Revisiting the Anion Framework Conservation in Cation Exchange Processes

We investigated the effect of cation exchange on the anionic framework of lightly doped CdSe:Te/CdS nanorods. In contrast with previously studied core/shell systems, the Te dopant, located in the center of the CdSe core, provides an extremely sensitive indicator for any structural changes of the anionic framework that may occur as a result of the cation exchange process. We first optimized the cation exchange procedure in order to retain the fluorescence properties of the CdSe:Te/CdS nanorods after exchange of Cd²⁺ for Cu⁺ and back to Cd²⁺. Next, using multiexciton spectroscopy, we were able to probe the magnitude of the exciton-exciton repulsion interaction and use that to assess the degree of crystal structure conservation. Our findings provide a much stronger proof that the anion framework is indeed rigid, showing no evidence of significant migration of the anionic dopant.