@phdthesis{Wirsing2023,
  author    = {Wirsing, Sara},
  title     = {Computational Spectroscopic Studies with Focus on Organic Semiconductor Systems},
  doi       = {10.25972/OPUS-28655},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-286552},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {This work presents excited state investigations on several systems with respect to experimental spectroscopic work. The majority of projects covers the temporal evolution of excitations in thin films of organic semiconductor materials. In the first chapters, thinfilm and interface systems are build from diindeno[1,2,3-cd:1',2',3'-lm]perylene (DIP) and N,N'-bis-(2-ethylhexyl)-dicyanoperylene-3,4:9,10-bis(dicarboximide) (PDIR-CN2) layers, in the third chapter bulk systems consist of 4,4',4"-tris[(3-methylphenyl)phenylamino] triphenylamine (m-MTDATA), 4,7-diphenyl-1,10-phenanthroline (BPhen) and tris-(2,4,6-trimethyl-3-(pyridin-3-yl)phenyl)borane (3TPYMB). These were investigated by aggregate-based calculations. Careful selection of methods and incorporation of geometrical relaxation and environmental effects allows for a precise energetical assignment of excitations. The biggest issue was a proper description of charge-transfer excitations, which was resolved by the application of ionization potential tuning on aggregates. Subsequent characterization of excitations and their interplay condenses the picture. Therefore, we could assign important features of the experimental spectroscopic data and explain differences between systems. The last chapter in this work covers the analysis of single molecule spectroscopy on methylbismut. This poses different challenges for computations, such as multi-reference character of low-lying excitations and an intrinsic need for a relativistic description. We resolved this by combining complete active space self-consistent field based methods with scalarrelativistic density-functional theory. Thus we were able to confidently assign the spectroscopic features and explain underlying processes.},
  subject      = {Theoretische Chemie},
  language  = {en}
}
@phdthesis{Erdmann2004,
  author    = {Erdmann, Marco},
  title     = {Coupled electron and nuclear dynamics in model systems},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-9968},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2004},
  abstract  = {Subject of this work was to investigate the influence of nonadiabatic coupling on the dynamical changes of electron and nuclear density. The properties of electron density have neither been discussed in the stationary case, nor for excited electronic states or for a coupled electronic and nuclear motion. In order to remove these restrictions one must describe the quantum mechanical motion of all particles in a system at the same level. This is only possible for very small systems. A model system developed by Shin and Metiu [1, 2] contains all necessary physical ingredients to describe a combined electronic and nuclear motion. It consists of a single nuclear and electronic degree of freedom and the particle interaction is parameterized in such a way as to allow for a facile switching between and adiabatic (Born-Oppenheimer type) and a strongly coupled dynamics. The first part of the work determined the "static" properties of the model system: The calculation of electronic eigenfunctions, adiabatic potential curves, kinetic coupling elements and transition dipole moments allowed for a prediction of the coupled dynamics. The potentials obtained from different parameterization showed two distinct cases: In the first case the ground and first excited state are separated by a large energy gap which is the typical Born-Oppenheimer case; the second one exhibits an avoided crossing which results in a breakdown of the adiabatic approximation. Due to the electronic properties of the system, the quantum dynamics in the two distinct situations is very different. This was illustrated by calculating nuclear and electron densities as a function of time. In the Born-Oppenheimer case, the electron density followed the vibrational motion of the nucleus. This was demonstrated in two examples. In the strongly coupled case the wave packet did not exhibit features caused by nonadiabatic coupling. However, projections of the wave function onto the electronic states revealed the usual picture obtained from solutions of the nuclear Schr{\"o}dinger equation involving coupled electronic states. In that case the nuclear motion triggered charge transfer via nonadiabatic coupling. The second part of the work demonstrated that the model system can easily be modified to yield binding situations often found in diatomic molecules. The different situations can be characterized in terms of bound and dissociative adiabatic potential curves. The investigation focussed on the case of an electronic predissociation, where the ground state is dissociative in the asymptotic limit of large internuclear distances. Within our model system we were able to demonstrate how the character of the electron density changes during the fragmentation process. In the third part we investigated the influence of external fields on the correlated dynamics of electron and nucleus. Employing adiabatic potential curves, the structure of absorption spectra can be understood within the weak-field limit. In the above described Born-Oppenheimer case the adiabatically calculated spectrum was in very good agreement with the exact one, whereas in the strongly coupled case the obtained spectrum was not able to resemble the exact one. Regarding the dynamics during a laser excitation process the time-dependent electron and nuclear densities nicely illustrated the famous Franck-Condon principle. The interaction with strong laser pulses lead to an excitation of many bound electronic and vibrational states. The electron density reflected the classical-like quiver motion of the electron induced by the fast variations of the electric field. The nucleus did not follow these fast oscillations because of its much larger mass. The last part of the work extended the original model system by including an additional electron. As a consequence of the Pauli principle, the spatial electronic wave function has to be either symmetric or anti-symmetric with respect to exchange of the two electrons. This corresponds to anti-parallel or parallel electron spins, respectively. The extended model already contains the physical properties of a many-electron system. Solving the time-dependent Schr{\"o}dinger equation for a typical vibrational wave packet motion clearly indicated that the electron density is no longer suited to "localize" single electrons. We extended the definition of the electron localization function (ELF) to an exact, time-dependent wave function and demonstrated, how the ELF can be used to further characterize a coupled electron and nuclear motion. Finally, we gave an outlook of how to define electron localization in the case of anti-parallel electron spins. We derived a quantity similar to the ELF denoted "anti-parallel spin electron localization function" (ALF) and demonstrated that the ALF allows to follow time-dependent changes of the electron localization in a numerical example. [1] S. Shin, H. Metiu, J. Chem. Phys. 1995, 102, 9285. [2] S. Shin, H. Metiu, J. Phys. Chem. 1996, 100, 7867.},
  subject      = {Nichtadiabatischer Prozess},
  language  = {en}
}
@article{ReuschHolzmeierGerlachetal.2019,
  author    = {Reusch, Engelbert and Holzmeier, Fabian and Gerlach, Marius and Fischer, Ingo and Hemberger, Patrick},
  title     = {Decomposition of Picolyl Radicals at High Temperature: A Mass Selective Threshold Photoelectron Spectroscopy Study},
  series = {Chemistry - A European Journal},
  volume    = {25},
  journal   = {Chemistry - A European Journal},
  number    = {72},
  doi       = {10.1002/chem.201903937},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-208132},
  pages     = {16652-16659},
  year      = {2019},
  abstract  = {The reaction products of the picolyl radicals at high temperature were characterized by mass-selective threshold photoelectron spectroscopy in the gas phase. Aminomethylpyridines were pyrolyzed to initially produce picolyl radicals (m /z =92). At higher temperatures further thermal reaction products are generated in the pyrolysis reactor. All compounds were identified by mass-selected threshold photoelectron spectroscopy and several hitherto unexplored reactive molecules were characterized. The mechanism for several dissociation pathways was outlined in computations. The spectrum of m /z =91, resulting from hydrogen loss of picolyl, shows four isomers, two ethynyl pyrroles with adiabatic ionization energies (IE\(_{ad}\)) of 7.99 eV (2-ethynyl-1H -pyrrole) and 8.12 eV (3-ethynyl-1H -pyrrole), and two cyclopentadiene carbonitriles with IE′s of 9.14 eV (cyclopenta-1,3-diene-1-carbonitrile) and 9.25 eV (cyclopenta-1,4-diene-1-carbonitrile). A second consecutive hydrogen loss forms the cyanocyclopentadienyl radical with IE′s of 9.07 eV (T\(_0\)) and 9.21 eV (S\(_1\)). This compound dissociates further to acetylene and the cyanopropynyl radical (IE=9.35 eV). Furthermore, the cyclopentadienyl radical, penta-1,3-diyne, cyclopentadiene and propargyl were identified in the spectra. Computations indicate that dissociation of picolyl proceeds initially via a resonance-stabilized seven-membered ring.},
  language  = {en}
}
@phdthesis{Dem2003,
  author    = {Dem, Claudiu Dorin},
  title     = {Design and construction of a device for light scattering studies on airborne particles},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-9605},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2003},
  abstract  = {This thesis is concerned with the development of an on-line in-situ device for a chemical characterisation of flowing aerosols. The thesis describes the principles and most important features of such a system, allowing also on-line measurements using Raman spectroscopy as a diagnostic technique An analysis of the effect of forced oscillations on the motion of the particle dispersed in a gas flow is given in Chapter 2. Also the most important particle parameters are introduced. A review of the particle/fluid interaction in laminar air flows and the response of the particle is presented. In Chapter 3 the behaviour of the particle under different external conditions (ion bombardment and electric fields) is extended. A brief review of the most important particle charging theories (diffusion, field, and alternating potential charging) shows, that the effect of the electrical properties (represented by the dielectric constant) of the particles affects the charging process. A non-contact method for particle charge measurement was also presented. In the second part of the chapter, the interaction between the electric field and the charged particle for the purpose of particle trapping is illustrated. The most common systems like the two or four ring electrodynamic balance and the quadrupole trap are pointed out. In Chapter 4 a short review of the possibility of using scattered light to study aerosol particles is presented. First, the conditions and the facilities of using the Mie theory for particle size and refractive index determination are mentioned, then some features concerning the classical treatment of the Raman effect are presented Supported by the theoretical considerations exposed in Chapter 2, 3, and 4 the construction and the tests of different devices are presented in Chapter 5. Following the goal of the thesis, first an overview of the used materials and methods for particle generation is presented. Then, the constructed charging devices are described (from the mechanical and electrical point of view) and compared by measuring the acquired charge on the particle. Charged particles can be trapped in different containers. Two types of axially symmetric electrodynamic balances (two ring or an extended four ring configuration) were presented. For a deeper understanding these systems were studied using analytic and numerical methods. Considering the presented purpose of the work another type of trapping system has been developed, namely the quadrupole trap. A similar theoretical characterisation (in term's of Mathieu equation) as for the electrodynamic balance was presented pointing out some specific features of this system. The incoming particle stream will be focused to the centre of the system simultaneously also the applied DC and AC potential onto the tube electrodes, yields a stable trapping of one or more particles. Chapter 6 consists of two parts: the system for single particle and for many particles investigation. The individual devices presented in Chapter 5 are now put together. The first part presents the method and the experimental realisation of a set-up for solid particle injection. In order to suppress the phase injection disadvantage found for the electrodynamic balance a developed program processes the information obtained from a particle cloud through an adequate electronic detection system, and reduces the number of particles until just one single particle is trapped. The method for one particle investigation can be extended for many particles. Using the presented set-up the particles are moved from one quadrupole to another and transformed from a particle cloud to a particle stream. A linearity between an external vertical mounted detector and the formed image of the particle stream on the CCD camera has been observed and used for simultaneous detection of many particles by Raman spectroscopy. For both methods Raman results are presented. One limitation of Raman Spectroscopy is the relatively long integration time needed for adequate signal-to-noise ratio. There are two factors which influence the integration time: first the incident radiation and the detector sensitivity, and second the intensity of the Raman bands. Using a CCD detector, the desired detector sensitivity should be achieved. So, the improvement of the signal-to-noise ratio should be the next goal in the system development. In order to reduce the integration time an optical system including optic fibres and the integration of an FT-Raman module operating in the visible region is planed. The goal of this work was to develop and construct an instrument for on-line in-situ single particle investigation by Raman spectroscopy. With the presented experimental set-up and the developed program the purpose of the work, the on-line in-situ near atmospheric pressure aerosol investigation was achieved. The Raman spectroscopy has been used successfully for a chemical characterisation of the aerosol particles.},
  subject      = {Aerosol},
  language  = {en}
}
@phdthesis{Becker2015,
  author    = {Becker, Johannes},
  title     = {Development and implementation of new simulation possibilities in the CAST program package},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-132032},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2015},
  abstract  = {The aim of the present work is the development and implementation of new simulation possibilities for the CAST program package. Development included, among other things, the partial parallelization of the already existing force fields, extension of the treatment of electrostatic interactions and implementation of molecular dynamics and free energy algorithms. The most time consuming part of force field calculations is the evaluation of the nonbonded interactions. The calculation of these interactions has been parallelized and it could be shown to yield a significant speed up for multi-core calculations compared to the serial execution on only one CPU. For both, simple energy/gradient as well as molecular dynamics simulations the computational time could be significantly reduced. To further increase the performance of calculations employing a cutoff radius, a linkedcell algorithm was implemented which is able to build up the non-bonded interaction list up to 7 times faster than the original algorithm. To provide access to dynamic properties based on the natural time evolution of a system, a molecular dynamics code has been implemented. The MD implementation features two integration schemes for the equations of motion which are able to generate stable trajectories. The basic MD algorithm as described in Section 1.2 leads to the sampling in the microcanonical (NVE) ensemble. The practical use of NVE simulations is limited though because it does not correspond to any experimentally realistic situation. More realistic simulation conditions are found in the isothermal (NVT) and isothermalisobaric (NPT) ensembles. To generate those ensembles, temperature and pressure control has been implemented. The temperature can be controlled in two ways: by direct velocity scaling and by a Nose-Hoover thermostat which produces a real canonical ensemble. The pressure coupling is realized by implementation of a Berendsen barostat. The pressure coupling can be used for isotropic or anisotropic box dimensions with the restriction that the angles of the box need to be 90� . A crucial simulation parameter in MD simulations is the length of the timestep. The timestep is usually in the rang of 1fs. Increasing the timestep beyond 1fs can lead to unstable trajectories since the fastest motion in the system, usually the H-X stretch vibration can not be sampled anymore. A way to allow for bigger timesteps is the use of a constraint algorithm which constrains the H-X bonds to the equilibrium distance. For this the RATTLE algorithm has been implemented in the CAST program. The velocity Verlet algorithm in combination with the RATTLE algorithm has been shown to yield stable trajectories for an arbitrary length of simulation time. In a first application the MD implementation is used in conjunction with the MOPAC interface for the investigation of PBI sidechains and their rigidity. The theoretical investigations show a nice agreement with experimentally obtained results. Based on the MD techniques two algorithms for the determination of free energy differences have been implemented. The umbrella sampling algorithm can be used to determine the free energy change along a reaction coordinate based on distances or dihedral angles. The implementation was tested on the stretching of a deca-L-alanine and the rotation barrier of butane in vacuum. The results are in nearly perfect agreement with literature values. For the FEP implementation calculations were performed for a zero-sum transformation of ethane in explicit solvent, the charging of a sodium ion in explicit solvent and the transformations of a tripeptide in explicit solvent. All results are in agreement with benchmark calculations of the NAMD program as well as literature values. The FEP formalism was then applied to determine the relative binding free energies between two inhibitors in an inhibitor-protein complex. Next to force fields, ab-initio methods can be used for simulations and global optimizations. Since the performance of such methods is usually significantly poorer than force field applications, the use for global optimizations is limited. Nevertheless significant progress has been made by porting these codes to GPUs. In order to make use of these developments a MPI interface has been implemented into CAST for communication with the DFT code TeraChem. The CAST/TeraChem combination has been tested on the \$H_2 O_{10}\$ cluster as well as the polypeptide met-Enkephalin. The pure ab-initio calculations showed a superior behavior compared to the standard procedure where the force field results are usually refined using quantum chemical methods.},
  subject      = {Molekulardynamik},
  language  = {en}
}
@phdthesis{Flachenecker2002,
  author    = {Flachenecker, G{\"u}nter},
  title     = {Die Dissoziations- und Rekombinations-Reaktion von Jodmolek{\"u}len in mikropor{\"o}sen Porosil-Kristalliten auf der Femtosekunden-Zeitskala},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-4472},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2002},
  abstract  = {In dieser Arbeit wurde die unimolekulare Dissoziations- und Rekombinations-Reaktion von Jodmolek{\"u}len untersucht, die in mikropor{\"o}sen Porosil-Kristalliten eingelagert waren. Hierf{\"u}r wurden sowohl experimentelle Pump-Probe-Experimente als auch theoretische Untersuchungen auf der Femtosekunden-Zeitskala durchgef{\"u}hrt. Die Idee, die diesen Experimenten zugrunde lag, bestand darin, zu erfahren, in welcher Weise und in welchem Maße die Struktur der Umgebung einen Einfluss auf die elementaren dynamischen Prozesse der Reaktion aus{\"u}bt. Die hier untersuchten Systeme I\$_2\$ in DDR-, TON-, FER- und MFI-Porosilen sind Modellsysteme f{\"u}r komplexere Molek{\"u}le, eingelagert in einer mikropor{\"o}sen kristallinen Umgebung.},
  subject      = {Tectosilicate},
  language  = {de}
}
@article{SchuergerEngel2023,
  author    = {Sch{\"u}rger, Peter and Engel, Volker},
  title     = {Differential Shannon entropies characterizing electron-nuclear dynamics and correlation: momentum-space versus coordinate-space wave packet motion},
  series = {Entropy},
  volume    = {25},
  journal   = {Entropy},
  number    = {7},
  issn      = {1099-4300},
  doi       = {10.3390/e25070970},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-362670},
  year      = {2023},
  abstract  = {We calculate differential Shannon entropies derived from time-dependent coordinate-space and momentum-space probability densities. This is performed for a prototype system of a coupled electron-nuclear motion. Two situations are considered, where one is a Born-Oppenheimer adiabatic dynamics, and the other is a diabatic motion involving strong non-adiabatic transitions. The information about coordinate- and momentum-space dynamics derived from the total and single-particle entropies is discussed and interpreted with the help of analytical models. From the entropies, we derive mutual information, which is a measure for the electron-nuclear correlation. In the adiabatic case, it is found that such correlations are manifested differently in coordinate- and momentum space. For the diabatic dynamics, we show that it is possible to decompose the entropies into state-specific contributions.},
  language  = {en}
}
@article{DostalFennelKochetal.2018,
  author    = {Dost{\´a}l, Jakub and Fennel, Franziska and Koch, Federico and Herbst, Stefanie and W{\"u}rthner, Frank and Brixner, Tobias},
  title     = {Direct observation of exciton-exciton interactions},
  series = {Nature Communications},
  volume    = {9},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-018-04884-4},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226271},
  year      = {2018},
  abstract  = {Natural light harvesting as well as optoelectronic and photovoltaic devices depend on efficient transport of energy following photoexcitation. Using common spectroscopic methods, however, it is challenging to discriminate one-exciton dynamics from multi-exciton interactions that arise when more than one excitation is present in the system. Here we introduce a coherent two-dimensional spectroscopic method that provides a signal only in case that the presence of one exciton influences the behavior of another one. Exemplarily, we monitor exciton diffusion by annihilation in a perylene bisimide-based J-aggregate. We determine quantitatively the exciton diffusion constant from exciton-exciton-interaction 2D spectra and reconstruct the annihilation-free dynamics for large pump powers. The latter enables for ultrafast spectroscopy at much higher intensities than conventionally possible and thus improves signal-to-noise ratios for multichromophore systems; the former recovers spatio-temporal dynamics for a broad range of phenomena in which exciton interactions are present.},
  language  = {en}
}
@phdthesis{Kroeker2012,
  author    = {Kr{\"o}ker, Kristin},
  title     = {DNA-Kohlenstoffnanorohr-Konjugate - Biokompatibilit{\"a}t, ex vivo-Verhalten, Funktionalisierung},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-74552},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2012},
  abstract  = {Einzelstrang-DNA-dispergierte und individualisierte (6,5)-chirale Kohlenstoffnanor{\"o}hren bilden als Konjugatsystem den Ausgangspunkt dieser Dissertation. Im Vordergrund stehen dabei Untersuchungen zur Biokompatibilit{\"a}t dieser ssDNA-SWNT-Konjugate sowie deren Verhalten nach Zellpenetration und eine Funktionalisierbarkeit zum Wirkstofftransportsystem. Das erste Projekt widmet sich in Kapitel 4 dem Studium der Konjugatstabilit{\"a}t unter physiologischen Bedingungen und einer Vertr{\"a}glichkeit gegen{\"u}ber zellul{\"a}ren Systemen. Experimente zur Biokompatibilit{\"a}t werden erstmals an Nanorohrkonjugaten durchgef{\"u}hrt, welche nach Ultrazentrifugation im Dichtegradienten sorgf{\"a}ltig individualisiert vorliegen. Die umgebungssensitiven photophysikalischen Charakteristika vereinzelter (6,5)-SWNTs k{\"o}nnen zu einer Beurteilung der Konjugatintegrit{\"a}t in physiologischem Milieu genutzt werden. Die Stabilit{\"a}t von ssDNA-SWNT-Strukturen wird in Anwesenheit des Restriktionsenzyms DNase I und dem in Zelln{\"a}hrmedien enthaltenen protein- und nukleasereichem Serum FBS auf die Probe gestellt. In beiden F{\"a}llen kann eine ausreichende ssDNA-SWNT-Integrit{\"a}t attestiert werden, die eine Verwendung unter Zellkultivierungsbedingungen erlaubt. Unter Ber{\"u}cksichtigung verschiedener in Zellen vorliegender pH-Umgebungen werden die Konjugate ebenfalls dieser Variation ausgesetzt. Bei Vorliegen stark saurer und basischer pH-Werte kann die Integrit{\"a}t von ssDNA-SWNT-Konjugaten nicht gew{\"a}hrleistet werden, was sich durch Aggregation bemerkbar macht. Innerhalb des breiten pH-Bereichs zwischen den Werten 3 und 11 hingegen kann eine gute Stabilit{\"a}t best{\"a}tigt werden. F{\"u}r zellul{\"a}re Anwendungen bedeutet dieser Befund keine Einschr{\"a}nkung, da in Kulturen lediglich neutrale bis schwach saure pH-Werte oberhalb von 4.5 zu finden sind. Nachdem die Biostabilit{\"a}t der ssDNA-SWNT-Konjugate gew{\"a}hrleistet ist, kann in Zytotoxizit{\"a}tsstudien eine ex vivo-Vertr{\"a}glichkeit des Nanomaterials getestet werden. Erste Untersuchungen mit der Mausmakrophagenlinie J774.1 weisen wie auch ausf{\"u}hrliche Studien gegen{\"u}ber menschlichen Epithelzellen HeLa auf eine uneingeschr{\"a}nkte Kompatibilit{\"a}t in den eingesetzten Konzentrationen hin. HeLa-Zellen, die mit DGU-gereinigten Nanorohrproben behandelt werden, zeigen eine geringf{\"u}gig h{\"o}here Vitalit{\"a}t als nach Inkubation mit einer Rohdispersion undefinierter SWNT-B{\"u}ndel. Im Gesamtbild ergibt sich somit eine zufriedenstellende Biokompatibilit{\"a}t individualisierter ssDNA-SWNT-Konjugate, womit das in dieser Arbeit zentrale Kohlenstoffnanorohrsystem den Anforderungen f{\"u}r dessen biomedizinische Verwendbarkeit gerecht wird. Der Schwerpunkt weiterer Untersuchungen liegt im zweiten Projekt aus Kapitel 5 auf dem Verhalten von ssDNA-SWNT-Konjugaten nach deren Aufnahme in HeLa-Zellen. Auch hier kann die starke Sensitivit{\"a}t der optischen Eigenschaften individualisierter (6,5)-Kohlenstoffnanor{\"o}hren gegen{\"u}ber Umgebungseinfl{\"u}ssen genutzt werden, um Ver{\"a}nderungen im Emissionsverhalten von SWNTs nach deren zellul{\"a}rer Aufnahme gegen{\"u}ber dem Ausgangszustand zu beobachten. Nach ausf{\"u}hrlicher Weißlicht-, Fluoreszenz- und SWNT-Photolumineszenzmikroskopie, aus deren Resultaten eine erfolgreiche Internalisierung von ssDNA-SWNTs in HeLa-Zellen eindeutig hervorgeht, stehen PL-spektroskopische Untersuchungen der Kohlenstoffnanor{\"o}hren im Vordergrund. Durch einen Vergleich des Emissionsverhaltens der ssDNA-SWNT-Konjugate in und außerhalb von Zellen k{\"o}nnen spektrale Verschiebungen, Linienverbreiterungen und verk{\"u}rzte Fluoreszenzlebensdauern nach zellul{\"a}rer Aufnahme festgestellt werden. Sowohl eine Aggregation von SWNTs als auch eine Beeinflussung durch die pH-Umgebung reichen nicht f{\"u}r eine vollst{\"a}ndige Erkl{\"a}rung des Befunds aus. Vielmehr kann die in endosomalen Kompartimenten durch das Gr{\"o}ßenverh{\"a}ltnis von Endosomen zu SWNTs entstehende r{\"a}umliche N{\"a}he einer großen Nanorohrmenge untereinander als Ursache f{\"u}r eine Ver{\"a}nderung der dielektrischen Umgebung und folglich des Emissionsverhaltens betrachtet werden. Durch Verwendung der Kohlenstoffnanor{\"o}hren als Marker und Sensor k{\"o}nnen ssDNA-SWNT-Konjugate in Zellen somit nicht nur lokalisiert, sondern dar{\"u}ber hinaus hinsichtlich einer m{\"o}glichen Aggregation untersucht werden. Aus den in dieser Arbeit vorgestellten Daten kann zwar eine vollst{\"a}ndige Aggregation der SWNTs durch deren Aufnahme in Zellen ausgeschlossen werden, sie muss jedoch in geringf{\"u}gigem Ausmaß neben einer Beeinflussung durch die pH-Umgebung und die große r{\"a}umliche N{\"a}he durchaus in Betracht gezogen werden. Individualisierte ssDNA-SWNT-Konjugate k{\"o}nnen damit erstmals zeitaufgel{\"o}st PL-mikrospektroskopisch in HeLa-Zellen charakterisiert werden. F{\"u}r das letzte Projekt werden in Kapitel 6 neuartige Funktionalisierungsm{\"o}glichkeiten von ssDNA-SWNT-Konjugaten zu zellul{\"a}ren Transportsystemen unter Erhalt der photophysikalischen Eigenschaften erforscht. Dazu soll das Dispergiermittel DNA als Kupplungsstelle f{\"u}r eine kovalente Anbindung eines Agenz genutzt werden. Anstelle eines Wirkstoffes werden die Untersuchungen mit einem Fluorophor als Modellverbindung durchgef{\"u}hrt, welcher den Vorteil einer einfachen Detektierbarkeit liefert. Prinzipiell besteht die M{\"o}glichkeit, das Oligomer mit dem Fluorophor vorzufunktionalisieren und anschließend auf die Oberfl{\"a}che der SWNTs zu bringen. Als effektiver erweist sich die Methode der direkten Kupplung des Farbstoffs an bereits DNA-dispergierte SWNTs. Der Erfolg in der Pr{\"a}paration von FluorophorssDNA- SWNT-Konjugaten wird {\"u}ber die Emission des Fluorophors mit entsprechenden Referenzexperimenten gemessen. Der Versuch einer Quantifizierung liefert jedoch sehr hohe Werte, die lediglich als eine obere Grenze f{\"u}r die gefundene Anzahl gebundener Fluorophore pro Nanor{\"o}hre angesehen werden k{\"o}nnen. Im Verlauf des Projekts kann eine Funktionalisierbarkeit der Nanor{\"o}hren {\"u}ber das Dispergieradditiv DNA als neue Strategie aufgezeigt werden. Im Gegensatz zu bekannten Wirkstofftransportsystemen bietet dieser Funktionalisierungsansatz den Vorteil, dass die optischen Eigenschaften der individualisierten ssDNA-SWNT-Konjugate erhalten bleiben, welche wieder um einen gleichzeitigen Einsatz der Nanor{\"o}hren als Transporter und Marker bzw. Sensor erlauben. Die vorliegende Dissertation liefert neben dieser bisher unbekannten Funktionalisierungsstrategie neue Erkenntnisse {\"u}ber die Biokompatibilit{\"a}t speziell von individualisierten ssDNA-SWNT-Konjugaten und deren Verhalten in HeLa-Zellen. Mit diesem Wissen kann der gezielte Wirkstofftransport durch Kohlenstoffnanor{\"o}hren als biokompatibles und zellg{\"a}ngiges Tr{\"a}gersystem anvisiert werden.},
  subject      = {Biokompatibilit{\"a}t},
  language  = {de}
}
@article{HirschPachnerFischeretal.2020,
  author    = {Hirsch, Florian and Pachner, Kai and Fischer, Ingo and Issler, Kevin and Petersen, Jens and Mitric, Roland and Bakels, Sjors and Rijs, Anouk M.},
  title     = {Do Xylylenes Isomerize in Pyrolysis?},
  series = {ChemPhysChem},
  volume    = {21},
  journal   = {ChemPhysChem},
  number    = {14},
  doi       = {10.1002/cphc.202000317},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-218316},
  pages     = {1515 -- 1518},
  year      = {2020},
  abstract  = {We report infrared spectra of xylylene isomers in the gas phase, using free electron laser (FEL) radiation. All xylylenes were generated by flash pyrolysis. The IR spectra were obtained by monitoring the ion dip signal, using a IR/UV double resonance scheme. A gas phase IR spectrum of para-xylylene  was recorded, whereas ortho- and meta-xylylene were found to partially rearrange to benzocyclobutene and styrene. Computations of the UV oscillator strength  for all molecules were carried out and provde an explanation for the observation of the isomerization products.},
  language  = {en}
}