Inorganic-Organic Hybrid Compounds: Discovery, Optimisation, Characterisation and Application

Diese Dissertation beschäftigt sich mit der Synthese neuer und der Syntheseoptimierung bekannter aluminiumhaltiger Metall-Organischer Gerüstverbindungen (Al-MOFs) sowie der Implementierung ultraschallgestützter Synthesen in den Arbeitsablauf der Hochdurchsatzmethodik. Das System AlCl3*6H2O/cis-H2CDC/trans-H2CDC/Lösemittel (H2CDC: 1,4-Cyclohexandicarbonsäure) wurde mit den am Arbeitskreis etablierten Hochdurchsatzmethoden, die auf auf solvothermale Reaktionen spezialisiert sind, untersucht. Es wurden zwei neue kristalline Verbindungen gefunden, die aus Ketten trans-eckenverknüpfter AlO6-Oktaeder aufgebaut sind, welche über entweder cis- oder trans-CDC2--Ionen miteinander verknüpft sind. Bei der Verbindung, die trans-CDC2--Ionen enthält, handelt es sich um einen mikroporösen MOF mit interessanten Sorptionseigenschaften: In Abhängigkeit der Menge und Art eingelagerter Gastmoleküle ändert sich das Elementarzellvolumen und damit die Gitterpositionen der Atome reversibel und ohne merklichen Verlust der Kristallinität - [Al(OH)(trans-CDC)] (genannt CAU-13) "atmet". Neben der detaillierten Aufklärung der Eigenschaften von CAU-13 wurden auch kinetische Untersuchungen zur Kristallisation mittels in-situ-EDXRD (energiedispersive Röntgenbeugung) durchgeführt. An CAU-13 wurde der Einsatz des auf dem lokalen Optimierungs-Algorithmus BOBYQA basierenden Computerprogramms CHRYSOP zur gezielten Verkleinerung der Partikelgröße erprobt. Die Partikelgröße von [Al4(OH)2(OCH3)4(BDC-NH2)3]*xH2O (CAU-1-NH2) wurde in Abhängigkeit der Änderung physikalischer und chemischer Parameter untersucht. Der Einsatz einer Monocarbonsäure als Modulator zeigte eine Verkleinerung der kristallinen Domänen des Produkts bei nahezu gleichbleibendem hydrodynamischen Durchmesser der Partikel. Durch unregelmäßigere Partikelform wurden hierarchische Mesoporen in diesen Produkten generiert. Die Erkenntnisse aus dieser Studie wurden genutzt, um Dispersionen von CAU-1-NH2 herzustellen, die für den Aufbau photonischer Kristalle, sogenannter Bragg-Stacks eingesetzt wurden. Zur Untersuchung des Systems CaCl2*6H2O/H2O3P-C(OH)(CH3)-PO3H2(HEDP)/H2O/KOH wurden Hochdurchsatzmethodik und ultraschallgestützte Synthese kombiniert. Es wurden drei neue Verbindungen, [Ca(HO3P-C(OH)(CH3)-PO3H)(H2O)]*2.5H2O, [CaK(HO3P-C(OH)(CH3)-PO3)(H2O)]*H2O und [CaK2(O3P-C(OH)(CH3)-PO3)(H2O)6], in Abhängigkeit des pH-Wertes des Reaktionsgemisches und der Reaktionszeit erhalten. Die ultraschallgestützten Synthesen wurden mit Synthesen bei erhöhten Temperaturen und unter Bewegung des Reaktors verglichen. Es konnte gezeigt werden, dass der Haupteinfluss des Ultraschalls auf die Reaktionsbeschleunigung in der besseren Durchmischung der Edukte und der schnelleren Auflösung fester Intermediate liegt.This thesis deals with the synthesis of new and the synthesis optimisation of known aluminum containig Metal-Organic Frameworks (Al-MOFs) as well as the implementation of ultrasound-assisted syntheses into a high-throughput workflow. The system AlCl3*6H2O/cis-H2CDC/trans-H2CDC/solvent (H2CDC: 1,4-cyclohexanedicarboxylic acid) was explored applying high throughput methods specially made for the investigation of solvothermal reactions. Two new crystalline compounds built up of chains of trans-corner sharing AlO6-octahedra were discovered. The chains are either connected by cis- or trans-CDC2- ions. The compound based on trans-CDC2- is a microporous MOF with interesting sorption properties: Depending on the presence of guest molecules the unit cell volume and atomic positions change reversibly and without a remarkable loss of crystallinity - [Al(OH)(trans-CDC)] (denoted CAU-13) "breathes". Besides the detailed characterisation of the properties of CAU-13 investigations on the crystallisation kinetic were performed with in situ EDXRD experiments. Furthermore the computer program CHRYSOP based on the local optimisation algorithm BOBYQA was used to reduce the particle size of CAU-13. The influence of certain physical and chemical reaction parameters on the particle size of [Al4(OH)2(OCH3)4(BDC-NH2)3]*xH2O (CAU-1-NH2) was also determined. The use of a monocarboxylic acid as modulator allowed to decrease the size of the product's crystalline domains while maintaining the particles' hydrodynamic diameter. By the irregular shape of the particles hierarchical mesopores were generated in these products. The findings of this study were used to prepare dispersions of CAU-1-NH2, which were apllied in the construction of photonic crystals, so called Braggs Stacks. To investigate the system CaCl2*6H2O/H2O3P-C(OH)(CH3)-PO3H2(HEDP)/H2O/KOH high-througput methods were combined with the concept of ultrasound-assisted synthesis. Three new crystalline compounds, Ca(HO3P-C(OH)(CH3)-PO3H)(H2O)]*2.5H2O, [CaK(HO3P-C(OH)(CH3)-PO3)(H2O)]*H2O and [CaK2(O3P-C(OH)(CH3)-PO3)(H2O)6], were found depending on the pH of the reaction mixture and the sonication time. The ultrasound-assisted syntheses were compared to syntheses carried out at elevated temperatures and under agitation. It was found that the main contribution of ulrasound to the increased reaction times is due to better mixing and the faster dissolution of solid intermediates

Technologieentwicklung und -unterstützung für Ionenfallenbasierte-Quantencomputer (TeufIQ)

The project TeufIQ aims to support the companies located at the Innovation Center Hamburg (IZHH) in providing research service to build ion-trap quantum computers. Building on the expertise and background in micro- and nanotechnology of the DLR division QTIMN, we address in close collaboration with the industry partners, open research questions and develop technologies facilitating iontrap based quantum computers

Technologieentwicklung und -unterstützung für Ionenfallenbasierte Quantencomputer (TeufIQ)

Purpose of the TeufIQ project is to support the industrial partners of QC-I in developing and manufacturing prototypes of ion-trap based quantum computers. The project framework encompasses a wide range of research services for the QC-I partners placed at the Innovation Center Hamburg (IZHH). The project’s foundation is the expertise and the experience in micro- and nanotechnology of the DLR division QT-IMN in Ulm. We particularly address close collaboration working on open research questions and the development of related technological solutions to facilitate the production of ion-trap based quantum computers in future

Combined in situ mechanical testing and scale-bridging 3D analysis of nanoporous gold

In this work we present results on in situ small scale testing of nanoporous gold (npg) in scanning electron microscopy (SEM) and transmission electron microscopy (TEM). By combining nano- and micromechanical testing of pillar structures with advanced tomographic imaging, a 3D characterization of the plastic deformation process in different states of deformation is achieved. For small strut sizes 360° electron tomography (ET) is applied enabling high quality reconstructions of the 3D morphology of npg without missing-wedge artefacts. Combining the geometric information with mechanical data from in situ testing in SEM and TEM the yield strength is precisely determined. Furthermore, the experimentally derived 3D data are used as input for large-scale molecular dynamics (MD) simulations in order to understand the role of strain localization and identify predominant defect processes. Please click Additional Files below to see the full abstract

Thin-Film-Based SAW Magnetic Field Sensors

In this work, the first surface acoustic-wave-based magnetic field sensor using thin-film AlScN as piezoelectric material deposited on a silicon substrate is presented. The fabrication is based on standard semiconductor technology. The acoustically active area consists of an AlScN layer that can be excited with interdigital transducers, a smoothing SiO2 layer, and a magnetostrictive FeCoSiB film. The detection limit of this sensor is 2.4 nT/Hz at 10 Hz and 72 pT/Hz at 10 kHz at an input power of 20 dBm. The dynamic range was found to span from about ±1.7 mT to the corresponding limit of detection, leading to an interval of about 8 orders of magnitude. Fabrication, achieved sensitivity, and noise floor of the sensors are presented

Ultrasensitive Magnetoelectric Sensing System for pico-Tesla MagnetoMyoGraphy

MagnetoMyoGraphy (MMG) with superconducting quantum interference devices (SQUIDs) enabled the measurement of very weak magnetic fields (femto to pico Tesla) generated from the human skeletal muscles during contraction. However, SQUIDs are bulky, costly and require working in a temperature-controlled environment, limiting wide-spread clinical use. We introduce a low-profile magnetoelectric (ME) sensor with analog frontend circuitry that has sensitivity to measure pico-Tesla MMG signals at room temperature. It comprises magnetostrictive and piezoelectric materials, FeCoSiB/AlN. Accurate device modelling and simulation are presented to predict device fabrication process comprehensively using the finite element method (FEM) in COMSOL Multiphysics®. The fabricated ME chip with its readout circuit was characterized under a dynamic geomagnetic field cancellation technique. The ME sensor experiment validate a very linear response with high sensitivities of up to 378 V/T driven at a resonance frequency of fres = 7.76 kHz. Measurements show the sensor limit of detections of down to 175 pT/Hz at resonance, which is in the range of MMG signals. Such a small-scale sensor has the potential to monitor chronic movement disorders and improve the end-user acceptance of human-machine interfaces

MEMS magnetic field source for frequency conversion approaches for ME sensors

Some magnetoelectric sensors require predefined external magnetic fields to satisfy optimal operation depending on their resonance frequency. While coils commonly generate this external magnetic field, a microelectromechanical systems (MEMS) resonator integrated with permanent magnets could be a possible replacement. In this proof-of-concept study, the interaction of a MEMS resonator and the ME sensor is investigated and compared with the standard approach to achieve the best possible sensor operation in terms of sensitivity. The achievable sensor sensitivity was evaluated experimentally by generating the magnetic excitation signal by a coil or a small-sized MEMS resonator. Moreover, the possibility of using both approaches simultaneously was also analysed. The MEMS resonator operated with 20 Vpp at 1.377 kHz has achieved a sensor sensitivity of 221.21 mV/T. This sensitivity is comparable with the standard approach, where only a coil for sensor excitation is used. The enhanced sensitivity of 277.0 mV/T could be identified by generating the excitation signal simultaneously by a coil and the MEMS resonator in parallel. In conclusion, these MEMS resonator methods can potentially increase the sensitivity of the ME sensor even further. The unequal excitation frequency of the MEMS resonator and the resonance frequency of the ME sensor currently limit the performance. Furthermore, the MEMS resonator as a coil replacement also enables the complete sensor system to be scaled down. Therefore, optimizations to match both frequencies even better are under investigation

Non-destructive detection of cross-sectional strain and defect structure in an individual Ag five-fold twinned nanowire by 3D electron diffraction mapping

Coherent x-ray diffraction investigations on Ag five-fold twinned nanowires (FTNWs) have drawn controversial conclusions concerning whether the intrinsic 7.35° angular gap could be compensated homogeneously through phase transformation or inhomogeneously by forming disclination strain field. In those studies, the x-ray techniques only provided an ensemble average of the structural information from all the Ag nanowires. Here, using three-dimensional (3D) electron diffraction mapping approach, we non-destructively explore the cross-sectional strain and the related strain-relief defect structures of an individual Ag FTNW with diameter about 30 nm. The quantitative analysis of the fine structure of intensity distribution combining with kinematic electron diffraction simulation confirms that for such a Ag FTNW, the intrinsic 7.35° angular deficiency results in an inhomogeneous strain field within each single crystalline segment consistent with the disclination model of stress-relief. Moreover, the five crystalline segments are found to be strained differently. Modeling analysis in combination with system energy calculation further indicates that the elastic strain energy within some crystalline segments, could be partially relieved by the creation of stacking fault layers near the twin boundaries. Our study demonstrates that 3D electron diffraction mapping is a powerful tool for the cross-sectional strain analysis of complex 1D nanostructures