Argonne National Laboratory

Colloquium Series

The Center for Nanoscale Materials holds a regular biweekly colloquium on alternate Wednesdays at 11:00 a.m. in Bldg. 440, Room A105/106. The goal of the series is to provide a forum for topical multidisciplinary talks in areas of interest to the CNM and also to offer a mechanism for fostering interactions with potential facility users.

Committee Members:

  • Xiao-Min Lin (Chair)
  • Pierre Darancet
  • Ralu Divan
  • Xuedan Ma
  • Elena Rozhkova
  • Jianguo Wen
Jan. 10, 2018

"Electronic Excitations in the Condensed Phase"Tim Berkelbach, University of Chicago.  Host: Pierre Darancet

I will present recent work developing predictive theories and ab initio computational techniques for the description of excited states in nanoscale and condensed-phase materials.  First, I will describe a low-energy theory of band gaps and excitons in atomically-thin semiconductors, focusing on the transition-metal dichalcogenides.  In particular, the theory is naturally adapted to include environmental effects, which are critically important for such atomically-thin materials.  The presented approach can be viewed as a poor-man's GW+BSE, which is a successful suite of techniques for excitations in solids, but one which breaks down for more strongly correlated materials.  To address this, I will describe the software development and applications of wavefunction-based quantum chemistry techniques for solid-state problems.  In particularly the use of coupled-cluster theory for solids is demonstrated to provide an accurate description of satellite structure in the photoemission of metals, correlation-driven bandwidth narrowing, and high-accuracy band gaps in semiconductors.  The formal relation to the GW approximation will be briefly discussed.

Jan. 24, 2018

"AWE-somes: All Water-Emulsion Bodies formed by Polelectrolytes at Interfaces"Kathleen J. Stebe, University of Pennsylvania, Host: Xiao-Min Lin

Interfaces between fluids are rich environments to trap materials and build films. Particles and molecules adsorb at interfaces to lower the interfacial energy, and so can be collected from bulk fluid phases to form interfaces covered with monolayer or multilayer structures. This system is an excellent platform for capsule formation. By placing droplets in an external phase, materials from either the dispersed or continuous phases can be incorporated into films. Judicious selection of these components can lead to highly versatile, tailored structures. We are developing encapsulation methods via interfacial complexation of polyelectrolytes and other charged species in all aqueous two phase systems to make multi-functional all water emulsion bodiesAWE-somes. Such capsules might be particularly interesting for sequestration of delicate components, including proteins and microbes, which should not be placed in contact with oils or hydrophobic media. Here we discuss the example of the PEG-Dextran-water system, which separates into PEG-rich and dextran-rich phases. The interfacial tension between the phases is quite low. Furthermore, many molecules, including polyelectrolytes, partition freely between the two phases. These factors make interfacial structure formation especially challenging. We develop strategies to build membranes from complementary polyelectrolytes in each phase by balancing their rates of transport to the interface. To impart additional functionality, we develop methods to include charged nanoparticles (NPs) in such membranes. Here, nanoparticles can be selected that preferentially partition into one of the phases, facilitating interfacial transport, and creating an osmotic imbalance that leads to spontaneous formation of encapsulated multiple emulsions. These AWE-somes, with internal structures reminiscent of membraneless organelles in cells, provide a rich platform for separation, partitioning, reaction, and transport, suggesting AWE-somes might be developed into capsules that mimic biological-cell functions, or protocell systems. 

Feb. 7, 2018 Pierre-Nicholas Roy, University of Waterloo, Host: Stephen Gray
Feb. 21, 2018 Alexandra Boltasseva, Purdue University, Host: Gary Wiederrecht
Apr. 18, 2018 Nicholas A. Kotov, University of Michigan.  Host:  Gleiciani de Queiros Silveira
May 2, 2018 David S. Ginger, University of Washington, Host: Pierre Darancet
May 16, 2018 Gong Gu, University of Tennessee, Host: Lifen Wang
May 30, 2018 Yugang Sun, Temple University.  Host:  Gary Wiederrecht
Jun. 13, 2018 Mike Arnold, University of Wisconsin, Host: Nathan Guisinger
Jun. 27, 2018 James Alexander Liddle, National Institute of  Standards and Technology (NIST), Host: Ralu Divan
Jul. 11, 2018  
Jul. 25, 2018 Quanxi Jia, State University of New York (SUNY), Host:  Liliana Stan
Aug. 8, 2018  Itai Cohens, Cornell University, Host: Xiao-Min Lin
Sep. 5, 2018 Dongling Ma, Institut National de la Recherche Scientifiue (INRS), Host: Gary Wiederrecht
Sep. 19, 2018  
Oct. 3, 2018  
Oct. 17, 2018 Stephan Lany, National Renewable Energy Laboratory (NREL), Host: Maria Chan
Oct. 31, 2018  
Nov. 14, 2018

Stephen G. Sligar, University of Illinois, Host: Elena Rozhkova

Dec. 12, 2018 P. James Schuck, Columbia University, Host: Pierre Darancet
Jan. 16, 2019 Juejun Hu, Massachusetts Institute of Technology (MIT), Host: Peijun Guo