| 1. |
- Riedel, J. N., et al.
(författare)
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H-2/D-2 exchange reaction on mono-disperse Pt clusters: enhanced activity from minute O-2 concentrations
- 2016
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Ingår i: Catalysis Science and Technology. - : Royal Society of Chemistry (RSC). - 2044-4753 .- 2044-4761. ; 6:18, s. 6893-6900
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Tidskriftsartikel (refereegranskat)abstract
- The H-2/D-2 exchange reaction was studied on mono-disperse Pt-8 clusters in a mu-reactor. The chemical activity was studied at temperatures varying from room temperature to 180 degrees C using mass spectrometry. It was found that minute amounts of O-2 in the gas stream increased the chemical activity significantly. XPS and ISS before and after reaction suggest little or no sintering during reaction. A reaction pathway is suggested based on DFT. H-2 desorption is identified as the rate- limiting step and O-2 is confirmed as the source of the increased activity. The binding energy of platinum atoms in a SiO2 supported Pt-8 cluster is found to be comparable to the interatomic binding energies of bulk platinum, underlining the stability of the model system.
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| 2. |
- Wettergren, Kristina, 1974, et al.
(författare)
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High Sintering Resistance of Size-Selected Platinum Cluster Catalysts by Suppressed Ostwald Ripening
- 2014
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 14:10, s. 5803-5809
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Tidskriftsartikel (refereegranskat)abstract
- Employing rationally designed model systems with precise atom-by-atom particle size control, we demonstrate by means of combining noninvasive in situ indirect nano-plasmonic sensing and ex situ scanning transmission electron microscopy that monomodal size-selected platinum cluster catalysts on different supports exhibit remarkable intrinsic sintering resistance even under reaction conditions. The observed stability is related to suppression of Oftwald ripening by elimination of its main driving force via size-selection. This study thus constitutes a general blueprint for the rational design of sintering resistant catalyst systems and for efficient experimental strategies to determine sintering mechanisms. Moreover, this is the first systematic experimental investigation of sintering processes in nanoparticle systems with an initially perfectly monomodal size distribution under ambient conditions.
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| 3. |
- Zhdanov, Vladimir, 1952, et al.
(författare)
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Ostwald ripening of supported Pt nanoclusters with initial size-selected distributions
- 2015
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 631, s. 21-25
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Tidskriftsartikel (refereegranskat)abstract
- The use of a laser ablation cluster source made it recently possible to study Ostwald ripening of supported Pt nanoclusters with atomic control of the initial size distributions, such as Pt-68 or Pt-22 + Pt-68 (K. Wettergren et al., Nano Lett. (2014)). Monodispersed clusters were found to be more stable compared to the bimodal ones and to those with wide polydisperse initial size distribution. To clarify the results of the experiments, we present here the corresponding kinetic Monte Carlo simulations of Ostwald ripening with emphasis on the role of the initial size distribution with control at the atomic level.
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| 4. |
- Margittai, M., et al.
(författare)
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Single-molecule fluorescence resonance energy transfer reveals a dynamic equilibrium between closed and open conformations of syntaxin 1
- 2003
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 100:26, s. 15516-15521
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Tidskriftsartikel (refereegranskat)abstract
- Protein conformational transitions form the molecular basis of many cellular processes, such as signal transduction and membrane traffic. However, in many cases, little is known about their structural dynamics. Here we have used dynamic single-molecule fluorescence to study at high time resolution, conformational transitions of syntaxin 1, a soluble N-ethylmaleimide-sensitive factor attachment protein receptors protein essential for exocytotic membrane fusion. Sets of syntaxin double mutants were randomly labeled with a mix of donor and acceptor dye and their fluorescence resonance energy transfer was measured. For each set, all fluorescence information was recorded simultaneously with high time resolution, providing detailed information on distances and dynamics that were used to create structural models. We found that free syntaxin switches between an inactive closed and an active open configuration with a relaxation time of 0.8 ms, explaining why regulatory proteins are needed to arrest the protein in one conformational state.
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