This book uses text and photographs to highlight a transdisciplinary research project (2018-2022) about artisanal and small-scale gold mining that involved transdisciplinary collaboration between... Show moreThis book uses text and photographs to highlight a transdisciplinary research project (2018-2022) about artisanal and small-scale gold mining that involved transdisciplinary collaboration between academics, artists, and gold miners. With the title Exploring Transformations to Sustainability in Artisanal and Small-scale Gold Mining: Trans-regional and Multi-Actor Perspectives, or Gold Matters for short, the project examined whether and how societal transformations towards sustainable mining futures are possible in artisanal and small-scale gold mining. It brought together a multi-national team to conduct research in Brazil, Suriname, Ghana, Burkina Faso, Guinea Conakry, and Uganda. Show less
Abstract Electrochemical reactions in general, and the CO2 reduction reaction (CO2RR) in particular, are commonly studied at room temperature. However, practical electrolysers may use elevated... Show moreAbstract Electrochemical reactions in general, and the CO2 reduction reaction (CO2RR) in particular, are commonly studied at room temperature. However, practical electrolysers may use elevated temperatures. There is currently a lack of fundamental understanding of the effect of temperature on the CO2RR. Here, we performed temperature-dependent studies on the CO2RR on a relatively simple electrode material, namely gold, to obtain insights into how temperature influences this reaction and the competing hydrogen evolution reaction. A rotating ring disk electrode setup was used to show that the CO2RR activity and selectivity increased with temperature, and to obtain kinetic parameters such as the apparent activation energy and transfer coefficient. The magnitude of the temperature effect and the activation energy was affected by both the cation identity and concentration in the electrolyte. Moreover, the positive effect of temperature on the kinetics of the CO2RR was counteracted by the lower CO2 solubility, making efficient mass transport even more important at higher temperatures. Show less
Bicarbonate buffer is largely found in nature due to its ability to regulate pH variations around neutral values. As the pH changes, so does the speciation of the buffer. At low pH the main buffer... Show moreBicarbonate buffer is largely found in nature due to its ability to regulate pH variations around neutral values. As the pH changes, so does the speciation of the buffer. At low pH the main buffer species is carbon dioxide, which for increasing pH transforms into bicarbonate, and then into carbonate. Besides the acid-base reactions in solution, the buffer species may react at the electrified interface to be reduced or oxidized.Given the importance of storing intermittent renewable electricity into chemical bonds using abundant reactants, such as carbon dioxide, it is crucial to understand the interplay of electrochemical and homogeneous reactions. Hence, in this PhD thesis we studied how the presence of a buffer in the electrolytes affects relevant electrocatalytic reactions, i.e. CO2 electrochemical reduction (Chapter 2 and 4), hydrogen evolution reaction (Chapter 4 and 5) and CO electrooxidation (Chapter 3). A special focus is placed on the employment of well-defined mass transport techniques in combination with digital simulations. Show less
This work describes several studies into the electroreduction of carbon dioxide (CO2RR), both regarding mechanistical aspects and catalyst stability considerations. Mechanistic insights into carbon... Show moreThis work describes several studies into the electroreduction of carbon dioxide (CO2RR), both regarding mechanistical aspects and catalyst stability considerations. Mechanistic insights into carbon-carbon bond formation on a silver catalyst are described in Ch 2, were we find an acetaldehyde-like surface adsorbate to be a key intermediate. Gold stability in alkaline environment under strongly reducing conditions and the effect of near-surface CO on said stability is reported on in Ch 3, showing catalyst degradation under reductive conditions which is furthermore exacerbated by CO adsorption. Chapter 4 details the voltammetric behavior of variously oriented copper surfaces when prepared via a non-standard methodology, showing good agreement with prior literature. The last chapter (Ch 5) contains investigations into the stability of copper under reductive conditions in near-neutral buffered electrolyte and in alkaline electrolyte, where it was observed that copper is morphologically stable under strongly alkaline conditions and neutral conditions in the presence of CO2 and buffer ions, so long as strictly reducing potentials are applied. Show less
Gold nanorods are ideal candidates for complementing fluorophores in labelling applications. The presence of the surface plasmon resonance generates large absorption and scattering cross sections,... Show moreGold nanorods are ideal candidates for complementing fluorophores in labelling applications. The presence of the surface plasmon resonance generates large absorption and scattering cross sections, thus making the detection of single nanoparticles possible under a light microscope. The plasmon of gold nanorods depends on the ratio between their width and length and covers the range between 540nm for spheres and even above 800nm for elongated particles, thus almost the entire visible and near-infrared spectrum. The surface plasmon presents great opportunities in (bio-)sensing, enhanced spectroscopies, photothermal therapy and for concentrating light below the diffraction limit. Show less
Catalysis is one of the most important technical and scientific developments, on which present-day society is based. For example, it is crucial to the production of fertilizers or clean... Show more Catalysis is one of the most important technical and scientific developments, on which present-day society is based. For example, it is crucial to the production of fertilizers or clean fuels and needed for the abatement of exhaust gases. Frequently, the employed catalysts are being discovered in a very empirical way; by trial and error. However, designing catalysts based on detailed understanding is preferred. Obtaining understanding is very difficult, because catalysts are very complex materials. Furthermore, its properties often depend on the atmosphere surrounding the catalysts, i.e., the temperature and pressure of reactants and products, which they are exposed to, and these properties also change over time. The major part of this thesis focuses on structural changes of Pt model catalysts exposed to high oxygen pressures at elevated temperatures. The changes were measured with a ReactorSTM, a special version of a scanning tunneling microscope (STM) adapted to operate at high pressure and temperatures. These observations show that various surface oxide with a single-layer thickness form under reaction conditions. These oxides are structurally and chemically different from the Pt bulk oxides. The second part describes a set of experiments to understand the role of low-coordinated atoms and water in Au-catalyzed CO oxidation. Show less
Clearly gold deposited as nanoparticles on a support is a very active catalyst in contrast to bulk gold which does not show any catalytic activity. The question arises if this particle size effect... Show moreClearly gold deposited as nanoparticles on a support is a very active catalyst in contrast to bulk gold which does not show any catalytic activity. The question arises if this particle size effect is exclusively valid for gold catalysis or can a similar effect be found in other metals? In the research described in this thesis we investigated copper and silver based catalysts for similar particle size effects as for gold based catalysts. In contrast to gold bulk silver and copper are known to be active in catalysis and both metals are used as catalysts. Silver is the metal of choice for the formation of ethylene oxide from ethylene but also for the formation of formaldehyde in the BASF process. A Cu/Zn-based catalyst is used for the synthesis of methanol from CO and \hydrogen, and copper-based catalysts are also active in oxidation reactions. As the interaction between the gold nanoparticles with the additives is very important for the catalytic activity, the effect of additions of lithiumoxide and ceria have also been investigated for the silver and copper based catalysts. These additives stabilize the nanoparticles and ceria which is known for its oxygen storage and oxidation capacities and is one of the best additives for gold based catalysts. Various oxidation and dehydrogenation reactions have been investigated over copper, silver and gold based catalysts, which are presented in this thesis. In chapter 2 the preferential oxidation of CO is discussed. Chapter 3 deals with the selective oxidation of \ammonia. Chapter 4 is devoted to the oxidation and dehydrogenation of methanol. Chapter 5 presents the results of formation of ethylene oxide in the oxidation and dehydrogenation of ethanol on silver and copper based catalysts. In chapter 6 more results of ethanol dehydrogenation and oxidation on gold based catalysts are presented. Chapter 7 gives insight into the activity of gold based catalysts in oxidation and dehydrogenation of 1-propanol and 2-propanol. Show less
The design of novel anticancer agents is one of the most active fields in Medicinal Chemistry, as the number of effective drugs for treatment of cancer is still very limited. This demand for new... Show moreThe design of novel anticancer agents is one of the most active fields in Medicinal Chemistry, as the number of effective drugs for treatment of cancer is still very limited. This demand for new drugs is even higher, considering the high cancer-prevalence rate in our society. The therapeutic application of metal complexes is an under-developed area of research and basic principles in the development of metallopharmaceuticals are lacking, or at least just recently being discovered. Metal-containing agents may offer unique therapeutic opportunities. However, significant obstacles, including potential metal accumulations and toxicities, require further research before a promising metal compound may be introduced in the clinic. In particular several ruthenium and gold coordination compounds have shown promising application as anticancer agents. In these terms, this thesis project, performed in the Coordination and Bioinorganic Chemistry group in the Leiden Institute of Chemistry, comprises the design, synthesis, detailed characterization (i.e. elemental analysis, UV-Vis spectroscopy, IR, far-IR, NMR, mass spectroscopy and X-ray single-crystal structure determination) and also the biological evaluation of novel gold compounds and ruthenium compounds. The promising cytotoxic activity developed for several of these compounds and the findings from this research are providing a better understanding of chemistry of Ru(III) and Ru(II) and Au(III) coordination compounds and their structure-activity relationships and may lead to the development of improved ruthenium and gold-chemotherapeutic drugs. Show less
Against the background of a regional crisis caused by dynastic change in China and the closure of Japan in the middle of the seventeenth century, the Vietnamese kingdom of Tonkin rose to the fore... Show moreAgainst the background of a regional crisis caused by dynastic change in China and the closure of Japan in the middle of the seventeenth century, the Vietnamese kingdom of Tonkin rose to the fore as the major silk producing and exporting region in East Asia.Based on a wealth of so far unused primary sources from the Dutch East India Company (VOC) archives, this monograph explains how Dutch maritime traders played a critical role in Tonkin’s dramatic emergence as a trading power. The author examines the vicissitudes in political relations, the varying trends in the VOC-Tonkin import and export trade, and the Dutch influence on the seventeenth-century Vietnamese feudal society. Show less
