1. Electronic Impurity Doping in CdSeNanocrystalsWayne L. Gladfelter, University of Minnesota Twin-Cities, DMR 0908629 Semiconductor nanocrystals (NCs) are finding applications in a variety of opto-electronic devices. As with bulk semiconductors being able to control the electrical properties is critical for optimal device performance. Upon incorporation of silver impurities into CdSenanocrystalswe discovered dramatic changes in their optical and electrical properties. The addition of just a few Ag atoms per nanocrystal causes a large enhancement in the fluorescence. While Ag was expected to be a substitutionalacceptor, nonmonotonictrends in the fluorescence and Fermi level suggest that Ag changes from an interstitial (n-type) to a substitutional (p-type) impurity with increased doping. Sahu, et al, Nano Lett. 2012, 12, 2587-2594 Fluorescence from equal concentrations of CdSenanocrystals showing the dramatic change in emission intensity as a function of doping with silver. In the center vial the Ag ions are located in interstitial sites in the CdSelattice and donate electrons to the conduction band. As the concentration of Ag increases (right vial), it substitutes for cadmium in the lattice and switches to a p-type dopant.

2. Scientific Collaboration with Univ. of Duisburg-EssenWayne L. Gladfelter, University of Minnesota Twin-Cities, DMR 0908629 The NSF-MWN grant provided Shay Wallace, a University of Minnesota undergraduate in Materials Science, the opportunity to work with Prof. Winterer’s group at the University of Duisburg-Essen for 10 weeks during the summer of 2012. His project focused on the use of aerosol methods to prepare nanocrystals. U of M Chemistry graduate student, Josh Halverson worked with Winterer's group collecting and analyzing extended X-ray adsorption fine structure (EXAFS) data on doped CdSenanocrystals. Prof. Wayne Gladfelter visited UDE in June, 2012 to present a talk at the celebration of the 5th anniversary of UDE’s Nanoengineering program. Data collection at the Advanced Photon Source at Argonne National Lab in August 2012 from left to right, Shay Wallace (UMN undergrad), Prof. Markus Winterer, APS staff member, Alexander Kompsch (UDE grad student), Josh Halverson (UMN grad student)