Cathodic corrosion is a relatively unknown phenomenon that can severely etch metallic electrodes at cathodic (negative) potentials. In spite of these remarkable changes that are caused by cathodic... Show moreCathodic corrosion is a relatively unknown phenomenon that can severely etch metallic electrodes at cathodic (negative) potentials. In spite of these remarkable changes that are caused by cathodic corrosion, the phenomenon is stil not fully understood. Cathodic corrosion is therefore the focus of this PhD thesis. The first three experimental chapters of the thesis focus on characterizing platinum, rhodium and gold electrodes before and after cathodic corrosion in a variety of working solutions. In doing so, these chapters establish surprisingly mild corrosion onset potentials and reveal an etching anistropy that depends on the cation in the working solution. Additional density functional theory calculations suggest a similarly significant role for adsorbed hydrogen. These result suggest the existence of ternary metal hydrides during cathodic corrosion. The role of hydrides is further studied in the fourth experimental chapter through X-ray absorption spectroscopy. These four fundamental chapters are followed by two more applied chapters. The first of these tailors the activity of a platinum single crystal towards oxygen reduction, by using cathodic corrosion. The second applied chapter uses cathodic corrosion to create and thoroughly characterize alloyed nanoparticles. Combined, these fundamental and applied chapters provide valuable new information towards understanding and applying cathodic corrosion. Show less
In summary, the collective results described in this thesis show that nanoparticulate vaccines can be delivered intradermally by coated and hollow microneedles and evoke antigen-specific immune... Show moreIn summary, the collective results described in this thesis show that nanoparticulate vaccines can be delivered intradermally by coated and hollow microneedles and evoke antigen-specific immune responses. The choice of both the nanoparticles and the microneedle(s) could have important influences on the immune responses. Microneedle arrays coated with antigen loaded and lipid bilayer fused mesoporous silica nanoparticles (MSNs) could be a promising system for convenient and fast intradermal delivery of protein antigen, although our results indicate that the system needs to be improved in order to obtain optimal immune responses. Moreover, antigen and adjuvant loaded nanoparticles can increase IgG2a (Th1) and CD8+ responses after intradermal delivery by hollow microneedles. This effect depends on the type and the physicochemical characteristics of the nanoparticles, in which smaller size and controlled release properties of antigen and adjuvant were found to correlate with the stronger effect. Finally, the combination of separate antigen loaded and adjuvant loaded nanoparticles may be as efficient as the antigen and adjuvant co-encapsulated nanoparticles for modification of the immune responses following intradermal immunization. Show less
