Aarhus Universitets segl

Studying the Surface Chemistry of Nature: Utilizing SFG spectroscopy and NEXAFS imaging and spectroscopy

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandling

In this thesis, the experiments are centered around studying the surface
chemistry of highly specialised animals and plants. The first experimen-
tal method is based on studying the vibrational modes utilizing sum fre-
quency generator (SFG) vibrational spectroscopy, and the second method
is studying the molecular bonds at the interface utilizing near edge X-ray
absorption fine structure (NEXAFS) imaging and spectroscopy. Both of
these techniques contribute to information from the interface about the
type of molecules and the molecular order at the surface.
The first project was the determination of the molecules and the min-
erals part of the head protrusion of the Eudicella gralli scarab. It was
determined that the mineral aragonite is biomineralised in the tissue of
the head. This project resulted in the creation of a mineral library with
high resolution spectra for 11 calcium based mineral found in nature. The
next project was the investigation of the surface chemistry for three differ-
ent snakes. It showed that the desert snake had a ordered lipid layer on
both the ventral (belly) and dorsal (back) scales, whereas the two other
snakes only have an ordered lipid layer at the ventral scales. These two
snakes move only with the ventral scales in contract with the environment,
whereas the desert snake is covered in its environment. Gecko tissue in-
vestigated have a thin lipid layer at the adhesion pad. In addition, angle
dependent measurement showed that the β-sheet are stacked closely to-
gether with a flat configuration of the sheets. The last project, is a study
of the adhesion from the basil seed adhering to two different interfaces;
CaF2 and polystyrene. Here, the experimental data showed that the seeds
have a high molecular order at both interfaces, but the binding strength is
higher for the seed bound to the polystyrene interface where the structure
is more disordered. The adhesion dynamics is investigated for seeds ad-
hering to both interfaces as the seeds adhesion is drying. No noteworthy
difference was observed in the time dynamics of the drying, but it was
solely due to the difference in the interface.
The results from this thesis provides more information about the surface
chemistry of these four system, and hopefully this can help in the devel-
opment and improvement of coatings, lubrications and adhesions.
Bidragets oversatte titelStudie af Naturens Overfladekemi: Ved brug af SFG spektroskopi og NEXAFS afbildning og spektroskopi
Antal sider213
StatusUdgivet - 2023

Bibliografisk note

Published May 2023

Note vedr. afhandling

Supervisor: Tobias Weidner. Defence in August 2023

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