CAREER: Position-Controlled Doping of Semiconductor Nanocrystals Y. Charles Cao, University of Florida, DMR Doping refers to the process of intentionally introducing impurities into a nearly pure semiconductor. Impurity-doping is critical in controlling the electric and magnetic properties of the bulk seminconductors; the ability to precisely control impurity-doping in bulk semiconductors has enabled most modern semiconductor applications such as computer chips. The importance of doping in bulk semiconductors has stimulated research efforts to develop synthetic methods to incorporate dopants into colloidal semiconductor nanocrystals. Recently, we have developed a three-step colloidal synthesis for doping semiconductor nanocrystals. In this new synthesis, impurity doping only occurs in the nanocrystal growth stage, which allows for the easy control of doping level and the position of dopants inside a spherical nanocrystal. The ability to control these material parameters creates a new opportunity to tailor the optical, electronic and magnetic properties of semiconductor nanocrystals, which can lead to a new class of doping-based nanostructures for developing technological applications such as biomedical diagnosis, more efficient solar cells, and spintronic devices for the next generation of computers. Scheme of Position-controlled doping of spherical nanocrystals with a homogeneous structure (A) and a core/shell structure (B)

CAREER: Position-Controlled Doping of Semiconductor Nanocrystals Y. Charles Cao, University of Florida, DMR A three-step synthesis for doping colloidal semiconductor nanocrystals: (1)synthesis of “starting host particle,” (2) dopant growth, and (3) host-shell growth. Because the intensity of exciton wavefunctions and crystallinity of materials depend on the radial positions in a spherical nanocrystal, the ability to control the radial position of dopants is important in synthesizing impurity-doped nanocrystals with homogeneous optical, electronic and magnetic properties. In addition, the ability to control dopant positions and doping levels in a nanocrystal opens an opportunity to systematically study nanocrystal properties as a function of these two parameters which is of fundamental interest to the design of nanomaterial with new functions. Indeed, based on the three-step synthesis, we have demonstrated the first example in which optical properties of Mn- doped nanocrystals strongly depend on Mn radial positions inside the nanocrystals.

CAREER: Position-Controlled Doping of Semiconductor Nanocrystals Y. Charles Cao, University of Florida, DMR This CAREER project takes place in the field of nanotechnology at the intersection of chemistry, physics, and material sciences. The development in nanotechnology is likely to change the traditional methods of design, analysis, and manufacturing for a wide range of functional materials. This impact creates a need to educate students with the necessary knowledge, understanding, and skills to interact and provide leadership in the emerging world of nanotechnology. This CAREER project sets two broad educational goals: to develop nanotechnology education for students at various levels (graduate, undergraduate and K-12 students), and to help weak students at both undergraduate and graduate levels. The major education efforts will focus on three specific educational tasks: (1) undergraduate curriculum development for analytical chemistry, (2) new graduate course development on nanotechnology, and (3) development of nano-synthesis experiments for high-school students. The research and teaching plan described herein will build up a foundation for a long-term integrated scientific and educational program that will last beyond the award period.