Scattering and Instrumentation Sciences
- Ultrafast Materials Science
- Soft Matter Electron Microscopy
- In-Situ Liquid Cell Electron Microscopy: Atomic Level Heterogeneity and Fluctuations at Solid Liquid Interfaces
This program seeks to investigate the properties of strongly correlated materials by shining light onto them. Intense laser pulses have been used to restructure the free-energy landscape of these materials, and to generate rapid switching between the various forms of order deriving from the strong correlation. State of the art highs harmonic generation photoemission spectroscopy and time- and spin- resolved photoemission spectroscopy systems have been developed. The future goal is to stimulate materials at selective excitations with higher intensity laser pulses to establish a mean for manipulation and control of materials properties.
C. L. Smallwood, T. L Miller, W. T. Zhang, R. A. Kaindl, A. Lanzara. Nonequilibrium electron dynamics in a solid with a changing nodal excitation gap. Physical Review B 23, 235107 (2016).
W. T. Zhang, T. Miller, C. Smallwood, T. Yoshida, H. Eisaki, R. A. Kaindl, D. H. Lee, A. Lanzara. Stimulated emission of Cooper pairs in a high-temperature cuprate superconductor. Scientific Reports 6, 29100 (2016).
T. Miller, C. L. Smallwood, W. Zhang, H. Eisaki, J. Orenstein, A. Lanzara. Photoinduced changes of the chemical potential in superconducting Bi2Sr2CaCu2O8+δ. Physical Review B 92, 144506 (2015).top
We aim to produce images of soft materials with atomic resolution using electron microscopy. This is inherently challenging because soft materials are unstable under the electron beam. To do so, we will design and implement a pre-specimen phase plate that takes advantage of a recently demonstrated scanning transmission electron microscopy (STEM) imaging mode that is more efficient than conventional high-resolution STEM. Sophisticated averaging algorithms will also be used to extract high resolution information from low exposure images, where Fourier transforms along orthogonal directions will be used to align individual images. To demonstrate these imaging concepts, we will use crystalline nanostructures formed by self-assembly of amphiphilic peptoid molecules in water. Of particular interest are structures formed by diblock copolypeptoids where conventional wisdom suggests that these molecules should form micellar aggregates with collapsed hydrophobic cores. In contrast, we obtain hollow crystalline tubes with hydrophobic groups exposed to water. Confirming this by atomic-scale imaging is important for a general understanding of molecular self-assembly. A series of peptoids with sequences of monomers specifically designed to enable high resolution electron microscopy will be synthesized by solid phase synthesis. Molecular dynamics will be used to characterize thermal fluctuations and disorder, and this information will be convoluted with the contrast transfer function of the microscope used in experiments to obtain theoretical images. This new framework for atomic resolution imaging on model peptoids will be applied to improve the resolution of electron microscopy of more conventional soft polymeric materials.
J. Sun, X. Jiang, R. Lund, K.H. Downing, N.P. Balsara, and R.N. Zuckermann. Self-assembly of crystalline nanotubes from monodisperse amphiphilic diblock copolypeptoid tiles. Proceedings of the National Academy of Sciences, vol. 113(1), pg. 52–57 (2016).
J. Sun, X. Jiang, A. Siegmund, M. D. Connolly, K.H. Downing, N.P. Balsara, R.N. Zuckermann. Morphology and Proton Transport in Humidified Phosphonated Peptoid Block Copolymers. Macromolecules, vol. 49(8), pg. 3083–3090 (2016).
K. J. Harry, X. Liao, D.Y. Parkinson, A.M. Minor, N.P. Balsara. Electrochemical Deposition and Stripping Behavior of Lithium Metal across a Rigid Block Copolymer Electrolyte Membrane. Journal of the Electrochemical Society, vol. 162(3), p. A389-A405, (2015).top
In-Situ Liquid Cell Electron Microscopy: Atomic Level Heterogeneity and Fluctuations at Solid Liquid Interfaces
The overarching goal of this program is to develop and utilize the advanced in-situ liquid cell transmission electron microscopy (TEM) to elucidate how atomic level heterogeneity and fluctuations at solid-liquid interfaces determine the physical and chemical properties and processes of materials, currently with a focus on nucleation, precipitation and dissolution at solid-liquid interfaces. With the development of liquid cell TEM, we investigate the transient nucleation events in an oversaturated solution and precipitation and dissolution at solid-liquid interfaces under an external stimulus, such as an electrochemical potential. Special attention will be made on correlation of concentration fluctuations to structural ordering during nucleation processes; characteristics of prenucleation clusters or intermediates; and how surface defects or inhomogeneity change the nucleation process and reduce the nucleation barrier. The development of advanced instrumentation for imaging and chemical identification with atomic resolution provides transformative opportunities for investigation of the dynamic phenomena at solid-liquid interfaces in this program and many other dynamic processes at the frontiers of basic energy science.
To be added shortly...top