Selective Cation Exchange in the Core Region of Cu(2–x)Se/Cu(2–x)S Core/Shell Nanocrystals

[Image: see text] We studied cation exchange (CE) in core/shell Cu(2–x)Se/Cu(2–x)S nanorods with two cations, Ag(+) and Hg(2+), which are known to induce rapid exchange within metal chalcogenide nanocrystals (NCs) at room temperature. At the initial stage of the reaction, the guest ions diffused through the Cu(2–x)S shell and reached the Cu(2–x)Se core, replacing first Cu(+) ions within the latter region. These experiments prove that CE in copper chalcogenide NCs is facilitated by the high diffusivity of guest cations in the lattice, such that they can probe the whole host structure and identify the preferred regions where to initiate the exchange. For both guest ions, CE is thermodynamically driven as it aims for the formation of the chalcogen phase characterized by the lower solubility under the specific reaction conditions.