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- ItemFe3O4 Nanoparticles Grown on Cellulose/GO Hydrogels as Advanced Catalytic Materials for the Heterogeneous Fenton-like Reaction(Washington, DC : ACS Publications, 2019) Chen, Yian; Pötschke, Petra; Pionteck, Jürgen; Voit, Brigitte; Qi, HaisongCellulose/graphene oxide (GO)/iron oxide (Fe3O4) composites were prepared by coprecipitating iron salts onto cellulose/GO hydrogels in a basic solution. X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared, and X-ray diffraction characterization showed that Fe3O4 was successfully coated on GO sheets and cellulose. Cellulose/GO/Fe3O4 composites showed excellent catalytic activity by maintaining almost 98% of the removal of acid orange 7 (AO7) and showed stability over 20 consecutive cycles. This performance is attributable to the synergistic effect of Fe3O4 and GO during the heterogeneous Fenton-like reaction. Especially, the cellulose/GO/Fe3O4 composites preserve their activity by keeping the ratio of Fe3+/Fe2+ at 2 even after 20 catalysis cycles, which is supported by XPS analysis.
- ItemSynthesis of Modified Poly(vinyl Alcohol)s and Their Degradation Using an Enzymatic Cascade(Weinheim : Wiley-VCH, 2023) von Haugwitz, Gerlis; Donnelly, Kian; Di Filippo, Mara; Breite, Daniel; Phippard, Max; Schulze, Agnes; Wei, Ren; Baumann, Marcus; Bornscheuer, Uwe T.Poly(vinyl alcohol) (PVA) is a water-soluble synthetic vinyl polymer with remarkable physical properties including thermostability and viscosity. Its biodegradability, however, is low even though a large amount of PVA is released into the environment. Established physical-chemical degradation methods for PVA have several disadvantages such as high price, low efficiency, and secondary pollution. Biodegradation of PVA by microorganisms is slow and frequently involves pyrroloquinoline quinone (PQQ)-dependent enzymes, making it expensive due to the costly cofactor and hence unattractive for industrial applications. In this study, we present a modified PVA film with improved properties as well as a PQQ-independent novel enzymatic cascade for the degradation of modified and unmodified PVA. The cascade consists of four steps catalyzed by three enzymes with in situ cofactor recycling technology making this cascade suitable for industrial applications.
- ItemDegradation Behavior of Silk Nanoparticles - Enzyme Responsiveness(Washington, DC : ACS Publ., 2018) Wongpinyochit, Thidarat; Johnston, Blair F.; Seib, F. PhilippSilk nanoparticles are viewed as promising vectors for intracellular drug delivery as they can be taken up into cells by endocytosis and trafficked to lysosomes, where lysosomal enzymes and the low pH trigger payload release. However, the subsequent degradation of the silk nanoparticles themselves still requires study. Here, we report the responsiveness of native and PEGylated silk nanoparticles to degradation following exposure to proteolytic enzymes (protease XIV and α-chymotrypsin) and papain, a cysteine protease. Both native and PEGylated silk nanoparticles showed similar degradation behavior over a 20 day exposure period (degradation rate: protease XIV > papain ≫ α-chymotrypsin). Within 1 day, the silk nanoparticles were rapidly degraded by protease XIV, resulting in a ∼50% mass loss, an increase in particle size, and a reduction in the amorphous content of the silk secondary structure. By contrast, 10 days of papain treatment was necessary to observe any significant change in nanoparticle properties, and α-chymotrypsin treatment had no effect on silk nanoparticle characteristics over the 20-day study period. Silk nanoparticles were also exposed ex vivo to mammalian lysosomal enzyme preparations to mimic the complex lysosomal microenvironment. Preliminary results indicated a 45% reduction in the silk nanoparticle size over a 5-day exposure. Overall, the results demonstrate that silk nanoparticles undergo enzymatic degradation, but the extent and kinetics are enzyme-specific.
- ItemPhotocatalytic degradation and toxicity evaluation of diclofenac by nanotubular titanium dioxide–PES membrane in a static and continuous setup(London : RSC Publishing, 2015) Fischer, K.; Kühnert, M.; Gläser, R.; Schulze, A.Diclofenac is a commonly used anti-inflammatory drug, which has been found in surface waters. Advanced oxidation processes (AOPs) seem to be the most suitable technique to prevent the entry of diclofenac and other pollutants into surface waters. TiO2 is especially reliable in mineralizing many organic molecules. The combination of TiO2 nanotubes with a polymer microfiltration membrane (polyethersulfone, PES) showed high photocatalytic activity by degrading diclofenac combined with an excellent membrane performance and long-term stability. By continuously degrading pollutants from water via a cross-flow setup, the molecules to be degraded are transported right to the membrane surface so that the overall reaction rate is increased. The toxicity of diclofenac was reduced by photocatalysis and photolysis; however, photocatalysis had greater impact. Moreover, the complete degradation of pollutants is very important to avoid highly toxic intermediate products.
- ItemSonication-assisted liquid phase exfoliation of two-dimensional CrTe3 under inert conditions(Amsterdam [u.a.] : Elsevier Science, 2023) Synnatschke, Kevin; Moses Badlyan, Narine; Wrzesińska, Angelika; Lozano Onrubia, Guillermo; Hansen, Anna–Lena; Wolff, Stefan; Tornatzky, Hans; Bensch, Wolfgang; Vaynzof, Yana; Maultzsch, Janina; Backes, ClaudiaLiquid phase exfoliation (LPE) has been used for the successful fabrication of nanosheets from a large number of van der Waals materials. While this allows to study fundamental changes of material properties’ associated with reduced dimensions, it also changes the chemistry of many materials due to a significant increase of the effective surface area, often accompanied with enhanced reactivity and accelerated oxidation. To prevent material decomposition, LPE and processing in inert atmosphere have been developed, which enables the preparation of pristine nanomaterials, and to systematically study compositional changes over time for different storage conditions. Here, we demonstrate the inert exfoliation of the oxidation-sensitive van der Waals crystal, CrTe3. The pristine nanomaterial was purified and size-selected by centrifugation, nanosheet dimensions in the fractions quantified by atomic force microscopy and studied by Raman, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX) and photo spectroscopic measurements. We find a dependence of the relative intensities of the CrTe3 Raman modes on the propagation direction of the incident light, which prevents a correlation of the Raman spectral profile to the nanosheet dimensions. XPS and EDX reveal that the contribution of surface oxides to the spectra is reduced after exfoliation compared to the bulk material. Further, the decomposition mechanism of the nanosheets was studied by time-dependent extinction measurements after water titration experiments to initially dry solvents, which suggest that water plays a significant role in the material decomposition.