Revealing the emergence of order and heterogeneity at the nanoscale with liquid-phase transmission electron microscopy

Liu, Chang

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https://hdl.handle.net/2142/121254 Copy

Description

Title

Revealing the emergence of order and heterogeneity at the nanoscale with liquid-phase transmission electron microscopy

Author(s)

Liu, Chang

Issue Date

2023-07-13

Director of Research (if dissertation) or Advisor (if thesis)

Chen, Qian

Doctoral Committee Chair(s)

Chen, Qian

Committee Member(s)

• Zuo, Jian-Min
• Wang, Hua
• Johnson, Harley T.

Department of Study

Materials Science & Engineerng

Discipline

Materials Science & Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• liquid-phase TEM
• nanoscale
• in situ
• self-assembly

Abstract

The universe is full of order and heterogeneity. Ranging from birth of galaxy to formation of atomic crystals, order brings about the beauty of simplicity and facilitates the emergence of novel collective properties while heterogeneity induces more possibilities with variations. In materials science, both can be illustrated in various physical and chemical processes and be used to guide the design of functional materials. However, little of either is known when it comes to direct real-time and real-space imaging at the nanoscale in soft material systems. This dissertation focuses on developing the technique of liquid-phase transmission electron microscopy (TEM) and exploring different nanoentities to obtain their in-situ information, focusing on assembly, heterogeneity, and related properties involved. I first characterize the nanoscale dynamics and interactions of metal nanoparticles and their assemblies. Here, complexity and tunability play very important roles in the functionality of the assembly structure. By either increasing the complexity of the nanoparticles for the assembly or constructing specific structures that have more handles to control such as layered structure and corresponding misalignment between the layers. For these two directions, gold nanoarrows (GNAs) and gold nanorods (GNRs) are synthesized and used in liquid-phase TEM for studying their assembly and dynamics. Beyond self-assembly, I also introduce the external electric fields to realize unique assembly behaviors of gold nanospheres (GNSs), which have distinctive features from reported equilibrium self-assembly. I also work on extending liquid-phase TEM to challenging low-contrast materials and extracting the inner structure information of nanomaterials. I introduce low-crosslinked, fragile hydrogel nanoparticles, poly(N-isopropylacrylamide) (PNIPAM) microgels, to liquid-phase TEM. By optimizing the experimental protocols, I manage to maintain the sample integrity, collect data with good contrast, and interpret them to understand the inner structure of the microgels. Furthermore, I incorporate four-dimensional scanning transmission electron microscopy (4D-STEM) and obtain cohesive real-space and reciprocal-space information at the nanoscale. By using graphene liquid cell (GLC), I focus on the reaction of etching of GNRs as a straightforward demonstration of the capability of liquid-phase 4D-STEM. This dissertation demonstrates the capability of liquid-phase TEM in revealing the nanoscale ordering and heterogeneity in different soft materials, enriches the fundamental understandings in the nanoscale interactions and dynamics, and can serve as a guideline for further development of functional materials.

Graduation Semester

2023-08

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Chang Liu

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