Continuous Flow Synthesis of Noble Metal Patchy Particles

The syntheses of noble metal nanoparticles of gold, silver or platinum have attracted high interest in research since several decades. Known potential applications can be found e.g. in the fields of biomedicine, plasmonics, sensors or catalysis. Especially, the synthesis and the control of asymmetrical particle morphologies, which often bring enhanced functionality, by simple and scalable methods is one of the major hurdles to their exploitation. By this poster a simple continuous one-step flow process will be shown to synthesize noble metal patchy particles. In the context of this work, patchy particles are defined as particles having at least one surface region – the so called patch – of a different material which provides an additional surface chemistry or functionality. A well-known example of these relatively new types of particles are Janus particles which show a surface contribution of different material and/-or functionality of 50%. Most of the fabrication methods for combining noble metals and non-metallic core-particles are based on the immobilization of spherical core particles onto a substrate to shadow a desired fraction of the particles’ surface against further chemical or physical treatments like the functionalization of the surface by capping molecules or the deposition of different materials like gold by e.g. sputtering. Such methods include several steps which lead to a high complexity and a limited scalability of the whole process. In our group we have developed an approach which is based on the cooperative interaction of metal precursors and other reagents with a core particle’s surface. We have shown that this leads to a strong preference for heterogeneous nucleation and surface diffusion, leading to the surface conformal growth of noble metal patches. By this poster the three patch/core particles systems of Ag@SiO₂, Au@PS (polystyrene) and Pt@PS will be presented. Our results show that in case of Au@PS and Pt@PS ascorbic acid plays an essential surface guiding function in addition to its’ role as reducing agent. Independent of the combination of noble metal and core particle, the synthesis is processed at aqueous conditions by a simple T-mixer based flow process in the millimeter scale. This allows the production of larger quantities of patchy particles at lab scale for the exploration of potential applications and further shows an option of process design which has the potential of classical scalability up to a certain limit or the possibility to increase the throughput of product particles by numbering up method.