microscopy

Unexpected Epitaxial Growth of a Few WS2 Layers on 1100 Facets of ZnO Nanowires

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Boris Polyakov, Alexei Kuzmin, Krisjanis Smits, Janis Zideluns, Edgars Butanovs,
Jelena Butikova, Sergei Vlassov, Sergei Piskunov, and Yuri F. Zhukovskii

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Core-shell nanowires is an interesting and perspective class of radially heterostructured nanomaterials where epitaxial growth of the shell can be realized even at signi ficant core-shell lattice mismatch. In this study epitaxial hexagonally-shaped shell consisting of WS2 nanolayers was grown on f1100g facets of prismatic wurtzite-structured
[0001]-oriented ZnO nanowires for the first time. A synthesis was performed by annealing in a sulfur atmosphere of ZnO/WO3 core-shell structures, produced by reactive
DC magnetron sputtering of amorphous a-WO3 layer on top of ZnO nanowire array.
The morphology and phase composition of synthesized ZnO/WS2 core-shell nanowires were con firmed by scanning and transmission electron microscopy (SEM and TEM),micro-Raman and photoluminescence spectroscopy. Epitaxial growth of WS2(0001) layer(s) on f1100g facets of ZnO nanowire is unexpected due to incompatibility of their symmetry and structure parameters. To relax the interfacial incoherence, we propose a model of ZnO/WS2 interface containing WS2 bridging groups inside and use first-principles simulations to support its feasibility.

J. Phys. Chem. C

DOI: 10.1021/acs.jpcc.6b06139

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Ag sensitized TiO2 and NiFe2O4 three-component nanoheterostructures: synthesis, electronic structure and strongly enhanced visible light photocatalytic activity

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A. Šutka, T.
Käämbre, R. Pärna, N. Doebelin, M. Vanags, K. Smits and V. Kisand

This study reports on the synthesis and characterisation of two- and three-component visible light active photocatalytic
nanoparticle heterostructures, based on TiO2 and NiFe2O4 and sensitized with Ag. We observe that Ag content as small as
1 at.% in the TiO2/NiFe2O4 heterostructure increases by more than an order of magnitude the rate constant for the visible
light photocatalytic process. We rationalise this in terms of the measured structure and electronic structure data of the
binary and ternary combinations of the component materials and focus on details, which show that an optimised
deposition sequence is vital for attaining the high values of photocatalytic efficiency, because the charge transfer across
the interfaces appears to be sensitive to where the Ag is loaded in the heterostructure. The overall higher visible light
photocatalytic activity of the TiO2/Ag/NiFe2O4 heterostructure was observed and is attributed to enhanced charge carrier
separation efficiency and migration via vectorial electron transfer.

RSC Advances., 2016,

DOI: 10.1039/C6RA00728G

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