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 state 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.

The wet chemical synthesis of energy and sensor relevant nanomaterials often requires large amounts of high boiling point solvents, grams of reactants, solvent-based purification, and the use of oxygen free atmospheres. These synthetic routes are also prone to poor scalability due to requirements of precise control of high temperatures. Because of this, the potential use of metallic nanoparticles and semiconductive quantum dots (q-dots) in energy transfer and real time biosensor applications is labor intensive and expensive. We have explored a green alternative route that involves the colloidal synthesis of CdSe and CdTe quantum dots under well-controlled hydrothermal conditions (100-200°C) using simple inorganic precursors. The resulting nanomaterials are of high quality, and are easily processed depending upon application, and their synthesis is scalable. Temperature control, and synthetic scalability is provided by the use of a synthetic microwave reactor, which employs computer-controlled dielectric heating for the rapid and controllable heating.