<p align="justify">Le but de ce travail a été l'étude de la technique d'électropolymérisation en vue d'obtenir les meilleurs films possibles pour l'application de protection contre la corrosion de métaux non nobles, par formation à leur surface de films de polymères.</p><p><p align="justify">Une étude bibliographique des divers cas déjà envisagés dans la littérature nous a permis de nous faire une opinion sur les composés susceptibles de présenter un intérêt et de choisir ceux que nous allions étudier. Cette étude bibliographique est assez volumineuse, de nombreux cas ayant été abordés par divers groupes de chercheurs partout dans le monde. Chacun des laboratoires s'est attaché à l'étude d'une propriété ou d'un paramètre particulier et il est assez difficile de synthétiser ces résultats. Nous avons relevé la liste des paramètres importants ayant une influence tant au point de vue des propriétés de conductivité des dépôts obtenus qu'en ce qui concerne leurs propriétés mécaniques, leur morphologie et leur adhérence au substrat. Ces paramètres comprennent la nature du substrat sur lequel on réalise l'électropolymérisation, le type de solvant, le type et la concentration en électrolyte support dans la solution, la concentration en monomère, les conditions de synthèse (mode potentiostatique, intensiostatique ou balayage en potentiel, durée de maintien du potentiel ou de la densité de courant, valeur de ce potentiel ou de cette densité de courant ou encore vitesse du balayage en potentiel, température), etc. Il faut d'ailleurs signaler qu'il existe bien entendu des influences croisées, entre autres entre la morphologie, la conductivité, la couleur et le taux de dopage.</p><p><p align="justify">Le choix d'un composé doit se faire en tenant compte des propriétés intrinsèques et de l'usage que l'on veut faire du polymère obtenu. Le choix des paramètres de synthèse devra résulter d'un compromis puisque plusieurs propriétés des films sont influencées en sens divers par ces paramètres. Par exemple, une structure plus régulière, et donc a priori plus conductrice, semble être obtenue par augmentation de la taille du contre-ion dopant dans le cas du pyrrole, mais le changement de nature du contre-ion peut également faire varier le taux d'insertion de ceux-ci dans le polymère, facteur qui aura aussi un effet sur la conductivité et sur la morphologie du film formé. Le type de substituant et sa position sur le monomère sont aussi à prendre en considération.</p><p><p align="justify">Le premier composé envisagé dans la partie expérimentale est la 2-vinylpyridine. Ce cas a été choisi parce qu'il s'agissait d'une électropolymérisation par réduction, méthode qui nous paraissait intéressante puisqu'elle présente l'avantage d'éviter tout risque d'oxydation du substrat lors de la formation du film. La réaction secondaire de dégagement d'hydrogène simultanée à la formation du film nous a cependant conduit à la conclusion que ce procédé n'offrait pas que des avantages.</p><p><p align="justify">Les films de poly-2-vinylpyridine formés semblent être constitués de polymères à assez faible degré de polymérisation et relativement adhérents au substrat métallique, mais présentent l'inconvénient d'être poreux et irréguliers du fait du dégagement d'hydrogène gazeux au cours du processus de synthèse. Ils sont constitués principalement de carbone et d'azote, et ce dans un rapport proche de celui du monomère. D'après les comparaisons des spectres infrarouge et ultraviolet de ces films avec ceux de poly-2-vinylpyridines obtenues par voie chimique, il s'agirait bien de ce composé. Bien que notre but n'était pas de déduire le mécanisme conduisant à la formation du polymère, nous avons pu déterminer que la réduction conduisant à la formation de ces dépôts nécessitait un échange d'un électron par molécule de monomère présente dans la chaîne polymérique. La conductivité électronique des films est faible. Leur croissance aurait plutôt lieu par un mécanisme ionique dans lequel des molécules de monomère pourraient diffuser au travers de la couche polyédrique déjà formée et qui, une fois chargées, pourraient soit se combiner à d'autres monomères au niveau du substrat, soit diffuser dans le film et aller former du polymère à sa surface, au contact de la solution d'électropolymérisation.</p><p><p align="justify">Parmi les composés qui peuvent être obtenus lors d'une électropolymérisation par oxydation, nous avons choisi le pyrrole qui nous a semblé particulièrement intéressant pour une application de protection vis-à-vis de la corrosion de l'acier doux. Ce dérivé hétéroaromatique possède en effet, par rapport à ses homologues thiophène et furanne, un potentiel d'oxydation relativement peu élevé, c'est-à-dire peu anodique. Il est de plus bien soluble dans des milieux aqueux et possède de bonnes propriétés d'adhérence pour autant qu'il soit formé en présence d'électrolyte conduisant à la passivation du fer. Son électropolymérisation n'est pas inhibée par la présence d'eau comme c'est le cas du thiophène. Les propriétés mécaniques du polypyrrole, meilleures que celles de la polyaniline qui est également obtenue par oxydation électrochimique, constituent également un élément en sa faveur.<p>Parmi les solutions dignes d'intérêt pour la polymérisation électrochimique de ce monomère, le cas de la solution aqueuse d'acide oxalique s'est révélé particulièrement intéressant. Elle permet en effet la formation d'un film passivant d'oxalate de fer sur le substrat, suivie d'un dépôt polymérique très adhérent, noir et conducteur.</p><p><p><p> / Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished

<div>Enantioselective syntheses of hexacyclic aspidoalbidine alkaloids (+)-fendleridine and (+)-acetylaspidoalbidine are described. These syntheses feature an asymmetric decarboxylative allylation and photocyclization of a highly substituted enaminone. Also, the synthesis highlights the formation of a C19-hemiaminal ether via a reduction/condensation/intramolecular cyclization cascade with the C21-alcohol. The present synthesis provides convenient access to the aspidoalbidine hexacyclic alkaloid family in an efficient manner.</div><div>A copper-catalyzed cross-coupling is described. Use of Cu(I) salts in the presence of allyl bromides and organostannyl furans were found to undergo catalytic turnover under ambient conditions and afford the coupled products in good to great yields. Model substrate screening led to conditions used in the concise formal synthesis of FR901464 analogues. Optimization of the described coupling step led to suppression of undesired isomers and byproducts affording the desired diene coupled product in high yield, stereo-, and regioselectivity on a multigram scale. Novel protection of the resulting diene moiety as an unconventional protecting group, and a facile four-step single column chromatographic stereoselective sequence are also reported.</div>

Raman multivariate curve resolution (Raman-MCR) spectroscopy is used to study water-mediated interactions by decomposing Raman spectra of aqueous solutions into bulk water and solute-correlated (SC) spectral components. The SC spectra are minimum-area difference spectra that reveal solute-induced perturbations of water structure, including changes in water hydrogen-bonding strength, tetrahedral structure, and formation of dangling (non-hydrogen-bonded) OH defects in a solute's hydration shell. Additionally, Raman-active intramolecular vibrational modes of the solute may be used to uncover complementary information regarding solute--solute interactions. Herein, Raman-MCR is applied to address fundamental questions related to: (1) confined cavity water and its connection to host-guest binding, (2) hydrophobic hydration of fluorinated solutes, (3) specific ion effects on nonionic micelle formation, and (4) ion pairing in aqueous solutions.

<p>  </p> <p>Experimental and computational techniques are used to study physico-chemical phenomena occurring in water on which hydrophobic interactions play a role. In particular, hydrophobic self-aggregation, including host-guest binding, and the affinity of ions to oil/water interfaces are investigated. Raman multivariate curve resolution (Raman-MCR) spectroscopy was the experimental technique used to unveil intermolecular interactions through the analysis of solute-correlated (SC) vibrational spectra. Molecular simulations, including molecular dynamics (MD) simulations, quantum-mechanical calculations, or a combination of both, were carried out to assist with the molecular-level interpretation of the experimental SC spectra.</p>

<p dir="ltr">Transitioning to a carbon-neutral future will require a broad portfolio of green energy generation and storage solutions. With the abundant availability of solar radiation across the Earth’s surface, energy generation from photovoltaics (PVs) will be an important part of this green energy portfolio. While silicon-based solar cells currently dominate the PV market, temperatures exceeding 1000 °C are needed for purification of silicon, and batch processing of silicon wafers limits how rapidly Si-based PV can be deployed. Furthermore, silicon’s indirect band gap necessitates absorber layers to exceed 100 µm thick, limiting its applications to rigid substrates.</p><p dir="ltr">Solution processed thin-film solar cells may allow for the realization of continuous, high-throughput manufacturing of PV modules. Thin-film absorber materials have direct band gaps, allowing them to absorb light more efficiently, and thus, they can be as thin as a few hundred nanometers and can be deposited on flexible substrates. Solution deposition of these absorber materials utilizing molecular precursor-based inks could be done in a roll-to-roll format, drastically increasing the throughput of PV manufacturing, and reducing installation costs. In this dissertation, solution processed synthesis and the characterization of two emerging direct band gap absorber materials consisting of earth abundant elements is discussed: the enargite phase of Cu₃AsS₄ and the distorted perovskite phase of BaZrS₃.</p><p dir="ltr">The enargite phase of Cu₃AsS₄ (ENG) is an emerging PV material with a 1.42 eV band gap, making it an ideal single-junction absorber material for photovoltaic applications. Unfortunately, ENG-based PV devices have historically been shown to have low power conversion efficiencies, potentially due to defects in the material. A combined computational and experimental study was completed where DFT-based calculations from collaborators were used inform synthesis strategies to improve the defect properties of ENG utilizing new synthesis techniques, including silver alloying, to reduce the density of harmful defects.</p><p dir="ltr">Chalcogenide perovskites are viewed as a stable alternative to halide perovskites, with BaZrS₃ being the most widely studied. With a band gap of 1.8 eV, BaZrS₃ could be an excellent wide-bandgap partner for a silicon-based tandem solar cell.Historically, sputtering, and solid-state approaches have been used to synthesize chalcogenide perovskites, but these methods require synthesis temperatures exceeding 800 °C, making them incompatible with the glass substrates and rear-contact layers required to create a PV device. In this dissertation, these high synthesis temperatures are bypassed through the development of a solution-processed deposition technique.A unique chemistry was developed to create fully soluble molecular precursor inks consisting of alkaline earth metal dithiocarboxylates and transition metal dithiocarbamates for direct-to-substrate synthesis of BaZrS₃ and BaHfS₃ at temperatures below 600 °C.</p><p dir="ltr">However, many challenges must be overcome before chalcogenide perovskites can be used for the creation of photovoltaic devices including oxide and Ruddlesden-Popper secondary phases, isolated grain growth, and deep level defects. Nevertheless, the development of a moderate temperature solution-based synthesis route makes chalcogenide perovskite research accessible to labs which do not have high temperature furnaces or sputtering equipment, further increasing research interest in this quickly developing absorber material.</p>

M. Tech (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Activated carbons have been produced from various carbonaceous source materials including nutshells, peat, wood, coir, lignite, coal and petroleum pitch and the produced carbons have been used for adsorption of inorganic and organic compounds from numerous matrices. Activated carbons are characterized by large surface area and high degree of microporosity. The ability of activated carbon to adsorb gold from solutions, which is present in very low concentrations while loading to fairly high concentrations, has made it an attractive material for the concentration of gold from dilute solutions. Consequently, the use of activated carbons for the recovery of gold from cyanide-leached liquors has gained wide acceptance in the mining industry. However, the price of commercially prepared carbons, the time taken for them to arrive, the breakage of the carbon during transportation and the interest in utilization of various local wastes for the generation of adsorbents has led to a search of more cost effective and time friendly source for the activated carbons. The focus of this research was to conduct a study in which a comparison was conducted between untreated coconut shell derived activated carbon (CAC) and Macadamia nutshell derived activated carbon (MAC) for the adsorption of gold. These activated carbons were modified with HNO3 and H3PO4 to increase their surface adsorption properties. This was done in order to explore if these activated carbons prepared from Macadamia shells could be an attractive alternative or a complementary supplement to the coconut shell based carbons that are currently being used in the gold extraction industry. The modification of the commercially prepared Macadamia activated carbons was done with 3 different concentrations for both nitric acid and phosphoric acid. The modified activated carbons were labelled MACP20%, MACP40% and MACP60%, to signify the materials prepared from 20% (v/v) H3PO4, 40% (v/v) H3PO4 and 60% (v/v) H3PO4 , respectively . Same labelling was used for 20% (v/v) HNO3, 40% (v/v) HNO3 and 55% (v/v) HNO3 modifications to correspond to MACN20%, MACN40% and MACN55%, respectively. Also, untreated coconut shell derived activated carbon (CAC) and Macadamia nutshell derived activated carbon (MAC) were investigated for gold adsorption for comparison purposes. All the activated carbons prepared in the iii | P a g e study were characterized with Brunauer-Emmet-Teller (BET), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Thermo gravimetric analysis (TGA), elemental analysis (EL) and X-ray diffraction spectroscopy (XRD). The physical properties of the activated carbons were done by determining attrition, ash content, volatile matter, and moisture content of all the activated carbons. Various parameters that affect selective adsorption such as the effect of initial concentration, time, agitation speed, interfering species, and dose of the adsorbent were investigated. Optimal parameters for gold ion adsorption were as follows: solution pH, 10; contact time, 6 h; agitation speed 150 rpm; sorbent amount 4 g and 5.5 ppm for initial concentration of gold. The observed selectivity order was not the same for all the adsorbents but the adsorption of gold was found to be mostly influenced by the presence of nickel and least influenced by copper. The MACP60% was found to be the most effective from the three concentrations investigated for the phosphoric acid modified activated carbons yet proved to have lower adsorption capabilities compared to CAC. The MACN55% was found to be the most efficient and displayed similar adsorption capabilities to those of CAC.

<div>Inorganic metal chalcogenide materials are of great importance in the semiconducting field for various electronic applications such as photovoltaics, thermoelectrics, sensors, and many others. Compared to traditional vacuum processing routes, solution processing provides an alternate cost-effective route to synthesize these inorganic materials through its ease of synthesis and device fabrication, higher material utilization, mild processing conditions, and opportunity for roll-to-roll manufacturing. One such versatile solution chemistry involving a mixture of amine and thiol species has evolved in the past few years as a common solvent for various precursor dissolutions including metal salts, metal oxides, elemental metals, and chalcogens.</div><div><br></div><div>The amine-thiol solvent system has been used by various researchers for the fabrication of inorganic materials, but without the complete understanding of the chemistry involved in this system, utilizing its full potential, and overcoming any inherent limitations will be difficult. So, to identify the organometallic complexes and their reaction pathways, the precursor dissolutions in amine-thiol solutions, specifically for elemental metals like Cu, In and chalcogens like Se, Te were studied using X-ray absorption, nuclear magnetic resonance, infrared, and Raman spectroscopy along with electrospray ionization mass spectrometry techniques. These analyses suggested the formation of metal thiolate complexes in the solution with the release of hydrogen gas in the case of metal dissolutions confirming irreversibility of the dissolution. Insights gained for chalcogen dissolutions confirmed the formation of different species like monoatomic or polyatomic clusters when different amine-thiol pair is used for dissolution. Results from these analyses also identified the role of each component in the dissolution which allowed for tuning of the solutions by isolating the complexes to reduce their reactivity and corrosivity for commercial applications.</div><div><br></div><div>After identifying complexes in metal dissolution for Cu and In metals, the decomposition pathway for these complexes was studied using X-ray diffraction and gas chromatography mass spectrometry techniques which confirmed the formation of phase pure metal chalcogenide material with a release of volatile byproducts like hydrogen sulfide and thiirane. This allowed for the fabrication of impurity-free thin-film Cu(In,Ga)S2 material for use in photovoltaic applications. The film fabrication with reduced carbon impurity achieved using this solvent system yielded a preliminary promising efficiency beyond 12% for heavy alkali-free, low bandgap CuInSe2 material. Along with promising devices, by utilizing the understanding of the chalcogen complexation, a new method for CuInSe2 film fabrication was developed with the addition of selenide precursors and elemental selenium which enabled first-ever fabrication of a solution-processed CuInSe2 thin film with thickness above 2 μm and absence of any secondary fine-grain layer.</div><div><br></div><div>Along with thin-film fabrication, a room temperature synthesis route for lead chalcogenide materials (PbS, PbSe, PbTe) with controlled size, shape, crystallinity, and composition of nanoparticle self-assemblies was demonstrated. Micro-assemblies formed via this route, especially the ones with hollow-core morphology were subjected to a solution-based anion and cation exchange to introduced desired foreign elements suitable for improving the thermoelectric properties of the material. Adopting from traditional hot injection and heat up synthesis routes, a versatile synthesis procedure for various binary, ternary, and quaternary metal chalcogenide (sulfide and sulfoselenide) nanoparticles from elemental metals like Cu, Zn, Sn, In, Ga, and Se was developed. This new synthesis avoids the incorporation of impurities like O, Cl, I, Br arising from a traditional metal oxide, halide, acetate, or other similar metal salt precursors giving an opportunity for truly impurity-free colloidal metal chalcogenide nanoparticle synthesis.</div>

No description available.

No description available.

<div>Delayed fracture healing is a major health issue involved with aging. Therefore, strategies to improve the pace of repair and prevent non-union are needed in order to improve patient outcomes and lower healthcare costs. In order to accelerate bone fracture healing noninvasively, we sought to develop a drug delivery system that could safely and effectively be used to deliver therapeutics to the site of a bone fracture. We elected to pursue the promising strategy of using small-molecule drug conjugates that deliver therapeutics to bone in an attempt to increase the efficacy and safety of drugs for treating bone-related diseases.</div><div>This strategy also opened the door for new methods of administering drugs. Traditionally, administering bone anabolic agents to treat bone fractures has relied entirely on local surgical application. However, because it is so invasive, this method’s use and development has been limited. By conjugating bone anabolic agents to bone-homing molecules, bone fracture treatment can be performed through minimally invasive subcutaneous administration. The exposure of raw hydroxyapatite that occurs with a bone fracture allows these high-affinity molecules to chelate the calcium component of hydroxyapatite and localize primarily to the fracture site.</div><div>Many bone-homing molecules (such as bisphosphonates and tetracycline targeting) have been developed to treat osteoporosis. However, many of these molecules have toxicity associated with them. We have found that short oligopeptides of acidic amino acids can localize to bone fractures with high selectivity and with very low toxicity compared to bisphosphonates and tetracyclines.</div><div>We have also demonstrated that these molecules can be used to target peptides of all chemical classes: hydrophobic, neutral, cationic, anionic, short, and long. This ability is particularly useful because many bone anabolics are peptidic in nature. We have found that acidic oligopeptides have better persistence at the site of the fracture than bisphosphonate-targeted therapeutics. This method allows for a systemic administration of bone anabolics to treat bone fractures, which it achieves by accumulating the bone anabolic at the fracture site. It also opens the door for a new way of treating the prevalent afflictions of broken bones and the deaths associated with them.</div><div>We further developed this technology by using it to deliver anabolic peptides derived from growth factors, angiogenic agents, neuropeptides, and extracellular matrix fragments. We found several promising therapeutics that accelerated the healing of bone fractures by improving the mineralization of the callus and improving the overall strength. We optimized the performance of these molecules by improving their stability, targeting ligands, linkers, dose, and dosing frequency.</div><div>We also found that these therapeutics could be used to accelerate bone fracture repair even in the presence of severe comorbidities (such as diabetes and osteoporosis) that typically slow the repair process. We found that, unlike the currently approved therapeutic for fracture healing (BMP2), our therapeutics improved functionality and reduced pain in addition to strengthening the bone. These optimized targeted bone anabolics were not only effective at healing bone fractures but they also demonstrated that they could be used to speed up spinal fusion. Additionally, we demonstrated that acidic oligopeptides have potential to be used to treat other bone diseases with damaged bone.</div><div>With these targeted therapeutics, we no longer have to limit bone fracture healing to casts or invasive surgeries. Rather, we can apply these promising therapeutics that can be administered non-invasively to augment existing orthopedic practices. As these therapeutics move into clinical development, we anticipate that they will be able to reduce the immobilization time that is the source of so many of the deadly complications associated with bone fracture healing, particularly in the elderly.</div>