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1. Charge transfer in (PbSe) _1+δ (NbSe ₂ ) ₂ and (SnSe) _1+δ (NbSe ₂ ) ₂ ferecrystals investigated by photoelectron spectroscopy

   https://doi.org/10.1088/1361-648X/aaa212  

   Göhler, Fabian; Mitchson, Gavin; Alemayehu, Matti B; Speck, Florian; Wanke, Martina; Johnson, David C; Seyller, Thomas (February 2018, Journal of Physics: Condensed Matter)
2. Free-standing bilayered vanadium oxide films synthesized by liquid exfoliation of chemically preintercalated δ-Li _x V ₂ O ₅ · n H ₂ O

   https://doi.org/10.1039/D1MA00085C  

   Houseman, Luke; Mukherjee, Santanu; Andris, Ryan; Zachman, Michael J.; Pomerantseva, Ekaterina (April 2021, Materials Advances)

   null (Ed.)

   A free-standing film composed of bilayered vanadium oxide nanoflakes is for the first time synthesized using a new low-energy process. The precursor powder, δ-Li x V 2 O 5 · n H 2 O, was prepared using a simple sol–gel based chemical preintercalation synthesis procedure. δ-Li x V 2 O 5 · n H 2 O was dispersed and probe sonicated in N -methyl pyrrolidone to exfoliate the bilayers followed by vacuum filtration resulting in the formation of a free-standing film with obsidian color. X-ray diffraction showed lamellar ordering of a single-phase material with a decreased interlayer distance compared to that of the precursor powder. Scanning electron microscopy images demonstrated stacking of the individual nanoflakes. This morphology was further confirmed with scanning transmission electron microscopy that showed highly malleable nanoflakes consisting of ∼10–100 vanadium oxide bilayers. One of the most important consequences of this morphological rearrangement is that the electronic conductivity of the free-standing film, measured by the four-probe method, increased by an order of magnitude compared to conductivity of the pressed pellet made of precursor powder. X-ray photoelectron spectroscopy measurements showed the coexistence of both V 5+ and V 4+ oxidation states in the exfoliated sample, possibly contributing to the change in electronic conductivity. The developed approach provides the ability to maintain the phase purity and crystallographic order during the exfoliation process, coupled with the formation of a free-standing film of enhanced conductivity. The produced bilayered vanadium oxide nanoflakes can be used as the building blocks for the synthesis of versatile two-dimensional heterostructures to create innovative electrodes for electrochemical energy storage applications. 

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3. A Promising Composite Anode for Solid Oxide Fuel Cells: Sr ₂ FeMo _0.65 Ni _0.35 O _6-δ -Gd _0.1 Ce _0.9 O _2-δ

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   Yang, Yanru; Yang, Zhibin; Chen, Yu; Chen, Fanglin; Peng, Suping (January 2019, Journal of The Electrochemical Society)
4. LaNi _x Fe _1–x O _3−δ as a Robust Redox Catalyst for CO ₂ Splitting and Methane Partial Oxidation

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5. Synthesis and Characterization of SrFe _x Mn _1–x (O,F) _3−δ Oxide (δ = 0 and 0.5) and Oxyfluoride Perovskite Films

   https://doi.org/10.1021/acs.inorgchem.0c01148  

   Wang, Jiayi; Lefler, Benjamin M.; May, Steven J. (July 2020, Inorganic Chemistry)

   We report the synthesis and characterization of as-grown SrFexMn1-xO2.5 epitaxial films, which were also subjected to post-growth oxidation and topotactic fluorination to obtain SrFexMn1-xO3 and SrFexMn1-xO(2.5-d)Fg films. We show how both the B-site cation and anion composition influence the structural, electronic, and optical properties of this family of perovskite materials. The Fe substitution of Mn in SrMnO2.5 gradually expands the c-axis parameter, as indicated by X-ray diffraction. With increasing x, the F content incorporated under identical fluorination conditions increases, reaching its maximum in SrFeO(2.5-d)Fg. In the compounds with mixed B-site occupation, the Fe 2p photoemission peaks are shifted upon fluorination while the Mn 2p peaks are not, suggesting inductive effects lead to asymmetric responses in how F alters the Mn and Fe bonds. Electronic transport measurements reveal all compounds are insulators, with the exception of SrFeO3, and demonstrate that fluorination increases resistivity for all values of x. Optical absorption spectra in the SrFexMn1-xO2.5 and SrFexMn1-xO3 films evolve systematically as a function of x, consistent with a physical scenario in which optical changes with Fe substitution arise from a linear combination of Mn and Fe 3d bands within the electronic structure. In contrast, the F incorporation induces non-linear changes to the optical response, suggesting a more complex impact on the electronic structure in materials with concurrent B-site and anion site substitution. 

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