In this study, we investigated the
synthesis of copper selenide
nanoplatelets (NPLs) through a cation exchange reaction (CER) in 5-monolayer-thick
CdSe NPLs using Cu(I) and Cu(II) precursors. We discovered that the
exposure of CdSe NPLs to a Cu(I) precursor led to the transformation
of NPLs into Cu2–x
Se while maintaining
their nanoplatelet morphology. The replacement of Cd(II) with Cu(I)
prevailed over the formation of doped structures. In the case of the
Cu(II) precursor, we observed that Cu(II) was first reduced to Cu(I)
before being intercalated into the host lattice, resulting in the
synthesis of Cu2–x
Se, similar to
CER with Cu(I) precursors but without preservation of the initial
morphology of NPLs. Interestingly, the presence of oxygen was found
to facilitate the cation exchange processes in CdSe NPLs, whereas
a nitrogen atmosphere suppressed the CER. Despite the similar ionic
sizes of Cu(I) and Cu(II), the substitution of Cd(II) with Cu(II)
was found to be challenging, possibly due to the involvement of redox
processes resulting in the significant deterioration of initial CdSe
NPLs. We demonstrate that CER can achieve near-complete substitution
of cadmium atoms with monovalent copper at room temperature. Understanding
the processes involved in CERs is crucial for engineering more complex
structures, such as high-entropy nanoparticles involving cation exchange
with different oxidation states and development of material synthesis
using machine learning and artificial intelligence approaches.