Size Control and Photophysical Properties of Quantum Dots Prepared via a Novel Tunable Hydrothermal Route

The use of quantum dot (qdot) nanomaterials in aqueous media for biosensing, imaging, and energy conversion typically requires multistep phase transfer routes based on tailoring surface chemistry. Such surface modification can lead to instability, and increased hydrodynamic diameters, which affect utility. Thus, the ability to synthesize qdots under aqueous conditions with improved photophysical properties that are comparable to the slate of the art would be very beneficial. One limitation to this is the availability of high temperature aqueous protocols, which limits size control and crystalline annealing. Here, we show the ability to fabricate highly emissive CdSe, CdSe/CdS, and CdSe/CdS/ZnS qdots under fine-tuned hydrothermal conditions. The novelty of this approach is the use of a synthetic microwave reactor for dielectric heating that provides both kinetic control, and in situ monitoring of temperature and pressure. Results indicate the dramatic improvement for core and core-shell qdot luminescence at hydrothermal temperatures, as indicated by increased monodispersity, quantum yields, qdot brightness, and lifetimes.