Synthesis of Novel Quantum Dot Emitters in Molten Inorganic Salts

Many functional nanomaterials used for catalysis, healthcare, solid-state lighting, and displays are synthesized by colloidal techniques. The scope of chemical transformations accessible to colloidal chemists is determined by the stability and compatibility of solvents and surfactants used as a reaction medium. For example, very few traditional solvents can handle temperatures above 400C, while many inorganic phases require even higher temperatures to form. We are developing comprehensive understanding of a novel class of colloidal systems, colloids in molten inorganic salts. Nanoparticles of different transition metals, semiconductors, oxides, and magnetic materials can form true colloids in molten inorganic salts. The colloidal stability of nanoparticles in molten salts could not be explained by traditional electrostatic and steric stabilization mechanisms. Our experimental and computational studies point to the importance of the long-range ion correlations in the molten salt near the nanocrystal interface.<br/>In addition to the fundamental exploration of new colloidal systems, molten salts expand the boundaries for solution synthesis of many nanomaterials that have been out of reach for colloidal chemists. We have used molten salts to synthesize colloidal GaAs, In_xGa_1-xAs, In_xGa_1-xP and GaN quantum dots, which resisted numerous synthetic attempts for over two decades. By further developing colloidal chemistry in molten salts, we hope to enable synthetic routes toward various functional nanomaterials previously considered unsynthesizable by colloidal methods.