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Author: Weller, H. ×

Publications Search Results

Now showing 1 - 7 of 7
  • Publication
    Durability of Colloidally Stabilized Supported Nickel and Nickel Platinum Nanoparticles during Redox-Cycling
    ( 2021)
    Gutknecht, V.
    ;
    Walther, B.
    ;
    Noei, H.
    ;
    Vonk, V.
    ;
    Heller, H.
    ;
    Stierle, A.
    ;
    Weller, H.
    We report on the oxidation and reduction behavior of colloidally stabilized Ni nanoparticles and Pt@NiPt core-shell nanoparticles with a platinum content of 4%. Thin films of both nanoparticle systems were deposited on yttria-stabilized zirconia substrates by spin-coating. Oxidation-reduction cycles were used to remove oxides and organics and obtain metallic particles. The cycling conditions necessary to clean and reduce Pt@NiPt core-shell nanoparticles were milder than for the Ni nanoparticles, which also needed several cycles to burn off residual organics. During cycling, the Ni nanoparticles lost their initially epitaxial relationship with the substrate and adopted a random orientation, while no epitaxial orientation was observable for the core-shell nanoparticles. Reasons for this are discussed together with the influence of platinum on Ni reduction. The Ni and Pt@NiPt nanoparticles sintered during the process but retained crystalline domain diameters close to the original particle diameters. Our results show that colloidally stabilized nanoparticles can be transferred onto a technologically relevant substrate and be reduced to metallic nanoparticles. The fabrication and final structures are discussed as a feasible route to realize solid oxide fuel cell anodes with tailored nickel particle diameter.
  • Publication
    Little Adjustments Significantly Simplify the Gram-Scale Synthesis of High-Quality Iron Oxide Nanocubes
    ( 2021)
    Kampferbeck, M.
    ;
    Klauke, L.R.
    ;
    Weller, H.
    ;
    Vossmeyer, T.
    This work presents a facile one-step protocol for the gram-scale synthesis of iron oxide nanocubes with adjustable sizes ranging from 13 to 20 nm and with size distributions between 7 and 12%. As X-ray diffraction indicated the initial formation of the wüstite phase, a formation mechanism of the nanocubes based on the wüstite crystal structure is proposed. When exposed to ambient conditions, the nanoparticles rapidly oxidize to magnetite/maghemite with a remaining wüstite core. The cubic morphology is attributed to the thermodynamic stability of the exposed {100} facets and the control over the growth rate via the use of a sodium oleate/oleic acid mixed ligand system. In contrast to previously reported procedures, the described synthetic approach does not require the initial preparation and isolation of iron oleate. Therefore, the amount of work and the consumption of hazardous solvents are significantly reduced. Thus, the method presented is much more efficient and environmentally more friendly while maintaining excellent control over the particles' shape, size, and size distribution.
  • Publication
    X-ray-Based Techniques to Study the Nano-Bio Interface
    ( 2021)
    Sanchez-Cano, Carlos
    ;
    Alvarez-Puebla, Ramon A.
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    Abendroth, John M.
    ;
    Beck, Tobias
    ;
    Blick, Robert
    ;
    Cao, Yuan
    ;
    Caruso, Frank
    ;
    Chakraborty, Indranath
    ;
    Chapman, Henry N.
    ;
    Chen, Chunying
    ;
    Cohen, Bruce E.
    ;
    Conceição, Andrew L.C.
    ;
    Cormode, David P.
    ;
    Cui, Daxiang
    ;
    Dawson, Kenneth A.
    ;
    Falkenberg, Gerald
    ;
    Fan, Chunhai
    ;
    Feliu, Neus
    ;
    Gao, Mingyuan
    ;
    Gargioni, Elisabetta
    ;
    Glüer, Claus-C.
    ;
    Grüner, Florian
    ;
    Hassan, Moustapha
    ;
    Hu, Yong
    ;
    Huang, Yalan
    ;
    Huber, Samuel
    ;
    Huse, Nils
    ;
    Kang, Yanan
    ;
    Khademhosseini, Ali
    ;
    Keller, Thomas F.
    ;
    Körnig, Christian
    ;
    Kotov, Nicholas A.
    ;
    Koziej, Dorota
    ;
    Liang, Xing-Jie
    ;
    Liu, Beibei
    ;
    Liu, Sijin
    ;
    Liu, Yang
    ;
    Liu, Ziyao
    ;
    Liz-Marzan, Luis M.
    ;
    Ma, Xiaowei
    ;
    Machicote, A.
    ;
    Maison, W.
    ;
    Mancuso, A.P.
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    Megahed, S.
    ;
    Nickel, B.
    ;
    Otto, F.
    ;
    Palencia, C.
    ;
    Pascarelli, S.
    ;
    Pearson, A.
    ;
    Penate-Medina, O.
    ;
    Qi, B.
    ;
    Rädler, J.
    ;
    Richardson, J.J.
    ;
    Rosenhahn, A.
    ;
    Rothkamm, K.
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    Rübhausen, M.
    ;
    Sanyal, M.K.
    ;
    Schaak, R.E.
    ;
    Schlemmer, H.-P.
    ;
    Schmidt, M.
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    Schmutzler, O.
    ;
    Schotten, Theo
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    Schulz, F.
    ;
    Sood, A.K.
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    Spiers, K.M.
    ;
    Staufer, T.
    ;
    Stemer, D.M.
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    Stierle, A.
    ;
    Sun, X.
    ;
    Tsakanova, G.
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    Weiss, P.S.
    ;
    Weller, H.
    ;
    Westermeier, F.
    ;
    Xu, M.
    ;
    Yan, H.
    ;
    Zeng, Y.
    ;
    Zhao, Y.
    ;
    Zhao, Y.
    ;
    Zhu, D.
    ;
    Zhu, Y.
    ;
    Parak, W.J.
    X-ray-based analytics are routinely applied in many fields, including physics, chemistry, materials science, and engineering. The full potential of such techniques in the life sciences and medicine, however, has not yet been fully exploited. We highlight current and upcoming advances in this direction. We describe different X-ray-based methodologies (including those performed at synchrotron light sources and X-ray free-electron lasers) and their potentials for application to investigate the nano-bio interface. The discussion is predominantly guided by asking how such methods could better help to understand and to improve nanoparticle-based drug delivery, though the concepts also apply to nano-bio interactions in general. We discuss current limitations and how they might be overcome, particularly for future use in vivo.
  • Publication
    Seeded growth synthesis of zirconia@gold particles in aqueous solution
    ( 2020)
    Dahl, G.T.
    ;
    Krueger, J.-D.
    ;
    Döring, S.
    ;
    Weller, H.
    ;
    Vossmeyer, T.
    Metal-ceramic composite particles are of increasing interest due to their potential applications in photonic metamaterials as well as next-generation catalysts. The zirconia-gold system has received little attention due to the lack of controllable preparation methods. Well-known methods for the deposition of gold nanoshells on silica spheres, however, should be adaptable for similar zirconia-based materials. Here, we present a novel synthetic approach to the well-controlled deposition of gold on the surface of sol-gel derived zirconia mesoparticles by a stepwise method involving the immobilization of gold nanoparticles and repeated seeded-growth steps. We show that the immobilization efficiency is strongly enhanced by acidification with hydrochloric acid and additional employment of aminomethylphosphonic acid as coupling agent. The optimum conditions are identified and the subsequent incremental growth by seeded reduction of gold is demonstrated. The results shed light on the parameters governing the preparation of zirconia@gold composite particles and our synthetic approach provides a promising tool for future developments in complex nanomaterials design.
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