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We present the synthesis of a noveltype of chalcogenide nanoplatelets.Starting from CdS core or CdSe/CdS core/shell nanoplatelets, we usesequential cation exchange to copper and then to either zinc or leadto obtain ZnS and PbS core or ZnSe/ZnS and PbSe/PbS core/shell structures.The procedure preserves well the 2D geometry of the nanoplatelets,provided that they are more than 6 monolayers (∼1.8 nm) thick.The core/shell structure is also well conserved during the cationexchange as verified by TEM images. The nanoplatelets exchanged withZn crystallize in a zinc blende structure, like the initial Cd-basedmaterial, whereas when Pb is used, the final nanoplatelets have arock-salt crystal structure. We explored the copper cation exchangeprocess using energy dispersive X-ray spectrometry with 1 nm resolutionon nanoplatelets standing on their edges, and we show that copperions diffuse uniformly from the outside of the nanoplatelet to theinside during the exchange. [ABSTRACT FROM AUTHOR]

We report the continuous lateral extension of cadmiumselenidenanoplatelets into nanosheets using continuous injection of precursorsat high temperature. We show that we can obtain CdSe nanosheets withlateral dimensions up to 700 nm and a well-defined thickness thatcan be tuned with atomic precision. When the nanosheets’ lateralsize increases, they roll on themselves to form nanoscrolls that canunroll upon surface modification. The final geometry of the nanosheetscan be tuned to different morphologies using precursors that favorthe growth of specific crystal facets. We provide a detailed studyof the CdSe nanosheets growth and its optimization for three differentthicknesses. [ABSTRACT FROM AUTHOR]