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Aus der österreichischen Pavlovienfundstelle Krems-Wachtberg liegen zwei Fundobjekte vor, die aufgrund ihres intentionellen Farbauftrages dem Kunstbereich zugeordnet werden. Ihr stratigraphischer Kontext datiert sie auf rund 28 300-26 800 14C-Jahre vor heute. Bei dem Artefakt WA-88015 handelt es sich um ein langschmales Elfenbeinobjekt, das auf seiner konkaven Innenfläche elf rote parallel gereihte Querstreifen zeigt. Das Stück ist in der Länge gebrochen, sodass die Zahl der Farbstreifen ursprünglich höher gewesen sein könnte. Chemische Farbanalysen bestimmen ein eisenhaltiges Pigment als verwendetes Farbmittel. Das zweite Kunstwerk mit der Fundnummer WA-181748 ist ein Mammutrippenbruchstück mit ebenfalls roter Bemalung. Aufgrund der Fragmentierung ist die ursprüngliche Bildbotschaft nur partiell erhalten. Nach der chemischen Farbanalyse des Farbauftrages wurde wie im Fall des Elfenbeinartefaktes ein eisenhaltiges Pigment benutzt. Aus dem Gravettien Mitteleuropas ist die Nutzung von Pigmenten gut belegt, und es finden sich neben Rohstücken auch Objekte mit unstrukturierten Farbspuren. Ein Vergleichsfund mit intentionellem Farbauftrag und abstraktem Design stammt aus der tschechischen Pavlovienfundstelle Předmostí. Wie bei den beiden Kunstwerken aus Krems-Wachtberg ist auch hier durch die Fragmentierung des Fundstückes das Bildfeld nur z. T. erhalten. Für das Pavlovien Mitteleuropas zeigen diese Artefakte, dass zum vielfältigen Konzept der Farbnutzung auch die Bemalung mobiler Objekte gehört., Archäologisches Korrespondenzblatt, Bd. 50 Nr. 1 (2020): Archäologisches Korrespondenzblatt

Fragestellung: Um dem „Stress-Shielding“-Effekt herkömmlicher Titan-Cages entgegenzuwirken, schlagen wir ein neuartiges Fusionsimplantat („Amplifix“) vor, das durch seinen inneren Aufbau aus gegenläufigen, beweglichen Lamellen die für die Osteogenese wichtigen[zum vollständigen Text gelangen Sie über die oben angegebene URL], Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2015)

Obituary for Joachim Haupt (1941 - 2013)

Der Zusammenhang von Zylinder-Epithel ausgekleideten Abschnitten des Ösophagus mit der Entwicklung eines ösophagealen Adenokarzinoms ist nun schon seit fast 50 Jahren bekannt. Im Jahre 2008 geht man davon aus, dass jährlich etwa 0.5% der Patienten mit Barrett-Ösophagus ein Adenokarzinom entwickeln. Trotz verbesserter Operationstechnik und der zusätzlich angewandten neoadjuvanten Therapie bleibt die Prognose des Adenokarzinom infaust, nicht zuletzt weil sich die Patienten mangels eindrücklicher Frühsymptome oft erst in weit fortgeschrittenen Stadien präsentieren. Bei insgesamt kleinen Fallzahlen für das Adenokarzinom, der hohen Prävalenz der GERD-Symptomatik und des hohen Anteils der Patienten mit Barrett-Ösophagus die offensichtlich nie zu einem Adenokarzinom progredieren, erscheint ein weit angelegtes Screening durch Gastroskopien mit Biopsie-Entnahmen ineffektiv und unökonomisch. Aus dem Ende der Neunziger Jahre prospektiv angelegten Barrett-Register der chirurgischen Universitätsklinik Würzburg wurden 125 Patienten mit Barrett-Diagnose über 819 Patientenjahre verfolgt. Hier wurde lediglich ein Adenokarzinom mit begleitender high-grade Dysplasie beobachtet, das sich nach einem Intervall von 8 Jahren aus einem nicht-dysplastischen Barrett-Segment entwickelte. Weiterhin wurde in einer Patientin mit einem long-segment Barrett-Ösophagus die Rückbildung einer low-grade Dysplasie in ein nicht-dysplastisches Zylinderepithel beobachtet. Die um in etwa ein Drittel erniedrigte Inzidenz des Adenokarzinoms in dieser Studie (1,22 pro 1000 Patientenjahre) könnte sich durch ein längeres Follow-Up an die in der Literatur beschriebene Inzidenz durch das Auftreten weniger Fälle angleichen. Eine regelmäßige endoskopische Überwachung der Barrett-Schleimhaut bleibt, solange noch keine anderen Modalitäten zur sicheren Risikostratifizierung erhältlich sind, eine zwar belastende, im Einzelfall aber lebenswichtige Maßnahme., In a population of 125 patients with histological confirmed non-dysplastic Barrett's esophagus progression to adenocarcinoma was a rare event (1 case in 819 patient years). 76,8% of patients underwent Nissen fundoplication in this population. The high percentage of surgically treated patients is explained by pre-selection, as the study population was recruited from a patient base in the surgical unit of an University Hospital.

RWTH-Themen : Berichte aus der Rheinisch-Westfälischen Technischen Hochschule Aachen 2004(1), 54-57(2004). special issue: "Vielfalt des Nanokosmos / [hrsg. im Auftr. des Rektors: Dezernat Presse und Öffentlichkeitsarbeit der RWTH Aachen. Verantw.: Toni Wimmer]", Published by RWTH, Aachen

RWTH-Themen : Berichte aus der Rheinisch-Westfälischen Technischen Hochschule Aachen 2004(1), 48-50(2004). special issue: "Vielfalt des Nanokosmos / [hrsg. im Auftr. des Rektors: Dezernat Presse und Öffentlichkeitsarbeit der RWTH Aachen. Verantw.: Toni Wimmer]", Published by RWTH, Aachen

Die Entdeckung von Zeolithen, von "siedenden Steinen", hat eine ungewöhnliche Eigenschaft von festen Stoffen zutage gebracht: Unsere Vorstellung von einem Kristall oder von einem Mineral als dichtem Festkörper mit eng aneinander gepackten Atomen, Ionen oder Molekülen gilt offenbar nicht immer. Zudem warten die Zeolithe mit ihren Hohlräumen und Kanälen im Nanometerbereich mit erstaunlichen Eigenschaften auf.

[Simon Ulrich Pistoris]

The measurement of pH and temperature plays an important role in many applications, including food analysis, environmental monitoring, chemical manufacturing, and medicine. Integration of pH and temperature sensors into packaging and electronic devices will continue to grow in importance as the world moves further towards Industry 4.0 and the Internet of Things, particularly as more industries become data-driven. New applications would also become possible by fabricating sensors on flexible substrates. Furthermore, building and operating a pH sensor without a reference electrode would provide many advantages, such as simpler manufacturing processes and long-term stability of the sensor. In a step towards achieving this goal, additive manufacturing of tantalum oxide films for pH sensing was explored in this work. Specifically, the sol-gel process and flash lamp annealing were used to deposit these films on gold metallized polyethylene terephthalate (PET) foils. After deposition of the sensing layers on the foil, both an extended-gate field-effect transistor (EGFET) and an impedimetric configuration were used to test the tantalum oxide layers for pH sensing. Additionally, a discovered negative temperature coefficient (NTC) in sol-gel derived ruthenium-tantalum oxide layers was examined for use as a temperature sensor, where the layers were thermally annealed with no photocuring on borosilicate wafer. In preparing the tantalum sol-gel solution for eventual layer deposition via photocuring, an optimized synthesis procedure for β-diketonate and β-ketoester complex formation with tantalum in 1,3-propanediol was conducted and the thin films characterized for photosensitivity in the near-UV range. Suboptimal synthesis procedures still work for device fabrication and were used in the production of the pH sensors. These solutions are stable in atmosphere, which is important for inkjet printing the solutions both in a laboratory and in an industrial environment. Inkjet printing of the solutions to form layers was then performed, followed by thermal annealing and flash lamp treatment of the layers. Photocured tantalum oxide layers derived from these solutions were characterized via various material characterization techniques. Exposure of the material to acidic and basic solutions in an EGFET configuration for pH sensing was also performed, and the layer was shown to withstand solutions in the range between pH 2 and pH 12.A photocured tantalum oxide layer was then tested for pH sensing in an impedimetric configuration on interdigitated electrodes (IDEs) without a reference electrode. A pH dependent double layer capacitance was found in solutions of high ionic strength. The data was fitted with an equivalent circuit consisting of a double layer capacitance in parallel with an interfering ion specific adsorption capacitance. Finally, the NTC of sol-gel derived ruthenium-tantalum oxide layers was characterized. A first material was tested from 20°C to 100°C, and then down to cryogenic temperatures. This was followed by investigating a second material, with an improved preparation procedure from the first material, and tested from -20°C to 60°C. In both cases, a reproducible NTC was observed which could potentially be combined as a temperature sensor with the fabricated pH sensor in a single device.

Dissertation, RWTH Aachen University, 2022; Aachen : RWTH Aachen University 1 Online-Ressource : Illustrationen, Diagramme (2023). = Dissertation, RWTH Aachen University, 2022, Supramolecular cyclic coordination oligomers developed in the working group are excellent hosts for fullerene guest molecules as C60 and C70. It is therefore interesting to explore, whether other guest compounds of comparable size, such as gold clusters, can be stabilized in these host structures, as well. Therefore, the reaction of cyclic coordination oligomers with different gold compounds, i.e. triphenyl phosphine (TPP) Au(I)-complexes, TPP stabilized Au9- and Au55-clusters was investigated. Surprisingly, it could be observed that the reaction, irrespective of the starting compounds, resulted in the formation of TPP-stabilized Au11-clusters, comprising slight structural variations, but having a cluster core size complementary to the cyclic coordination oligomers cavity. In this dissertation the results and the attempts in understanding these unexpected findings are shown. Various coordination compounds such as dimers, triple and quadruple layer structures are used to investigate the influence of cavities and interactions., Published by RWTH Aachen University, Aachen

Dissertation, RWTH Aachen University, 2021; Aachen : RWTH Aachen University 1 Online-Ressource : Illustrationen, Diagramme (2022). = Dissertation, RWTH Aachen University, 2021, Lean-burn engines are one of the most prevalent types of engines used in modern day vehicles. Due to the increasingly strict guidelines for their exhaust gas emissions, new systems for exhaust gas catalysis are constantly developed. However, the new systems need novel catalyst materials for proper functionality which requires a comprehensive understanding of their structure-activity relationship. Therefore, this work investigates the structure-activity relationship of copper-based water-gas shift catalysts for high temperature applications. Initially, catalysts with varying ratios of copper, zinc and aluminum were synthesized with a modified co-precipitation method and then calcined at harsh conditions to simulate ageing in an exhaust gas system. The catalyst structure showed a high dependence on their aluminum content, since a high amount of aluminum resulted in the formation of CuAl2O4-spinel structures. The formation of CuAl2O4 could be observed at temperatures as low as 400 ��C. The influence of the zinc content on the other hand was negligible for the catalyst structure and thermal stability. The reduction of the spinel-structures formed highly dispersed copper particles with specific copper surface areas up to 5 m��/gKat. Due to a close relation between the copper surface area and the CO-conversion in the water-gas shift reaction, the bulk of the catalysts outperformed an aged commercial water-gas shift catalyst, which was used as a reference. The best performing catalyst with 87 % aluminum and a 1:1 ratio of copper and zinc could reach a CO-conversion of 77 % at 250��C as well as 87 % at 350 ��C.This material was then doped with small amounts of magnesia, gold, palladium and platinum. While the doping with noble metals did not show any improvement of the catalysts, the doping with certain amounts of magnesia showed an increase in specific copper surface area. This was caused by the integration of Mg2+-Ions in the spinel structure which effectively decreases copper particle size and facilitates their reduction. At the same time, magnesia also diminished the turnover-frequency of the catalysts, so that no significant increase in CO-conversion could be observed. Based on the discussed results, various catalysts were industrially prepared by Sasol Germany GmbH and investigated in this work for their performance in the water-gas shift reaction. The resulting materials showed a high stability against thermal ageing and a high performance in the water-gas shift reaction at elevated temperatures. At 350 ��C, a CO-conversion of almost 80 % could be reached., Published by RWTH Aachen University, Aachen

Dissertation, RWTH Aachen University, 2021; Aachen : RWTH Aachen University 1 Online-Ressource : Illustrationen, Diagramme (2021). = Dissertation, RWTH Aachen University, 2021, Flame retardants, i.e. additives that decrease polymer flammability, are of immense importance due to the abundance of hydrocarbon plastics and textiles in everyday life. Different classes of substances are available for this, each however coming with their own limitations. While very effective halogenated flame retardants are being phased out due to environmental and health concerns, the environmentally benign mineral flame retardants exhibit rather low flame retardancy. Through synergistic interaction of different substances, however, hybrid flame retardants that are both effective as well as environmentally friendly can be produced. Therefore, this thesis covers the combination of phosphorus-containing building blocks with highly branched polyalkoxysiloxanes and polyalkoxysilsesquioxanes. To achieve this, in the first, part the commercially available silane (diethylphosphatoethyl)triethoxysilane is converted to a phosphorus-modified, highly branched polyalkoxysiloxane through a one-pot synthesis with tetraethylorthosilicate. The focus here is the synthesis and characterization of polyalkoxysiloxanes with varying contents of phosphorus-containing groups. In the second part, methods are investigated to incorporate 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, a molecule already being used as a flame retardant, into the structure of a highly branched polyalkoxysiloxane. The third part covers cyclophosphazenes, a much-investigated class of substances with high potential for flame retardancy. By crosslinking of chlorocyclophosphazenes with aminopolysilsesquioxanes, hybrid colloids are produced and characterized. Finally, these three systems are applied as textile coatings and evaluated based on their flame retardant properties., Published by RWTH Aachen University, Aachen

Dissertation, RWTH Aachen University, 2021; Aachen : RWTH Aachen University 1 Online-Ressource : Illustrationen, Diagramme (2021). = Dissertation, RWTH Aachen University, 2021, Hybrid electrolytes are electrolytes for lithium ion batteries (LIB) with lithium anode meeting the requirements of safety, performance and processing. Hybrid electrolytes are defined as composites that combine two or more ionically conducting materials. In the scope of this thesis an organic polymer electrolyte poly(ethylene oxide) with lithium bis(trifluoromethanesulfonyl)imide (PEO with LiTFSI) and an inorganic solid-state electrolyte Li7-xLa3Zr2-xTaxO12 (Ta-LLZO) were used. Cubic Ta-LLZO possesses a higher ionic conductivity than the tetragonal phase of Ta-LLZO and was synthesized via a classical all-solid-state and a sol-gel route. For the application of Ta-LLZO in hybrid electrolytes, the powder was remilled after calcination reducing the average particle size. The composition of the hybrid electrolyte was optimized regarding the ionic conductivity. Influencing parameters such as Ta-LLZO particle properties, LiTFSI salt concentration, Ta-LLZO weight fraction and substitution with biopolymers were investigated. In comparison to a pure polymer electrolyte PEO12LiTFSI a higher ionic conductivity was measured for a hybrid electrolyte with 20 wt.-% Ta-LLZO in a PEO6LiTFSI polymer matrix. The substitution of PEO with biopolymers, specifically chitosan mesylate or cellulose acetate, was an approach for more sustainable materials in LIB, but resulted in a loss of performance. The applicability of hybrid electrolytes in Li-LiFePO4 (Li-LFP) cells was confirmed. LFP cathode sheets were adapted to the requirements of the hybrid electrolytes by using PEO6LiTFSI as binder and lithium ion conductor. Compared to the polymer electrolyte, an increase in the electrochemical stability of the hybrid electrolyte was obtained. The substitution of PEO by cellulose acetate further increased the electrochemical stability. The interfacial layer at the organic-inorganic interface was characterized on microscopic level using Infrared Spectroscopy and Electrochemical Strain Microscopy (ESM). Interactions of polymer and ceramic lead to an increase of mobile charge carriers. Moreover, ESM measurements visualized the possible formation of an interfacial layer in the polymer phase near the interface with the ceramic. This supports the assumption that interfacial percolation substantially influences the ionic conductivity of hybrid electrolytes on macroscopic level., Published by RWTH Aachen University, Aachen

Dissertation, RWTH Aachen University, 2020; Aachen 1 Online-Ressource (VII, 223 Seiten) : Illustrationen, Diagramme (2020). = Dissertation, RWTH Aachen University, 2020, Ruthenium terpyridines (Ru TP) are thanks to their linear structure and their high intensely studied complexes. Their application in nanoelectronics promises enormous potential, as the delocalized electron system offers conductivity, while the redox-active ruthenium centre enables electrical switching. In this thesis different methods to functionalize gold surfaces and gold nanoparticles (AuNP) have been investigated. In the first part of this thesis the syntheses and the characterization of the TP and Ru TP are discussed. The pH-dependent configuration change of the TP ligands could be shown. Further the syntheses and characterization of two new Ru TP complexes was proven using NMR, UV/VIS, IR and Raman spectroscopy, as well as mass spectrometry (MS). By stimulation the metal-ligand charge-transfer transition of the Ru-TP complexes resonant Raman spectra were also recorded. In the second part Ru-TP-wire were growth on Au surfaces in a stepwise approach. This approach was monitored via different surface sensitive methods, namely infrared-reflection-adsorption-spectroscopy and surface enhanced Raman spectroscopy and further followed by variable angle spectroscopic ellipsometry (VASE). To support the resulting spectra DFT calculation were performed and solid phase spectra of model substances recorded. By comparing those spectra and calculation of the dipole derivative unit vector the orientation of the molecules could be deduced. Through this the repetition count to bridge a two nanoelectrodes could be calculated and the suitability of those Ru TP wires could be tested. In the third part of this thesis synthesis conditions for the functionalization of AuNP with TP and Ru TP were found. The TP AuNP and Ru TP AuNP-hybrid systems were studied by means of UV/Vis, DLS, as well as Raman spectroscopy with two excitation wavelengths. Further TEM at high magnification were recorded to measure the distance between the AuNP. The DLS and TEM data indicate an increasing rising ligand layer thickness with increasing number of TP groups, while the UV/Vis date were found to be ambiguous due to solvent effects. Besides isotropically functionalized AuNP Janus-AuNP with TP and Ru TP ligands were synthesized, as well. Both ligands could be identified by measuring Raman at two excitation wavelengths. The distribution of TP and Ru TP could be determined using ICP-MS (induced coupled plasma MS). Further the coverage density and the footprint of all synthesized AuNP was determined through ICP MS. Moreover, the electrical properties of isotropic TP and Ru TP could already be investigated., Published by Aachen

Dissertation, RWTH Aachen University, 2020; Aachen 1 Online-Ressource (133 xlix, I Seiten) : Illustrationen, Diagramme (2020). = Dissertation, RWTH Aachen University, 2020, Die vorgestellte Dissertation fand unter der Anleitung von Prof. Dr. Dominik Wöll an Institut für Physikalische Chemie der RWTH Aachen University im Rahmen des Sonderforschungsbereiches 985 „Funktionelle Mikrogele und Mikrogelsysteme“ statt. Bei den hier vorgestellten Ergebnissen steht die Erforschung von Mikrogelen an der fest-flüssig-Grenzfläche, sowie die Analyse mittels fluoreszenzspektroskopischer Verfahren im Vordergrund. Im Laufe der Dissertation ist auch die automatisierte Datenanalyse durch die Entwicklung entsprechender Software und Algorithmen hinzugekommen. Eines der in dieser Arbeit vorgestellten SFB-Projekte beschäftigt sich mit dem Deformationsverhalten von Mikrogelen an der Oberfläche. Dabei wurde die Mikrogelkonformation auf Oberflächen unterschiedlicher Hydrophilie mittels moderner 3D Fluoreszenzmikroskopiemethoden untersucht. Es konnte gezeigt werden, dass eine hydrophile Oberfläche das Lösungsmittel imitiert und das Mikrogel dadurch seine native, sphärische Struktur behält. Auf hydrophoben Oberflächen dagegen konnte die sogenannte „Spiegelei“-Konformation abgebildet werden. Die Deformation von Mikrogelen wurde weiterhin in Abhängigkeit der Depositionsmethode auf der Oberfläche untersucht. Die gängigen Labortechniken „drop-casting“, „spin-coating“, sowie Adsorption aus der Lösung wurden dafür verglichen. Es konnte gezeigt werden, dass der Einfluss des Lösungsmittelverdampfens eine wichtige Rolle neben der Oberflächenhydrophilie einnimmt. Die Ergebnisse wurden ferner im Rahmen einer SFB-Kooperation mittels Computersimulationen verifiziert, und die Kompatibilität der existierenden theoretischen Modelle zur Mikrogeldeformation mit den empirischen Ergebnissen der hier vorgestellten Arbeit gezeigt. Weiterhin wurde in einem zweiten Projekt in einer Kooperation innerhalb des Sonderforschungsbereichs eine neue Methode zur Immobilisierung von Mikrogelen an ein definiertes Oberflächenmuster entwickelt. Hierfür wurden die bekannten Techniken der chemischen Elektronenstrahllithographie und der Photolithographie kombiniert. Die Forschungsergebnisse konnten zeigen, dass es möglich ist, DNA-funktionalisierte Mikrogele gezielt über DNA-Hybridisierung an ein Oberflächenmuster anzubringen. Durch die gewonnene Expertise im Bereich vernetzter Polymere an Oberflächen wurde im Rahmen dieser Arbeit eine Kooperation mit dem Institut für Organische Chemie der RWTH Aachen University ins Leben gerufen. Es wurde eine neue Methode zum Strecken von DNA-Molekülen in thermoresponsiven Hydrogelen entwickelt. Dies erlaubt die Analyse von DNA-Proben in Hinblick auf (epi-)genetische Veränderungen durch fluoreszenzbasierte optische Kartierung (optical Mapping). Das zugrundeliegende Konzept zum Linearisieren von DNA-Molekülen wurde in Form eines Verfahrenspatents angemeldet, welches zum Zeitpunkt der Abgabe dieser Dissertation geprüft wird., Published by Aachen

The development of lithium-ion cells with higher energy densities is being driven forward by the use of alloy materials, among other things. Anodes are combined with high nickel contents in the cathode to further increase the energy density in 18650 cells. Both the dense packing of the materials and the alloy formation by silicon in the anode increase the volume expansion and thus the mechanical stress inside the cell, which accelerats cell ageing. The mechanical properties of lithium-ion cells are particularly important for applications with maximum energy density and lifetime [1], [2]. Due to the variations in volume during use of lithium-ion cells, geometric variations and the induced mechanical stresses must be taken into account when integrating the cells into modules, packs and systems [3], [4]. In this context, an unsuitable design leads to premature ageing of components at all levels. In extreme cases, a mismatch of volume requirements and device integration can lead to catastrophic failure [5]. Mechanical ageing caused by a volume change could be one of the reasons for early and unexpected cell death. Especially since the volume of graphite can change within the specified voltage limits by up to 7-12% [3], [6], [7], lithium-nickel-cobalt-aluminum-oxide by up to 5% [3], lithium-nickel-manganese-cobalt-oxide by up to 1-2% [3], [8], [9] and silicon by up to 280% [10]. The question to be answered is therefore, how serious the influence of volume expansion on cell ageing in commercially relevant cells is with regard to the application. The aim of this work is the systematic investigation of volume expansion and its effects on the ageing of lithium-ion cells. A cylindrical lithium-ion cell, the Samsung SDI INR18650 35E (Samsung 35E), is considered as an example. A strain gauge is used to monitor the volume expansion, here the diameter change. A total of 45 cells were examined under twelve different ageing conditions. The cyclic ageing conditions differ in their average state of charge and depth of discharge. Using strain gauges, a stable and reproducible method for analyzing the volume expansion of 18650 lithium-ion cells was introduced. The following main findings were elaborated in this thesis:•A complete characterization of the Samsung 35E is performed. •The characteristic curve shape of the diameter change depends on the State-of-Charge and the direction of load. The characteristic curve shape consists of three areas. A minimum at high State-of-Charge (SOC), a constant slope (plateau) at medium SOC and a flattening of the diameter change at low SOC. •The characteristic curve shape of the diameter change changes with ageing. The SOC dependent geometric changes are reversible. In addition, an irreversible increase in the diameter change over the lifetime can be observed. •The average mean diameter change and the loss of capacity correlate positively. Thus, by measuring the average mean diameter change, the State-of-Health can be determined and sudden cell death can be predicted. •The deformation of the jelly roll is caused by cyclic ageing. With the help of computed tomography images, the starting time of the deformation was determined. When the Samsung 35E ages with an average SOC of 10% and a cycle depth of 20%, the deformation of the jelly roll starts at the same time as sudden cell death. The knowledge gained should help to better design future lithium-ion cells with regard to their volume expansion and to extend their lifetime through optimized utilization.

Dissertation, RWTH Aachen University, 2019; Aachen 1 Online-Ressource (xiii, 137, XXXIII Seiten) : Illustrationen, Diagramme (2019). = Dissertation, RWTH Aachen University, 2019, In this work the use of DRIFT spectroscopy for the investigation of molecular processes on different catalytic converters for exhaust gases of lean burn engines was investigated. The results were correlated with the outcomes of different integral measurement methods. By that, a better understanding of underlying processes resulting in certain integral observations was approached. With the help of DRIFT spectroscopy, the interpretation of HF-IS measurements on a SCR converter was improved: The already known correlation of resonance frequency and the mobility of adsorbed NH3 species was sharpened by a precise definition of the kind of mobile species. In addition to that, the influence of highly mobile [CuI(NH3)2]+ complexes on the resonance frequency was proofed. During this work, initial experiments for the correlation of integral and local investigation methods on several, technically relevant LNTs were performed. First, detailed DRIFTS investigations were correlated with high-resolution methods for material analysis such as TEM-EDX to obtain detailed information about cross effects between the different compounds and their de- or increase by different converter architectures. The results were then correlated with catalytical tests. The correlation showed a critical impact of ceria as well as barium-containing components on the NOx storage behavior. Additionally, the time-resolved formation as well as decomposition of different reaction intermediates as well as products in dependence of different LNT compositions was investigated. By that, the interpretation of measurement results from laboratory gas test bench were improved: The observed high NOx storage of one investigated catalyst was traced back to very high precious metal dispersion over the active components. Also, the use of ceria as low temperature NOx-storage was found to be critical for the performance of the LNTs during regeneration as it increases the direct oxidation of hydrocarbons and by this lowers the regeneration performance of the LNT. Additionally, an optimal dispersion of precious metals and BaCO3 were identified to be crucial to the systems performance. In the last chapter of this work the desorption of 1-Octanol from a oxidation catalyst was investigated by TP-DRIFTS. With the help of these investigations, the formation of any liquid phase during adsorption was excluded and the decomposition processes of 1-Octanol during TPO experiments were confirmed with the help of observed intermediates., Published by Aachen

Dissertation, RWTH Aachen University, 2018; Aachen 1 Online-Ressource (163 Seiten) : Illustrationen, Diagramme (2018). = Dissertation, RWTH Aachen University, 2018, This work includes the synthesis and characterization of various gold nanoparticle (AuNP) hybrid systems, in solution as well as on surfaces. Different interactions were used to bind AuNP to organic molecular systems: unspecific or electrostatic interactions and programmable interactions through the use of DNA. This has enabled the development of new multifunctional structures that could potentially be applied in biomedicine, e. g. as drug delivery systems. In the first part of this thesis, the formation of a hybrid system is described, consisting of negatively charged 1.4 nm cytotoxic AuNP and positively charged microgels (μGs). It was possible to release them by external stimuli such as pH and temperature change. In the second part of the thesis, the formation of hybrid systems by programmable interactions is described by using oligonucleotides (DNA for simplification) as linkers between 12 nm AuNP and μG. Different DNA-functionalized μGs were synthesized. The μGs were pNIPAM-, pNIPMAM and pVCL-based μGs into which DNA was covalently bound via corresponding co-monomers. Complementary DNA strands and DNA-functionalized AuNP could reversibly be attached to the DNA. These hybrid systems could be imaged by SEM-T and in situ-STEM, whereby the distribution of AuNP inside the μG was analyzed. A system with defined structure was developed by using DNA strands with hairpin motifs to connect the AuNPs. Thus, these structures should also be switchable. Dimers and networks were synthesized. The networks were synthesized by control of concentration of isotropically functionalized AuNP by combination of isotropically and anisotropically functionalized AuNP. The third part of the thesis describes the immobilization of μGs via DNA hybridization on AuNP immobilized on a substrate. The interactions of the μGs with the substrate were investigated and attempts were made to minimize the interaction by using a highly fluorinated backfill. DNA hybridization allowed μGs to be reversibly immobilized, which enabled further characterization by AFM and fluorescence microscopy., Published by Aachen

Dissertation, RWTH Aachen University, 2018; Aachen 1 Online-Ressource (vii, 117 Seiten) : Illustrationen, Diagramme (2018). = Dissertation, RWTH Aachen University, 2018, The main motivation of this work is the development of materials that can be used for the electrochemical conversion of alcohols or for the photoelectrochemical oxidation of water molecules to gaseous energy carriers. The possibility of using monodisperse Au or Pd nanoparticles for the electrocatalytic oxidation of methanol is shown. The synthesized nanoparticles are aligned into two-dimensional arrays by self-assembly, mounted onto substrates and used as anodes for the electrochemical methanol oxidation in a self-built reactor. Furthermore, the thesis shows novel electrode systems for the photoelectrochemical water oxidation. The photoanodes have a semiconductor/semiconductor (CuWO4/Ag2NCN) or semiconductor/electrocatalyst (BiVO4/CoPd, SrTaO2N/Feh and WO3/CuWO4/Au) interface system. Numerous electrochemical and spectroscopic methods are used to investigate the activities of the composite photoanodes. Resulting efficiencies are explained by the energy band model for oxide-based semiconductor materials or by interface effects for semiconductor/electrocatalyst systems., Published by Aachen

The increasing use of lithium-ion batteries as well as the high requirements, e.g. for fast charging of electric car, require a more detailed understanding of the cell system. For use under extreme conditions such as high charging currents, which can lead to strong aging due to lithium plating, an exact knowledge of the battery's internal state variables is necessary in order to be able to protect them with optimized battery diagnostics. The use of fundamental-based physico-electrochemical simulation models can help to provide the necessary understanding for these applications, as well as to reduce the otherwise required test effort for cell characterization. They allow to look at the processes taking place internally and thus the identification of the internal state variables which are decisive for the operation of the cell. This work starts with the description of the enhancements and implementation of a physico-electrochemical battery model, which greatly increases the flexibility and extensibility to new effects. Instead of the usual simulation of a cell as a 1D cross section, the extension to 2D and 3D structures makes it possible to reproduce inhomogeneities. It allows the free variation and combination of different material properties. In addition, double-layer capacitances were implemented in the electrical model, which allows the simulation of impedance spectra.In order to simulate a battery, the material parameters of the components used in the cell are required. The procedure for parameterizing these material data is described by means of a prismatic high-performance cell. This includes investigations of the electrolyte as well as the active materials, which are examined directly or electrochemically by use in laboratory cells. In addition, an analysis of the thermal properties is carried out since the self-heating of the cell and its effects on the cell performance cannot be neglected here. The quality of the determined data set is demonstrated by a validation based on discharge and charging curves, pulse tests, impedance spectra and a realistic driving profile, all at different temperatures. The parameterized model is used to perform exemplary simulations. In a model-based cell analysis, the effects of a particle size distribution are considered under various aspects. The components occurring in impedance spectra are assigned to the respective processes and properties. Furthermore, three effects which have occurred in aging tests are examined and the theories which have been developed are simulated. Thus, from the implementation of the model to the acquisition of the necessary material parameters up to the exemplary application, the possibilities of physico-electrochemical battery modelling are presented and their applicability and usefulness are demonstrated.

Dissertation, RWTH Aachen University, 2017; Aachen, 1 Online-Ressource (viii, 193 Seiten) : Illustrationen, Diagramme (2017). = Dissertation, RWTH Aachen University, 2017, Gold nanoparticles (AuNP) show unique size-dependent physical and chemical properties. Their size, shape and surface functionalization can be easily modified by adjusting the synthetic procedure or by using specific stabilizing molecules. One parameter influencing the particles’ stability is therefore, the ligand molecule. In the present work, tailor-made ligand molecules were used to enable a cross-linkage of the ligand sphere on the AuNP surface to increase the stability. In order to realize a surface polymerization, diacetylene units within the molecular structure were used. They polymerize upon thermal treatment or ultraviolet (UV)-irradiation to build up so-called polydiacetylenes (PDA). Those DA units were integrated into the molecular scaffold, bound to the AuNP’s surface and subsequently polymerized. For applications in molecular electronics ligand molecules stabilizing AuNP have to fulfill certain requirements. It was elucidated, if these requirements were in coincidence with the ones needed for a successful polymerization. Therefore, a possible stability enhancement as well as the electrical transport characteristics of the AuNP were investigated. Taking the above mentioned considerations into account, the work emphasizes on four points. The first one covers the design and synthesis of the corresponding ligand molecules and their characterization. To gain an insight in the polymerization behavior, polymerization of those molecules was first investigated without AuNP. The next key aspect was the functionalization of AuNP and the characterization of this polymer metal hybrid system. The stability of those functionalized AuNP was investigated directly dependent on the polymerization condition. Those experiments revealed a limitation in stability enhancement. The fourth part covers some application-oriented experiments, which were performed with the functionalized AuNP. The electrical transport characteristics of a nanoelectrode device in which AuNP were integrated showed a nonlinear dependency of current on voltage. It could be described with a tunneling mechanism. Moreover, the possibility to remove the gold core via etching reaction was investigated to keep the ligand sphere as a hollow polymeric nanosphere. The adsorption behavior of nitrile terminated functionalized AuNP on possible electrode materials was also subject of investigation. Moreover, since nitrile groups are able to undergo complexation reactions, the complexation of the nitrile AuNP with a ruthenium complex was performed., Published by Aachen

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.

This thesis discuss in situ reaction monitoring by means of impedance spectroscopy (IS). As a model reaction DeNOx-SCR at zeolites was chosen. This work is based on solvate supported proton transport mechanisms in zeolites. This conductivity could be measured in situ using impedance spectrsocopy. In a first step the descrimination of thermal desorption and catalytic conversion of ammonia over pure and metal-loaded zeolites was demonstrated by means of temperature as well as time depending IS. For detailed analysis a special-build measuring setup for simultaneous IS and DRIFTS was used. Additional to zeolites a porous zirconia-phosphate-based heterostructure was analyzed by means of IS in this thesis. It was shown that the general solvate-supported proton transport mechanisms could be transfered to this new class of materials. In a third part of this thesis the non-porous, semiconductiong material ammonia paratungstate (APT-4) was analyzed. For this material the thermal decomposition as well as the transformation of tungsten suboxide to tungsten oxide was monitored by in situ IS.

During the past few years considerable interest in ultrasmall gold nonoparticles (usNP) was expressed. Due to their unique electronic properties, NP are promising candidates for applications in molecular electronics, catalysis, photovoltaics, or biolabeling. These properties are in a transient regime between molecule and bulk, caused by the small number of interconnected gold atoms. Their central characteristic is the gap between the highest occupied and lowest unoccupied electronic state (EGap). EGap can be predicted by relatively simple models, or determined via optical, voltammetric or numerical methods. So far, a systematic evaluation of EGap of ligand-stabilized usNP with less than 25 gold atoms and a known crystal structure was non existent. In addition, usNP are about the same size as sub cellular structures. Therefore, they show an exceptional behavior within biologic environments. Particles with a hydrodynamic diameter smaller than about 20 nm possess the ability to leave blood vessels and infiltrate tumorous tissue. This relationship is of importance for the application of gold nanoparticles (AuNP) in methods for preclinical oncology, i. e. photoacoustic (PA) tomography. Investigations of the last years on AuNP with core sizes larger than 10 nm have revealed them as potent PA contrast agents. Nevertheless, no systematic comparison of the optical extinction and PA-efficacy of water soluble AuNP of different shape and size, including usNP, had been conducted until now. Against this background, usNP and larger AuNP have been synthesized, characterized in detail and transferred into water soluble PA contrast agents. Phosphane-stabilized gold clusters have been prepared and crystallized in organic solution. The determination of their crystal and electronic structure by means of x-ray crystallography, optical, voltammetrical and numerical techniques resulted in a profound understanding of the structure-property relationship of these materials. A systematic evaluation revealed the dependency of EGap on the number of gold atoms within the usNP, which correlates to the prediction by the models. Water soluble AuNP were synthesized in a comparable manner from gold solutions or by ligand exchange reactions. The choice of appropriate ligands and an optimal coupling chemistry led to PA contrast agents of low cytotoxicity, which were equipped with entities to recognize tumors and markers of angiogenesis. Further, AuNP of different shapes with core sizes between 1 and 90 nm were systematically analyzed respecting their extinction- and PA-properties. This investigation enabled the comparison between the PA-efficacy of the AuNP and a common organic PA contrast agent.

In the context of this work it was demonstrated that DNA-functionalized gold nanoparticles equipped with glycoconjugates were bound by carbohydrate binding proteins (lectins) in a specific manner. Biomolecular self recogonition led to the formation of particle lectin networks which were able to dissociate by two independent stimuli, namely temperature and addition of sugar. Further it was demonstrated that the uptake or binding of the nanoparticle conjugates by hepatocytes (HepG2) was mediated by charge driven interactions, as likely by scavenger receptors, while a specific recognition of the glyco termini by the asialoglycoprotein receptor (ASGP R) could not be proven. Amino-modified glyco conjugates (N-acetyl-D-glucosamin (GlcNAc) and (poly-)N-acetyllactosamin ((poly-)LacNAc)) were used for glyco functionalization of gold nanoparticles. By binding the amino group to N-hydroxysuccinimide esters the carbohydrates were coupled covalently with disulfide modified PEG ligands or oligonucleotides respectively which allow the binding to the surface of gold nanoparticles. The specific binding of different lectins (Griffonia (Bandeiraea) simplicifolia Lectin II (GS-II) or Galektin 1 and 8 respectively) to the carbohydrates in the periphery of the ligand shell led to cross-linking of the nanoparticles which was observable in a change of the plasmon band, an increase of the hydrodynamic diameter or in the formation of a structure factor in the scattering curve. By competition with free sugar particle networks were dissociated or the lectin-mediated assembly was inhibited. Networks built up by DNA-functionalized gold nanoparticles and lectins could further be dissociated by thermal DNA melting. In addition to specific interactions unspecific attractive interactions between DNA-functionalized gold nanoparticles and galectins were observed. Based on the specific addressability of lectins in solutions by glyco-DNA-gold nanoparticles ASGP-R, a cell membrane bound lectin with affinity for terminal D-galactose, should be addressed in order to achieve a specific uptake or binding of DNA-functionalized gold nanoparticles by certain cells. The interactions between di-LacNAc-DNA-functionalized gold nanoparticles and hepatocytes (HepG2 cells) were investigated. Besides ASGP-R these cells express scavenger receptors (SR-BI). By blocking both receptors with D-lactose and fucoidan respectively it was demonstrated by flow cytometry that di-LacNAc-DNA-functionalized gold nanoparticles were taken up likely by scavenger receptors while a specific interaction with the ASGP-R could not be demonstrated. Besides this other pathways for particle uptake are possible. Poly-LacNAc-DNA-functionalized gold nanoparticles could be potentially used to address galectin overexpressing cancer cells. This could lead to applications in the field of targeted drug release or gene regulation.

The combination of top-down- and bottom-up-techniques is a promising approach to the fabrication of nanoscaled functional structures, e. g. electrical devices. In this thesis the local reduction of sulfonic acid terminated into thiol terminated silane monolayers on SiO2- and ITO-surfaces via electron irradiation is presented. After exposure the irradiated areas show a different contrast in SEM images indicating a local conversion of the monolayer. The formation of thiol head groups via electron irradiation was proven with X-ray photoelectron spectroscopy by measuring the binding energy of the S2s orbital. Afterwards these thiol patterns were used to selectively immobilise 16nm AuNP from solution through formation of covalent Au-S-bonds. Aside from single circular structures with diameters of approx. 100nm the fabrication of ring-like and linear structures was also possible. In addition to the decoration of solid silicon wafers it was possible to generate patterns of AuNPs on-top of 40nm thick SiO2-membranes. These patterns could be visualised in scanning transmission electron microscopy. Furthermore, the process was also adapted to flexible ITO-covered PET-foils. The formation of electrical conducting structures was achieved by electro-less plating of the generated AuNP patterns with gold enhancement solution. Thereby, resistivities in the range of 4*10^-7 Ohm*m and 3*10^-6 Ohm*m were determined. These values are in accordance to known literature values. By incubation of irradiated monolayers with 6nm AuNP patterns of smaller nanoparticles were generated. Due to the detection of periodic super structures the general feasibility of the fabrication of single particle patterns was shown. In order to generate a large area pattern of single particles designs of individual exposuring spots were used for structuring. After incubation with 6nm AuNP a pattern of mostly single particles and pairs of particles with high periodicity could be fabricated. Thereby, the huge potential of fabricating single particle patterns by self-assembly on EBL-structured monolayers was shown.

Am Beispiel von ferroelektrischen Systemen auf Bismut-Basis (Bismutmolybdat, Bismutwolframat und Bismuttitanat) und von Strontiumbariumniobat werden neue Möglichkeiten zur Synthese solcher Nanopartikel aufgezeigt. Die Integration der Nanopartikel in transparente Nanokompositmaterialien und die Entwicklung neuer Precursoren für die Herstellung von Dünnschichtproben gehen den Untersuchungen zur Anwendung als elektrooptische aktive Materialien voraus. Durch weitere Anwendungsmöglichkeiten in der Photokatalyse, dem Test dampfadsorptiver Eigenschaften mit Hilfe eines neuartigen Adsorptionstesters (Infrasorb) und auch mit Hilfe der Ergebnisse der ferroelektrischen Charakterisierung von gesinterten Probenkörpern aus einem Spark-Plasma-Prozess wird ein gesamtheitlicher Überblick über die vielfältigen Aspekte in der Arbeit mit nanoskaligen, ferroelektrischen Materialien gegeben.:Inhaltsverzeichnis...........................................................................................................5 Abkürzungsverzeichnis ...................................................................................................9 1. Motivation....................................................................................................................11 2. Stand der Forschung und theoretischer Teil ...............................................................14 2.1. Nanoskalige Materialien...........................................................................................15 2.1.1. Nanopartikel und Nanokompositmaterialien ....................................................... 15 2.1.2. Dünnschichten..................................................................................................... 21 2.1.3. Anwendungen in der Photokatalyse.................................................................... 22 2.1.4. Anwendungen in der Gas- und Dampfsensorik.................................................... 24 2.2. Ferroelektrika .........................................................................................................26 2.2.1. Bismutmolybdat................................................................................................... 32 2.2.2. Bismutwolframat.................................................................................................. 34 2.2.3. Bismuttitanat ....................................................................................................... 36 2.2.4. Strontiumbariumniobat......................................................................................... 37 2.3. Verwendete Methoden.............................................................................................40 2.3.1. Spark-Plasma-Sintering ........................................................................................40 2.3.2. Bestimmung ferroelektrischer Eigenschaften ...................................................... 42 2.3.3. Charakterisierung nichtlinearer, elektrooptischer Eigenschaften......................... 43 3. Experimenteller Teil ....................................................................................................51 3.1. Synthesevorschriften................................................................................................52 3.1.1. Verwendete Chemikalien und Substrate.............................................................. 52 3.1.2. Solvothermalsynthese von Bi2MO6 (M = Mo, W)................................................... 55 3.1.3. Phasentransfersynthese von Bi2MO6 (M = Mo, W)............................................... 56 3.1.4. Präparation von Bi2MO6/PLA Nanokompositmaterialien (M = Mo, W) ................... 57 3.1.5. Sol-Gel-Synthese von Bi2MO6 (M = Mo, W), Bi4Ti3O12 und Ba0.25Sr0.75Nb2O6 und Dünnschichten..................... 57 3.1.6. Mikroemulsionssynthese von Bi4Ti3O12 ............................................................... 59 3.1.7. Sol-Gel-Synthese von Bi2Ti2O7............................................................................. 60 3.1.8. Synthese von BiOH(C2O4), BiOCH3COO und Bi(CH3COO)3................................... 61 3.2. Vorschriften zur Durchführung und Charakterisierung...............................................62 3.2.1. Verwendete Geräte und Einstellungen ................................................................ 62 3.2.2. Spark Plasma Sintering von Bi2MO6 (M = Mo,W) und Bestimmung ferroelektrischer Eigenschaften ........................ 65 3.2.3. Prüfung elektrooptischer Eigenschaften, Präparation der Bauteile und Messaufbau .............................................. 67 3.2.4. Durchführung photokatalytischer Messungen ....................................................... 69 3.2.5. Messung der Dampfadsorption an Nanopartikeln mit Hilfe berührungsloser Detektion ........................................... 70 4. Ergebnisse und Diskussion...........................................................................................71 4.1. Synthese und Eigenschaften von nanoskaligen Materialien......................................72 4.1.1. Synthese von Bi2MO6 (M = Mo, W) Nanopartikeln................................................. 72 4.1.2. Nanokompositmaterialien mit Bi2MO6 (M = Mo, W)................................................ 81 4.1.3. Synthese der Bismuttitanate Bi4Ti3O12 und Bi2Ti2O7 .......................................... 84 4.1.4. Herstellung von Dünnschichten der Systeme Bi2MO6 (M = Mo, W), Bi4Ti3O12 und Sr0.75Ba0.25Nb2O6 ................. 88 4.2. Funktion der nanoskaligen Materialien .....................................................................100 4.2.1. Bismuthaltige Nanopartikel in der Photokatalyse ..................................................100 4.2.2. Spark-Plasma-Sintern von Bi2MO6-Nanopartikel (M = Mo, W)................................103 4.2.3. Elektrooptische Eigenschaften von Dünnschichten und Kompositmaterialien ............................................................108 4.2.4. Messung der Dampfadsorption an Bi2MO6 (M = Mo, W)-Nanopartikeln mit Hilfe berührungsloser Detektion ............114 4.3. Synthese von BiOH(C2O4), BiO(CH3COO) und Bi(CH3COO)3....................................118 5. Zusammenfassung ......................................................................................................127 6. Ausblick .......................................................................................................................131 7. Literatur ......................................................................................................................132 8. Abbildungs- und Tabellenverzeichnis ..........................................................................146 8.1. Abbildungsverzeichnis...............................................................................................146 8.2. Tabellenverzeichnis...................................................................................................152 9. Anhang ........................................................................................................................154 9.1. Synthese und Eigenschaften von nanoskaligen Materialien......................................155 9.1.1. Solvothermalsynthese von Bi2MO6 (M = Mo, W).....................................................155 9.1.2. Phasentransfersynthese von Bi2MO6 (M = Mo, W).................................................156 9.1.3. Synthese der Bismutmolybdate Bi4Ti3O12 und Bi2Ti2O7 .......................................156 9.1.4. Herstellung von Dünnschichten der Systeme Bi2MO6 (M = Mo, W), Bi4Ti3O12 und Sr0.75Ba0.25Nb2O6 .................159 9.2. Funktion der nanoskaligen Materialien ......................................................................164 9.2.1. Spark-Plasma-Sintern..............................................................................................164 9.2.2. Elektro-optische Eigenschaften von Dünnschichten und Kompositmaterialien .........................................................166 9.2.3. Messung der Dampfadsorption an Bi2MO6 (M = Mo, W)-Nanopartikeln mit Hilfe berührungsloser Detektion ...........174 9.3. Synthese von BiOH(C2O4), BiO(CH3COO) und Bi(CH3COO)3.....................................175 9.3.1. DTA-TG-Ergebnisse .................................................................................................175 9.3.2. Kristalldaten und Strukturverfeinerung ...................................................................177 9.4. Quelltexte ..................................................................................................................181 9.4.1. MATLAB-Skript zur Auswertung elektrooptischer Koeffizienten................................181 9.4.2. MATLAB-Skript zur Auswertung dampfadsorptiver Eigenschaften............................182

This thesis is motivated by the idea, to implement functional building blocks with silicon nanoparticles by means of printable electronics. Hence, the topic of this work is the investigation of the charge transport in thin layers made of silicon nanoparticles. As model systems commercially available as well as self prepared silicon nanoparticles were used and modified with different organic surface functionalities. In the first part of this work the surface modification of commercially available silicon nanoparticles synthesized in the gas phase is described: Initially, the surface oxide of the 20 nm large nanoparticles was removed by means of etching with acidic fluorine-containing solutions. Subsequently, the resulting hydrogen-terminated surface was modified via hydrosilylation using different 1-alkenes. In the second part of this work the preparation of modified silicon nanoparticles in liquid phase is observed: Based on silicon tetrachloride hydrogen-terminated silicon nanoparticles with a size between 1.2 nm and 4.5 nm as well as chlorine-terminated silicon nanoparticles with a size between 2 nm and 6 nm wered synthesized as intermediate and subsequently modified using hydrosilylation or silanization, respectively. The electrical characterization of thin layers made of modified silicon nanoparticles was performed using impedance spectroscopy. With regard to apply modified silicon nanoparticles as active material using printable electronics it was shown that the electrical transport in thin and compact layers made of the nanoparticles is thermically activated and, in the relevant area of room temperature, could be described using an ARRHENIUS approach. The activation energies were in the range of a half electron volt and could be influenced by thickness and permittivity of the organic modification. As electron transport mechanism nearest neighbor hopping was identified, as it was expected for a statistically distribution of localized states in the considered temperature range.

The spatial dimensions of nanoparticles resemble those of biomolecules. The properties of nanoparticles can be adjusted by chemical synthesis and the particles are good sensors and actuators of biomolecular processes. By attaching biomlecules to nanoparticles they can be marked selectively, signals can be tapped from and transmitted to them. Gold nanoparticles with a diameter of two up to circa 100 nm are characterised by their intensive light absorption which is caused by excitation of collective oscillations of valence band electrons, the so called plasmon resonance. The plasmon resonance wavelength is, amongst others, a function of the direct particle environment such that changes therein can be monitored spectroscopically. In this thesis, biomolecule gold nanoparticle hybrid materials are shown to not only be a sensor but also an actuator of biomolecular processes on the nanoparticle surface. Therefore, biomolecule nanoparticle suspensions were irradiated by continuous laser light and simultaneously monitored by UV/Vis spectroscopy. First, DNA double strand functionalized gold nanoparticles were investigated. The aim was to induce DNA dissociation by photothermally heating the particles but the temperature dependence of the optical properties of the applied aggregates was considered to low to give unambiguous results. Then, DNA double strand gold nanoparticle networks were analyzed. They exhibited a spectral blueshift of the plasmon resonance wavelength by several nm when heated a few °C. Here, DNA dissociation could be triggered photothermally without markedly damaging the DNA molecules. Using in situ UV/Vis spectroscopy this could be monitored and it was possible to quantify the photothermal temperature increase in DNA melting experiments. Also, first evidence was found that the photothermal temperature increase was a function of the goldnanoparticle network size. Further, using horse radish peroxidase functionalized gold nanoparticles an enzymatic oxidation reaction was successfully manipulated for the first time. Again, this was monitored using in situ UV/Vis spectroscopy and by comparing the activity of non-irradiated and irradiated enzyme nanoparticle suspensions the photothermal temperature increases was determined.

The area of electrochemistry of non aqueous non-polar liquids has not been intensely studied. Coming from the issue of electrochemical sensors on non-polar liquids the analysis of lubrication oils in the engine of a motor vehicle was taken as an example. The investigation of electrode materials in these media appears interesting from a scientific as well as from a technical approach. An overview of the basics of oil chemistry emphases the importance of additives for the formulation of lubricating oils. These improve the characteristics of the carbon hydrates in important areas (viscosity, stability etc.), and make the quality of modern engine oils possible. With the introduction of a controlled aging process of the oils in combination with a classical wet chemical analysis the fabrication of oils with defined grades of degradation was possible. First, an overview of known technical concepts on oil condition measurement was given. This broad field of physical and electrochemical methods was enlarged by the first application of the SPME technique. With this method, polar substances were identified in the gas phase of the oil. Through gas and mass chromatography it was shown that these substances were mainly additives, their by-products and organic acids. The amount of these changes with ongoing aging of the oil and can thereby be used as an indicator for the oil condition. Only organic acids with seven carbon atoms or more were detected. These organic acids should be detected via a simple and robust sensor. Looking back at the known measurement concepts, potentiometry was identified and the electrochemical basics were shown. For the fabrication of the electrodes materials were used that are known to show a pH-sensitive behaviour: iridium(IV) oxide, ruthenium(IV) oxide and antimony electrodes were produced using screen printing, sputtering and galvanic deposition. The electrodes were then physically characterized. From the area of gas sensors it is known that often no rational parameters can be given for the tuning of the desired performance of the sensor. Small changes during fabrication or the microstructure of the sensor can have grave influence on the performance. This fact founded the area of combinatorial chemistry. In view of this area, concepts were developed to also use this approach in this work. A combinatorial screen printing technique was implemented and combined with a robotic based measurement of these substrates. The sensors were electrochemically characterized. First, their principal function in water was demonstrated. There, the sputtered sensors should a response closest to the theoretical Nernstian behaviour. As model media for non-polar fluids with low permittivity decane was chosen. Here, the screen printed iridium(IV) oxide sensor showed the best performance. A measurement in oil also showed a changing potential when the acid content was changed. This potential change though was going in the other direction as with water and decane. Finally, a qualitative model of the electrochemical reactions was developed. With some systems, the behaviour could be explained. The different course of the potential in oil can be explained by the adsorption of additive molecules to the surface of the electrode. Therefore, only secondary reactions can be seen there which are due to residual water on the surface and certain additives in the oil.

For the development of new gas sensor materials surface and volume doped nanoscalic metal oxides were investigated, whereas high-throughput techniques were applied. The necessary synthesis and characterisation methods were provided by modification of a pipetting robot for a parallel material synthesis and sample deposition on special multi-electrode substrates, as well as the further development of a screening reactor and single sensor test station. Making use of the polyol method opened a simple synthetic access to nanoscalic metal oxides like ZnO, In2O3 and SnO2, which were used as basic materials for the preparation of highly diverse functionalised surface and volume doped material libraries. To acquire their sensoric properties a screening program was used which comprised of test gases of H2, CO, NO, NO2 and C3H6 in synthetic air in the temperature range from 523 to 673 K. To analyse the resulting high amounts of data the Q/S-plot was developed and applied, which enables by comparing the relative selectivity and sensitivity a fast visual identification of the best promising material combinations. As an example doping by silver cluster led to a distinct increase of the sensitivity of various metal oxides against hydrogen; a mixture of rhodium, gold and palladium increased the sensoric properties of SnO2 towards the detection of CO, whereas using silver as a dopant increased distinctly the response to NO2. These screening results were further investigated by making use of single sensor elements, whereas e.g. the silver doped SnO2 showed an extrapolated limit of detection of about 100 ppb of NO2.

This PhD thesis deals with the development of a measuring system, that allows determining, in analogy to the well-known temperature-programmed desorption measurement of NH3 (NH3-TPD), the acidic properties of zeolites (H-ZSM-5 with SiO2/Al2O3 ratios from 30 to 1000). This new method, denoted IS-TPD, is based on a combination of NH3-TPD with impedance spectroscopy measurements (IS). The IS-TPD new method, with a zeolite sensor, is used for the NH3 detection instead of the usual one based on gas chromatography, whose functionality is based on the impedance spectroscopic measurement of the proton conductivity. With these developments it was possible to refinement the known mechanistic picture to the adsorption behaviour of NH3 in H-form-zeolites, which finally led to a new understanding of the functional principle of NH3-Sensors based on H-form-zeolites. Both impedance and NH3-TPD measurements were accomplished to provide a basis for the methodical development of the IS-TPD. The results of these measurements as well as the detailed picture of a model for the ammonia supported proton transport, which were developed in the so far completely independently regarded methods, provided a consistent picture of the supported proton transport mechanism in zeolites. Hence, the transition of a Grotthus-like, vehicle and hopping mechanisms, respectively, depending on the loading of the sample with NH3, was derived from the impedance measurements. These are compatible with the interpretation of the NH3-TPD profiles. This again forms the basis for the following combination of the two methods for the development of a new IS-TPD measuring system. Therein, the zeolite samples were coated in form of a thick-film on a directly heated inter-digital capacitor (idc) chip, with which the sample quantity was reduced of approximately 80 mg by the NH3-TPD to 0,5 mg. The outcome of this was a clearly smaller time of contact with same flow rate. This was manifested in a shift of the desorption maxima around 60°C (for the low temperature (LT) peak) and around 90°C (for the high temperature (HT) peak) and is to be explained by decreased readsorption. Furthermore it was found that the quantity of desorbed NH3 became smaller for each Brønsted acid site with decreasingly SiO2/Al2O3 ratios. This disagreed in first glance to the assumption that the samples were saturated with NH3. Hence, a new model picture for the functionality of the zeolite sensors was derived, which included the fact that the saturation measured by means of IS corresponds presumanly just to a saturation within surface-near range, which in this work was denoted “electrical saturation”. Accordingly, the samples will already achieve a constant impedance value in ammonia, if the conductivity within near-surface by far exceeds the volume saturation. In this case a further volume saturation obviously does not lead to a further increase of the conductivity. For model verification in the new IS-TPD measuring system the zeolites H-Y and H-beta were investigated, which showed similar behaviour than H-ZSM-5. Thus the work represents a new experimental basis for the characterisation of Brønsted acid sites in solids.

This work shows the synthesis and characterization of one-, two- and three-dimensional DNA-gold-nanoparticle hybridstructures, whereby DNA serves as a building block. The main part of this work focuses on structural characterizations, which are a big challenge to the available imaging and spectroscopic methods like atomic force, scanning electron and optical microscopy. The synthesis of one-dimensional assemblies was realized by the reduction of metal salt solutions at the backbone of DNA. Another strategy was the connection of pre-synthesized, cysteamine functionalized gold-nanoparticles along DNA strands, whereby the connection was done by using cis-platinum as linker. The resulting structures were characterized by TEM, SEM and AFM. While electron microscopy only allows to visualize the gold nanoparticles, AFM height and phase information was used to verify both DNA and particles. The two-dimensional structures, built up from immobilized and cross-linked gold-nanoparticles with DNA, were investigated by AFM and UV/Vis-spectroscopy. The attention was directed to the influence of the amount of crosslinking DNA and the resulting degree of aggregation, which led to two-dimensional assemblies. Here, a qualitative connection between structural and optical features was shown.

This thesis deals with two- and threedimensional assemblies of ligand stabilised gold nanoparticles and their distance dependent electric properties. The assemblies were built up by DNA-hybridisation, covalent attachment and electrostatic attraction. The thesis delineates the nanoparticle synthesis, the assembly into two- and three-dimensional particle systems, the structural characterisation via scanning probe and scanning electron microscopy and the investigation of the electric properties by direct current measurements and temperature dependent impedance spectroscopy.It is reported that two- and three-dimensional samples show thermally activated conductivity with Arrhenius-like behaviour. This allows for a calculation of activation energies which are significantly determined by inter-particle distances and the sample disorder.Further on the thesis describes impedance spectroscopical capacitance measurements performed on multilayers consisting of Au55-cluster double layers and silicon oxide layers with varying thickness. These cluster/SiOx-composite systems reveal a distinct thermally activated frequency dependence of the sample permittivity which is caused by interactions of the cluster layers via dipoles that can be formed in the double layers. The cluster/SiOx- systems show a significant increase of the permittivity with increasing number of layers and temperature dependent capacity measurements indicate a thermal activation of these polarisation processe inside the cluster layers.

Bedingt durch die stete Zunahme des Kraftfahrzeugverkehrs in den vergangenen Jahrzehnten hat die Umweltbelastung durch das Gas NO extrem zugenommen. Derzeit ist jedoch noch kein technisch relevanter NO-Sensor für den Einsatz im heißen Kfz-Abgas bekannt. In einem Patent von C. Plog et al. aus dem Jahr 1997 wird eine NO-beta"-Al2O3-Keramik zur Konstruktion eines einfachen potentiometrischen NO-Sensors ähnlich der bekannten Lambdasonde vorgeschlagen. Im Rahmen der vorliegenden Arbeit wurden die Optimierung des Sensormaterials hinsichtlich Austauschgrad versucht sowie impedanzspektroskopische Untersuchungen zur ihrer Wechselwirkung mit NOx zum Verständnis der Sensorfunktion durchgeführt. Der NO+-Austausch in Keramiken der Schichtstruktur Na-beta"-Al2O3 und der drei-dimensionalen Kanalstruktur von kubischem KSbO3 erfolgte in der Schmelze des NO+-haltigen Addukts NOCl?AlCl3. Anhand der Bestimmung des Restnatrium- bzw. Restkaliumgehaltes konnte der vollständige NO+-Austausch in der Schmelze nach-vollzogen werden. Jedoch konnte dieses Rohprodukt infolge des Einbaus von H3O+ bei der Aufarbeitung nicht isoliert werden. Na,NO-beta"-Al2O3 ist bis ca. 100°C beständig, (K,NO)SbO3 bis ca. 300°C. Wie temperaturabhängige impedanzspektroskopische Untersuchungen an Na-beta"-Al2O3-Pulverpreßlingen zeigten, wurde die Aktivierungsenthalpie des Korngrenz-prozesses in Gegenwart von NO unterhalb von 550°C durch der Bildung von NaNO2- und NaNO3-Sekundärphasen an den Korngrenzen bestimmt. Bei partialdruck-abhängigen Untersuchungen bei 800°C nahm die Korngrenzleitfähigkeit mit dem NO-Partialdruck zu, was auf das Ausheilen thermisch bedingter Sauerstoffdefekte an den Korngrenzen zurückgeführt werden konnte. Hingegen wurde KSbO3 in Gegenwart von NO infolge der Reduktion von Sb-V zu Sb-III zum gemischten Elektronen-/Ionenleiter, worauf das uneinheitliche Leitfähigkeitsverhalten hindeutete. Somit kann abschließend gesagt werden, daß Na,NO-beta"-Al2O3 und (K,NO)SbO3 als Material zur Konstruktion eines NO-Sensors im heißen Kfz-Abgas aufgrund ihrer Temperaturstabilität nicht uneingeschränkt eingesetzt werden können. Dissertation, Universität Duisburg-Essen, 2001