@PhdThesis{diss_mods_00017961,
  author = 	{K{\"o}hntopp, Anja},
  title = 	{Photochemical Properties and Ultrafast Dynamics of Azobenzene-Functionalized Gold Nanoparticles},
  year = 	{2015},
  publisher = 	{Christian-Albrechts-Universit{\"a}t zu Kiel},
  address = 	{Kiel},
  keywords = 	{ultrafast dynamics; azobenzene; gold nanoparticles},
  abstract = 	{The main goal of the present Thesis was the investigation of the photoinduced
isomerization processes of azobenzenes (ABs) attached to
small gold nanoparticles (AuNPs) by static and femtosecond timeresolved
transient absorption spectroscopy. ABs functionalized with linker chains of three different lengths (C3, C7, C11)
were brought onto the surface of {\~}4 nm diameter AuNPs in a mixed
self-assembled monolayer (mSAM) with decanethiol or pentanethiol
as co-ligand. The AB-functionalized AuNPs show excellent photoisomerization
yields independent from the linker chain length. AuNPs functionalized with ABs bearing long alkyl
linker chains and short co-ligands reversibly
aggregate when switched to their cis state and disaggregate when isomerized
back to their trans state. The time-resolved absorption data
reveal excited-state absorption of AB and strong
signals of the simultaneously excited localized surface plasmon resonance
(LSPR). The excited-state dynamics of AB show surprisingly
little difference compared to the AB dynamics in solution, leading to
the conclusion that the AB photochrome and the AuNP core are efficiently
decoupled by the long (C11) linker chain. Furthermore, the
excited-state dynamics of Disperse
Red 1 in a mSAM with decanethiol on a AuNP surface
were investigated.
A second goal of this Thesis was the spectroscopic investigation
of the ultrafast relaxation dynamics of functionalized AuNPs themselves,
especially the hot electron cooling dynamics, and how they
are influenced by different ligands. AB-functionalized AuNPs show
the same hot electron lifetime of $\tau${\~}2 ps as purely decanethiol
functionalized AuNPs, revealing that the electronic states of AB do
not participate in the electron cooling process. A study investigating
the influence of (i) the ligand heat capacity and (ii) resonant coupling
between ligand absorption band and LSPR was performed.},
  url = 	{https://macau.uni-kiel.de/receive/diss_mods_00017961},
  file = 	{:https://macau.uni-kiel.de/servlets/MCRFileNodeServlet/dissertation_derivate_00006373/Dissertation_Koehntopp2015.pdf:PDF},
  language = 	{en}
}