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@PHDTHESIS{Linn:566341,
author = {Linn, Malte Jonathan},
othercontributors = {von Plessen, Gero and Simon, Ulrich},
title = {{G}rößen- und {S}trukturabhängigkeit der optischen
{E}igenschaften von {DNA}-{G}oldnanopartikel-{N}etzwerken},
school = {RWTH Aachen},
type = {Dissertation},
address = {Aachen},
reportid = {RWTH-2016-00434},
pages = {1 Online-Ressource (x, 242 Seiten) : Illustrationen,
Diagramme},
year = {2015},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University 2016; Dissertation, RWTH Aachen, 2015},
abstract = {Noble-metal nanoparticles are widely used in the field of
nanoscience and nanotechnological applictions. When
irradiated with visible or infrared light, these particles
exhibit unique optical properties. The most important
features are a strong local field enhancement and resonantly
enhanced light-scattering and light-absorption. Especially,
gold nanoparticles are widely used for therapeutic and
diagnostic applications in nanomedicine and bionanoscience,
since they are biocompatible and enable a diverse surface
chemistry. Therefore, gold nanoparticles are the basic
elements for bio-nano-hybrid systems. The strong light
absorption of gold nanoparticles allows an efficient and
localized deposition of light energy in terms of heat into
such a system. This enables the remote control of
temperature sensitive biomolecular reactions. Since the
optical properties of gold nanoparticles or rather
nanoparticle systems is governed by their size, internal
structure and their direct environment, photothermally
induced changes in bio-nano-hybrid systems can be monitored
optically. A prominent example of such sample systems are
DNA-gold-nanoparticle networks, where the gold nanoparticles
are linked by double-stranded DNA. These networks can be
switched between different states, by heating and thus
dehybridizing the DNA double-strands into single strands.
The subsequent network dissociation is reversible upon
cooling.This thesis is devoted to the question how the size
and internal structure of different DNA-gold-nanoparticles
influences their optical and photothermal properties.
Spectroscopic methods are used to determine the
characteristic light scattering and extinction properties of
networks with different sizes and morphologies. The
networks' ability to scatter light increases with increasing
network size. Additionally, the measured resonance curves
are spectraclly shifted and broadened with increasing
network size. These phenomena are used to detect the network
dissociation of networks with one and two transitions
spectroscopically. Doing so, the photothermally induced
temperature rise inside the networks, when irradiated with
continuous wave laser light, is found to rise with both
laser intensity and network size. By using exact
electrodynamic caluclations together with numerical heat
transport calculations, the experimental findings can be
confirmed qualitatively. The DNA-gold-nanoparticle networks,
consisting of up to thousands of particles, show new,
wavelength-dependent optical phenomena: The calculated
electric field-distribution inside the networks shows the
development of standing light waves. The spacial positions
of the nodes and antinodes of these standing waves relates
directly to the positions of low and high absorption inside
the network. Further, narrow, high-intensity light beams,
so-called photonic nanojets, can arise behind the networks.
Another main emphasis of this work is the detailed analysis
of heat transport phenomena. By using interferometric
methods, the photothermally induced temperature profile
inside a nanoparticle suspension is obtained. Also, the
onset of convective effects in such solutions is studied and
quantified. Besides, the influence of convective flows has a
strong influence on time-resolved measurements of the
network dissociation process under continuous wave laser
irradiation.},
cin = {131820 / 130000},
ddc = {530},
cid = {$I:(DE-82)131820_20140620$ / $I:(DE-82)130000_20140620$},
typ = {PUB:(DE-HGF)11},
urn = {urn:nbn:de:hbz:82-rwth-2016-004343},
url = {https://publications.rwth-aachen.de/record/566341},
}