@article{64002, abstract = {{The production of formaldehyde on industrial scale requires huge amounts of energy due to the involvement of reforming processes in combination with the demand in the megaton scale. Hence, a direct route for the transformation of (bio)methane to formaldehyde would decrease costs and puts less pressure on the environment. Herein, we report on the use of zinc modified silicas as possible support materials for vanadium catalysts and the resulting consequences for the performance in the selective oxidation of methane to formaldehyde. After optimization of the Zn content and reaction conditions, a remarkably high space-time yield of 12.4 kgCH2O·kgcat−1·h−1 was achieved. As a result of the extensive characterization by means of UV–vis, Raman, XANES and NMR spectroscopy it was found that vanadium is in the vicinity of highly dispersed zinc atoms which promote the formation of active vanadium species as supposed by theoretical calculations. This work presents a further step of catalyst development towards direct industrial methane conversion which may help to overcome current limitations in the future.}}, author = {{Kunkel, Benny and Seeburg, Dominik and Kabelitz, Anke and Witte, Steffen and Gutmann, Torsten and Breitzke, Hergen and Buntkowsky, Gerd and Buzanich, Ana Guilherme and Wohlrab, Sebastian}}, journal = {{Catalysis Today}}, keywords = {{Formaldehyde, Local coordination, SBA-15, Vanadium oxo species, XANES, Zinc doped silica}}, pages = {{114643}}, title = {{{Highly productive V/Zn-SiO2 catalysts for the selective oxidation of methane}}}, doi = {{10.1016/j.cattod.2024.114643}}, volume = {{432}}, year = {{2024}}, } @article{63991, abstract = {{A series of 1 and 2 nm sized platinum nanoparticles (Pt-NPs) deposited on different support materials, namely, gamma-alumina (gamma-Al2O3), titanium dioxide (TiO2), silicon dioxide (SiO2) and fumed silica are investigated by solid-state NMR and dynamic nuclear polarization enhanced NMR spectroscopy (DNP). DNP signal enhancement factors up to 170 enable gaining deeper insight into the surface chemistry of Pt-NPs. Carbon monoxide is used as a probe molecule to analyze the adsorption process and the surface chemistry on the supported Pt-NPs. The studied systems show significant catalytic activity in carbon monoxide oxidation on their surface at room temperature. The underlying catalytic mechanism is the water-gas shift reaction. In the case of alumina as the support the produced CO2 reacts with the surface to form carbonate, which is revealed by solid-state NMR. A similar carbonate formation is also observed when physical mixtures of neat alumina with silica, fumed silica and titania supported Pt-NPs are studied.}}, author = {{Klimavicius, V. and Neumann, S. and Kunz, S. and Gutmann, Torsten and Buntkowsky, G.}}, issn = {{2044-4753}}, journal = {{Catalysis Science & Technology}}, keywords = {{Chemistry, gamma-alumina, hydrogenation, silica, c-13, interactions, metal-catalysts, particle-size, platinum nanoparticles, sites, surface, water-gas shift}}, number = {{14}}, pages = {{3743–3752}}, title = {{{Room temperature CO oxidation catalysed by supported Pt nanoparticles revealed by solid-state NMR and DNP spectroscopy}}}, doi = {{10.1039/c9cy00684b}}, volume = {{9}}, year = {{2019}}, } @article{6543, abstract = {{Up to 400 mW of near-IR (1370-1500 nm) femtosecond pulses are generated from an optical parametric amplifier directly driven by a Yb:fiber oscillator delivering 100\&\#x00A0;fs pulses at 1036 nm. The process is seeded by a stable supercontinuum obtained from a photonic crystal fiber. We use a single pass through a 3 mm, magnesium oxide-doped, periodically poled LiNbO3 downconversion crystal to produce a near-IR pulse train with a remarkable power stability of 1.4 % (RMS) during one hour. Tuning is achieved by the temperature and the poling period of the nonlinear crystal.}}, author = {{Mundry, J. and Lohrenz, J. and Betz, M.}}, journal = {{Applied Optics}}, keywords = {{Infrared and far-infrared lasers, Ultrafast lasers, Nonlinear optics, parametric processes, Parametric oscillators and amplifiers, Femtosecond pulses, Fiber lasers, Fused silica, Laser systems, Photonic crystal fibers, Pulse propagation}}, number = {{11}}, pages = {{3104--3108}}, publisher = {{OSA}}, title = {{{Tunable femtosecond near-IR source by pumping an OPA directly with a 90 MHz Yb:fiber source}}}, doi = {{10.1364/AO.56.003104}}, volume = {{56}}, year = {{2017}}, } @article{63956, abstract = {{The synthesis of novel robust and stable iridium-based immobilized catalysts on silica-polymer hybrid materials (Si-PB-Ir) is described. These catalysts are characterized by a combination of 1D P-31 CP-MAS and 2D P-31-H-1 HETCOR and J-resolved multinuclear solid state NMR experiments. Different binding situations such as singly and multiply coordinated phosphines are identified. Density functional theory (DFT) calculations are performed to corroborate the interpretation of the experimental NMR data, in order to propose a structural model of the heterogenized catalysts. Finally, the catalytic activity of the Si-PB-Ir catalysts is investigated for the hydrogenation of styrene employing para-enriched hydrogen gas.}}, author = {{Gutmann, Torsten and Alkhagani, S. and Rothermel, N. and Limbach, H. H. and Breitzke, H. and Buntkowsky, G.}}, issn = {{0942-9352}}, journal = {{Zeitschrift Fur Physikalische Chemie-International Journal of Research in Physical Chemistry & Chemical Physics}}, keywords = {{Chemistry, dynamic nuclear-polarization, solid-state nmr, DFT, heterogeneous catalysis, hydrido complexes, hydrogenation, immobilized catalyst, inorganic hybrid, iridium, materials, mesoporous, molecular-orbital methods, PHIP, phosphine complexes, reusable catalysts, silica, solid-state-NMR, wilkinsons catalyst}}, number = {{3}}, pages = {{653–669}}, title = {{{P-31-Solid-State NMR Characterization and Catalytic Hydrogenation Tests of Novel heterogenized Iridium-Catalysts}}}, doi = {{10.1515/zpch-2016-0837}}, volume = {{231}}, year = {{2017}}, } @article{64039, abstract = {{The preparation of hierarchical and sophisticated particle architectures for mimicking structural colors known from nature still remains a challenge. In this study, the preparation of novel opal and double-inverse opal films based on thermally treated metallopolymer core particles with a silica shell is described. Thermal treatment leads to the formation of magnetic nanorattle-type particles. The main challenge of artificial particles is to ensure sufficient dispersibility after several synthetic steps. Especially silica particles providing surface hydroxyl groups tend to sinter at high temperatures leading to agglomeration. We present the introduction of trimethyl ethoxy silane (TMES) as an excellent functionalization reagent as the key reaction step. The necessity and success of functionalization are investigated by transmission electron microscopy (TEM) and zeta potential measurements. Importantly, solid state NMR techniques are employed to gain deeper insights into the chemical structure of the surface-attached reagent. Finally, by this convenient functionalization the preparation of elastomeric opal films and double-inverse opal films is proven successful revealing excellent optical film properties. Moreover, magnetic properties of these novel films are investigated by using magnetic force microscopy (MFM). The herein established route is expected to pave the way for the preparation of a variety of advanced and stimuli-responsive optical materials.}}, author = {{Scheid, D. and Stock, D. and Winter, T. and Gutmann, Torsten and Dietz, C. and Gallei, M.}}, issn = {{2050-7526}}, journal = {{Journal of Materials Chemistry C}}, keywords = {{Materials Science, silica, Physics, nmr, colloidal photonic crystals, light, polymerization, solids, structural color, thermo}}, number = {{11}}, pages = {{2187–2196}}, title = {{{The pivotal step of nanoparticle functionalization for the preparation of functional and magnetic hybrid opal films}}}, doi = {{10.1039/c5tc04388c}}, volume = {{4}}, year = {{2016}}, }