Electron holography and particle dynamics in liquid phase transmission electron microscopy

    Research output: Book/ReportPh.D. thesisResearch


    Liquid phase transmission electron microscopy (LPTEM) enables us to visualize structures and the evolution of processes directly within liquid environments, with high spatial and temporal resolution. As such, LPTEM can shed light on both fundamental questions in physics, materials science, chemistry, soft matter and bioscience. In this thesis, an LPTEM platform was developed, based on silicon nitride membrane encapsulation of the liquid sample. This thesis explores three questions leading to new ways to perform LPTEM and providing new types of information on fundamental processes:

    - Is it possible to perform LPTEM studies of freely diffusing particles’ dynamics? Detailed LPTEM observations were made of free Brownian motion of nanoparticles in liquids, where all previous studies have focused on the far slower particles that are strongly interacting with the membranes. We measure to what extent it is influenced by the electron beam and discuss how this may be used for new LPTEM studies that may better model bulk liquid behavior than particles trapped on the membrane.
    - Can electron holography be used to measure electrical potentials in liquids? Electron holography has been widely used in mapping electromagnetic fields in solid matter, and if electron holography can be reliably applied in LPTEM it could lead to better understanding of the driving forces in electrochemistry, imaging magnetic interactions etc.
    Quantitative liquid phase electron holography is demonstrated in LPTEM using a newly developed nanochannel liquid cell. The mean inner potential (MIP, V0) of liquid water is measured to be V0,H2O = 4.48 ± 0.19 V, which is comparable to revised quantum mechanical model calculations. The consistency between the quantum mechanical MIP and experimental MIP is an essential benchmark to improve the quantum mechanical models that help us understand water interactions in liquid processes.
    - Can we measure local charge distributions of nanostructures in liquid by using electron holography?
    Mapping charge distributions on nanostructures in the liquid phase would provide a new approach to understanding the important electrostatic interactions in liquids.
    Electron holographic analysis was used to explore the possibility to quantify the charge distributions in LPTEM systems and on individual nanoparticles immersed in liquid.

    This thesis takes the first initial steps in developing LPTEM holography, and find it is a promising method that likely will open up many fascinating possibilities to study electromagnetic interactions at the nanoscale in liquids, and hence lead to new insights in nanoscale dynamics.
    Original languageEnglish
    PublisherDTU Nanotech
    Number of pages144
    Publication statusPublished - 2018


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