Date: Tuesday, June 3, 2014
Time: 11:00 am
Speaker: Delia Milliron, Department of Chemical Engineering, University of Texas at Austin
Title: The Role of Surfaces and Interfaces in Nanocrystal-Based Materials
Location: 67-3111 Chemla Room
In materials constructed from few-nanometer scale building blocks, a large fraction of the total volume lies within a few atomic layers of a surface or an interface. Within the context of plasmonic metal oxide nanocrystals, I will describe a few examples of how these surfaces and interfaces play key roles in the assembly of nanocrystal-based materials and in determining their resulting optoelectronic properties. Wide bandgap oxide semiconductors can be made plasmonic by heavily doping them with aliovalent impurities, resulting in tunable surface plasmon resonance phenomena in the near infrared (NIR) spectral range. Furthermore, we showed that the electron concentration in films of plasmonic oxide nanocrystals is dynamically tunable by applying an electrochemical potential. The resulting strong modulation of solar NIR with high visible transparency is useful for a new breed of energy-saving smart windows. Furthermore, the same nanocrystals can be incorporated into metal oxide nanocomposites by chemically exchanging their surface ligands for transition metal oxo clusters. The embedded nanocrystal-glass interfaces resulting from this process are structurally reconstructed. These composites modulate NIR and visible light transmittance, with 5-fold enhanced optical contrast compared to the pure transitional metal oxide glass. Finally, surfaces hold the key to refining optoelectronic properties of plasmonic oxide nanocrystals. We discovered that sculpting the electrostatic landscape by near-surface doping dramatically reduces plasmon damping and impacts both electronic and optical properties.