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1,567 results on '"Tremel, Wolfgang"'

205. Drug Delivery: Dendritic Mesoporous Silica Nanoparticles for pH-Stimuli-Responsive Drug Delivery of TNF-Alpha (Adv. Healthcare Mater. 13/2017)

Author

Kienzle, Arne, primary, Kurch, Sven, additional, Schlöder, Janine, additional, Berges, Carsten, additional, Ose, Robert, additional, Schupp, Jonathan, additional, Tuettenberg, Andrea, additional, Weiss, Henning, additional, Schultze, Jennifer, additional, Winzen, Svenja, additional, Schinnerer, Meike, additional, Koynov, Kaloian, additional, Mezger, Markus, additional, Haass, Nikolas K., additional, Tremel, Wolfgang, additional, and Jonuleit, Helmut, additional

Published
2017
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207. Dendritic Mesoporous Silica Nanoparticles for pH‐Stimuli‐Responsive Drug Delivery of TNF‐Alpha

Author

Kienzle, Arne, primary, Kurch, Sven, additional, Schlöder, Janine, additional, Berges, Carsten, additional, Ose, Robert, additional, Schupp, Jonathan, additional, Tuettenberg, Andrea, additional, Weiss, Henning, additional, Schultze, Jennifer, additional, Winzen, Svenja, additional, Schinnerer, Meike, additional, Koynov, Kaloian, additional, Mezger, Markus, additional, Haass, Nikolas K., additional, Tremel, Wolfgang, additional, and Jonuleit, Helmut, additional

Published
2017
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212. Benzyl Alcohol Assisted Synthesis and Characterization of Highly Reduced Graphene Oxide (HRG)@ZrO2 Nanocomposites

Author

Shaik, Mohammed R., primary, Al-Marri, Abdulhadi H., additional, Adil, Syed F., additional, Mohri, Nils, additional, Barton, Bastian, additional, Siddiqui, Mohammed R. H., additional, Al-Warthan, Abdulrahman, additional, Labis, Joselito P., additional, Tremel, Wolfgang, additional, Khan, Mujeeb, additional, and Tahir, Muhammad N., additional

Published
2017
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214. Hofmann-Like Frameworks Fe(2-methylpyrazine)n[M(CN)2]2(M = Au, Ag): Spin-Crossover Defined by the Precious Metal

Author

Shylin, Sergii I., Kucheriv, Olesia I., Shova, Sergiu, Ksenofontov, Vadim, Tremel, Wolfgang, and Gural’skiy, Il’ya A.

Abstract

Hofmann-like cyanometalates constitute a large class of spin-crossover iron(II) complexes with variable switching properties. However, it is not yet clearly understood how the temperature and cooperativity of a spin transition are influenced by their structure. In this paper, we report the synthesis and crystal structures of the metal–organic coordination polymers {FeII(Mepz)[AuI(CN)2]2} ([Au]) and {FeII(Mepz)2[AgI(CN)2]2} ([Ag]), where Mepz = 2-methylpyrazine, along with characterization of their spin-state behavior by variable-temperature SQUID magnetometry and Mössbauer spectroscopy. The compounds are built of cyanoheterometallic layers, which are pillared by the bridging Mepz ligands in [Au]but separated in [Ag]. The complex [Au]exhibits an incomplete stepped spin transition as a function of the temperature with TSCO1= 170 K and TSCO2= 308 K for the two subsequent steps. In contrast, the complex [Ag]attains the high-spin state over the whole temperature range. In the crystal structure of [Ag], weak interlayer contacts (Ag−π, Me−π, and Ag–N) are found that may be responsible for an unusual axial elongation of the FeN6polyhedra. We propose that this structural distortion contributes to the trapping of iron in its high-spin state.

Published
2020
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215. Solid State Fluorination on the Minute Scale: Synthesis of WO3−xFx with Photocatalytic Activity.

Author

Lange, Martin Alexander, Krysiak, Yaşar, Hartmann, Jens, Dewald, Georg, Cerretti, Giacomo, Tahir, Muhammad Nawaz, Panthöfer, Martin, Barton, Bastian, Reich, Tobias, Zeier, Wolfgang G., Mondeshki, Mihail, Kolb, Ute, and Tremel, Wolfgang

Subjects
TUNGSTEN alloys, NUCLEAR magnetic resonance spectroscopy, MAGIC angle spinning, FLUORINATION, NUCLEAR magnetic resonance, MELTING points
Abstract

Solid state reactions are notoriously slow, because the rate‐limiting step is diffusion of atoms or ions through reactant, intermediate, and product crystalline phases. This requires days or even weeks of high temperature treatment, consuming large amounts of energy. Metal oxides are particularly difficult to react, because they have high melting points. The study reports a high‐speed solid state fluorination of WO3 with Teflon to the oxyfluorides WO3–xFx on a minute (<10 min) scale by spark plasma sintering, a technique that is used typically for a high‐speed consolidation of powders. Automated electron diffraction analysis reveals an orthorhombic ReO3‐type structure of WO3–xFx with F atom disorder as demonstrated by 19F magic angle spinning nuclear magnetic resonance spectroscopy. The potential of this new approach is demonstrated by the following results. i) Mixed‐ valent tungsten oxide fluorides WO3–xFx with high F content (0 < x < 0.65) are obtained as metastable products in copious amounts within minutes. ii) The spark plasma sintering technique yields WO3–xFx nanoparticles with high photocatalytic activity, whereas the corresponding bulk phases obtained by conventional solid‐state (ampoule) reactions have no photocatalytic activity. iii) The catalytic activity is caused by the microstructure originating from the processing by spark plasma sintering. [ABSTRACT FROM AUTHOR]

Published
2020
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216. Effect of anion substitution on the structural and transport properties of argyrodites Cu7PSe6−xSx.

Author

Reissig, Friederike, Heep, Barbara, Panthöfer, Martin, Wood, Max, Anand, Shashwat, Snyder, G. Jeffrey, and Tremel, Wolfgang

Subjects
SUPERIONIC conductors, ANIONS, RIETVELD refinement, SOLID solutions, X-ray diffraction, LOW temperatures
Abstract

Inspired by the good performance of argyrodites as ion conducting thermoelectrics and as solid electrolytes we investigated the effect of isovalent S2− substitution for Se2− in Cu7PSe6. At room temperature Cu7PSe6 crystallizes in the primitive cubic β-polymorph of the argyrodite structure and transforms to the face-centered high-temperature (HT) γ-modification above 320 K. The transition for the homologous Cu7PS6 occurs at 510 K. Promising thermoelectric and ion conducting properties are observed only in the HT modification, where the cations are mobile. Using Rietveld refinements against X-ray diffraction data the effect of isovalent S2− substitution for Se2− on the structural and transport properties in Cu7PSe6−xSx was analyzed. While a step-wise incorporation of S2− showed typical behavior for a homogeneous solid solution series, the analysis of the diffraction data gave clear evidence of anion ordering due to site preference of the sulfide ions, which can be rationalized using Pearson's HSAB concept. This leads to a stabilization of the HT structure even at lower temperatures. This selective control enables new strategies for the design of argyrodite materials, as isovalent substitution not only allows an engineering of properties, but also permits the stabilization of the polymorph with the most promising properties. [ABSTRACT FROM AUTHOR]

Published
2019
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217. Self‐Organized Arrays of SnO2 Microplates with Photocatalytic and Antimicrobial Properties.

Author

Mohri, Nils, Kerschbaumer, Hannes, Link, Thorben, Andre, Rute, Panthöfer, Martin, Ksenofontov, Vadim, and Tremel, Wolfgang

Subjects
PHOTOELECTRON spectroscopy, MOSSBAUER spectroscopy, POROUS metals, X-ray spectroscopy, METALLIC oxides, TIN, ORGANIC water pollutants
Abstract

Porous anodic metal oxides have been widely used for the development of various functional nanostructures. So far, these self‐organized pore structures were prepared as hexagonal arrangements of nanopores, which have become a popular template system for the fabrication of functional nanostructures. Here we report a new oxalic acid‐based anodization process for long‐range ordered arrays of submicrometer tin dioxide plates at low applied voltages in buffered solution, which prevents the precipitation of SnC2O4 on the Sn anode surface. The chemical composition of the surface SnO2 was established by Mössbauer spectroscopy and X‐ray photoemission spectroscopy (XPS). The growth direction of the SnO2 nanoplates was shown to be related to the orientation of the domains of the underlying polycrystalline yet oriented β‐Sn foil. The structured SnO2 surface is highly photoactive and generates superoxide radicals (O2·–) upon UV exposure resulting in a strong degradation of organic contaminants and a strong antimicrobial activity. Upon illumination the SnO2 coating exhibits a switchable amphiphilic behavior, which – in combination with its photoactivity – creates a self‐cleaning surface. [ABSTRACT FROM AUTHOR]

Published
2019
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218. Surface Chemistry Directs the Tunable Assembly of TiO2 Anatase Nanocubes into Three‐Dimensional Mesocrystals.

Author

Huesmann, Hannah, Schechtel, Eugen, Lieberwirth, Ingo, Panthöfer, Martin, and Tremel, Wolfgang

Subjects
TITANIUM dioxide, NANOCHEMISTRY, DISCONTINUOUS precipitation, IONIC interactions, SURFACE chemistry, SURFACE charges
Abstract

An important step in nanocrystal self‐assembly is programming the large‐area organization of nanocrystals into superlattices with tunable packing efficiencies. Here we utilize nanoscale surface chemistry to direct the self‐assembly of TiO2 (anatase) nanocubes into distinct three‐dimensional mesocrystals. High nanocrystal solubility combined with weak electrostatic attraction induced by the pH mediated surface charge was sufficient to organize 3,4‐dihydroxyhydrocinnamic acid (DHCA) functionalized nanocubes into large superstructures with both translational and orientational order. The finding that translational and orientational order of nanocrystal superlattices can be induced by the interplay of thermal energy, steric repulsion, and ionic interactions in a nucleation and growth self‐assembly process offers insight into the importance of the initial nucleation stage in the self‐assembly process and suggests new routes for controlled self‐assembly of nanocrystals. [ABSTRACT FROM AUTHOR]

Published
2019
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220. Surface defects as a tool to solubilize and functionalize WS2 nanotubes

Author

Tremel, Wolfgang, Spetter, Dmitri, Hoshyargar, Faegheh, Sahoo, Jugal Kishore, Tahir, Muhammad Nawaz, Branscheid, Robert, Barton, Bastian, Panthofer, Martin, Kolb, Ute, Tremel, Wolfgang, Spetter, Dmitri, Hoshyargar, Faegheh, Sahoo, Jugal Kishore, Tahir, Muhammad Nawaz, Branscheid, Robert, Barton, Bastian, Panthofer, Martin, and Kolb, Ute

Abstract

Layered transition metal dichalcogenides contain a number of crystal defects which significantly change their properties may be beneficial or detrimental for a specific application. We have prepared defect-rich multiwalled WS2 nanotubes by reductive sulfidization of W18O49 nanowires that were obtained solvothermally from tungsten chloride in different alcohols. The synthesis of the W18O49 nanowires was monitored and their morphological characteristics (e. g. length, rigidity and aspect ratio) are described in detail. The effect of morphology of the nanowires on the synthesis of WS2 nanotubes was investigated in order to obtain WS2 nanotubes that are highly solvent dispersible. Dispersions of the WS2 nanotubes in organic solvents were very stable for several days. The nanotubes could easily be functionalized with noble metals, metal oxides and Janus-type metal@metal oxide nanoparticles. The synthesis of nanowires and nanotubes and the immobilization of the nanoparticles is demonstrated by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) combined with energy dispersive X-ray spectroscopy (EDX), electron diffraction, X-ray diffraction (XRD) and Raman spectroscopy.

Published
2017

221. Aktiviertes MAPK-Signalling durch metallische Nanopartikel im respiratorischen Epithel

Author

Heim, Julia, Tahir, Nawaz, Tremel, Wolfgang, and Brieger, Jürgen

Subjects
ddc: 610, 610 Medical sciences, Medicine
Abstract

Metalloxid-Nanopartikel (NP) werden aus diversen Quellen in die Umwelt entlassen und u.a. über das respiratorische Epithel internalisiert. In der vorliegenden Studie untersuchten wir eine mögliche Aktivierung der MAPK/ERK- and PI3K/Akt-Signalwege als Teil einer zellulären Stressantwort.[for full text, please go to the a.m. URL], 85. Jahresversammlung der Deutschen Gesellschaft für Hals-Nasen-Ohren-Heilkunde, Kopf- und Hals-Chirurgie

Published
2014
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224. Pd@Fe2O3 Superparticles with Enhanced Peroxidase Activity by Solution Phase Epitaxial Growth

Author

Kluenker, Martin, primary, Nawaz Tahir, Muhammad, additional, Ragg, Ruben, additional, Korschelt, Karsten, additional, Simon, Paul, additional, Gorelik, Tatiana E., additional, Barton, Bastian, additional, Shylin, Sergii I., additional, Panthöfer, Martin, additional, Herzberger, Jana, additional, Frey, Holger, additional, Ksenofontov, Vadim, additional, Möller, Angela, additional, Kolb, Ute, additional, Grin, Juri, additional, and Tremel, Wolfgang, additional

Published
2017
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226. Glycine-functionalized copper(ii) hydroxide nanoparticles with high intrinsic superoxide dismutase activity

Author

Korschelt, Karsten, primary, Ragg, Ruben, additional, Metzger, Carmen S., additional, Kluenker, Martin, additional, Oster, Michael, additional, Barton, Bastian, additional, Panthöfer, Martin, additional, Strand, Dennis, additional, Kolb, Ute, additional, Mondeshki, Mihail, additional, Strand, Susanne, additional, Brieger, Jürgen, additional, Nawaz Tahir, M., additional, and Tremel, Wolfgang, additional

Published
2017
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227. A highly reduced graphene oxide/ZrOx–MnCO3 or –Mn2O3 nanocomposite as an efficient catalyst for selective aerial oxidation of benzylic alcohols

Author

Assal, Mohamed E., primary, Shaik, Mohammed Rafi, additional, Kuniyil, Mufsir, additional, Khan, Mujeeb, additional, Al-Warthan, Abdulrahman, additional, Siddiqui, Mohammed Rafiq H., additional, Khan, Sohail M. A., additional, Tremel, Wolfgang, additional, Tahir, Muhammad Nawaz, additional, and Adil, Syed Farooq, additional

Published
2017
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231. Haloperoxidase Mimicry by CeO2−xNanorods Combats Biofouling

Author

Herget, Karoline, primary, Hubach, Patrick, additional, Pusch, Stefan, additional, Deglmann, Peter, additional, Götz, Hermann, additional, Gorelik, Tatiana E., additional, Gural'skiy, Il'ya A., additional, Pfitzner, Felix, additional, Link, Thorben, additional, Schenk, Stephan, additional, Panthöfer, Martin, additional, Ksenofontov, Vadim, additional, Kolb, Ute, additional, Opatz, Till, additional, André, Rute, additional, and Tremel, Wolfgang, additional

Published
2016
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234. Comparative evaluation of the impact on endothelial cells induced by different nanoparticle structures and functionalization

Author

Landgraf, Lisa, primary, Müller, Ines, additional, Ernst, Peter, additional, Schäfer, Miriam, additional, Rosman, Christina, additional, Schick, Isabel, additional, Köhler, Oskar, additional, Oehring, Hartmut, additional, Breus, Vladimir V, additional, Basché, Thomas, additional, Sönnichsen, Carsten, additional, Tremel, Wolfgang, additional, and Hilger, Ingrid, additional

Published
2016
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242. Coatings with nano-sized vanadium pentoxide offer protection against marine fouling

Author

Tremel, Wolfgang

Subjects
Fouling of ship bottoms -- Research, Vanadium pentoxide -- Protection and preservation, Coatings -- Usage -- Research, Business, Chemicals, plastics and rubber industries, High technology industry, Metals, metalworking and machinery industries
Abstract

The aggregation of small marine microorganisms, such as bacteria and algae on surfaces exposed directly to seawater is known as marine bio-fouling. Marine fouling is a major problem, which costs [...]

Published
2012

243. Bond strength dependent superionic phase transformation in the solid solution series Cu_2ZnGeSe_(4-x)S_x

Author

Zeier, Wolfgang G., Heinrich, Christophe P., Day, Tristan, Panithipongwut, Chatr, Kieslich, Gregor, Brunklaus, Gunther, Snyder, G. Jeffrey, and Tremel, Wolfgang

Abstract

Recently, copper selenides have shown to be promising thermoelectric materials due to their possible superionic character resulting from mobile copper cations. Inspired by this recent development in the class of quaternary copper selenides we have focused on the structure-to-property relationships in the solid solution series Cu_2ZnGeSe_(4-x)S_x. The material exhibits an insulator-to-metal transition at higher temperatures, with a transition temperature dependent on the sulfur content. However, the lattice parameters show linear thermal expansion at elevated temperatures only and therefore no indication of a structural phase transformation. ^(63)Cu nuclear magnetic resonance shows clear indications of Cu located on at least two distinct sites, which eventually merge into one (apparent) site above the phase transformation. In this manuscript the temperature dependent lattice parameters and electronic properties of the solid solution Cu_2ZnGeSe_(4-x)S_x are reported in combination with ^(63)Cu NMR, and an attempt will be made to relate the nature of the electronic phase transformation to a superionic phase transformation and a changing covalent character of the lattice upon anion substitution in this class of materials.

Published
2013

244. Hydrothermal growth mechanism of SnO2 nanorods in aqueous HCl.

Author

Leidich, Patrick, Mondeshki, Mihail, Barton, Bastian, Kolb, Ute, Panthöfer, Martin, and Tremel, Wolfgang

Subjects
HYDROTHERMAL synthesis, NANORODS, AQUEOUS solutions, NUCLEAR magnetic resonance, X-ray diffraction
Abstract

Rutile-type nanorods of SnO2 were obtained in a one-pot hydrothermal synthesis starting from SnCl4·5H2O and HCl in a temperature range between 200 and 240°C. Although the nanorods are polydisperse, the average length of the nanorods could be adjusted from 13 to 65 nm by varying of the reaction temperature. The resulting anisotropic nanocrystals were characterized using powder X-ray diffraction (PXRD), (high resolution-) transmission electron microscopy (HR-TEM), and selected area electron diffraction (SAED). The particle growth proceeds via a dissolution-recrystallization process with soluble [SnCl5(H2O)]− intermediates, as confirmed by PXRD, Raman spectroscopy, and magic angle spinning nuclear magnetic resonance (MAS-NMR). [ABSTRACT FROM AUTHOR]

Published
2018
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249. Removal of Surface Oxygen Vacancies Increases Conductance Through TiO2Thin Films for Perovskite Solar Cells

Author

Klasen, Alexander, Baumli, Philipp, Sheng, Qu, Johannes, Ewald, Bretschneider, Simon A., Hermes, Ilka M., Bergmann, Victor W., Gort, Christopher, Axt, Amelie, Weber, Stefan A. L., Kim, Heejae, Butt, Hans-Jürgen, Tremel, Wolfgang, and Berger, Rüdiger

Abstract

We report that UV–ozone treatment of TiO2anatase thin films is an efficient method to increase the conductance through the film by more than 2 orders of magnitude. The increase in conductance is quantified via conductive scanning force microscopy on freshly annealed and UV–ozone-treated TiO2anatase thin films on fluorine-doped tin oxide substrates. The increased conductance of TiO2anatase thin films results in a 2% increase of the average power conversion efficiency (PCE) of methylammonium lead iodide-based perovskite solar cells. PCE values up to 19.5% for mesoporous solar cells are realized. The additional UV–ozone treatment results in a reduced number of oxygen vacancies at the surface, inferred from X-ray photoelectron spectroscopy. These oxygen vacancies at the surface act as charge carrier traps and hinder charge extraction from the adjacent material. Terahertz measurements indicate only minor changes of the bulk conductance, which underlines the importance of UV–ozone treatment to control surface-based defects.

Published
2019
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