Putting the Needle to the Haystack: Submolecular Structure Elucidation with Atomic Force Microscopy in Ultra High Vacuum

Atomic Force Microscopy and related methods like Kelvin Probe Force Microscopy and Scanning Tunneling Microscopy are valuable assets to investigate structures and sample morphologies beyond the capabilities of optical microscopic methods. Over the course of this work, these shall be employed to perform submolecular structure elucidations in several different systems. In order to be able to distinguish sample molecules from the background they are residing on, the overall works starts with the investigation and preparation of suitable substrates. After parameters for preparation procedures have been established, the molecular scale investigations start with large ligand-metal complexes and therefore validifying their successful synthesis with direct imaging. The next topic are self-assembling monolayers. These classes of molecules can take on a highly ordered quasi-crystallin state when being adsorbed onto a substrate. Different classes of there are studied, as well as the influence of difference substrates like gold and silver on their assembling behavior. When irradiated with electrons, the individual molecules of the self-assembled monolayer form bonds until eventually the whole layer forms an amorphous membrane. These carbon nanomembranes possess remarkable properties like selective permeation. Since the exact origin of this extraordinary high water permeation was so far unknown, this work aims at directly imaging pores that shall give these membranes their properties. In doing so, a scheme was devised to classify pore size distributions, which was subsequently applied to other membrane systems, like cyclodextrin-based filters. The final part revolves around the interaction of DNA with dinuclear metal-complexes. These are designed in such a way to bind to two neighboring phosphate groups of the DNA backbone. This effect aims at blocking polymerase processes in order to stop tumor growth in chemotherapy. While this effect has been shown with several methods, their direct visual confirmation of this binding mode was missing so far. In addition to successfully observing individual molecules bonded onto DNA, an interaction with the vacuum environment was observed, where double strands dissociate into single strands. A causal relation with the complex molecules could be shown with a statistical simulation.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Universität Bielefeld

Year

2023

Author dc:creator

• Biere, Niklas

Repository record source_url

https://pub.uni-bielefeld.de/record/2982183

OAI identifier oai:identifier

oai:pub.uni-bielefeld.de:2982183