{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/127332"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/127332","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Angstrom-scale imaging of 2D molecular materials via scanning transmission electron microscopy and ptychography","abstract":"Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2026-12-01","abstract_html":"Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2026-12-01","abstract_has_math":false,"creators":["Kharel, Priti"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Chemistry","degree_department":null,"school":null,"contributors":["Huang, Pinshane","Murphy, Catherine Jones","Lopez, Joaquin Rodriguez","Zuo, Jian-Min"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2024,"date_issued":"2024-10-23","date_published":"2024-10-23","updated_at":"2026-07-22T22:25:03Z","subjects":["Structure Determination","Molecular Crystals","Covalent Organic Framework","3d Structure","Scanning Transmission Electron Microscopy","Atomic Resolution","Stacking Disorder"],"languages":["eng","en"],"rights":["Copyright 2024 Priti Kharel"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/2142/127332","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Huang, Pinshane","Murphy, Catherine Jones","Lopez, Joaquin Rodriguez","Zuo, Jian-Min"]},{"key":"dc:creator","label":"Author","values":["Kharel, Priti"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2024-10-23","2024-12"]},{"key":"dc:type","label":"Dc Type","values":["text","Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Chemistry"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Structure Determination","Molecular Crystals","Covalent Organic Framework","3d Structure","Scanning Transmission Electron Microscopy","Atomic Resolution","Stacking Disorder"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng","en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2024 Priti Kharel"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://hdl.handle.net/2142/127332"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2026-12-01","The student, Priti Kharel, accepted the attached license on 2024-10-22 at 02:30.","The student, Priti Kharel, submitted this Dissertation for approval on 2024-10-22 at 03:02.","This Dissertation was approved for publication on 2024-10-23 at 14:11.","DSpace SAF Submission Ingestion Package generated from Vireo submission #21259 on 2025-03-28 at 14:42:46","Accurate structural determination of 2D molecular materials is crucial for their development and application across diverse fields, including biomedicine, energy storage, and electronics. However, conventional diffraction-based techniques often provide limited structural information, particularly for systems such as thin films, polycrystalline particles, and nanopowders— forms in which many 2D molecular materials are commonly synthesized. This thesis presents a direct approach for resolving structures of such 2D molecular materials using scanning transmission electron microscopy (STEM) to image atomic connectivity and higher-order 3D structures. We address the longstanding challenges of radiation damage and weak electron scattering through a multi-pronged strategy that includes using protective graphene substrates, low-dose imaging, maximizing signal to noise ratio in the images, and advanced data processing. In atomically thin 2D small molecular crystals, our methods yield elementally sensitive images with a resolution of up to 1.3 Å, enabling the distinction of light elements such as carbon and nitrogen. When applied to 2D covalent organic frameworks (2D COFs), we uncover significant disorder in inter-layer stacking with nanometer-scale offsets, challenging their previous depictions as average eclipsed structure. Using multi-slice electron ptychography, we extend our imaging to three dimensions, revealing the 3D arrangement of COF layers and distortions in the shape of the pore channels that are critical for their charge and mass transport applications. Overall, this thesis introduces powerful new direct techniques for the structural characterization of 2D molecular materials, providing synthetic chemists and materials scientists with an invaluable tool for ab initio structure determination and accurate exploration of structure-property relationships."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Angstrom-scale imaging of 2D molecular materials via scanning transmission electron microscopy and ptychography"]}]}],"canonical_facts":{"dc:contributor":["Huang, Pinshane","Murphy, Catherine Jones","Lopez, Joaquin Rodriguez","Zuo, Jian-Min"],"dc:creator":["Kharel, Priti"],"dc:date":["2024-10-23","2024-12"],"dc:description":["Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2026-12-01","The student, Priti Kharel, accepted the attached license on 2024-10-22 at 02:30.","The student, Priti Kharel, submitted this Dissertation for approval on 2024-10-22 at 03:02.","This Dissertation was approved for publication on 2024-10-23 at 14:11.","DSpace SAF Submission Ingestion Package generated from Vireo submission #21259 on 2025-03-28 at 14:42:46","Accurate structural determination of 2D molecular materials is crucial for their development and application across diverse fields, including biomedicine, energy storage, and electronics. However, conventional diffraction-based techniques often provide limited structural information, particularly for systems such as thin films, polycrystalline particles, and nanopowders— forms in which many 2D molecular materials are commonly synthesized. This thesis presents a direct approach for resolving structures of such 2D molecular materials using scanning transmission electron microscopy (STEM) to image atomic connectivity and higher-order 3D structures. We address the longstanding challenges of radiation damage and weak electron scattering through a multi-pronged strategy that includes using protective graphene substrates, low-dose imaging, maximizing signal to noise ratio in the images, and advanced data processing. In atomically thin 2D small molecular crystals, our methods yield elementally sensitive images with a resolution of up to 1.3 Å, enabling the distinction of light elements such as carbon and nitrogen. When applied to 2D covalent organic frameworks (2D COFs), we uncover significant disorder in inter-layer stacking with nanometer-scale offsets, challenging their previous depictions as average eclipsed structure. Using multi-slice electron ptychography, we extend our imaging to three dimensions, revealing the 3D arrangement of COF layers and distortions in the shape of the pore channels that are critical for their charge and mass transport applications. Overall, this thesis introduces powerful new direct techniques for the structural characterization of 2D molecular materials, providing synthetic chemists and materials scientists with an invaluable tool for ab initio structure determination and accurate exploration of structure-property relationships."],"dc:format":["application/pdf"],"dc:identifier":["https://hdl.handle.net/2142/127332"],"dc:language":["eng","en"],"dc:rights":["Copyright 2024 Priti Kharel"],"dc:subject":["Structure Determination","Molecular Crystals","Covalent Organic Framework","3d Structure","Scanning Transmission Electron Microscopy","Atomic Resolution","Stacking Disorder"],"dc:title":["Angstrom-scale imaging of 2D molecular materials via scanning transmission electron microscopy and ptychography"],"dc:type":["text","Thesis"],"thesis:degree_discipline":["Chemistry"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:25:03Z"}