(65ao) Microwave Synthesis of Biocompatible Quantum Dots

Fluorescent quantum dots (QD) are collections of semiconductor atoms on the order of a few nanometers. Their emission properties are dictated by the surface state and traps of the nanoparticles, and the size of the particle. Quantum dots are an emerging alternative to traditional dyes for solar cells and bio-imaging because of the ability to tailor the chemistry of the QD surface, their high quantum efficiency and their stable emission. One of the draw backs of QDs is the requirement of oxygen and water free synthesis conditions, and difficulty producing high quantum efficiency water soluble particles. We present a general method of synthesizing water soluble core-shell cadmium selenide (CdSe) QDs with quantum efficiencies of greater than 20 percent; the highest reported to date for water soluble quantum dots. The water soluble core-shell QDs are synthesized by microwave heating from commercially available precursors in the presence of water and oxygen in a matter of minutes. This methodology allows for the controlled synthesis of an array of different QDs, and the ability to tailor the chemical functionality of the QD surface with ligands. We also present a method of encapsulating the CdSe QD cores in a zinc sulfide shell to fill in electronic traps and increase the particles' quantum efficiency. We have further been able to increase the quantum efficiency by altering the surface chemistry of the cores. To date we have successfully synthesized QD cores of the yellow-red spectrum. Our current research focuses on revising previously developed procedures to synthesize CdSe QD cores of the full color spectrum as well as cores of other metals.