Extending the Spectral Range of Double-Heterojunction Nanorods by Cation Exchange-Induced Alloying

Composition variation and formation of core/shell heterostructures have allowed the extension and applicability of size-tunable optical properties of colloidal semiconductor nanocrystals. Anisotropic shapes such as nanorods (NRs) provide new and further refined properties but relatively simple and empowering approaches such as alloying and controlled heterostructure formation are much more challenging to apply to these materials. Here, we start from a well-defined CdS/CdSe barbell-shaped NR heterostructure and perform sequential cation exchanges first with Cu and then with Cd/Zn under relatively mild conditions to achieve alloying while preserving the structure. By using a mixture of Cd and Zn in the presence of a thiol, controllable amounts of alloying in both components could be achieved. Growth of a final ZnSe shell enhances the photoluminescence and allows the creation of a series of double-heterojunction NRs with emission spanning the visible spectral range.