Dissertation / PhD Thesis

PUBDB-2026-01909

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png In situ Studies of Photo-Induced Dynamics atLiquid Interfaces and in Solution Utilising X-rayand Neutron Scattering Techniques

Hoevelmann, S. C. (Corresponding author)Extern* ; Murphy, B. (Thesis advisor)Extern*XFEL.EU*DESY* ; Lindhorst, T. K. (Thesis advisor)

2025

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Please use a persistent id in citations: urn:nbn:de:gbv:8:3-2025-01241-7  doi:10.3204/PUBDB-2026-01909

Abstract: Studying the morphology of lyotropic liquid crystals formed by compositions of phospholipids and artificial azobenzene amphiphiles with in situ small angle X-ray scattering identified their shapes and mesophases and light-induced mesophase transitions from a lamellar to a cubic mesophase were revealed. The formation and transition between cubic mesophases are of high interest for designing drug delivery systems and to study membrane properties during membrane fusions. Embedding photoswitchable glycolipids containing an azobenzene switch into model membranes revealed changes of the monolayer structure and the possibility to control the head group orientation of the glycolipid. The changes in the layer thickness and disappearance of the head group ordering were observed with complementary in situ X-ray reflectivity, grazing incidence diffraction and neutron reflectivity studies. These findings show high potential for photoswitchable glycolipids to control protein and bacteria adhesion at lipid membranes. X-ray reflectivity and fluorescence near total reflection studies on surface near ions in aqueous sodium iodide salt solutions showed a deviation from the expected ion concentration in the bulk suggesting an enrichment of iodide ions at the interface at room temperature. Under UV laser irradiation, the data indicated a change of the iodide concentration at the interface. Studying ion enrichment and depletion at liquid interfaces contributes to understanding and explaining chemical reactions at liquid surfaces. Moreover, ions can be excited by UV laser pulses and the photoreactions occur on time scales of few fs to µs. In preparation to study such photoexcitation, the laser pump - X-ray probe setup at the LISA endstation at P08, PETRA III was upgraded within this thesis to extend the range of delays between the laser and X-ray pulses, to create a uniform laser intensity distribution for heat sensitive samples and to enhance operability.

Note: Dissertation, Christian-Albrechts-Universität zu Kiel, 2025

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Contributing Institute(s):

1. DOOR-User (DOOR ; HAS-User)

Research Program(s):

1. 6G3 - PETRA III (DESY) (POF4-6G3) (POF4-6G3)
2. FS-Proposal: II-20230678 (II-20230678) (II-20230678)
3. 05K22FK3 - LISA-dymanics: Aufbau für die Untersuchung von schneller und ultraschneller Dynamik an flüssigen Grenzflächen mittels optischer Pump-Röntgen-Probe Techniken. (BMBF-05K22FK3) (BMBF-05K22FK3)
4. DFG project G:(GEPRIS)460248799 - DAPHNE4NFDI - DAten aus PHoton- und Neutronen Experimenten für NFDI (460248799) (460248799)

Experiment(s):

1. PETRA Beamline P08 (PETRA III)

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