Les trois dernières décennies ont vu l’émergence de l’électronique organique ainsi que son établissement en tant que domaine scientifique interdisciplinaire et dans notre vie quotidienne. On dénombre actuellement deux défis scientifiques majeurs dans ce domaine. Le premier est de s’attacher à augmenter l’efficacité des dispositifs par l’utilisation de nouveaux matériaux, plutôt le deuxième consiste en l’intégration de fonctionnalités multiples un seul dispositif. Atteindre ces objectifs nécessite la compréhension des mécanismes fondamentaux de la physico-chimie, gouvernants les propriétés de base de l’électronique organique tels l’injection ou le transfert de charge et le transport. Ces travaux de thèse rapport le développement de systèmes complexes, auto assemblés, dont les propriétés électriques et optiques au sein de dispositifs organo-électroniques peuvent être modulées en réponse aux stimuli extérieurs. Ce but a été obtenu par le développement des briques élémentaires et par l’étude de leurs propriétés physico-chimiques afin de modéliser tous les mécanismes impliqués. / In the last three decades Organic Electronics emerged and established itself as an interdisciplinary field of science and as part of our daily life. Presently, the greatest scientific challenges in this field of research are two: the former relies on the improvement of devices efficiency which can be accomplished by using new materials, whereas the latter consist in the integration of multiple functionalities in a single device. To accomplish these goals one needs to develop a deep understanding on the fundamental physical-chemistry ruling the properties which are on the basis of organic electronics such as charge injection, charge transfer and transport. This PhD project reports the developing of efficient multicomponent electroactive self-assembled systems whose electro- and optical properties can be modulated, in devices, as a response to multiple external and independent stimuli. This goal has been achieved by engineering of the proper building blocks and the study of the the physico-chemical properties to be able to model all the mechanisms involved.

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The importance of porous materials has risen substantially in the last few decades due to their ability to reduce the size and cost of bioanalytical devices and fuel cells. First, this work aims to describe the fabrication of nanoporous gold (NPG) electrodes that are resistant to electrode passivation due to fibrinogen biofouling in redox solutions. The effect on potentiometric and voltammetric experiments was seen as a deviation from ideal behavior on planar gold electrodes, whereas NPG electrodes were consistently behaving in a Nernstian fashion at low concentrations of ferri-ferrocyanide (£100 mM). An improvement in electrode behavior on NPG electrodes versus planar gold was seen in solutions containing ascorbic acid as well as blood plasma. Second, cost effective NPG electrodes were fabricated using a glass substrate to test the response in the presence of a variety of redox molecules. The optical transparency of these electrodes allowed for microdroplet measurements to be made using an inverted microscope in several redox solutions for validation and subsequent biological applicability. Nernstian behavior was demonstrated for all one- and two-electron transfer systems in both poised and unpoised solutions. All experiments were conducted using volumes between 280 and 1400 pL producing rapid results in less than one minute. Third, in order to decrease the requirement for complex instrumentation, microdroplet fabrication technique was used to create mini-nanoporous gold (mNPG) electrodes on glass capillary tubes. The cylindrical shape of the electrodes allowed for testing in sample volumes of 100 mL. The response to ferri-ferrocyanide, ascorbic acid, cysteine, and uric acid was then investigated with Nernstian behavior shown. However, the mNPG electrodes were insensitive to glucose and hydrogen peroxide. In order to increase the sensitivity of the electrodes, a minimal amount of platinum was electrodeposited onto the NPG surface using a low concentration of platinum salt (0.75 mM) for a short deposition time (2 seconds) producing a Nernstian response to both glucose and hydrogen peroxide. Lastly, to test the viability of crossover applications, the platinum incorporated NPG electrode was employed as a fuel cell anode material, testing their oxidation capability with methanol, ethanol, and formic acid.

Gold Nanoclusters are of particular interest due to their many possible applications across a wide range of scientific fields. More specifically, nano-sized gold particles have potential to be used in drug delivery systems, cancer therapy and catalysis. This dissertation focuses on improving our understanding of ligated gold nanoclusters by examining the role of a variety of phosphine based ligands, novel methods to produce monodisperse solutions, and investigating the kinetics of water soluble ligated gold nanoclusters. The addition of ligands to solutions of Au have shown to produce small (< 20 Au atoms) clusters. All nanocluster solutions were prepared in a similar manner. Typically, a gold salt, either Chloro(triphenylphosphine) gold(I) (Au(PPh3)Cl), or Potassium gold (III) chloride (KAuCl4), were dissolved in various solvents. Next, an equal concentration of ligand was added to the solution and stirred until completely dissolved. Finally, all were reduced with 5X the concentration of borane-tert-butylamine (BTBC) after which were sonicated for ~20 minutes. The timing and method of adding the ligands and reducing agent varied depending on the solution and solubility of the ligands. Primarily we used Electrospray Ionization Mass Spectrometry (ESI-MS) and Ultraviolet – Visible Spectroscopy (UV-VIS) for the characterization of samples, however, occasionally Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD) and X-Ray Photoemission Spectroscopy (XPS) were used. The most recent research took advantage of the size selective nature of an alpha hemolysin (a-HL) nanopore to investigate the kinetics of thiol-ligated Au clusters ~2 nm in size. The relationship between ligand rigidity and solvent polarity and the size and dispersity of Au cluster suspensions was investigated. We observed the formation of stable monodisperse clusters with the shortest ligand, (L3), independent of solvent. With a longer flexible ligand, (L6), we observed primarily Au8-10 cores depending on the ratio of L6/PPh3. All other ligands yielded polydisperse distributions. These dispersions contained clusters with a nuclearity between 8 and 11, for example [Au10(PPh3)9]3+ in LBn and [Au8(PPh3)7]2+ in LBp, were observed in the initial stages, but they were not stable and precipitated out or plated the glass vial. We also observed that the polarity of the solvent did not play a significant role in the formation of MPC’s, however a correlation between the size of the solvent and MPC formation was observed. The growth and evolution of two unique gold structures was also observed via UV-Vis and ESI-MS. Solutions were prepared which contained Potassium gold (III) chloride and PPh2(CH2)3PPh2, i.e., 1,3-bis(diphenylphosphino)propane, denoted by L3, reduced with Borane tert-butylamine complex (BTBC) in a 1:1 diethyl ether:methanol mix, which yielded a stable [Au11(L3)5]+3. Starting with this known Au11 solution, the addition of Mn2+ has shown to lead to the formation of a stable diphosphine ligated Au8 and a new Au14 species. Additionally, we show that the co-reduction of NiCl2 and Au in the absence of the ligand (L3) does give us a simple method for the production of a monodisperse [Au9(PPh3)8]2+ cluster solution and via electroless deposition does give us a potential low temperature pathway to the formation of a AuNi nanoalloy particle.

This dissertation examines the history of gold mining among the Wanyamongo people of Tarime District from the 1930s to 2009. It argues that the establishment of gold mines in Nyamongo in the early 1930s created intra-community conflicts among the Wanyamongo people. These conflicts divided the community, turning young men against elders and wives against their husbands. This tension rarely reached overt levels during the colonial period, although violent confrontations were not totally absent. However, the conflicts are discernible in the narratives about gold mining. The dissertation argues that these conflictual discourses about gold mining continued into the post-colonial era, although their content changed over time. From the turn of this century these conflicts increasingly became violent. Often characterized as evidence of local communities' opposition to the intrusion of foreign companies I draw on oral sources and Tanzanian archives to argue that such turbulence is best understood by examining the social and economic relations of the residents of such communities. In Nyamongo this violence often pitted unemployed young men against fellow Kuria-speaking men who were employed by the mine as guards and in the Community Relations Department. I also argue that the young men who invaded the mine did not want the mine to close because their very survival was dependent upon the presence of a large company that can bring deeper ore to the surface. The dissertation also argues that, contrary to common wisdom that recognizes the Second World War as the beginning of the decline of the gold mining sector, in the Lake Province gold production actually continued to increase until the late 1950s. I also argue that when these mines closed in the 1960s and early 1970s it was not because of Julius Nyerere's economic policy, as is commonly believed. When Nyerere's government nationalized the industry in 1973, all of Tanzania's big gold mines had already closed. In the 1970s and 1980s Tanzania experienced an economic crisis marked by high inflation and a shortage of basic commodities. I argue that the miners of Nyamongo escaped this crisis because gold allowed them to engage in a lucrative trade that revolved around the smuggling of gold to Kenya. The dissertation also shows that when the Tanzanian government adopted neo-liberal economic reforms in the mid-1980s, the residents of Nyamongo embraced large-scale foreign investment in the form of an Australian-owned mining company. This embrace challenges the conventional view that depicts foreign mining companies as unwanted intruders in Tanzania's mining communities and the local small-scale miners as victims of neo-liberal economic policies.

A bulk silicon temperature sensor is fabricated in this work. The objective is to develop a low-cost high resolution temperature sensor. The target applications are a Conductivity-Temperature-Depth (CTD) sensor for oceanic applications and a magnetocaloric microcooler. The properties of silicon are modified by thermal diffusion of gold. Gold is a fast diffuser in silicon and its diffusion contributes to the increase in resistivity of silicon. The addition of gold to n-type silicon creates a negative temperature coefficient device. The effect of the diffusing environment was investigated by diffusing in oxygen and nitrogen ambient at various temperatures. The influence of area of gold diffusion was also investigated. The effect of temperature on resistance was measured and was used to calibrate the sensor. Although the sensors fabricated in an oxygen environment have an exponential type response, they can be used in the CTD application because of enhanced sensitivity in the 10˚C - 30˚C temperature range. Sensors fabricated in a nitrogen environment are found to have linear response with sensitivity ranging from 7Ω/˚C to 3000Ω/˚C and can be used for both applications. The fabricated sensors have a 0.1˚C resolution.

Le paludisme est la plus importante infection parasitaire dans le monde, menaçant environ 40% de la population humaine. Dans les dernières années c'est devenu un problème de santé publique majeur en raison de l'augmentation des parasites résistants aux traitements actuels. Certains complexes NHC-or(I) présentent des activités antipaludiques, et sont une alternative très prometteuse dans le traitement du paludisme en raison de leur potentiel inhibiteur de la thiorédoxine réductase (TrxR) qui joue un rôle majeur dans la chaîne respiratoire mitochondriale (une des deux voies actives à l'état de quiescence des parasites résistants). Dans ce travail de thèse, un panel de complexes médicament-NHC-or(I) a été synthétisé et caractérisé. Le premier groupe de molécules concerne une famille de complexes cationiques bis-NHC-or(I) et de complexes neutres mono-NHC-or(I) fonctionnalisés avec substituents aliphatiques ou aromatiques. Le groupe comprend trois séries. Les trois séries ont été testées contre la souche sensible de F32-TEM de P. falciparum présentant des activités élevées, avec des valeurs d'IC50 de l'orde du nM. Le deuxième groupe concerne une série de complexes cationiques bis-NHC-or(I) fonctionnalisés avec des substituants aliphatiques ou aromatiques comprenant un groupement triclosan relié par un connecteur aliphatique. Le triclosan inhibe la voie de synthèse des acides gras, qui reste également active chez les parasites résistants. Ces complexes ont été testés contre P. falciparum, montrant des activités élevées avec des valeurs IC50 dans la gamme du nM. Les ligands de cette série et leurs complexes respectifs ont également été testés contre L. infantum, l'un des parasites provoquant la leishmaniose, et se sont révélés très efficaces sous les formes amastigote et promastigote, avec des valeurs d'IC50 dans le bas µM. / Malaria is the most important parasitic infection in people, threatening around 40% of the human population. In the last years it has become a bigger public health concern because of the augmentation of malaria parasites resistant to artemisinin and its derivatives. Some NHC-gold(I) complexes show antimalarial activities, being a very promising alternative in malaria treatment because of their potential to inhibit thioredoxin reductase (TrxR) that plays a major role in mitochondrial respiratory chain (one of the two pathways that remains active in the quiescent state of the resistant parasites). In this work of thesis a panel of drug-NHC-gold(I) complexes including artemisinin and triclosan moieties has been synthesized and characterized with the objective of developing hybrid molecules with a dual mode of action able to overcome plasmodium resistance to artemisinin and its derivatives. The first group of molecules concerns a family of aliphatic or aromatic-functionalized cationic bis-NHC-gold(I) and neutral mono-NHC-gold(I) complexes with an artemisinin moiety connected through an aliphatic linker. The group includes three series depending on the length of the aliphatic linker (C3, C4, and C5). The three series have been tested against the sensible F32-TEM strain of P. falciparum showing high activities with IC50 values in the nM range. The second group concerns a series of aliphatic or aromatic-functionalized bis-NHC-gold(I) complexes with an triclosan moiety connected through an aliphatic linker. Triclosan inhibits the fatty acid synthesis pathway, which also remains active in the quiescent state on resistant parasites. These complexes were tested against P. falciparum showing, high activities with IC50 values in the nM range. The ligands of this series and their respective complexes have been also tested against one of the leishmaniosis causing parasites, L. infantum, being very effective in both, amastigote and promastigote forms, with IC50 values in the low µM range.

Philosophiae Doctor - PhD / The field of nanotechnology continues to offer solutions for biotechnologists whose target is to improve the quality of life by finding new therapies to combat diseases. Gold nanoparticles (AuNPs) have been showing great potentials in many biomedical applications. The antibacterial activity of the AuNPs presents a therapeutic option for conditions caused by bacterial infections such as chronic wounds. Also, these versatile particles can offer solutions in the treatments of infectious diseases and can also be exploited as “smart” vehicles to carry drugs, such as antibiotics, for improved efficiency. Moreover, the anti-inflammatory activity of AuNPs makes them useful in the management of prolonged inflammation caused by bacterial infections. The synthesis of AuNPs can be achieved by variety of physical and chemical methods that have been successfully applied in labs and industry. Nonetheless, the drawbacks of these “conventional” methods in terms of high cost, adverse health side effects and incompatibility with the ecosystem cannot be overlooked. Thus, new safer and more cost-effective protocols have been reported for the synthesis of AuNPs. Plants have provided alternate synthesis methods in which the reducing capabilities of the phytochemicals, found in the aqueous plant extracts, can be used to chemically synthesize AuNPs from gold precursors. The biosynthesis and characterization of AuNPs from the phytochemicals of several South African plants is investigated in this study. The study also reports the optimization of the AuNPs biosynthesis by varying reaction conditions such as temperature and plant extracts’ concentrations. Furthermore, the study highlights the wound healing activity of the AuNPs synthesized from selected plants by investigating their antibacterial activity on bacterial strains known to cause chronic wounds. The ability of these AuNPs to carry ampicillin in order to enhance the antibacterial activity is also described herein. The cytotoxicity of the biosynthesized AuNPs was evaluated on human normal fibroblasts cells (KMST-6). Additionally, the immunomodulatory effect of the biosynthesized AuNPs on the cytokines production from macrophages and Natural Killer (NK) cells was examined. The study was successful to produce biocompatible and safe AuNPs synthesized from the tested aqueous plant extracts. The resulted AuNPs showed different physicochemical properties by varying the reaction conditions. The AuNPs exhibited antibacterial activity against several Gram-positive and Gram-negative bacteria. Also, ampicillin was successfully loaded on the biosynthesized AuNPs, which led to the formation of more antibacterial active conjugated AuNPs compared to the free AuNPs. The green synthesized AuNPs were also found to have anti-inflammatory responses as shown by the reduction of pro-inflammatory cytokines from immune cells. In vitro assays showed that the biogenic AuNPs were not toxic to KMST-6 cells. Overall, the data suggest that plant extracts produce biologically safe AuNPs with antibacterial and anti-inflammatory activities that can be exploited in the treatment of chronic wounds and in the management of chronic inflammation.

Over the last 100 Years, the cyanidation process has been the most popular method for recovering gold from its ores. Despite this, there are still efforts to improve the efficiency of the process, particularly as ores become more difficult to treat. Many investigators have studied the cyanidation process, although a large proportion of these studies have obtained contradictory results. This thesis presents a kinetic and electrochemical study of the leaching of gold in cyanide solutions, and emphasis is placed on rationalising the conflicting results which have been published in the past.The leaching rate of gold was measured using a rotating electrochemical quartz crystal microbalance, an instrument which allows the simultaneous measurement of electrochemical data and mass changes at the solid-solution interface in real time. A proportion of this project was devoted to the on-going design of this instrument, and a number of modifications are discussed in detail. Initially, the leaching of gold in cyanide solutions was investigated under conditions of high purity. Under these conditions, it was found that the gold surface is blocked by a passive film, presumably AuCN. The presence of such a film results in the reaction being chemically controlled, and under typical cyanidation conditions (4 mM cyanide, pH 10.0), the rate of dissolution is very low. These kinetic results were supported by complimentary electrochemical studies, which showed that gold is passive in the potential region where cyanidation occurs.The second part of this thesis presents a study of the effect of system purity on the leaching of gold in cyanide solutions. Solution phase purity was investigated by adding controlled amounts of lead or silver to the leach solutions. It was found that in the presence of low concentrations of lead, the dissolution of gold in 20 mM cyanide solutions was oxygen ++ / diffusion controlled (as compared to chemical control for gold in the absence of lead). However, high concentrations of lead were found to be detrimental to the leaching process. It is believed that the role of lead is to modify the surface by cementation, hence reducing the effect of the passive film. Silver was also found to be effective at reducing passivation, and the role of silver believed to be similar to that of lead. It was found that unlike lead, high concentrations of silver are not detrimental to the dissolution of gold in cyanide solutions.Solid phase purity was also found to be important in the leaching of gold, and it was found that the leaching of a gold sample which contains 1 % silver is diffusion controlled. This finding is important from an industrial viewpoint, as most native gold contains some silver. Consequently, attempts were made to rationalise the leaching of gold/silver with current plant practice. Discussion on the effect of cyanide and oxygen concentrations, temperature and lead addition is presented.

The primary objective of this thesis was to date the age of gold mineralization in the Jiaodong and Liaodong Peninsulas, China. Based on SHRIMP U-Pb zircon ages of dykes and host rocks at 13 gold deposits in the two peninsulas and the 40(subscript)Ar-39(subscript)Ar dating of sericite at the Cangshang deposit in the Jiaodong Peninsula, a single gold mineralization event at ca. 122 - 119 Ma has been identified.Ten gold deposits in the Jiaodong Peninsula and three gold deposits in the Liaodong Peninsula were examined. Gold mineralization can be divided into the disseminated-and-veinlet type (Jiaojla-style) and vein type (Linglong-style) and all these deposits are strongly controlled by faults. The most common host rocks are granitoids, with a SHRIMP 206(subscript)Pb/238(subscript)U age of 150 - 165 Ma. The youngest host rocks in the Jiaodong Peninsula are granodiorite, with an age of ca. 128 Ma. The oldest dated host rock in the Jiaodong Peninsula is amphibolite with a metamorphic zircon age of 1852 plus or minus 37 Ma; in the Liaodong Peninsula, the oldest host rock is metasandstone with the youngest detrital zircon giving an age of 1886 plus or minus16 Ma. The Jiaodong and Liaodong Peninsulas are underlain by Precambrian basement with components up to ca. 3.7 Ga old and these are reflected in the zircon population. There are three main peaks of inherited zircons, which yield Late Archaean (ca. 2500 Ma), Palaeoproterozoic (1800-2200 Ma) and Early Mesozoic (ca. 200-250 Ma) ages.The close spatial and temporal relationships between dykes and gold mineralization has only recently been recognized in China. Based on the cross-cutting relationship between dykes and gold lodes (and the alteration style of dykes), three types of dykes are recognized: pre-, syn- and post-mineralization dykes. Premineralization dykes yield an age of ca. 124 Ma; syn-mineralization dykes give an ++ / age of ca. 122-119 Ma, which can also be interpreted as the time of gold mineralization; further work is needed to date post-mineralization dykes, since no suitable samples were identified during this study.40(subscript)Ar-39(subscript)Ar dating of sericite has been used to determine the timing of gold mineralization at the Cangshang Gold Deposit. It gives a well-defined 40(subscript)Ar-39(subscript)Ar age of 121.3 plus or minus 0.2 Ma.The second objective of this thesis was to understand why the tectonic setting of the Jiaodong and Liaodong Peninsulas is favourable for gold formation and what is a sound genetic model for these gold deposits. Based on this study, it is interpreted that multiple orogenic events created a favourable tectonic environment for the Jiaodong and Liaodong gold deposits. It is suggested that delamination related to orogenic events occurred beneath the Jiaodong and Liaodong Peninsulas. The substantial heat and fluid transfer caused by delamination allowed mantle-derived magma and auriferous fluids to be channelled along deep faults to favourable structures within the crust. This probably explains why the dykes and gold lodes are closely associated in both time and space.