1. CFN Colloquium Series

    "Chemical Design of Nanocrystal Based Periodic and Aperiodic Metamaterials"

    Presented by Christopher Murray, University of Pennsylvania

    Tuesday, March 12, 2013, 11 am
    Bldg. 735 — Seminar Room, 2nd Floor

    Hosted by: Chuck Black

    Colloidal nanocrystals (NCs) with controlled crystal shape, structure and surface passivation provide ideal building blocks for assembly of new thin films and devices. Nanocrystals are "artificial atoms" with tunable electronic, magnetic, and optical properties. This talk will briefly outline some of the current "best practices" in preparation, isolation and characterization of semiconducting quantum dots and magnetic NCs. I will discuss the organization of monodisperse NCs into single component superlattices retaining and enhancing many of the desirable mesoscopic properties of individual NCs. I will then explore how these novel building blocks can be integrated in to a range of electronic, magnetic and optical devices. The potential to design new materials and devices expands dramatically with the creation binary NC superlattices. I will show how we have synthesized different-sized PbS, PbSe, CoPt3, Fe2O3, Au, Ag, Pd and NaYF4:Re (Re= rare earths) nanocrystals and then assembled these nanoscale building blocks into a rich array of multi-functional nanocomposites or metamaterials. We have also identified a novel method to direct superlattice formation by control of nanoparticle charging and by design of nanocrystal shape. Although modular nano-assembly approaches have already been extended to a wide range of NC systems, we believe we have produced only a tiny fraction of the materials that will soon be accessible. Progress in the assembly of quasicrystalline (aperiodic) packings of particles will be shared, as well as methods to characterize these novel materials. Devices based on these new multi-component nanoscale assemblies will be discussed along with some new research directions that focus on emergent physical phenomena in NC assemblies.