Abstract

Structural Complexity and Local Heterogeneity by Coherent X-ray Diffraction Imaging

Hyunjung Kim

Center for Ultrafast Phase Transformation, Department of Physics, Sogang University, Seoul 04107, Korea

 Nanoparticle structure, including strain-field distribution and crystallographic orientation, and local heterogeneities are crucial in many applications since they are key aspects of their functionalities. In particular, identifying chiral nanoparticles with abnormally tuned morphology in three dimensions is essential for optical, catalytic, and biological applications. A fundamental understanding of structural changes of the nanocatalysts is also important for revealing underlying mechanisms and optimizing efficiencies. In my presentation, I show how the atomic level of interaction of reactants affects the nanoparticles and nanoporous zeolites as strain-induced and defect dynamics during the catalytic process by exploiting the merits of Bragg coherent X-ray diffraction imaging. I also present a new methodology for identifying the 3D information of chiral gold nanoparticles with highly concaved gaps. It provides the 3D crystallographic and strain-field distribution of the nanoparticles to the fields where complicated structure and local heterogeneity are crucial, such as plasmonics.

 This research was supported by the National Research Foundation of Korea (NRF-2021R1A3B1077076).

 References:

1.     W. Cha, et.al., “Core-Shell Strain Structure of Zeolite Microcrystals”, Nature Materials 12, 729-734 (2013).

2.     D. Kim, et.al., “Active site localization of methane oxidation on Pt nanocrystals”, Nat. Commun. 9, 3422 (2018).

3.     D. Kim, et.al., “Nanoscale Strain Imaging using Coherent X-ray Light Sources”, J. of Kor. Phys. Soc. 73, 793-804 (2018).

4.     D. Kim, et.al., “Defect Dynamics at a Single Pt Nanoparticle during Catalytic Oxidation”, Nano Lett. 19, 5044-5052 (2019).

5.     S. Choi, et.al., “In Situ Strain Evolution on Pt Nanoparticles during Hydrogen Peroxide Decomposition” Nano Lett. 20, 8541-8548 (2020).

6.     J. Kang, et.al., “Time-resolved in situ visualization of the structural response of zeolites during catalysis” Nat. Commun. 11, 5901 (2020).

7.     J. Kang, et.al., “ Strain Development of Selective Adsorption of Hydrocarbons in a Cu-ZSM‑5 Crystal”, ACS Appl. Mater. Interfaces, 43, 50892-50899 (2021).

8.     S. Choi, et.al., “Strain and Crystallographic Identification of the Helically Concaved Surfaces of Nanoparticles” (submitted).

9.     W. Cha, S. Choi, and H. Kim, Coherent X-ray Diffraction Studies of Inorganic Materials, Comprehensive Inorganic Chemistry III, Elsevier (2022).

Bio

Hyunjung Kim is the director of the Center for Ultrafast Phase Transformation and Center of Nanomaterials and a professor in the Department of Physics at Sogang University, Seoul, Korea. She has led an active research group focusing on coherent x-ray scattering to study dynamics and nanostructures by X-ray Photon Correlation Spectroscopy and Coherent X-ray Diffraction Imaging using synchrotrons and XFELs. Her recent research interests are directed more toward ultrafast phenomena combining pump-probe techniques with coherent applications on thermoelectric materials, phase change materials, energy-related materials, and catalytic nanoparticles. She received a Simke award for excellent achievement in Synchrotron science by Pohang Accelerator Laboratory in Korea in 2013. She has served as an International Advisory Committee member of Pohang Accelerator Laboratory and on proposal review panels for several synchrotrons and XFELs (LCLS, PETRA III, Pohang Light Source, and PAL-XFEL). She was the president of the Korean Synchrotron User Association Committee, Korea, from 2020-2021. She has served as chair for the “X-ray Science” of Gordon Conference in 2017 and “SXNS-15” in 2018.

The CoWork webinar series is dedicated to the exploitation of the coherence properties of X-rays for advanced materials characterization, with a special focus on inverse microscopy techniques, such as Coherent Diffraction Imaging (CDI), Ptychography and Holography. It is an introduction to Coherent X-ray imaging methods to facilitate the access to advanced microscopy techniques to new users and it welcomes all researchers intrigued by the spectacular coherence properties of X-rays produced at modern synchrotron sources – of which MAX IV is a first example.