Atomic structure characterization at the nanoscale using multi-modal electron diffraction

The emerging properties of materials at the nanoscale have opened new technological opportunities, including applications in optoelectronics, renewable energy, medicine, and smart materials, as well as enabling continued miniaturization. Many unique phenomena at this intermediate length scale, between individual atoms and bulk materials, have been revealed through direct observation of shape, size, and internal structure of nanomaterials using electron microscopy. While synthesis and structural characterization have traditionally progressed in tandem, the growing structural and chemical complexity of these materials now pushes the limits of current characterization capabilities. Challenges include the need to resolve heterogeneity, hierarchical structures, and dynamic processes in native environments. To understand structures that terminate at the nanoscale through the lens of chemical bonding and theory, electron diffraction offers necessary spatial resolution and sensitivity to access local structural and chemical information, which is further improved by recent instrumentation development. This thesis employs multi-modal electron diffraction techniques to explore new directions in atomic structure characterization and determination at the nanoscale. We address the challenges of performing scanning electron nano-diffraction in a graphene liquid cell “nano-aquarium,” enabling continuous observation of dynamic processes in solution while preserving the native environment. Using the same technique, we map the strain field of a polycrystalline, five-fold twinned nanoparticle whose intrinsic strain arises from the mismatch between lattice symmetry and particle geometry. We not only systematically study the size effect of strain fields and lattice pseudosymmetry, but also develop diverse analyses for diffraction datasets to tackle fundamental questions that have persisted for decades. Lastly, we present structural studies of organic materials in intermediate states that are difficult to access using conventional methods, by selected-area electron diffraction and microcrystal electron diffraction. We characterize the packing and morphology of semiconducting polymers in their solution-aggregated state, as well as the molecular structure of small molecules at different stages of an electrochemical reaction. These structural insights not only correlate with real-world performance but also provide guidance for future materials optimization. Overall, this thesis introduces new approaches to extract the atomic information in chemically and structurally complex systems, expanding our ability to explore structure–property relationships at the nanoscale.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Lin, Oliver

Contributors dc:contributor

• Chen, Qian
• Gruebele, Martin
• Murphy, Catherine
• Zuo, Jian-min

• Nanomaterials
• Electron diffraction

Statement dc:rights

• Copyright 2025 Oliver Lin

Language dc:language

en

Handle dc:identifier

https://hdl.handle.net/2142/132614

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/132614