Inorganic nanoparticles are attractive materials due to their unique properties and prominent role in the fields of material science, nanotechnology and nanomedicine. Modern therapies aim to... Show moreInorganic nanoparticles are attractive materials due to their unique properties and prominent role in the fields of material science, nanotechnology and nanomedicine. Modern therapies aim to deliver drugs specifically to defective cells and mesoporous silica nanoparticles (MSNs) are considered to be promising candidates for this goal. In this thesis the synthesis, characterization and bio-applications of silica nanoparticles will be discussed. Moreover, the potential application of mesoporous silica nanoparticles as drug delivery systems will be discussed using two animal models: the Xenopus laevis and the Danio rerio. Show less
This project has dealt with the mechanistic study of the electrocatalytic nitrite reduction, the selectivity-determining step of nitrate reduction. Nitrate is a polluting ion targeted by wastewater... Show moreThis project has dealt with the mechanistic study of the electrocatalytic nitrite reduction, the selectivity-determining step of nitrate reduction. Nitrate is a polluting ion targeted by wastewater remediation; electrochemistry strives to achieve selectivity to harmless products (N2). A multi-pronged approach has been followed, aimed at establishing the influence of several variables (electrocatalyst material, surface structure, pH and electrode potential) on the catalytic activity and the product distribution, which has been determined with in situ analytical techniques (mass spectrometry and infrared spectroscopy). The molecular underpinnings of nitrite reduction have thereby been unravelled for transition metals, showing that an optimal catalytic performance is achieved when metals intermediate affinities to reaction intermediates (Sabatier Principle). The all-important concept of structure sensitivity also applies to nitrite reduction at Pt electrodes, although only in alkaline media: a Pt(100) single-crystal is the sole Pt surface able to achieve the desired direct conversion of nitrite into 100% N2. Such selectivity is unparalleled for a simple monometallic surface and is an outstanding finding. Additionally, the nitrite-reducing performance of bio-inspired catalysts, (electroactive metalloporphyrins) was investigated. A further side-project of this PhD thesis has also been the electrochemical characterization of preferentially-oriented cuboid Pt nanoparticles synthesized with the innovative __cathodic corrosion__. Show less
Microneedle-based transcutaneous immunisation is an appealing alternative to the classical manner of injecting vaccines by intramuscular or subcutaneous route. Importantly, as a consequence of the... Show moreMicroneedle-based transcutaneous immunisation is an appealing alternative to the classical manner of injecting vaccines by intramuscular or subcutaneous route. Importantly, as a consequence of the fact that the skin is in direct contact with the environment and should protect the body against pathogens, it contains more antigen presenting cells, such as dendritic cells than the muscles or subcutaneous tissue and thereby offers the possibility to induce a more effective immune response. The combination of microneedles and adjuvanted subunit vaccines may offer effective vaccination whereas ensuring patient safety and vaccine application in a painless manner. The principal aim of this thesis was to design subunit vaccine formulations that can be combined with microneedles for transcutaneous immunisation. The approaches described in this thesis have generated new insights into the main requirements for transcutaneous immunisation. Microneedles definitively have the potential to be an excellent utensil for the delivery of vaccines into the skin. However, the skin is a very elastic organ and the actual conduits formed by microneedle pre-treatment will be considerably smaller than the diameter of the microneedles. Therefore, a small antigen-adjuvant entity is the preferred formulation, as it will be transported efficiently through the microneedle conduits while it retains the co-delivery of antigen and adjuvant. 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
