Synthesis of tailor-made colloidal semiconductor heterostructures

The field of colloidal nanocrystal synthesis has progressed rapidly to the point where spherical colloids of diverse sizes and compositions are commercially available or can be synthesized with minimal synthetic training. As quantum dots work their way into a greater array of technologies, it has become increasingly important to maximize the uniformity of these nanoscale structures and the efficiency of associated photophysical processes. Anisotropic quantum nanocrystals and quantum confined heterostructures offer even greater customization and tunability of specific electronic and photonic properties compared to their spherical counterparts. However, synthetic access to these more advanced structures is less well understood, and existing synthetic approaches are often challenging to execute or replicate. This feature article provides an account of the various bottom-up and top-down methods that have been developed to prepare more complex quantum confined structures and highlights the progress that has been made in the preparation of colloidal semiconductor nanocrystal heterostructures. From this survey of existing methods, it becomes clear that seeded assembly of heterostructure architectures combines many of the advantages of both bottom-up and top-down approaches to enable the greatest potential control over a diversity of new, customizable heterostructures with added functionality.