne des micelles sphériques de P123, pour progressivement former des micelles hybrides cylindriques organiques/inorganiques, qui vont ensuite précipiter en une mésophase hybride 2D-hexagonale. Ce modèle de synthèse est appelé « transition sphères-cylindres ». De plus, afin de comprendre les mécanismes de formation du matériau à toutes les échelles, nous avons étudié l’influence des conditions de synthèse sur la morphologie des grains de matériau méso-structurés. En effet, nous avons montré que sans agitation pendant la synthèse, les grains de matériaux présentent une forme d’équilibre qui dépend fortement de la température de synthèse. En fonction de la température, il est donc possible de former des matériaux hybrides de forme grains de riz, bâtons (courts ou longs) ou mêmes sous forme de tores. Nous proposons un modèle théorique qui permet d’expliquer l’ensemble des morphologies observées, en fonction des tensions de surfaces et des énergies de courbures de cristal-liquide 2D-hexagonal lors de la précipitation de la mésophase hybride. Nous appuyons ce modèle théorique sur des études en diffusion des rayons X à très petits angles (USAXS), qui permettent d’étudier la croissance des grains. Grâce à ces études, nous proposons une description très complète de la formation du matériau SBA-15. Fort de ces connaissances, nous avons pu, grâce à de nouvelles études de SAXS in situ, appliquer le modèle de précipitation de type « transition sphères-cylindres » à d’autres matériaux, issus de tensioactifs non-ioniques fluorés, et ainsi expliquer la formation de matériaux dits « bimodaux », c’est-à-dire issus d’un mélange entre P123 et un tensioactif fluoré(Rf₈(EO)₉ et qui présentent deux ordres poreux bien définis. Enfin, nous avons cherché à utiliser nos connaissances pour la fabrication de matériaux innovants, en remplaçant la solution micellaire par des émulsions dopées en nanoparticules d’or (NPs), afin de fabriquer des matériaux hybrides dopés en NPs. / Meso-structured materials are materials with a well-controlled porosity, designed from sol/gel syntheses between surfactant micelles and an inorganic precursor, most often a silica precursor. Among them, the SBA-15 material, formed in super-acid solution from P123 (a tri-block copolymer) as surfactant and TEOS a silica precursor, is one of the most studied. Synthesis of this material has been studied by in situ Small Angle X-Ray Scattering (SAXS), which allowed to describe both qualitatively and quantitatively the self-assembly mechanisms between surfactant micelles and silica particles. In details, our results showed that TEOS hydrolysis-condensation allow the formation of silica oligomers that interact with the corona of the spherical micelles of P123, and progressively the micelles reshape in hybrid organic/inorganic cylindrical micelles. The hybrid micelles, first free in solution, eventually precipitate in a hybrid 2D-hexagonal mesophase. This model of synthesis is called “sphere-to-rod transition”. Moreover, in order to understand the material mechanisms of formation at every length scales, we studied the influence of the synthesis conditions on the morphology of the meso-structured material grains. Indeed, in agreement with a previous study, our results show that if the synthesis is made without stirring, the material grains has an equilibrium shape that strongly depends on the synthesis temperature. By changing the temperature, one can form hybrid materials with a “rice grain” shape, or a (short or long) rod shape, or even a torus shape. We propose a theoretical model to explain all the observed morphologies, model that takes into account surface tensions and curvature energy of the newly formed 2D-hexagonal liquid-crystal at the precipitation of the hybrid mesophase. We measured the nucleation and growth of the grains by Ultra Small Angle X-Ray Scattering (USAXS). Thanks to all these studies, we present a complete description of the formation of the SBA-15 material. Our knowledge were used to describe new in situ SAXS measurements of new materials: our “sphere-to-rod transition” model was able to describe the formation of two materials, form two fluorinated surfactants and allowed to explain the formation of a “bimodal” material, which means a material with two well-defined porous order, that is synthesized from a mix of two surfactant (P123 and (Rf₈(EO)₉). Finally, we tried to use our knowledge to form innovative materials, by replacing the micellar solution as template by an emulsion doped in gold nanoparticles (NPs) to form hybrid materials doped in NPs.