Publikationen am Institut für Chemie und Biotechnik

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Täuscher, Eric; Freiberger, Emma
Cholesterin aus Hirn. - In: Nachrichten aus der Chemie, ISSN 1439-9598, Bd. 71 (2023), 1, S. 30-32

Cholesterin hat es bis in den Alltagssprachgebrauch gebracht. Allein deshalb ist es für Praktika im Chemiestudium ein interessanter Vertreter der Steroide. Zudem ist es einfach zu gewinnen.

Täuscher, Eric; Freiberger, Emma
Cholesterin aus Hirn. - In: Nachrichten aus der Chemie, ISSN 1868-0054, Bd. 71 (2023), 1, S. 30-32

Cholesterin hat es bis in den Alltagssprachgebrauch gebracht. Allein deshalb ist es für Praktika im Chemiestudium ein interessanter Vertreter der Steroide. Zudem ist es einfach zu gewinnen.
Tsierkezos, Nikos; Freiberger, Emma; Ritter, Uwe; Krischok, Stefan; Ullmann, Fabian; Köhler, Michael
Application of nitrogen-doped multi-walled carbon nanotubes decorated with gold nanoparticles in biosensing. - In: Journal of solid state electrochemistry, ISSN 1433-0768, Bd. 27 (2023), 10, S. 2645-2658

Novel films consisting of nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) were fabricated by means of chemical vapor deposition technique and decorated with gold nanoparticles (AuNPs) possessing diameter of 14.0 nm. Electron optical microscopy analysis reveals that decoration of N-MWCNTs with AuNPs does not have any influence on their bamboo-shaped configuration. The electrochemical response of fabricated composite films, further denoted as N-MWCNTs/AuNPs, towards oxidation of dopamine (DA) to dopamine-o-quinone (DAQ) in the presence of ascorbic acid (AA) and uric acid (UA) was probed in real pig serum by means of cyclic voltammetry (CV) and square wave voltammetry (SWV). The findings demonstrate that N-MWCNTs/AuNPs exhibit slightly greater electrochemical response and sensitivity towards DA/DAQ compared to unmodified N-MWCNTs. It is, consequently, obvious that AuNPs improve significantly the electrochemical response and detection ability of N-MWCNTs. The electrochemical response of N-MWCNTs/AuNPs towards DA/DAQ seems to be significantly greater compared to that of conventional electrodes, such as platinum and glassy carbon. The findings reveal that N-MWCNTs/AuNPs could serve as powerful analytical sensor enabling analysis of DA in real serum samples.
Tsierkezos, Nikos; Reddmann, Eike Felix; Ritter, Uwe
Synthesis and electrochemical properties of sulfur-nitrogen-doped multi-walled carbon nanotubes. - In: Fullerenes, nanotubes & carbon nanostructures, ISSN 1536-4046, Bd. 0 (2023), 0

Multi-walled carbon nanotubes doped with sulfur and nitrogen (S-N-MWCNTs) were grown onto silicon/silicon oxide wafer by means of chemical vapor deposition upon decomposition of dimethyl sulfoxide (DMSO) and acetonitrile (ACN) in presence of catalyst. The S-N-MWCNTs were characterized by scanning electron microscopy combined with energy dispersive X-ray spectroscopy. The findings demonstrate that S-N-MWCNTs exhibit bamboo-shaped nanostructure, quite similar to pure nitrogen-doped carbon nanotubes. The S-N-MWCNTs were investigated with respect to their electrochemical response to ferrocyanide/ferricyanide, [Fe(CN)6]^4-/3- in potassium chloride aqueous solutions by means of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. The recorded CVs demonstrate strong dependence of electrochemical response, electron transfer kinetics, and sensitivity of S-N-MWCNTs on concentration of decomposed DMSO precursor. Namely, upon increasing concentration of decayed DMSO up to 2% wt. the current density, the electron transfer kinetics, and the sensitivity of S-N-MWCNTs toward [Fe(CN)6]^4-/3- tend to enhance. The extracted EIS results approve that when DMSO reaches the optimum concentration of 2% wt. the barrier for electron transfer decreases significantly leading, consequently, to faster electron transfer kinetics. The S-N-MWCNTs exhibit considerable stability and excellent reproducibility, and thus it can be considered suitable analytical tool for detection of redox systems at micromolar level.
Ritter, Uwe; Nikolenko, Andrii; Alieksandrov, Maksim; Strelchuk, Viktor; Chumachenko, Vasyl; Kutsevol, Nataliya; Scharff, Peter; Prylutskyy, Yu I.
Structural and optical properties of C70 fullerenes in aqueous solution. - In: Fullerenes, nanotubes & carbon nanostructures, ISSN 1536-4046, Bd. 31 (2023), 10, S. 983-988

The simple method of preparation of highly stable and purified C70 fullerene aqueous solution (C70FAS) is proposed. The features of structural stabilization of C70 fullerenes in an aqueous solution by studying their structural and optical properties using Raman, photoluminescence, infrared reflection-absorption, UV-VIS absorption, and dynamic light scattering spectroscopy methods were analyzed. The experimental results showed that the most likely mechanism for C70 fullerenes stabilization in water is surface hydroxylation with covalent attachment of water hydroxyls to C70 fullerene carbons. Raman and infrared absorption spectra of C70FAS showed characteristic vibrational bands of C70 fullerenes with a slight broadening and low-frequency shift of ∼1 cm^−1, indicating the attachment of water hydroxyls to the C70 fullerene carbons. The photoluminescence spectra showed excitonic emission bands of C70 molecules with intensity depending on their content. UV-VIS absorption spectra demonstrate the absorption bands typical for monomeric C70 fullerene. Finally, the dynamic light scattering data confirmed that C70FAS is a typical colloidal fluid containing both individual C70 molecules and their nano aggregates up to 100 nm. These findings provide insights into the stabilization mechanism of C70 fullerenes in water and may have implications for their potential application in nanobiotechnology.
Xie, Ting; Ehrhardt, Linda; Günther, Mike; Köhler, Michael; Cao-Riehmer, Jialan
Current to biomass: media optimization and strain selection from cathode-associated microbial communities in a two-chamber electro-cultivation reactor. - In: Environments, ISSN 2076-3298, Bd. 10 (2023), 6, 97, S. 1-19

Cathode-associated microbial communities (caMCs) are the functional key elements in the conversion of excess electrical energy into biomass. In this study, we investigated the development of electrochemical caMCs based on two-chamber microbial electrolytic cells (MECs) after optimization of media composition. Microbial communities obtained from a historical soil sample were inoculated into the cathode chamber of MECs. The inorganic medium with (A) carbon dioxide in air or (B) 100 mM sodium bicarbonate as carbon source was used in the absence of any organic carbon source. After 12 days of operation, the experimental results showed that (1) the bacterial community in group B exhibited lush growth and (2) a single strain TX168 Epilithonimonas bovis isolated from group A indicated electrochemical activity and synthesized large volumes of biomass using sodium bicarbonate. We also analyzed the caMCs of the MECs and reference samples without electro-cultivation using 16S rRNA gene sequencing. The results showed that the caMCs of MECs in groups A and B were dominated by the genera Acinetobacter and Pseudomonas. The caMCs were further inoculated and cultured on different agars to isolate specific electroactive bacterial strains. Overall, our study highlights the possibility of converting excess energy into biomass by electro-cultivation and the importance of selecting appropriate media to enrich specific microbial communities and single strains in MECs.
van Steijn, Leonie; Wondergem, Joeri A. J.; Schakenraad, Koen; Heinrich, Doris; Merks, Roeland M. H.
Deformability and collision-induced reorientation enhance cell topotaxis in dense microenvironments. - In: Biophysical journal, ISSN 1542-0086, Bd. 122 (2023), 13, S. 2791-2807

In vivo, cells navigate through complex environments filled with obstacles such as other cells and the extracellular matrix. Recently, the term “topotaxis” has been introduced for navigation along topographic cues such as obstacle density gradients. Experimental and mathematical efforts have analyzed topotaxis of single cells in pillared grids with pillar density gradients. A previous model based on active Brownian particles (ABPs) has shown that ABPs perform topotaxis, i.e., drift toward lower pillar densities, due to decreased effective persistence lengths at high pillar densities. The ABP model predicted topotactic drifts of up to 1% of the instantaneous speed, whereas drifts of up to 5% have been observed experimentally. We hypothesized that the discrepancy between the ABP and the experimental observations could be in 1) cell deformability and 2) more complex cell-pillar interactions. Here, we introduce a more detailed model of topotaxis based on the cellular Potts model (CPM). To model persistent cells we use the Act model, which mimics actin-polymerization-driven motility, and a hybrid CPM-ABP model. Model parameters were fitted to simulate the experimentally found motion of Dictyostelium discoideum on a flat surface. For starved D. discoideum, the topotactic drifts predicted by both CPM variants are closer to the experimental results than the previous ABP model due to a larger decrease in persistence length. Furthermore, the Act model outperformed the hybrid model in terms of topotactic efficiency, as it shows a larger reduction in effective persistence time in dense pillar grids. Also pillar adhesion can slow down cells and decrease topotaxis. For slow and less-persistent vegetative D. discoideum cells, both CPMs predicted a similar small topotactic drift. We conclude that deformable cell volume results in higher topotactic drift compared with ABPs, and that feedback of cell-pillar collisions on cell persistence increases drift only in highly persistent cells.
Mazétyté-Stasinskiené, Raminta; Kronfeld, Klaus-Peter; Köhler, Michael
Five-level structural hierarchy: microfluidically supported synthesis of core-shell microparticles containing nested set of dispersed metal and polymer micro and nanoparticles. - In: Particle & particle systems characterization, ISSN 1521-4117, Bd. 0 (2023), 0, 2300030, S. 1-13

This study presents the development of a hierarchical design concept for the synthesis of multi-scale polymer particles with up to five levels of organization. The synthesis of core-shell microparticles containing nested sets of dispersed metal and polymer micro- and nanoparticles is achieved through in situ photopolymerization using a double co-axial capillaries microfluidic device. The flow rates of the carrier, shell, and core phases are optimized to control particle size and result in stable core-shell particles with well-dispersed three-level composites in the shell matrix. The robustness and reversibility of these core-shell particles are demonstrated through five cycles of drying and re-swelling, showing that the size and structure of core-shell particles remain unchanged. Additionally, the permeability and mobility of dye molecules within the shell matrix are tested and showed that different molecular weight dyes have different penetration times. This study highlights the potential of microfluidics as a powerful tool for the controlled and precise synthesis of complex structured materials and demonstrates the versatility and potential of these core-shell particles for sensing applications as particle-based surface-enhanced Raman scattering (SERS).
Endres, Patrick; Schütt, Timo; Kimmig, Julian; Bode, Stefan; Hager, Martin; Geitner, Robert; Schubert, Ulrich Sigmar
Oxymethylene ether (OME) fuel catalyst screening using in situ NMR spectroscopy. - In: Chemistry - a European journal, ISSN 1521-3765, Bd. 29 (2023), 33, e202203776, S. 1-9

Online NMR measurements are introduced in the current study as a new analytical setup for investigation of the oxymethylene dimethyl ether (OME) synthesis. For the validation of the setup, the newly established method is compared with state-of-the-art gas chromatographic analysis. Afterwards, the influence of different parameters, such as temperature, catalyst concentration and catalyst type on the OME fuel formation based on trioxane and dimethoxymethane is investigated. As catalysts, AmberlystTM 15 (A15) and trifluoromethanesulfonic acid (TfOH) are utilized. A kinetic model is applied to describe the reaction in more detail. Based on these results, the activation energy (A15: 48.0 kJ mol^-1 and TfOH: 72.3 kJ mol^-1) and the order in catalyst (A15: 1.1 and TfOH: 1.3) are calculated and discussed.
Adamopoulos, Nikolaos D.; Tsierkezos, Nikos; Ntziouni, Afroditi; Zhang, Fu; Terrones, Mauricio; Kordatos, Konstantinos V.
Synthesis, characterization, and electrochemical performance of reduced graphene oxide decorated with Ag, ZnO, and AgZnO nanoparticles. - In: Carbon, ISSN 0008-6223, Bd. 213 (2023), 118178

Graphene oxide (GO) derived from the oxidization of graphite exhibits high specific surface area with potential in electrochemical applications. Furthermore, silver and zinc oxide nanoparticles, further denoted as AgNPs and ZnONPs, respectively, display superior physicochemical and electronic properties, that would significantly improve the electrocatalytic properties by being applied in electrochemical sensing. Consequently, in the present work, three different hybrid nanomaterials consisting of reduced graphene oxide (rGO) modified with either AgNPs, ZnONPs, or combined AgZnONPs were synthesized and characterized. The synthesis of GO was performed by a modified Hummer's method, while the decoration of GO with the nanoparticles was carried out by self-assembly solvothermal processes. The Ag-rGO, ZnO-rGO, and AgZnO-rGO nanocomposite hybrid materials were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy (EDX). Furthermore, the electrochemical responses of the fabricated nanocomposites towards the standard ferrocyanide/ferricyanide [Fe(CN)6]3-/4- redox system were investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. The results have been explained in terms of structural differences between the nanoparticles formed on the surface of the fabricated nanocomposite materials. Namely, the improved electrochemical performance of ZnO-rGO can be attributed to the high surface to volume ratio of ZnO, which provides greater area of electrode/electrolyte junction and consequently, large number of sites at the electrolyte-ZnO interface. The aim of the present work is the fabrication of novel high-performance rGO-based nanomaterials for applications in electrochemical sensing.