03 Fakultät Chemie
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/4
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Item Open Access Designing covalent organic framework‐based light‐driven microswimmers toward therapeutic applications(2023) Sridhar, Varun; Yildiz, Erdost; Rodríguez‐Camargo, Andrés; Lyu, Xianglong; Yao, Liang; Wrede, Paul; Aghakhani, Amirreza; Akolpoglu, Birgul M.; Podjaski, Filip; Lotsch, Bettina V.; Sitti, MetinWhile micromachines with tailored functionalities enable therapeutic applications in biological environments, their controlled motion and targeted drug delivery in biological media require sophisticated designs for practical applications. Covalent organic frameworks (COFs), a new generation of crystalline and nanoporous polymers, offer new perspectives for light‐driven microswimmers in heterogeneous biological environments including intraocular fluids, thus setting the stage for biomedical applications such as retinal drug delivery. Two different types of COFs, uniformly spherical TABP‐PDA‐COF sub‐micrometer particles and texturally nanoporous, micrometer‐sized TpAzo‐COF particles are described and compared as light‐driven microrobots. They can be used as highly efficient visible‐light‐driven drug carriers in aqueous ionic and cellular media. Their absorption ranging down to red light enables phototaxis even in deeper and viscous biological media, while the organic nature of COFs ensures their biocompatibility. Their inherently porous structures with ≈2.6 and ≈3.4 nm pores, and large surface areas allow for targeted and efficient drug loading even for insoluble drugs, which can be released on demand. Additionally, indocyanine green (ICG) dye loading in the pores enables photoacoustic imaging, optical coherence tomography, and hyperthermia in operando conditions. This real‐time visualization of the drug‐loaded COF microswimmers enables unique insights into the action of photoactive porous drug carriers for therapeutic applications.Item Open Access Chromium in minerals as tracer of the polycyclic evolution of eclogite and related metabasite from the Pohorje Mountains, Slovenian Eastern Alps(2023) Li, Botao; Massonne, Hans‐JoachimSignificantly different peak pressure-temperature (P-T) conditions (18-26 kbar and 630-760°C versus 29-37 kbar and 750-940°C) have previously been published for eclogite and related metabasites from the south‐eastern flank of the Pohorje Mountains in Slovenia. These rocks can show a bimodal distribution of chromium in the rock‐forming minerals, particularly garnet, the role of which in their metamorphic evolution is unclear. Therefore, we studied an eclogite and a related rock with clinopyroxene containing only 17 mol% jadeite + acmite (sample 18Ca35a). KαCr intensity maps of garnet particularly in sample 18Ca35a show a sharp irregular boundary between the core (Gt1) and the mantle (Gt2). Gt1 of millimetre‐sized garnet in this rock is nearly Cr‐free and unzoned, whereas Gt2 is of different composition (0.22 wt.% Cr2O3) and slightly zoned. Nearly Cr‐free amphibole, (clino)zoisite, kyanite and staurolite inclusions are present in Gt1. The matrix consists of garnet and Cr‐bearing clinopyroxene, (clino)zoisite and amphibole. Thermodynamic modelling suggests peak P-T conditions of 22.5 ± 2 kbar at 710 ± 25°C (Gt1) and 23 ± 2 kbar at 700 ± 25°C (Gt2) in both samples. We interpret these findings to suggest that olivine‐ and hornblende‐bearing gabbros with some chromite experienced early metamorphism in the eclogite facies, when Gt1 formed. The rock was subsequently exhumed and cooled leading to significant garnet corrosion. A second stage of metamorphism, recognized by mappable Cr contents in garnet, led to the growth of Gt2 and other Cr‐bearing minerals at the expense of chromite relics, which survived stage I. The peak P-T conditions of stage II are compatible with those previously derived by same authors and support the view that probably no ultrahigh‐pressure eclogite exists in the Pohorje Mountains. We relate the two metamorphic events to the Cretaceous and Palaeogene high‐pressure events recently reported from micaschists of the Pohorje Mountains.Item Open Access Eclogite with biotite porphyroblasts : which conditions are responsible for their formation? An example from the northern Fleur‐de‐Lys Supergroup, Newfoundland, Canada(2024) Massonne, Hans‐JoachimAn eclogite from the Early Palaeozoic Fleur‐de‐Lys Supergroup in Newfoundland was studied because of its biotite porphyroblasts, which very rarely occur in this rock type. Thermodynamic modelling suggests that eclogitic biotite in common metabasite (former basalt-gabbro) is limited to (1) bulk‐rock compositions, which are relatively rich in Fe2+ and K and poor in Fe3+, and (2) the low‐pressure range of the eclogite facies. The latter reason is supported by the determination of the pressure-temperature (P-T) path of the Newfoundland eclogite. Chemical zonation of garnet, presence of phengite with Si contents of ~3.4 per formula unit, Zr contents in rutile and petrographic observations resulted in a P-T trajectory starting at medium‐pressure conditions. Nearly isothermal burial led to a peak pressure of 18-19 kbar at ~575°C, followed by exhumation and slight heating. Deformation occurred at or close to the peak pressure. Subsequent introduction of hydrous fluids caused the formation of porphyroblasts of biotite and Ca-amphibole in the pressure range of 12-17 kbar at peak temperatures of 625-640°C. Retrogression led to very fine‐grained symplectites around omphacite and phengite and marginal replacement of biotite porphyroblasts by plagioclase and titanite. Geodynamic scenarios invoking either a flat subduction of oceanic crust followed by continent-continent collision or intracontinental subduction along a transpressional fault system might best explain the formation of eclogite with biotite porphyroblasts in general. For the Newfoundland eclogite, the latter scenario is preferred.Item Open Access Metapelite from the high‐ to ultrahigh‐pressure terrane of the Eastern Alps (Pohorje Mountains, Slovenia) : new pressure, temperature and time constraints on a polymetamorphic rock(2021) Li, Botao; Massonne, Hans‐Joachim; Koller, Friedrich; Zhang, JunfengThe Austroalpine nappe stack of the Pohorje Mountains (Mts.) in northeastern Slovenia comprises a suite of eclogite facies metamorphic rocks that were partially assigned to Eo‐Alpine ultrahigh‐pressure metamorphism (UHPM). We selected a micaschist, which was previously related to this metamorphism, for a detailed study including the chemical zonation of garnet and potassic white mica, the identification of mineral inclusion assemblages, pseudosection modelling with PERPLE_X, and monazite in‐situ dating with the electron microprobe. Polymetamorphism was revealed by (at least) two generations of garnet and phengite and four populations of monazite yielding ages of 283.6 ± 6.1 (2σ), 94.1 ± 3.7, 47.9 ± 10.8 and 26.2 ± 2.8 Ma. The Permian monazite population is characterized by relatively high Y contents (~1.15 wt% Y) and low La/Gd mass ratios (8.7) indicating its formation before the growth of porphyroblastic garnet. The Eo‐Alpine population, however, grew synchronously with garnet based on low Y contents (~0.05 wt%) and high La/Gd ratios (21.4). The older Tertiary population (48 Ma) shows also high Y contents (1.1 wt%) and low La/Gd ratios (10.6) whereas the younger Tertiary population is characterized by low Y contents. The Permian P-T conditions of 7.5-10 kbar at 600-650°C were obtained using the inclusion assemblage of staurolite+rutile+biotite in porphyroblastic garnet. High pressure (HP) but no UHPM was reconstructed for both Eo‐Alpine coarse phengite (Si = 3.22 per formula unit = pfu) and small Tertiary garnet+fine‐grained phengite (Si = 3.27 pfu) at peak pressures ~16 kbar and 18.5-23 kbar respectively. Maximum temperatures close to 650°C were likely reached during the Eo‐Alpine HP event, whereas those of the Tertiary HP event were probably ~580°C. These HP metamorphic events suggest that the Pohorje Mts. experienced both an Eo‐Alpine and a Tertiary subduction-exhumation history, the latter of which was mainly reported for underlying Penninic nappes so far.