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1. Why are the Elemental Nonmetals (F ₂ , Cl ₂ , Br ₂ , I ₂ , S ₈ , P ₄ ) of so Many Hues or of Any Hues and Where is the Chromophore? Insight into Intera ‐X–X Bonds

   https://doi.org/10.1111/php.13270  

   Jabeen, Shakeela; Greer, Alexander; Edwards, Kathleen F.; Liebman, Joel F. (May 2020, Photochemistry and Photobiology)

   Abstract A unique approach is used to relate the HOMO‐LUMO energy difference to the difference between the ionization potential (IP) and electron affinity (EA) to assist in deducing not only the colors, but also chromophores in elemental nonmetals. Our analysis focuses on compounds with lone pair electrons and σ electrons, namely X₂(X = F, Cl, Br, I), S₈and P₄. For the dihalogens, the [IP – EA] energies are found to be: F₂(12.58 eV), Cl₂(8.98 eV), Br₂(7.90 eV), I₂(6.78 eV). We suggest that theinterahalogen X–X bond itself is the chromophore for these dihalogens, in which the light absorbed by the F₂, Cl₂, Br₂, I₂leads to longer wavelengths in the visible by a π → σ* transition. Trace impurities are a likely case of cyclic S₈which contains amounts of selenium leading to a yellow color, where the [IP – EA] energy of S₈is found to be 7.02 eV. Elemental P₄with an [IP – EA] energy of 9.09 eV contains a tetrahedral and σ aromatic structure. In future work, refinement of the analysis will be required for compounds with π electrons and σ electrons, such as polycyclic aromatic hydrocarbons (PAHs). 

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2. Structure Effect on Pseudocapacitive Properties of A ₂ LaMn ₂ O ₇ (A = Ca, Sr)

   https://doi.org/10.1002/ente.202201249  

   Kananke-Gamage, Chandana C. W.; Ramezanipour, Farshid (January 2023, Energy Technology)

   Herein, the effect of structure on pseudocapacitive properties in alkaline conditions is demonstrated through the investigation of isoelectronic oxides Ca₂LaMn₂O₇and Sr₂LaMn₂O₇, where the difference in ionic radii of Ca²⁺and Sr²⁺leads to a change in structure and lattice symmetry, resulting in an orthorhombicCmcmstructure for the former and a tetragonalI4/mmmstructure for the latter. While calcium and strontium do not make a direct contribution to the near‐surface faradaic processes that are essential to the pseudocapacitive properties, their effect on the structure leads to a change in the oxygen intercalation process and the associated pseudocapacitive energy storage. It is shown that Sr₂LaMn₂O₇has a significantly greater specific capacitance than Ca₂LaMn₂O₇. In addition, the former shows a considerably higher‐energy density compared to the latter. Furthermore, these materials show highly stable energy‐storage properties, and retain their specific capacitance over 10 000 cycles of charge–discharge in a symmetric pseudocapacitive cell. Importantly, these findings show the structure–property relationships, where a change in the structure and lattice symmetry can result in a significant change in pseudocapacitive charge–discharge properties in isoelectronic systems. 

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3. Enhanced Electrochemical Performance of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ with SiO ₂ Surface Coating Via Homogeneous Precipitation

   https://doi.org/10.1002/celc.202101230  

   Dou, Lintao; Hu, Pu; Shang, Chaoqun; Wang, Heng; Xiao, Dongdong; Ahuja, Utkarsh; Aifantis, Katerina; Zhang, Zhanhui; Huang, Zhiliang (November 2021, ChemElectroChem)

   Abstract Ni‐rich LiNi_0.8Co_0.1Mn_0.1O₂(NCM811) has been considered as a promising cathode material for high energy density lithium‐ion batteries. However, it experiences undesirable interfacial side‐reactions with the electrolyte, which lead to a rapid capacity decay. In this work, a homogeneous precipitation method is proposed for forming a uniform silicon dioxide (SiO₂) coating on the NCM811 surface. The strong Si−O network provided a stable protective layer between the NCM811 active material and electrolyte to improve the electrochemical stability. As a result, the NCM811@SiO₂cathode showed superior cycling stability (84.9 % after 100 cycles at 0.2 C) and rate capability (142.7 mA h g⁻¹at 5 C) compared to the pristine NCM811 cathode (56.6 % after 100 cycles, 127.9 mA h g⁻¹at 5 C). Moreover, the SiO₂coating effectively suppressed voltage decay and pulverization of the NCM811 particles during long term cycling. This uniform coating technique offers a viable approach for stabilizing Ni‐rich cathode materials for high‐energy density lithium‐ion batteries. 

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4. Singlet O ₂ from Ultraviolet Excitation of the Quinoline-O ₂ Complex

   https://doi.org/10.1021/acs.jpca.3c02024  

   Parsons, Bradley F.; Rivera, Marcos R.; Freitag, Mark A.; Reardon, Kylie A.; Pappas, Emerson S.; Rausch, Jack T. (June 2023, The Journal of Physical Chemistry A)

   We report results from experiments with the quinoline-O₂ complex, which was photodissociated using light near 312 nm. Photodissociation resulted in formation of the lowest excited state of oxygen, O₂ a ¹Δ_g, which we detected using resonance enhanced multiphoton ionization and velocity map ion imaging. The O₂⁺ ion image allowed for a determination of the center-of-mass translational energy distribution, P(E_T), following complex dissociation. We also report results of electronic structure calculations for the quinoline singlet ground state and lowest energy triplet state. From the CCSD/aug-cc-pVDZ//(U)MP2/cc-pVDZ calculations, we determined the lowest energy triplet state to have ππ* electronic character and to be 2.69 eV above the ground state. We also used electronic structure calculations to determine the geometry and binding energy for several quinoline-O2 complexes. The calculations indicated that the most strongly bound complex has a well depth of about 0.11 eV and places the O₂ moiety above and approximately parallel to the quinoline ring system. By comparing the experimental P(E_T) with the energy for the singlet ground state and the lowest energy triplet state, we concluded that the quinoline product was formed in the lowest energy triplet state. Finally, we found the experimental P(E_T) to be in agreement with a Prior translational energy distribution, which suggests a statistical dissociation for the complex. 

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5. Electrical properties of α-Ga ₂ O ₃ films grown by halide vapor phase epitaxy on sapphire with α-Cr ₂ O ₃ buffers

   https://doi.org/10.1063/5.0090832  

   Polyakov, Alexander; Nikolaev, Vladimir; Stepanov, Sergey; Almaev, Alexei; Pechnikov, Alexei; Yakimov, Eugene; Kushnarev, Bogdan O.; Shchemerov, Ivan; Scheglov, Mikhail; Chernykh, Alexey; et al (June 2022, Journal of Applied Physics)

   We report on growth and electrical properties of α-Ga₂O₃films prepared by halide vapor phase epitaxy (HVPE) at 500 °C on α-Cr₂O₃buffers predeposited on sapphire by magnetron sputtering. The α-Cr₂O₃buffers showed a wide microcathodoluminescence (MCL) peak near 350 nm corresponding to the α-Cr₂O₃bandgap and a sharp MCL line near 700 nm due to the Cr⁺intracenter transition. Ohmic contacts to Cr₂O₃were made with both Ti/Au or Ni, producing linear current–voltage ( I– V) characteristics over a wide temperature range with an activation energy of conductivity of ∼75 meV. The sign of thermoelectric power indicated p-type conductivity of the buffers. Sn-doped, 2- μm-thick α-Ga₂O₃films prepared on this buffer by HVPE showed donor ionization energies of 0.2–0.25 eV, while undoped films were resistive with the Fermi level pinned at E_Cof 0.3 eV. The I– V and capacitance–voltage ( C– V) characteristics of Ni Schottky diodes on Sn-doped samples using a Cr₂O₃buffer indicated the presence of two face-to-face junctions, one between n-Ga₂O₃and p-Cr₂O₃, the other due to the Ni Schottky diode with n-Ga₂O₃. The spectral dependence of the photocurrent measured on the structure showed the presence of three major deep traps with optical ionization thresholds near 1.3, 2, and 2.8 eV. Photoinduced current transient spectroscopy spectra of the structures were dominated by deep traps with an ionization energy of 0.95 eV. These experiments suggest another pathway to obtain p–n heterojunctions in the α-Ga₂O₃system. 

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