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TY - THES AU - Linn, Malte Jonathan TI - Größen- und Strukturabhängigkeit der optischen Eigenschaften von DNA-Goldnanopartikel-Netzwerken PB - RWTH Aachen VL - Dissertation CY - Aachen M1 - RWTH-2016-00434 SP - 1 Online-Ressource (x, 242 Seiten) : Illustrationen, Diagramme PY - 2015 N1 - Veröffentlicht auf dem Publikationsserver der RWTH Aachen University 2016 N1 - Dissertation, RWTH Aachen, 2015 AB - 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. LB - PUB:(DE-HGF)11 UR - https://publications.rwth-aachen.de/record/566341 ER -