Diffusion through the shells of yolk-shell and core-shell nanostructures in the liquid phase

Recent advances in synthetic materials sciences such as the incorporation of self-assembly, sol‐gel, and layer-by-layer deposition chemistry have afforded the development of many interesting and potentially useful nanostructures. Among those, nanoarchitectures in which a core nanoparticle, often a transition metal, is encapsulated by an outer layer of a second material, typically a porous oxide, have gained much popularity recently. The shells in these so-called core‐shell nanostructures can offer a number of functionalities, including protection of the core from the outside environment, help in maintaining its compositional and structural integrity, prevention of the core from aggregating or sintering into larger particles, selective percolation of molecules in and out of the interior of the shell, increases in solubility and/or biocompatibility, and addition of new physical or chemical properties. [1‐3] More sophisticated nanostructures can also be synthesized with a void space, in a yolk‐shell or rattle-type nanoarchitecture, to create individualized nanoreactors around the core nanoparticles. [4‐6] The new properties of these nanostructures have already been exploited in sensing, [7,8] drug delivery and biomedical imaging, [9‐11] catalysis and electrocatalysis (including fuel cells), [12‐14] and the development of batteries [15] and energy storage devices. [16]