ChBE Seminar Series: Moungi Bawendi
Tuesday, March 11, 2008
11:00 a.m.-12:00 p.m.
Room 2110 Chemical & Nuclear Engineering Bldg.
Professor Nam Sun Wang
Science and Technology of Semiconductor Nanocrystal Quantum Dots
Presented by Moungi Bawendi
Semiconductor nanocrystals, a.k.a. quantum dots, have become the prototypical material for the emergence of new properties when dimensions are reduced to the nanometer range. In the case of quantum dots it is the exciton radius in the bulk that determines the size transition from bulk-like electronic behavior to the size dependent properties that have made quantum dots a popular nanomaterial. In the size range of ~2 to 10 nm, the electronic structure of quantum dots becomes discrete at room temperature, leading to the size dependence of their band gap and of their fluorescence. The size dependent properties of excitons and multiexcitons in quantum dots, coupled with a material that can be processed from solution, has led to potential applications in fields that include emissive displays, solar energy conversion, and biological and biomedical fluorescence imaging. A fundamental understanding of exciton processes is critical for any of these applications to become realized. Synthesis of well characterized materials is obviously key, not only of the functional inorganic particle itself, but also the ligand shell that protects it and couples it chemically to molecules and matrices of interest. This talk will introduce the chemistry and photophysics of quantum dots and then explore the fundamental properties and challenges behind broadly applying quantum dots as light emitters and light absorbers in devices and for biological imaging.