(38g) The Geode Process: A Route to the Large-Scale Manufacturing of Functionally-Encoded Nanostructures

A wide range of high-tech applications require constituent materials and devices that must simultaneously exhibit nanoscale control of compositional heterogeneity and be produced at large scales. Semiconductor nanowires, for example, can be produced with exquisite control of composition and morphology using the vapor-liquid-solid (VLS) mechanism that, however, remains limited to very small production rates. Here, we introduce the Geode process to synthesize functionally-encoded semiconductor nanowires at throughputs orders of magnitude beyond the state-of-the art. Central to the Geode process are sacrificial, porous-walled, seed particle-lined silica microcapsules, whose interior surface serves as a high-surface area growth substrate. Microcapsules protect the growing nanostructures, are produced with a scalable emulsion templating technique, and are compatible with large-scale chemical reactors. We will show how microcapsule structure and drying is influenced by silica nanoparticle type and concentration, emulsification parameters, and nanoparticle cross-linking agent. We will also demonstrate the synthesis of Si nanowires with programmable dopant profiles on the microcapsule interior. The impact of the microcapsule wall on the transport of reactive species will be characterized by examining changes to dopant profile.