Selective
Cation Exchange in the Core Region of Cu<sub>2–<i>x</i></sub>Se/Cu<sub>2–<i>x</i></sub>S Core/Shell Nanocrystals
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Abstract
We studied cation exchange (CE) in
core/shell Cu<sub>2–<i>x</i></sub>Se/Cu<sub>2–<i>x</i></sub>S nanorods
with two cations, Ag<sup>+</sup> and Hg<sup>2+</sup>, 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<sub>2–<i>x</i></sub>S shell and reached the Cu<sub>2–<i>x</i></sub>Se
core, replacing first Cu<sup>+</sup> 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