La microscopie à force atomique (AFM) est un outil de caractérisation d’échantillons tant organiques qu’inorganiques d’intérêt en physique, en biologie et en métallurgie. Le champ d’investigation de la microscopie AFM reste néanmoins restreint à l’étude des propriétés surfaciques des échantillons et la caractérisation sub-surfacique à l’échelle nanométrique n’est pas envisageable au-delà de la nano-indentation. Lors de ce travail, nous nous sommes intéressés à deux techniques de sonde locale complémentaires pour l’investigation volumique haute résolution.La première technique proposée est la microscopie de champ proche ultrasonore (MS-AFM), mise en place et exploitée en collaboration avec Dr. L. Tétard de l’Université Centrale de Floride. Cette technique fournie des informations localisées en profondeur en utilisant des ondes acoustiques dans la gamme de fréquences du MHz. Une étude complète de l’influence des paramètres de fréquences a été réalisée sur des échantillons de calibration et a permis de valider un modèle d’interprétation numérique. Cette technique ultrasonore, non invasive, a été appliquée à la caractérisation de vésicules lipidiques au sein de bactéries lors d’une collaboration avec les Pr. A. Dazzi et M.-J. Virolle, de l’Université Paris Sud Orsay. Un couplage a été réalisé avec la microscopie AFM infra-rouge (AFM-IR). Cette étude a démontré le potentiel d’investigation et d’analyse volumique et chimique d’échantillons biologiques.La seconde technique étudiée est la microscopie micro-onde (SMM), développée en collaboration avec la société Keysight. Cette technique, tout comme la microscopie acoustique, est non invasive et conduit à une caractérisation physico-chimique basée sur l’interaction de micro-ondes (0.2-16 GHz) avec la matière. Dans le cas de métaux, un lien entre la fréquence et la profondeur d’investigation a été mis en évidence. Cette technique a été appliquée à l’étude de la diffusion d’élément chimique léger au sein de métaux et à la mesure des propriétés mécaniques des matériaux. L’ensemble de ces résultats ouvre un nouveau champ d’investigation de la tomographie 3D dans l’analyse volumique à l’échelle nanométrique que ce soit dans le domaine de la biologie ou de la métallurgie. / The atomic force microscope (AFM) is a powerful tool for the characterization of organic and inorganic materials of interest in physics, biology and metallurgy. However, conventional scanning probe microscopy techniques are limited to the probing surface properties, while the subsurface analysis remains difficult beyond nanoindentation methods. Thus, the present thesis is focused on two novel complementary scanning probe techniques for high-resolution volumetric investigation that were develop to tackle this persisting challenge in nanometrology. The first technique considered, called Mode Synthesizing Atomic Force Microscopy (MSAFM), has been exploited in collaboration with Dr. Laurene Tetard of University of Central Florida to explore the volume of materials with high spatial resolution by means of mechanical actuation of the tip and the sample with acoustic waves of frequencies in the MHz range. A comprehensive study of the impact of the frequency parameters on the performance of subsurface imaging has been conducted through the use of calibrated samples and led to the validation of a numerical model for quantitative interpretation. Furthermore, this non-invasive technique has been utilized to locate lipid vesicles inside bacteria (in collaboration with Pr. A. Dazzi and M.-J. Virolle of Université Paris Sud, Orsay). Furthermore, we have combined this ultrasonic approach with infra-red microscopy, to add chemical speciation aimed at identifying the subsurface features, which represents a great advance for volume and chemical characterization of biological samples. The second technique considered is the Scanning Microwave Microscopy, which was developed in collaboration with Keysight society. Similar to acoustic-based microscopy, this non-invasive technique provided physical and chemical characterizations based on the interaction of micro-waves radiations with the matter (with frequency ranging from 0.2 and 16 GHz). Particularly, for metallic samples we performed volumetric characterization based on the skin effect of the materials. On the other hand, we have used this technique to analyze the diffusion of light chemical elements in metals and measured the effect of changes in mechanical properties of materials on their conductivity.Overall, these results constitute a new line of research involving non-destructive subsurface high resolution analysis by means of the AFM of great potential for several fields of research.

Liquid crystalline materials forming columnar mesophases are of importance for both the fundamental research and technological applications due to their supramolecular architecture allowing for one-dimensional charge transport. The potential applications of these materials include light emitting diodes, solar cells, field effect transistors and photovoltaic cells. However, to design a LC material suitable for a particular application, a fundamental understanding of the structure-property relationships is needed.<p>In the present thesis, a variety of systems forming columnar mesophases have been explored. They include small molecular weight compounds (triphenylene, phthalocyanine derivatives and star-shaped mesogens) and polymer materials. The research was focused on the study of the influence of the molecular architecture and specific interactions such as hydrogen bonding on the supramolecular organization in the mesophase, as well as on the influence of columnar mesophase on crystal growth. The main results of the thesis are summarized below.<p>The influence of hydrogen bonding on the structure and charge carrier mobility was investigated for a triphenylene derivative, hexaazatriphenylene, having lateral alkyl chains linked to the core via amide groups. These linking groups provide the possibility to form inter- and intra-molecular hydrogen bonds. Acting as “clamps”, the inter-molecular hydrogen bonds are found to enforce the attractive interactions between the molecules in the column. Thus, the columnar mesophase formed by this system is characterized by the smallest inter-disk distance ever found in columnar mesophases (3.18 Å). The improved intra-columnar order brings about a higher charge carrier mobility (0.02 cm2/Vs) as compared to other triphenylene derivatives without hydrogen bonds. <p>Phthalocyanine derivatives, which are liquid crystalline at ambient temperature, could be suitable for opto-electronic applications due to their improved processibility and self-healing of structural defects. Our interest in these systems was inspired by the fact that, in spite of numerous studies performed to date, only very a few phthalocyanine derivatives were found to exhibit columnar mesophases at ambient temperature. We observed that by introducing branches in alkyl chains close to the core, we were able to render the material LC at ambient temperature. Analysis of X-ray diffraction patterns measured on oriented samples showed that these systems form hexagonal and rectangular ordered columnar mesophases. This finding is in contradiction with the general view stating that non-hexagonal mesophases can be only disordered. Since the absolute majority of applications require fabrication of films, it was very important to achieve the visualization of the organization of the phthalocyanine derivatives at the nanometer scale. AFM images on thick spin-coated films with columnar resolution are presented for the first time. They allowed the examination of columnar curvatures and breaks at the boundaries between different single crystal-like domains. <p>The possibility of templating columnar crystal growth was studied for a star-shaped mesogen using a combination of direct- and reciprocal-space techniques. AFM images with columnar resolution showed that the crystal growth initiated in the monotropic columnar mesophase occurs almost in register with the mesomorphic template. In the final crystalline structure, the placement of the crystalline columns is controlled by the mesomorphic tracks at the scale of an individual column, i.e. at the scale of approximately 3.5 nm. <p>The mesophase-assisted crystallization was also studied for the case of a polymer material forming columnar mesophase, poly(di-n-propylsiloxane). X-ray diffraction on oriented fibers allowed us to correct the previous indexation and solve the structure of the unit cell. The crystallization process was studied on samples crystallized in different conditions. It was found that, depending on crystallization conditions, both folded-chain and extended-chain crystals can be obtained. Thus, crystallization of the material from the mesophase results in the formation of 100-150nm thick crystals, which corresponds to a nearly extended-chain conformation. By contrast, when crystallized from a dilute solution, folded-chain crystals result. The mechanisms of chain unfolding was studied by variable temperature atomic force microscopy on PDPS single crystals. It was found that crystals rapidly thicken above the initial melting point, up to 80 nm. / Doctorat en sciences, Spécialisation physique / info:eu-repo/semantics/nonPublished

La microscopie à force atomique (AFM) permet de visualiser la topographie d’échantillons organiqueset inorganiques à l’échelle atomique. Les innovations les plus récentes offrent désormais la possibilitéd’accéder aux propriétés nano-mécaniques des échantillons (élasticité, adhésion…). Son panel defonctionnalités permet de pallier aux besoins des nanotechnologies, tant dans les domaines de laphysique, de la chimie que de la biologie.Cependant, les besoins nécessaires à la compréhension des processus biologiques imposent aumicroscope à force atomique des vitesses d’acquisitions rapides, inférieures à la seconde par image. Leséquipements classiques n’offrent pas cette possibilité. C’est pour s’affranchir de ce verrou technologique,pour l’étude dynamique, qu’un prototype de microscope à force atomique à haute-vitesse a étédéveloppé (HS-AFM) en partenariat avec l’équipe du Professeur T. Ando à l’Université de Kanazawa(Japon). Il permet d’atteindre des vitesses de balayage identiques aux vitesses vidéos : 25-50 images/s, enmilieu liquide. Le dispositif est en perpétuelle amélioration : nouvelle boucle d’asservissement, domainesde balayage augmentés. La haute résolution est, quant à elle, assurée par des leviers miniaturisés munisde sur-pointes en carbone. Parallèlement à l’innovation du microscope en lui-même, des modulescomplémentaires ont été développés : module pousse seringue et module chauffant.Le potentiel de ce prototype, développé dans le cadre d’un programme ANR PNANO 2008 HSnanobio-Imaging, a été montré via l’étude d’une petite protéine de choc thermique : la protéine sHspLo18. Cette protéine, issue de la bactérie lactique Oenococcus oeni, offrait la possibilité d’étudier deschangements de degrés d’oligomérisation en fonction du pH, ainsi que le rôle chaperon et lipochaperonen cas de stress environnemental d’autres complexes biologiques. L’utilisation des techniques demicroscopie couplée à des études biochimiques sur ce modèle protéique a permis d’appréhender l’effetdes surfaces sur l’adsorption et la dynamique des complexes biologiques. L’interaction protéine – surfacea pu être approchée et s’avère utile au développement des capteurs à protéines / The atomic force microscopy (AFM) gives access to the topography of organic and inorganic samplesat the atomic scale. The latest innovations offer the possiblity to understand the sample nano-mechanicalproperties (elasticity, adhesion...). Its feature set allows overcoming the demands of nanotechnology,both in the fields of physics, chemistry and biology.However, understanding biological processes require faster acquisitions for the atomic forcemicroscopy, less than a second per frame. As conventional equipment does not offer the possibility toovercome the constraint of time for dynamical studies, a prototype of high-speed atomic forcemicroscope (HS-AFM) was developed in partnership with Professor T. Ando group of Kanazawa University(Japan). It can reach scanning video speed: 25-50 frames/s in a liquid medium. The device is beingconstantly improved: new feedback control, larger scanning sizes. The resolution is provided byminiaturized cantilevers with carbon EBD-tips. In parallel to innovative modules on the microscope, addonshave been developed: syringe pump and heating modules.The potential of the prototype, developed within the framework of the program ANR PNANO 2008HS-nanobio-Imaging, has been shown through the study of a small heat shock protein: the protein sHspLo18. This protein, from the lactic acid bacterium Oenococcus oeni, offered the possibility of a variouschanges of oligomerization degrees according to the pH, and also the chaperone and lipochaperon activityof protein under the influence of an environmental stress. The use of these techniques of microscopiescoupled with biochemical studies on this proteic model allowed to dread the effect of surfaces on theadsorption and the dynamics of biological complexes. The interaction protein – surface coulb be toapprehend and proves to be useful for the development of protein sensors developed in the laboratory

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Many biological processes, pathogens, and pharmaceuticals act upon, cellular membranes. Accordingly, cell membrane mimics are attractive targets for biosensing, with research, pathology, and pharmacology applications. Lipid bilayers represent a versatile sensor functionalization platform providing antifouling properties, and many receptor integration options, uniquely including transmembrane proteins. Bilayer-coated sensors enable the kinetic characterization of membrane/analyte interactions. Addressed theoretically and experimentally is the self-assembly of model membranes on plasmonic sensors. Two categories of plasmonic sensors are studied in two parts. Part I aims to deposit raft-forming bilayers on planar nanoaperture arrays suitable for multiplexing and device integration. By vesicle fusion, planar bilayers are self-assembled on thiol-acid modified flame-annealed gold without the need for specific lipid head-group requirements. Identification of coexisting lipid phases is accomplished by AFM imaging and force spectroscopy mapping. These methods are successfully extended to metallic, plasmon-active nanohole arrays, nanoslit arrays and annular aperture arrays, with coexisting phases observed among the holes. Vis-NIR transmission spectra of the arrays are measured before and after deposition, indicating bilayer detection. Finally, the extraction of membrane proteins from cell cultures and incorporation into model supported bilayers is demonstrated. These natural membrane proteins potentially act as lipid-bound surface receptors. Part II aims to encapsulate in model lipid bilayers, metallic nanoparticles, which are used as probes in surface enhanced Raman spectroscopy. Three strategies of encapsulating particles, and incorporating Raman-active dyes are demonstrated, each using a different dye: malachite green, rhodamine-PE, and Tryptophan. Dye incorporation is verified by SERS and the bilayer is visualized and measured by TEM, with support from DLS and UV-Vis spectroscopy. In both parts, lipid-coated sensors are successfully fabricated and characterized. These results represent important and novel solutions to the functionalization of plasmonic surfaces with biologically relevant cell membrane mimics.

Polymer and organic electronic memory devices offer the potential for cheap, simple memories that could compete across the whole spectrum of digital memories, from low cost, low performance applications, up to universal memories capable of replacing all current market leading technologies, such as hard disc drives, random access memories and Flash memories. Polymer memory devices (PMDs) are simple, two terminal metal-insulator-metal (MIM) bistable devices that can exist in two distinct conductivity states, with each state being induced by applying different voltages across the device terminals. Currently there are many unknowns and much ambiguity concerning the working mechanisms behind many of these PMDs, which is impeding their development. This research explores some of these many unanswered questions and presents new experimental data concerning their operation. One prevalent theory for the conductivity change is based on charging and charge trapping of nanoparticles and other species contained in the PMD. The work in this research experimentally shows that gold nanoparticle charging is possible in these devices and in certain cases offers an explanation of the working mechanism. However, experimental evidence presented in this research, shows that in many reported devices the switching mechanism is more likely to be related to electrode effects, or a breakdown mechanism in the polymer layer. Gold nanoparticle charging via electrostatic force microscopy (EFM) was demonstrated, using a novel device structure involving depositing gold nanoparticles between lateral electrodes. This allowed the gold nanoparticles themselves to be imaged, rather than the nanoparticle loaded insulating films, which have previously been investigated. This method offers the advantages of being able to see the charging effects of nanoparticles without any influence from the insulating matrix and also allows charging voltages to be applied via the electrodes, permitting EFM images to capture the charging information in near real-time. Device characteristics of gold nanoparticle based PMDs are presented, and assessed for use under different scenarios. Configurations of memory devices based on metal-insulator-semiconductor (MIS) structures have also been demonstrated. Simple interface circuitry is presented which is capable of performing read, write and erase functions to multiple memory cells on a substrate. Electrical properties of polystyrene thin films in the nanometre thickness range are reported for the first time, with insulator trapped charges found to be present in comparable levels to those in silicon dioxide insulating films. The dielectric breakdown strength of the films was found to be significantly higher than bulk material testing would suggest, with a maximum dielectric strength of 4.7 MV•cm-1 found, compared with the manufacturers bulk value of 0.2 – 0.8 MV•cm-1. Conduction mechanisms in polystyrene were investigated with the dominant conduction mechanism found to be Schottky emission.

One of the most important prerequisites in the drug development is to attain a reproducible and robust product in terms of its nature, and its chemical and physical properties. This can be challenging, since the crystalline form of drugs and excipients can be directly transformed into the amorphous one during normal pharmaceutical processing, referred to as process-induced amorphisation or process-induced disorder. The intention of this thesis was to address the mechanisms causing disorder during powder flow and milling and, in association with this, to evaluate, the ability of Raman spectroscopy and atomic force microscopy (AFM) to quantify and characterize process-induced disorder. The amorphisation mechanisms were controlled by stress energy distribution during processing, which in turn was regulated by a series of process parameters. Compression and shearing stress caused by sliding were stress types that acted on the particles during powder flow and ball milling process. However, sliding was the most important inter-particulate contact process giving rise to amorphisation and the transformation was proposed to be caused by vitrification. The plastic stiffness and elastic stiffness of the milling-induced particles were similar to a two-state particle model, however the moisture sorption characteristics of these particles were different. Thus the milled particles could not be described solely by a two-state particle model with amorphous and crystalline domains.  Raman spectroscopy proved to be an appropriate and effective technique in the quantification of the apparent amorphous content of milled lactose powder. The disordered content below 1% could be quantified with Raman spectroscopy. AFM was a useful approach to characterize disorder on the particle surfaces. In summary, this thesis has provided insight into the mechanisms involved in process-induced amorphisation of pharmaceutical powders and presented new approaches for quantification and characterization of disordered content by Raman spectroscopy and atomic force microscopy.