Ultra-Small Silver Nanoparticles - Dynamic Behavior in Aqueous and Biological Environments

The utilization of silver nanoparticles in consumer related products has significantly increased over the last decade, especially due to their antimicrobial properties. Today they are used in a plethora of products ranging from cosmetics and textiles to medical instruments. Thus, investigations on nanoscale silver are attracting increasing interest in many fields, such as biomedicine or catalysis. Unfortunately, the results of these studies are diverse and do not lead to a consistent evaluation of the toxicity of silver nanoparticles. A major flaw is the usage of non-uniform and inadequate characterized particles with broad size distributions. To elucidate this problem this thesis deals with the synthesis and thorough characterization of a versatile silver nanoparticle system in a size at the lower end of the nanoscale. Poly(acrylic acid) (PAA)-stabilized silver nanoparticles with a nominal radius of 3 nm are synthesized using two methods. Firstly, they are produced in a classical batch synthesis and secondly in a microwave-assisted synthesis. The comparison of these two routes applying the same reaction conditions provides the opportunity to reveal whether non-thermal microwave effects, which are still under debate in literature, are present. The synthesized particles exhibit a high stability and are used in an inter-laboratory comparison proving their suitability for application in nanometrology, such as determination of nanoparticle sizes, size distribution widths, and particle concentrations. Furthermore, the high versatility of the silver nanoparticle system enables an easy ligand exchange to tune the surface of the particles on demand and improve their biocompatibility. Exemplarily, transfunctionalizations with albumin, glutathione, and tyrosine are performed and characterized by small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), UV/Vis and IR spectroscopy. These differently coated silver nanoparticles are used firstly in a catalytic application: the reduction of 4-nitrophenol. Therein, a ...