Dr. Jeunghoon Lee
Semiconductor nanocrystals, or quantum dots (QDs), exhibit unique size-dependent optical properties. Absorption and emission peaks of QDs shift to longer wavelengths as their sizes are increased due to a quantum confinement effect. Quantum dots are suitable for biological applications due to their high fluorescence quantum yield and resistance to photo-bleaching. CdSe QD cores were synthesized by thermal pyrolysis of Cd and Se precursors in the organic solvent octadecene. To increase the fluorescence quantum yield and the stability of QDs, a CdS shell was grown by alternate additions of Cd and S precursors. To render the QDs soluble in water and to use them in biological applications, 3-mercaptopropionic acid was used. Absorption and fluorescence of the QDs were measured to understand the relation between the surface structure and optical properties. Protein molecules will be attached to water-soluble QDs for further assembly with biological molecules and DNA nanostructures.