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Structure and electrochromism of two-dimensional octahedral molecular sieve h'-WO3.

ABSTRACT: Octahedral molecular sieves (OMS) are built of transition metal-oxygen octahedra that delimit sub-nanoscale cavities. Compared to other microporous solids, OMS exhibit larger versatility in properties, provided by various redox states and magnetic behaviors of transition metals. Hence, OMS offer opportunities in electrochemical energy harnessing devices, including batteries, electrochemical capacitors and electrochromic systems, provided two conditions are met: fast exchange of ions in the micropores and stability upon exchange. Here we unveil a novel OMS hexagonal polymorph of tungsten oxide called h'-WO3, built of (WO6)6 tunnel cavities. h'-WO3 is prepared by a one-step soft chemistry aqueous route leading to the hydrogen bronze h'-H0.07WO3. Gentle heating results in h'-WO3 with framework retention. The material exhibits an unusual combination of 1-dimensional crystal structure and 2-dimensional nanostructure that enhances and fastens proton (de)insertion for stable electrochromic devices. This discovery paves the way to a new family of mixed valence functional materials with tunable behaviors.

SUBMITTER: Besnardiere J

PROVIDER: S-EPMC6338762 | biostudies-literature | 2019 Jan

REPOSITORIES: biostudies-literature

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Structure and electrochromism of two-dimensional octahedral molecular sieve h'-WO<sub>3</sub>.

Besnardiere Julie J Ma Binghua B Torres-Pardo Almudena A Wallez Gilles G Kabbour Houria H González-Calbet José M JM González-Calbet José M JM Von Bardeleben Hans Jürgen HJ Fleury Benoit B Buissette Valérie V Sanchez Clément C Le Mercier Thierry T Cassaignon Sophie S Portehault David D

Nature communications 20190118 1

Octahedral molecular sieves (OMS) are built of transition metal-oxygen octahedra that delimit sub-nanoscale cavities. Compared to other microporous solids, OMS exhibit larger versatility in properties, provided by various redox states and magnetic behaviors of transition metals. Hence, OMS offer opportunities in electrochemical energy harnessing devices, including batteries, electrochemical capacitors and electrochromic systems, provided two conditions are met: fast exchange of ions in the micro ...[more]

PMID: 30659185

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Project description:We have studied the structure of (Ala)5, a model unfolded peptide, using a combination of 2D IR spectroscopy and molecular dynamics (MD) simulation. Two different isotopomers, each bis-labeled with (13)C?O and (13)C?(18)O, were strategically designed to shift individual site frequencies and uncouple neighboring amide-I' modes. 2D IR spectra taken under the double-crossed ??/4, -?/4, Y, Z? polarization show that the labeled four-oscillator systems can be approximated by three two-oscillator systems. By utilizing the different polarization dependence of diagonal and cross peaks, we extracted the coupling constants and angles between three pairs of amide-I' transition dipoles through spectral fitting. These parameters were related to the peptide backbone dihedral angles through DFT calculated maps. The derived dihedral angles are all located in the polyproline-II (ppII) region of the Ramachandran plot. These results were compared to the conformations sampled by Hamiltonian replica-exchange MD simulations with three different CHARMM force fields. The C36 force field predicted that ppII is the dominant conformation, consistent with the experimental findings, whereas C22/CMAP predicted similar population for ?+, ?, and ppII, and the polarizable Drude-2013 predicted dominating ? structure. Spectral simulation based on MD representative conformations and structure ensembles demonstrated the need to include multiple 2D spectral features, especially the cross-peak intensity ratio and shape, in structure determination. Using 2D reference spectra defined by the C36 structure ensemble, the best spectral simulation is achieved with nearly 100% ppII population, although the agreement with the experimental cross-peak intensity ratio is still insufficient. The dependence of population determination on the choice of reference structures/spectra and the current limitations on theoretical modeling relating peptide structures to spectral parameters are discussed. Compared with the previous results on alanine based oligopeptides, the dihedral angles of our fitted structure, and the most populated ppII structure from the C36 simulation are in good agreement with those suggesting a major ppII population. Our results provide further support for the importance of ppII conformation in the ensemble of unfolded peptides.

Dataset Information

Structure and electrochromism of two-dimensional octahedral molecular sieve h'-WO3.

Publications

Structure and electrochromism of two-dimensional octahedral molecular sieve h'-WO<sub>3</sub>.

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