Nanoscale engineering facilitated by controlled synthesis: From structure to function

It is now well known that the optical properties of semiconductor nanocrystal quantum dots (NQDs) – absorption onset and position of the photoluminescence maximum – can be precisely controlled by simple tuning of particle size within the quantum-confinement regime. More recently, however, the field has evolved beyond straightforward particle-size control to embrace more complex NQD heterostructures. As a result of the inclusion of internal, nanoscale compositional interfaces, heterostructured NQDs afford opportunities for enhanced, emergent and even multi-functional behavior and properties. A common structural motif for achieving such ‘engineered’ NQDs is to envelop the NQD core within a shell of a different composition. Herein, a summary of our recent research in the development, synthesis, characterization and application of ‘core/shell’ NQDs is provided. In the first part, enhancement of properties is demonstrated through our work in lead chalcogenide core/shell NQDs. In a subsequent section, emergence of novel properties resulting from specific combinations of core and shell physical and electronic structures is described in the context of non-blinking behavior and suppressed Auger recombination realized for our “giant” NQDs. Examples in this case entail both CdSe and InP cores. Application of these ultra-stable NQDs in the area of light-emission technologies is also demonstrated and discussed. Finally, multi-functionality is shown for the case of a coupled magnetic-semiconductor Co/CdSe core/shell nanocrystal system.