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Eingeladener Vortrag
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Die feuchte Wundbehandlung ist ein elementarer Bestandteil zeitgemäßer Wundversorgung. Bereits im 19. Jahrhundert wandte F. Hebra in Wien kontinuierliche Wasserbäder bei brandverletzten Patienten erfolgreich an. G. D. Winter zeigte 1962 erstmals experimentell am Schwein, dass es unter einem Okklusivverband innerhalb kürzerer Zeit zu einer vollständigeren Epithelisierung kommt als bei Luftexposition. Bei der Entwicklung von liposomalen Hydrogelen mit wundheilenden Eigenschaften kann somit das Verhalten der Wasserabgabe an die Haut bzw. das Abdampfverhalten von Wasser - bis hin zum Eintrocknen des Gels - ein qualitätsrelevanter Parameter sein. In diesem Rahmen wurde die Anwendungsbreite der Wasserdampfsorption auf halbfeste pharmazeutische Zubereitungen erweitert, um das Abdampfverhalten näher zu untersuchen und quantifizieren zu können.
Für die Untersuchungen wurden drei unterschiedlich hergestellte bzw. gelagerte wundheilende Gele verwendet.
Dazu wurden Wasserdampfsorptionmessungen an Hydrogelen unterschiedlicher Chargen durchgeführt. Die eingewogenen Proben wurden mit 2 unterschiedlichen DVS-Varianten vermessen:
1. bei einer konstanten Feuchte von 50% relativer Feuchte (r. F.)
2. mit einem vorgegebenen definierten Feuchteprofil (zunächst abnehmende Feuchte von 95% bis 0% r. F. in 5%-Schritten und danach analoger Wiederanstieg auf das Ausgangsniveau).
Eine vergleichbare Oberfläche wurde unter Verwendung einer definierten Tropfengröße (Spritze) erreicht. Jeweils durchgeführte Doppelbestimmungen zeigen die gute Reproduzierbarkeit der Messungen.
Zur Charakterisierung des Abdampfverhaltens wurden die Wasserdampfadsorptionsmessungen bezüglich des prozentualen Masseverlustes (m in %) und der Dynamik (dm/dt in %·min-1) ausgewertet. Zwei sehr ähnlich hergestellte Gele wiesen ein fast identisches Abdampfverhalten auf, der Masseverlust des dritten Gels war verlangsamt. Insbesondere bei den Versuchen unter konstanter relativer Feuchte zeigte Gel 3 eine deutlich abweichende Dynamik des Masseverlustes. Bei definiertem Feuchteprofil traten analoge Unterschiede auf.
Es konnten mit Hilfe der DVS-Methode gelspezifische Unterschiede bezüglich des Abdampfverhaltens des Wassers infolge einer veränderten Mikrostruktur der untersuchten Gele nachgewiesen werden. Auf der Grundlage dieser Informationen ist es möglich, maßgeschneiderte Hydrogele mit einem definierten Abdampfverhalten herzustellen und dadurch die Produkteigenschaften wundheilender Hydrogele zu verbessern.
Rare-earth based luminescent materials are key functional components for the rational design of light-conversion smart devices. Stable Eu3+-doped strontium fluoride (SrF2) nanoparticles were prepared at room temperature in ethylene glycol. Their luminescence depends on the Eu content and changes after heat treatment. The crystallinity of heat-treated material increases in comparison with as-synthesized samples. Particles were investigated in solution using X-ray diffraction, small-angle X-ray scattering, and X-ray spectroscopy. After heat treatment, the size of the disordered nanoparticles increases together with a change of their local structure. Interstitial fluoride ions can be localized near Eu3+ ions. Therefore, non-radiative relaxation from other mechanisms is decreased. Knowledge about the cation distribution is key information for understanding the luminescence properties of any material.
A facile and efficient methodology is described for the solvothermal synthesis of size-tunable, stable, and uniform NiCu core–shell nanoparticles (NPs) for application in catalysis. The diameter of the NPs is tuned in a range from 6 nm to 30 nm and to adjust the Ni:Cu ratio from 30:1 to 1:1. Furthermore, the influence of different reaction parameters on the final NPs is studied. The NPs are structurally characterized by a method combination of transmission electron microscopy, anomalous small-angle X-ray scattering, X-ray absorption fine structure, and X-ray photoelectron spectroscopy. Using these analytical methods, it is possible to elucidate a core–shell–shell structure of all particles and their chemical composition. In all cases, a depletion from the core to the shell is observed, with the core consisting of NiCu alloy, surrounded by an inner Ni-rich shell and an outer NiO shell. The SiO2-supported NiCu core–shell NPs show pronounced selectivity of >99% for CO in the catalytic reduction of CO2 to CO using hydrogen as reactant (reverse water–gas shift reaction) independent of size and Ni:Cu ratio.
In order to identify the best porous materials for the cryogenic physisorption of hydrogen, high-throughput calculations are performed starting, i.e., from the collected information in crystallographic databases. However, these calculations, like molecular simulations, require specific training and significant computational cost. Herein, a relatively simple procedure is proposed to estimate and compare hydrogen uptakes at 77 K and pressure values from 40 bar starting from the porous properties of MOF materials, without involving simulation tools. This procedure uses definitions for adsorption and considers the adsorbed phase as an incompressible fluid whose pressure-density change is that for the liquid phase at 19 K. For the 7000 structures from the CoRE MOF database, the average error of the predictions is only of 1% from reference values at 100 bar, with an SD of ±8%. This accuracy is lower than that from simulation tools, but involving lower computational cost and training.
Lanthanides doped coordination polymers (CPs) with different binding motifs were synthesized to investigate the influence of the different fluorine positions in the structure on the decay time τ of the excited states. Fluorine can be integrated into the network mechanochemically via a fluorinated organic linker, here barium tetrafluoroterephthalate Ba(p-BDC-F4)2 or directly via a metal-fluorine bond (barium terephthalate fluoride BaF(p-BDC)0.5). The CP with a metal-fluorine bond shows the highest lifetime of the excited states of lanthanides (Eu3+, Tb3+ or Eu3+& Tb3+). The excitation of the lanthanides can be performed directly via the excitation wavelength typical for lanthanides and via the excitation wavelength of the linker. This enabled the simultaneous excitation of Eu3+ and Tb3+ in one CP. In the emission spectra (λem = 393 nm) of the mixed doped CPs (Eu3+ and Tb3+) the bands of both lanthanides can be observed. The integration into the crystal lattice and the homogeneous distribution of the lanthanides in the CPs is shown by X-ray diffraction, TEM, STEM-EDS measurements and the long decay times.
Zeolitic imidazolate framework (ZIF) hybrid fluorescent nanoparticles and ZIF antibody conjugates have been synthesized, characterized, and employed in lateral-flow immunoassay (LFIA). The bright fluorescence of the conjugates and the possibility to tailor their mobility gives a huge potential for diagnostic assays. An enzyme-linked immunosorbent assay (ELISA) with horseradish peroxidase (HRP) as label, proved the integrity, stability, and dispersibility of the antibody conjugates, LC-MS/MS provided evidence that a covalent link was established between these metal-organic frameworks and lysine residues in IgG antibodies.
Zeolite synthesis was studied using two silica rich filtration residues (FR 1 and FR 2) as Si-source
and sodium aluminate in a direct synthesis at 60°C at strong alkaline conditions (8 M - 16 M NaOH).
In addition to these one-pot syntheses, a two-step process was investigated. Here, an alkaline digestion
of FR at 60°C was followed by gel precipitation with sodium aluminate and gel crystallization
under usual conditions of 80°C - 90°C. The results show that the substitution of chemical
reagent sodium silicate by a waste material like FR as Si-source is possible but requires fine tuning
of the reaction conditions as zeolite crystallization is a process under kinetic control. The
solubility behaviour and impurities of the inserted filtration residues strongly influenced the
course of reaction. Thus zeolites like hydrosodalite or intermediate zeolite between cancrinite
and sodalite, or zeolite NaA or Z-21 in cocrystallization with hydrosodalite could be observed in
the one pot syntheses already in a short time interval between 1 - 4 h depending on the alkalinity.
The two step process yield to zeolites NaA and NaX in very good quality. The reaction process of FR
in both reaction methods was characterized by chemical analyses, X-ray powder diffraction,
Fourier transform infrared spectroscopy as well as scanning electron microscopy. Surface area
and water content of selected products were further characterized by the BET-method and by
thermogravimetry. Summing up the results, we can show that zeolite formation from filtration residues
is possible by several reaction procedures as model cases for a re-use of industrial waste
materials. Beside the importance for environmental protection, the reactions are of interest for
zeolite chemistry as the re-use of FR is possible under economically conditions of low energy consumption
at 60°C and short reaction periods.
The pore structure of lightweight granules made from masonry rubble was studied in order to better understand their engineering properties. Thermally and hydrothermally hardened granules were tested. Analysis by ESEM, mercury porosimetry and sorption methods yield important insight into their microstructure. The thermal granules are characterised by partly melted vitreous areas and large internal macropores that are connected via narrow throats. They show a marginal specific surface area along with a hydrophobic behaviour. In contrast, the hydrothermal granules have an accessible mesoporous system containing plate-like and ink-bottle pores. The shape of their water isotherms depending on the granules CaO content is sensitive to the morphology of calcium silicate hydrate phases (CSH). The hysteresis changes from a narrow loop that closes at low pressures, which can be attributed to coarser more crystalline CSH, to a large triangular-shaped loop along with a low pressure hysteresis, which is characteristic for fine fibre-like CSH with ink-bottle and plate-like pore morphologies. Granules with fibre-like CSH have the higher specific surfaces areas but those with more crystalline CSH show stronger physisorption of water molecules.