La fonctionnalisation de la surface du verre par des molécules organiques permet de modifier son énergie de surface ou d’améliorer l’adhésion d’un revêtement. La méthode classique de fonctionnalisation directe du verre repose sur une réaction de silanisation, via la formation de ponts siloxanes Si O Si. Ces ponts ont tendance à s’hydrolyser en milieu salin ou alcalin, entrainant la perte de la fonctionnalité du verre. Une solution envisagée consiste à déposer une couche de nitrure de silicium (SixN4) sur le verre, permettant de greffer des molécules organiques via des liaisons covalentes robustes : Si C ou N C. Le nitrure de silicium présente l’avantage d’être un matériau très souvent utilisé dans l’industrie verrière en raison de sa capacité à bloquer la diffusion des ions sodium et de protéger ainsi le verre de la corrosion.L’objectif de ce travail de thèse est de caractériser et contrôler la surface du nitrure de silicium, puis d’optimiser et de comprendre la modification de sa surface par le greffage covalent de molécules organiques.Lorsque le nitrure de silicium est exposé à l’air, une couche d’oxynitrure est formée en surface. L’optimisation et la compréhension du décapage de cette couche d’oxynitrure natif en milieu liquide est l’objet de la première phase de ce travail. La composition chimique de la surface est finement caractérisée et quantifiée en combinant des mesures de spectroscopie infrarouge en mode de réflexion totale atténuée (IR-ATR), de spectroscopie de photoélectrons X (XPS) et des dosages chimiques de surface. Le décapage dans des solutions fluorées (HF et NH4F) permet de retirer efficacement la couche d’oxynitrure et laisse majoritairement en surface des liaisons Si-F et dans une moindre mesure des liaisons N H et Si OH. La composition chimique de la surface peut toutefois être modifiée pour former des groupements Si H, soit en enrichissant la couche du SixN4 en silicium, soit en soumettant la surface à un traitement par plasma d’hydrogène à l’issue du décapage. A partir des observations expérimentales, une proposition décrivant les mécanismes mis en jeu lors du décapage est présentée.Dans la seconde partie de la thèse, la surface du nitrure de silicium est modifiée par l’immobilisation de molécules organiques, plus spécifiquement par la réaction d’un 1 alcène sous activation thermique ou photochimique. La composition chimique de la surface et les conditions d’activation de la réaction modifient la réaction de greffage et la densité des couches organiques. En particulier, la présence de liaisons Si-H et l’enrichissement de la couche en silicium sont étudiés en détail. Dans une dernière partie, dans une visée plus applicative, des couches denses fluorées présentant un caractère hydrophobe naturel sont greffées sur la surface du nitrure de silicium. / Covalent grafting of organic molecules on glass can modify its surface physico-chemical properties or improve the adhesion of a coating. Such a functionalization usually relies on a silanisation reaction, bonding molecules to the surface through Si-O-Si bonds. Unfortunately, the resulting molecular layers do not exhibit long-term stability due to the hydrolysis of siloxane groups. One solution would consist in depositing a silicon nitride layer on glass, allowing the glass surface to be functionalized through more stable bonds N-C or Si-C. Silicon nitride layers are frequently used in glass industry. They are well-known for their durability properties and are often used as a protective layer against glass corrosion.The aim of this project is to characterize and control the non-oxidized silicon nitride surface, then to optimize and understand the surface modification by covalent grafting of organic molecules.When silicon nitride is exposed to atmosphere, an oxynitride layer is formed on its surface. Several efficient ways to remove this native oxynitride are first studied and optimized. The quantitative characterization and control of the surface chemical composition provide a reliable starting point for the functionalization step. The surface chemical composition is quantitatively investigated by combining Attenuated Total Reflection InfraRed spectroscopy (ATR-IR), X-ray photoelectron spectroscopy (XPS) and chemical dosing. The etching in HF-based solutions efficiently removes the oxynitride layer and leads to a surface mainly covered with Si-F bonds and smaller amounts of Si-OH and N-H bonds. The surface composition can be modified by a H2 plasma treatment performed after the wet etching or by changing the silicon nitride layer composition (silicon enrichment), leading in either case to the formation of Si-H bonds on surface. An etching mechanism is suggested from these experimental observations.The second part of this work is focused on the grafting of the alkyl chains on the silicon nitride surface. The surface is reacted with a 1-alkene, using photochemical or thermal activation. The grafting efficiency depends on the surface composition and the activation conditions. The presence of surface Si-H bonds and the effect of Si enrichment are considered in details. In a final part, in an applicative view, functional hydrophobic molecules are grafted on the silicon nitride surface.

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Nonalternant aromatic π-electron systems show promises for surface functionalization due to their unusual electronic structure. Based on our previous experiences for metal surfaces, we investigate the adsorption structures, adsorption dynamics and bonding characteristics of azulene and its alternant aromatic isomer naphthalene on the Si(001) surface. Using a combination of density functional theory, ab initio molecular dynamics, reaction path sampling and bonding analysis with the energy decomposition analysis for extended systems, we show that azulene shows direct adsorption paths into several, strongly bonded chemisorbed final structures with up to four covalent carbon–silicon bonds which can be described in a donor–acceptor and a shared-electron bonding picture nearly equivalently. Naphthalene also shows these tetra-σ-type bonding structures in accordance with an earlier study. But the adsorption path is pseudo-direct here with a precursor intermediate bonded via one aromatic ring and strong indications for a narrow adsorption funnel. The four surface-adsorbate bonds formed lead for both adsorbates to a strong corrugation and a loss of aromaticity.

Dropp-genereringstekniker är viktiga för industrier som läkemedelsindustrin, livsmedelsindustrin, kosmetikindustrin etc. Traditionella droppgenereringstekniker är dock begränsade i mängden av material som kan processas till droppform. Ett exempel inkjet som är en väletablerad teknik för att generera droppar med hög hastighet (1-10 kHz) och precision (10-20 μm), men kan bara stöta ut vätskor med låga viskositet, ungefär 10-100 gånger viskositeten av vattnet. Akustophoretisk utskrift motiv är att övervinna denna materialbegränsning och har framgångsrikt avkopplat dropputstötning från bläckviskositet. Metoden utnyttjar ickelinjära akustiska krafter för att skriva ut en stor mängd av material med hög kontroll, med viskositet som sträcker sig över fyra storleksordningar (0,5 mPa · s till 25 000 mPa · s). Emellertid är utstötningen baserad på bildandet av en hängande droppe, och i den aktuella prototypen begränsas materialpaletten av akustophoretisk utskrift genom sprider sig över munstycket, vilket begränsar den minsta tillåtnas ytspänningen till ungefär 60 mN / m. I detta arbete införs en munstycksbeläggningsteknik för att expandera mängden av utskrivbara material, med tillåtna ytspänningar så låga som 25 mN / m. Genom att utnyttja generera nanostrukturer med låg ytenergi på munstyckspetsen, tillverkas superavstötande beläggning. Grunden för nanostrukturerna genererades med hjälp av sot från ett paraffin-vaxljus. Ett robust tillverkningsprotokoll har etablerats, och beläggningen fysikaliska egenskaper och prestanda har karaktäriserats. Tre nya tillämpningsområden undersöktes, vilket demonstrerade noviteten hos denna nya metod. Detta arbete banar vägen för en ny uppsättning material som ska behandlas i en droppe-per droppe metodik. / Droplet generation techniques are essential for industries such as the pharmaceutical, food industry, cosmetic industry, etc. However, traditional droplet generation techniques are limited in the palette of materials that can processed in a droplet form. For example, inkjet which is a well-established technology to generate droplets of high speed (1-10 kHz) and precision (10-20 μm), but can only eject fluids with low viscosities, roughly 10-100 folds the one of water. Acoustophoretic printing aims to overcome this material limitation and have successfully decoupled droplet ejection from ink viscosity. The method harnesses nonlinear acoustic forces to print a wide range of materials on demand, spanning over four orders of magnitudes (0.5 mPa·sto 25,000 mPa·s). However, the ejection is based on the formation of a pendant drop, and in the current prototype, the material palette of acoustophoretic printing is limited by nozzle wetting, limiting the allowable minimum surface tension to about 60 mN/m. In this work, a nozzle coating technique is introduced in order to expand the material window by processing fluid with a surface tension as low as 25 mN/m. By leveraging self-assembling of nanostructures on the nozzle tip, superamphiphobic coating is successfully manufactured by using a candle soot template.A robust manufacturing protocol has been established, and the coating characterized in its physics and performance.

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Multifunctional nanomaterials can be engineered to aid in the diagnosis of diseases, enable efficient drug delivery, monitor treatment progress over time, and evaluate treatment outcomes. This strategy, known as theranostics, focuses on the combination of diagnostic and therapeutic techniques to provide new clinically safe and efficient personalized treatments. The evaluation of different nanomaterials’ properties and their customization for specific medical applications has therefore been a significant area of interest within the scientific community. Iron oxide nanoparticles, specifically those based on iron (II, III) oxide (magnetite, Fe3O4), have been prominently investigated for biomedical, theranostic applications due to their documented superparamagnetism, high biocompatibility, and other unique physicochemical properties. The aim of this thesis is to establish a viable set of methods for preparing magnetite (iron oxide) nanoparticles through hydrothermal synthesis and modifying their surfaces with organic functional groups in order to both modulate surface chemistry and facilitate the attachment of molecules such as peptides via covalent bond formations. Modifying their surfaces with biomolecules such as peptides can further increase their uptake into cells, which is a necessary step in the mechanisms of their desired biomedical applications. The methods of nanoparticle synthesis, surface functionalization, and characterization involving electron microscopy (e.g., SEM, TEM), zeta potential measurements, size analysis (i.e., DLS), and FT-IR spectroscopy will be presented. / Bioengineering