Segmented CdSe@CdS/ZnS Nanorods Synthesized via a Partial Ion Exchange Sequence

In this communication we present a synthetic pathway toward CdSe@CdS/ZnS nanorods which are built in a segment like manner (a CdSe core which is embedded in a CdS rod which then epitaxially ends in a ZnS rod). This structure is realized exploiting a sequential cation exchange mechanism. In a first step, CdSe@CdS rods are transformed into CdSe@CdS/Cu 2- x S rods. In a second step, the latter ones are converted into CdSe@CdS/ZnS rods. By varying the amount of Cu + precursor in the Cd 2+ to Cu + ion exchange step, the phase boundary between CdS and ZnS can be shifted in a controlled manner. This finding nicely demonstrates that cation exchange reactions in nanocrystals can not only be used to exchange the complete cation lattice but also only specifically selected parts of it. The obtained CdSe@CdS/ZnS nanorods are optically and electron microscopically characterized in depth.