Professor Delia Milliron

Departmental Seminar
Professor Delia Milliron
Department Chair of McKetta Department of Chemical Engineering
University of Texas at Austin
Host: Professor Gladfelter

Abstract

Plasmonic metal oxide nanocrystals and their gel assemblies

Metal oxide nanocrystals doped with a few percent of aliovalent dopants become electronically conducting and support strong light-matter interactions in the infrared due to localized surface plasmon resonance (LSPR). Focusing on the prototypical material, tin-doped indium oxide (ITO), we have found that the strength and spectrum of light absorption depend non-trivially on nanocrystal doping, size, and the radial distribution of dopants. Conductivity of nanocrystal films also depends systematically on dopant placement within the nanocrystals, due to associated changes in the near-surface depletion layers. Coupling of LSPR between nanocrystals in assemblies allows realization of materials whose properties depend both on the distinctive characteristics of their nanoscale building blocks and on their organization. Nanocrystal gel assemblies are interesting because their porous, percolating structures can in principle lead to tunable (valence-dependent) material properties with dynamic reconfigurability. We use dynamic covalent chemistry to create reversible gels of ITO nanocrystals under conditions guided by thermodynamic theory and rationalized with the help of simulations. The infrared optical response of the gels is broadened by coupling between the LSPR of the nanocrystals. Since assembly is reversible, the ITO nanocrystals gels are switchable infrared absorbers. Overall, plasmonic metal oxide nanocrystals offer compelling opportunities as building blocks for dynamic and tunable optical and electronic materials.

Research

Structuring materials on the nanoscale presents new opportunities to develop functionality not found in homogeneous, single-component materials. Energy devices, in particular, demand materials with complex combinations of properties that can also be processed at low cost and on large scale. Research in the Milliron group is motivated by new concepts for high performance electrochromic smart windows, batteries, and photovoltaic cells that take advantage of the unique optical, electronic, and processing characteristics of colloidal nanocrystals and other nanoscale building blocks.

Department Chair Delia Milliron

Bill L. Stanley Endowed Leadership Chair in Chemical Engineering
T. Brockett Hudson Professorship in Chemical Engineering