Hydrophobic Nanoreactor Soft-Templating: A Supramolecular Approach to Yolk[at]Shell Materials

Due to their unique morphology-related properties, yolk[at]shell materials are promising materials for catalysis, drug delivery, energy conversion, and storage. Despite their proven potential, large-scale applications are however limited due to demanding synthesis protocols. Overcoming these limitations, a simple soft-templated approach for the one-pot synthesis of yolk[at]shell nanocomposites and in particular of multicore metal nanoparticle[at]metal oxide nanostructures (M sub(NP)[at]MO sub(x)) is introduced. The approach here, as demonstrated for Au sub(NP)[at]ITO sub(TR) (ITO sub(TR) standing for tin-rich ITO), relies on polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) inverse micelles as two compartment nanoreactor templates. While the hydrophilic P4VP core incorporates the hydrophilic metal precursor, the hydrophobic PS corona takes up the hydrophobic metal oxide precursor. As a result, interfacial reactions between the precursors can take place, leading to the formation of yolk[at]shell structures in solution. Once calcined these micelles yield Au sub(NP)[at]ITO sub(TR) nanostructures, composed of multiple 6 nm sized Au NPs strongly anchored onto the inner surface of porous 35 nm sized ITO sub(TR) hollow spheres. Although of multicore nature, only limited sintering of the metal nanoparticles is observed at high temperatures (700 degree C). In addition, the as-synthesized yolk[at]shell structures exhibit high and stable activity toward CO electrooxidation, thus demonstrating the applicability of our approach for the design of functional yolk[at]shell nanocatalysts. A facile strategy for the one-pot synthesis of metal[at]metal oxide yolk[at]shell nanomaterials (M[at]MOx) is presented. As exemplified for gold nanoparticle[at]tin-rich ITO yolk[at]shell nanostructures (Au[at]ITO sub(TR)), our approach takes advantage of gold precursor loaded inverse micelles as two compartment nanoreactor templates. Simple calcination of the precursor micelles yields highly defined Au[at]ITO sub(TR) nanostuctures in line with the micellar size and compositon featuring high activity and stability for electrocatalytic CO oxidation.