Inorganic UV-filters in use today often occur as nanoparticles and have a photocatalytic effect, which can be a problem since they can cause negative health effects. This is why Upsalite®, a mesoporous magnesium carbonate recently has been investigated as a UV-filter. Upsalite® itself is however not suitable as a UV-filter since it mainly protects in the UVC range and hence it needs to be complemented by other substances. The substance studied to functionalize Upsalite® in this thesis is titanium dioxide which is an inorganic UV-filter commonly used in sunscreens. In this work two different sol-gel synthesis routes of titanium dioxide have been investigated as well as a co-synthesis of Upsalite® and titanium dioxide. In the first synthesis route already synthesized Upsalite® was mixed with titanium tetra-isopropoxide and 1-propanol. The second synthesis route was a modified version of synthesis routes described in literature where methanol solvent was used and the pressure was altered by CO2. This route was explored due to its resemblance with the Upsalite® synthesis. Pressure, temperature and amount of water were varied to optimize incorporation of Upsalite® and investigate possibilities for a co-synthesis. Subsequently a co-synthesis of Upsalite® and titanium dioxide was performed that resulted in two amorphous composite materials depending on if water was added in the drying procedure or not. When mixing Upsalite® in the synthesis liquid of titanium dioxide, titanium dioxide seems to be deposited on Upsalite®. It is however difficult to determine whether the pores of Upsalite® have been completely filled or if they have collapsed. The acid catalyst HCl promotes formation to crystalline titanium dioxide but Upsalite® instead prevents it. The limited crystallization of titanium dioxide when synthesized with Upsalite® may be due to confinement in the Upsalite® pores. The UV-blocking properties of the TiO2-Upsalite® without HCl are good with an sun protection factor (SPF) of 27 for a 10 wt% blend in a lotion and an SPF of 7 for the sample with HCl. The modified synthesis route of TiO2 showed that it is possible to perform a sol-gel synthesis with a considerably lower amount of water than found in literature and that alteration of temperature and pressure during the synthesis does not affect the crystallization temperature noteworthy. The materials obtained from the co-synthesis are slightly porous, probably consisting of one or several magnesium titanium oxides and a carbonate phase and showed a transmission cutoff in between Upsalite® and titanium dioxide corresponding to an SPF of 5.

Gold Nanoclusters are of particular interest due to their many possible applications across a wide range of scientific fields. More specifically, nano-sized gold particles have potential to be used in drug delivery systems, cancer therapy and catalysis. This dissertation focuses on improving our understanding of ligated gold nanoclusters by examining the role of a variety of phosphine based ligands, novel methods to produce monodisperse solutions, and investigating the kinetics of water soluble ligated gold nanoclusters. The addition of ligands to solutions of Au have shown to produce small (< 20 Au atoms) clusters. All nanocluster solutions were prepared in a similar manner. Typically, a gold salt, either Chloro(triphenylphosphine) gold(I) (Au(PPh3)Cl), or Potassium gold (III) chloride (KAuCl4), were dissolved in various solvents. Next, an equal concentration of ligand was added to the solution and stirred until completely dissolved. Finally, all were reduced with 5X the concentration of borane-tert-butylamine (BTBC) after which were sonicated for ~20 minutes. The timing and method of adding the ligands and reducing agent varied depending on the solution and solubility of the ligands. Primarily we used Electrospray Ionization Mass Spectrometry (ESI-MS) and Ultraviolet – Visible Spectroscopy (UV-VIS) for the characterization of samples, however, occasionally Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD) and X-Ray Photoemission Spectroscopy (XPS) were used. The most recent research took advantage of the size selective nature of an alpha hemolysin (a-HL) nanopore to investigate the kinetics of thiol-ligated Au clusters ~2 nm in size. The relationship between ligand rigidity and solvent polarity and the size and dispersity of Au cluster suspensions was investigated. We observed the formation of stable monodisperse clusters with the shortest ligand, (L3), independent of solvent. With a longer flexible ligand, (L6), we observed primarily Au8-10 cores depending on the ratio of L6/PPh3. All other ligands yielded polydisperse distributions. These dispersions contained clusters with a nuclearity between 8 and 11, for example [Au10(PPh3)9]3+ in LBn and [Au8(PPh3)7]2+ in LBp, were observed in the initial stages, but they were not stable and precipitated out or plated the glass vial. We also observed that the polarity of the solvent did not play a significant role in the formation of MPC’s, however a correlation between the size of the solvent and MPC formation was observed. The growth and evolution of two unique gold structures was also observed via UV-Vis and ESI-MS. Solutions were prepared which contained Potassium gold (III) chloride and PPh2(CH2)3PPh2, i.e., 1,3-bis(diphenylphosphino)propane, denoted by L3, reduced with Borane tert-butylamine complex (BTBC) in a 1:1 diethyl ether:methanol mix, which yielded a stable [Au11(L3)5]+3. Starting with this known Au11 solution, the addition of Mn2+ has shown to lead to the formation of a stable diphosphine ligated Au8 and a new Au14 species. Additionally, we show that the co-reduction of NiCl2 and Au in the absence of the ligand (L3) does give us a simple method for the production of a monodisperse [Au9(PPh3)8]2+ cluster solution and via electroless deposition does give us a potential low temperature pathway to the formation of a AuNi nanoalloy particle.

Time-resolved spectroscopic studies of energy transfer between molecules in solution form a basis for both, our understanding of fundamental natural processes like photosynthesis as well as directed synthetic approaches to optimize organic opto-electronic devices. Here, coherent two-dimensional (2D) spectroscopy opens up new possibilities, as it reveals the correlation between absorption and emission frequency and hence the full cause-and-effect chain. In this thesis two optical setups were developed and implemented, permitting the recording of electronic 2D spectra in the visible and in the hitherto unexplored ultraviolet spectral range. Both designs rely on the exclusive manipulation of beam pairs, which reduces the signal modulation to the difference between the transition frequency of the system and the laser frequency. Thus - as has been shown experimentally and theoretically - the timing precision as well as mechanical stability requirements are greatly reduced, from fractions of the oscillation period of the exciting light wave to fractions of the pulse duration. Two-dimensional spectroscopy and femtosecond transient absorption (TA) as well as different theoretical approaches and simulation models were then applied to coupled multichromophore systems of increasing complexity. Perylene bisimide-perylene monoimide dyads were investigated in cooperation with Prof. Dr. Frank Würthner and Prof. Dr. Bernd Engels at the University of Würzburg. In these simplest systems studied, global analysis of six different TA experiments unequivocally revealed an ultrafast interchromophoric energy transfer in the 100 fs range. Comparison between the obtained transfer rates and the predictions of Förster theory suggest a breakdown of this point-transition-dipole-based picture at the donor-acceptor distances realized in our compounds. Furthermore, a model including conformational changes and an interchromophoric charge transfer has been derived to consistently describe the observed pico- to nanosecond dynamics and fluorescence quantum yields. A second collaboration with Prof. Dr. Gregory Scholes (University of Toronto, Canada) and Prof. Dr. Paul Burn (University of Queensland, Australia) addressed the photophysics of a series of uorene-carbazole dendrimers. Here, a combination of 2D-UV spectroscopy and femtosecond ansiotropy decay experiments revealed the initial delocalization of the excited state wave function that saturates with the second generation. In room temperature solution, disorder-induced localization takes place on the time scales comparable to our instrument response, i.e. 100 fs, followed by energy transfer via incoherent hopping processes. Lastly, in tubular zinc chlorin aggregates, semi-synthetic analogues of natural lightharvesting antennae that had again been synthesized in the group of Prof. Dr. Frank Würthner, the interchromophoric coupling is so strong that coherently coupled domains prevail even at room temperature. From an analysis of intensity-dependent TA measurements the dimensions of these domains, the exciton delocalization length, could be determined to span 5-20 monomers. In addition, 2D spectra uncovered efficient energy transfer between neighboring domains, i.e. ultrafast exciton diffusion. / Zeitaufgelöste spektroskopische Untersuchungen zu Energietransferprozessen zwischen Molekülen in Lösung bilden die Grundlage nicht nur für unser Verständnis elementarer natürlicher Vorgänge wie der Photosynthese, sondern auch für gerichtete Synthesen zur Optimierung organischer opto-elektronischer Bauteile. Die kohärente zweidimensionale (2D) Spektroskopie eröffnet hier neue Möglichkeiten, da sie - durch Aufdeckung der Korrelation zwischen Absorptions- und Emissionsfrequenz - die konventionelle transiente Absorption (TA) um die Offenbarung der Ursache erweitert. Im Rahmen dieser Arbeit wurden zwei optische Aufbauten entworfen und umgesetzt, die die Aufnahme von elektronischen 2D Spektren im sichtbaren und im bis dahin unerschlossenen ultravioletten Spektralbereich ermöglichen. Beide Designs beruhen auf dem Prinzip der ausschließlich paarweisen Strahlführung, wodurch die Modulation des Signals auf die Differenz zwischen Übergangsfrequenz des Systems und Laserfrequenz reduziert wird. Damit verringern sich - wie theoretisch und experimentell gezeigt - die Anforderungen sowohl an die mechanische Stabilität der Laborumgebung als auch an die Genauigkeit der verwendeten Verzögerungsbühnen erheblich, von Bruchteilen der Oszillationsperiode des anregenden Lichts auf Bruchteile der Laserpulsdauer. Sowohl die 2D Spektroskopie als auch die transiente Absorption sowie unterschiedliche theoretische Ansätze und Simulationsmodelle wurden in den weiteren Teilen dieser Arbeit auf gekoppelte Multichromophor-Systeme unterschiedlicher Komplexität angewandt. Im einfachsten dieser Systeme, einem Perylen-basierten Heterodimer, einer Kooperation mit Prof. Dr. Frank Würthner und Prof. Dr. Bernd Engels an der Universität Würzburg, konnte durch globale Analyse von sechs verschiedenen TA-Messungen ein ultraschneller Energietransfer im 100 fs Bereich zweifelsfrei identifiziert werden. Ein Vergleich mit Vorhersagen aus der Förster-Theorie legt einen Zusammenbruch dieser auf punktförmigen Übergangsdipolen beruhenden Theorie bei den vorliegenden Interchromophor- Abständen nahe. Darüber hinaus wurde für die Piko- bis Nanosekunden-Zeitskalen ein Schema vorgestellt, das Konformationsänderungen sowie einen Ladungstransfer beinhaltet und das die beobachtete Dynamik wie auch die gemessenen Fluoreszenz-Quantenausbeuten konsistent beschreibt. In einer weiteren Kooperation wurden in Zusammenarbeit mit der Gruppe von Prof. Dr. Gregory Scholes (University of Toronto, Kanada) Fluoren-Carbazol-Makromoleküle untersucht, die in der Gruppe von Prof. Dr. Paul Burn (University of Queensland, Australien) synthetisiert worden waren. In diesen sogenannten Dendrimeren konnte durch die Kombination von 2D Spektroskopie und Femtosekunden-Anisotropie-Zerfalls-Experimenten eine anfängliche Delokalisierung der Wellenfunktion des angeregten Zustands abgeleitet werden, die mit der zweiten Generation saturiert. Die Umgebungsunordnung in Raumtemperatur-Lösung führt hier zu einer ultraschnellen Lokalisierung innerhalb der Zeitauflösung des Experiments, gefolgt von inkohärenten Energietransfer-Prozessen. In tubularen Zink Chlorin Aggregaten schließlich, semisynthetischen Analoga zu den Lichtsammelantennen natürlicher Chlorosome, die ebenfalls von Prof. Dr. Frank Würthner's Gruppe bereitgestellt wurden, ist die Kopplung zwischen den einzelnen Molekülen so stark, dass kohärent gekoppelte Segmente selbst bei Raumtemperatur Bestand haben. Die Ausdehnung dieser kohärenten Domänen, die Exzitonen-Delokalisierungslänge, konnte aus der Intensitätsabhängigkeit des transienten Absorptionssignals auf 5-20 Monomere bestimmt werden. 2D Spektren zeigten dabei den effizienten Energietransfer zwischen benachbarten Domänen im Aggregat, also einen ultraschnellen Exzitonen-Diffusionsprozess.

Im ersten Teil dieser Arbeit wurde die erfolgreiche Synthese einer Serie von bisTriarylamin (bisTAA) Verbindungen vorgestellt. Zum einen wurde das Substitutionmuster an der Benzol Brückeneinheit in Form einer meta- bzw. para-Ständigkeit der Redoxzentren (pX bzw. mX), und zum anderen die energetische Lage der Brückeneinheit durch zwei elektronen-schiebende oder ziehende Substituenten X (mit X = OMe, Me, Cl, CN, NO2) in 2,5-Position variiert. Im Falle der meta-Serie wurden auch einige in 4,6-Position substituierte Verbinungen hergestellt (mX46). Die neutral Verbindungen wurden bezüglich ihrer elektrochemischen und photophysikalischen Eigenschaften untersucht. Durch Oxidation konnten die gemischt valenten (MV), kationischen bisTAA-Verbindungen erzeugt werden. Der thermisch induzierte Lochtransfer (HT) wurde durch temperatur-abhängige ESR-Spektroskopie untersucht. Während die HT-Rate k und HT-Barriere ΔG in mX unbeeinflusst von den Substituenten X sind, steigen gleichzeitig k und ΔG in der pX-Serie mit zunehmenden Elektonenschub von X an. Diese zunächst widersprüchliche Beobachtung konnte durch einen ansteigenden Einfluss von Lösungsmitteleffekten und dadurch resultierend, einer zusätzlichen effektiven Barriere erklärt werden. Der optisch induzierte Lochtransfer wurde mittels UV/Vis/NIR-Spektroskopie untersucht. Die pX-Serie zeigte eine Zuhname der elektronischen Kopplung V und dementsprechende eine Abnahme von ΔG, mit Anstieg des elektonenschiebenden Charakters von X. Für mX war eine spektroskopische Bestimmung dieser Parameter nicht möglich. Die mX46-Serie zeigte ein intermediäres Verhalten, wobei MV-Verbindungen mit stark elektronenschiebenden X eine ähnliche hohe Kopplungen wie pX aufwiesen, was mit Hilfe von DFT-Rechnungen bezüglich der Molekülorbitale erklärt werden konnte. Im zweiten Teil dieser Arbeit wurde die Synthese einer Serie von Verbindungen mit Triarylamin (TAA) als Donor und Naphthalindiimid (NDI) als Akzeptor vorgestellt. Auch hier wurde zum einen das Substitutionmuster an der Benzol-Brückeneinheit in Form einer meta- bzw. para-Ständigkeit der Redoxzentren (pXNDI bzw. mXNDI) variieiet und die energetische Lage der durch X (mit X = OMe, Me, Cl, CN, NO2) in 2,5-Position variiert. Außerdem wurde die in 4,6-Position substituierte Verbinungen mOMe46NDI hergestellt. Alle Verbindungen wurden bezüglich ihrer elektochemischen und photophysikalischen Eigenschaften untersucht. Die Elektronentransferprozesse der Ladungsseparierung (CS) und Ladungsrekombination (CR) dieser Verbindungen sollten mittels transienter Absorptionsspektroskopie (TA) in Toluol untersucht werden. Für die Nitroverbindungen p-/mNO2NDI war dies nicht möglich, da sich diese unter Bestrahung zersetzten. Die CR von pXNDI waren nicht im ns-Bereich detektierbar, weshalb sich auf die mXNDI-Serie (mit X = OMe–CN) konzentriert wurde. Die CS wurde mittels fs-TA untersucht. Nach optischer Anregung konnte die Bildung eines CS-Zustandes detektiert werden, dessen Bildungsgeschwindigkeit hin zu elektronen-ziehenden Substituenten X steigt. Die CR wurde mit ns-TA untersucht. Sie findet in der Marcus invertierten Region statt und zeichnet sich wird durch ein biexponentialles Abklingverhaten, was durch ein Singulet-Triplett Gleichgewicht im CS-Zustand zustande kommt, aus. Durch Anlegen eines externen Magnetfeldes ließ sich das Abklingverhalten entscheidend verändern und es konnte eine Singulett-Triplett Aufspaltung nachgewiesen werden. Dieser Befund konnte weiterhin durch Simulation der Abklingkurven bestätigt werden. In beiden Teilen dieser Arbeit konnte ein entscheidender Einfluss der Benzolbrücke auf die auftretenden Ladungstransferprozesse gezeigt werden. Für den HT in Grundzustand der MV bisTAA Verbindungen, sowie der ET im angeregten Zustand der Donor-Akzeptor-Verbindungen, wurden die höchsten ET-Raten für die para-Serien pX und pXNDI gefunden, während die meta-Serien mX und mXNDI deutlch kleine Transferraten aufwiesen. In beiden Studien zeigten die meta46-Verbindungen mX46 und mOMeNDI46 ein intermediäres Verhalten, zwischen denen der para- und meta-Verbindungen. / In the first part of this thesis, the synthesis of a series of bistriarylamine (bisTAA) compounds was presented. On the one hand, the substitution pattern of the TAA at the benzene bridging unit was varied from meta- to para-position (pX and mX), on the other hand, the energetic position of the bridging unit was tuned by use of two electron-donating or electron-accepting substituents X (with X = OMe, Me, Cl, CN, NO2) in 2,5-position. In case of the meta-series, compounds with X in 4,6-position were synthesized (mX46). The photophysical and electrochemical properties of the neutral compounds were investigated. The cationic mixed valence (MV) bisTAA compounds could be generated by oxidation. Thermally induced hole transfer (HT) in the groud state was investigated by temperature depending ESR spectroscopy. While the HT rate k and HT barrier ΔG in mX are unaffected by the substituents X, k and ΔG in the pX series increase simultaneously with increasing electron-donating strength of X. This, at first contradictory observation can be explained by an increasingly important solvent dynamic effect and an additional, effective barrier. The optically induced HT was examined by UV/Vis/NIR spectroscopy. The pX-series revealed an increase of the electronic coupling V, and correspondingly a decrease of ΔG, with an increase of the electron donating character of X. For mX, a spectroscopic determination of these parameters was not possible. mX46 showed an intermediate behavior, MV compounds with strong electron-donating X, obtained coupling of similar magnitude as pX, which could be explained by means of DFT calculations, with regard to the molecular orbitals. In the second part of this work, the synthesis of a series of dyads with triarylamine (TAA) as a donor and naphthalene diimide (NDI) as an acceptor was presented. Again, the substitution pattern of the redox centers at the benzene bridging unit was varied in the form of a meta- or para-position (pXNDI or mXNDI) and the energetic position of the bridging unit was varied by X (with X = OMe, Me, Cl, CN, NO2) attached in the 2,5-position. Additionally, compound mOMe46NDI with methoxy substitution in 4,6-position was synthesized. The photophysical and electrochemical properties of these compounds were investigated. The electron transfer (ET) processes of charge separation (CS) and charge recombination (CR) of these were investigated by means of transient absorption (TA) spectroscopy in toluene. This was not possible for the nitro-compounds p-/mNO2NDI, since they decomposed under irradiation. In addition to that, the CR of pXNDI was not detectable by ns-setup, which is why the focus was given to the mXNDI series (with X = OMe–CN).The CS was examined by fs-TA spectroscopy, where the formation of a CS state could be detected. The rise time of the CS states decreases with increasing electron-withdrawing substituents X. CR was examined with ns-TA spectroscopy and shows a biexponential decay behavior, which is caused by singlet-triplet equilibrium in the CS state. By applying an external magnetic field, the decay behavior was decisively changed and the singlet-triplet splitting could be determined. This finding could also be confirmed by simulating the decay curves. In both parts of this work, the decisive influence of the benzene bridging unit on the appearing ET processes became obvious. For the HT in the ground state of the MV compound, as well as for the ET in the exited states of the DA compounds, the highest transfer rates were found for the para-series pX and pXNDI, and much smaller rates for the meta-series mX and mXNDI. The meta46-compounds mX46 and mOMeNDI46 showed an intermediate behavior in both parts of this work.

Chemnitz, Techn. Univ., Diss., 2008.

University, Diss., 2001--Bremen.

University, Diss., 2001--Bremen.

Techn. Universiẗat, Diss., 2002--Berlin.

University, Diss., 2005--Jena.

Made available in DSpace on 2014-06-11T19:25:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2003-12-18Bitstream added on 2014-06-13T19:12:22Z : No. of bitstreams: 1 maceti_h_me_rcla.pdf: 484546 bytes, checksum: 6d093c2c96c1a1dba6ae5a651183c6b5 (MD5) / Sonogéis de sílica foram preparados a partir da sonohidrólise de tetraetilortosilicato (TEOS) e, após o envelhecimento, a fase líquida do gel foi trocada por acetona, durante a fase saturada do processo. A evolução estrutural durante a secagem do sonogel úmido com a fase líquida trocada por acetona foi estudada por espalhamento de raio-x a baixo ângulo (SAXS). A evolução estrutural do xerogel derivado do sonogel com fase líquida trocada por acetona, foi estudada em função da temperatura, por meio de espectroscopia de absorção UV-visível, medidas de densidade real e aparente, medidas de contração linear, e análises térmicas (DTA, TG e DL). Os períodos associados à evolução estrutural determinados por SAXS estão de acordo com os períodos clássicos determinados a partir das características da taxa de evaporação da fase líquida, na obtenção de xerogéis. O gel úmido pode ser descrito como formado por partículas primárias (microclusters), com densidade de cerca de 1,8 g/cm3, tamanho característico a ~ 0,67 nm e superfície fractal, que se juntam para formar uma estrutura fractal de massa, com dimensão fractal de massa D ~ 2,2 e comprimento característico ? ~ 6,7 nm. À medida que a rede colapsa durante o período de taxa de evaporação constante, no qual o gel se mantém saturado com a frente de evaporação na superfície externa do gel, a estrutura fractal de massa vai se compactando, aumentando D e diminuindo ?, com alisamento da superfície fractal dos microclusters. O xerogel obtido ao término do processo de secagem apresenta características de um sistema com poros vazios e partículas não fractais, com superfície de interface lisa e área de superfície de cerca de 385 m2/g. Os resultados das medidas de densidade aparente, de DTA e TG, mostram que os géis perdem resíduos... . / Silica sonogels were prepared from the sonohydrolysis of tetraetilortosilicate (TEOS) and the liquid phase of the gel was exchanged by acetone during the saturated stage of the process. The structural evolution of the drying of the wet exchanged sonogel was studied by small-angle x-ray scattering (SAXS). The structural evolution of the xerogel derived from the exchanged sonogel was studied as a function of the temperature by means of UV-visible absorption spectroscopy, bulk and skeletal density measurements, linear contraction measurements, and thermal analysis (DTA, TG and DL). The periods associated to the structural evolution as determined by SAXS are in agreement with those classical ones as determined from the features of the evaporation rate of the liquid phase in the obtaining of xerogels. The wet gel can be described as formed by primary particles (or microclusters) with density of about 1.8 g/cm3, characteristic length a ~ 0.76 nm e surface fractal, linking together to form mass fractal structures with mass fractal dimension D ~ 2.2 in a length scale ? ~ 6.7 nm. As the network collapses, while the liquid/vapor meniscus is kept at the external evaporation surface of the gel, the mass fractal structure becomes more compacted by increasing D and decreasing ?, with smoothing of the fractal surface of the microclusters. The xerogel obtained at the end of the drying process presents characteristics of a system with empty pores and non-fractal particles, with smooth interface surface and surface area of about 385 m2/g. The results of bulk density measurements and of DTA and TG thermal analysis show that the gels lose organic residuals and more strongly bonded water at temperatures up to 200-250 oC. This event is related with the increase of the absorption in the UV region, which was found at temperatures up... (Complete abstract, click electronic address below).