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1. Revealing Coexisting Cu ⁰ –Cu ⁺ Sites in Cu ₃ N Nanoensembles for Selective CC Coupling of CO ₂ Under Low Overpotential

   https://doi.org/10.1002/cssc.202500003  

   Li, Junrui; Zhong, Hong; Hong_Lee, Soo; Li, Hui; Drisdell, Walter_S; Dun, Chaochao; Burciaga, Rihana; Ingram, Conrad; Beckman, Scott_P; Urban, Jeffrey_J; et al (June 2025, ChemSusChem)

   To address a long‐existing debate on what copper species are responsible for efficient CC coupling, especially ethanol formation, in electrochemical CO₂reduction reaction, herein, a comprehensive study using Cu₃N nanocubes with a uniform size and shape, alongside a single crystalline phase is reported. The Cu₃N nanoensemble electrode has a remarkable Faradaic efficiency (FE) of 64% for ethanol production at a relatively low potential of −0.6 V versus reversible hydrogen electrode. Throughin‐operandoX‐ray absorption spectroscopy study, a dynamic phase evolution that directly correlates with changes in FE across varying applied potentials is observed. Notably, the nanoensemble with a composition of ≈71% Cu⁺and 29% Cu⁰is identified as being selective for ethanol formation at the low overpotential. Conversely, a predominantly metallic Cu phase formed at potentials more negative than −0.6 V favors the hydrogen evolution reaction. Density functional theory calculations at the Cu₃N–Cu interface substantiate that the coexistence of Cu⁰–Cu⁺not only energetically favors the ethanol reaction pathway but also destabilizes the intermediates for ethylene pathway. 

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2. Effect of post-deposition annealing on crystal structure of RF magnetron sputtered germanium dioxide thin films

   https://doi.org/10.1116/6.0003960  

   Abed, Ahmad Matar; Peterson, Rebecca L (October 2024, Journal of Vacuum Science & Technology A)

   In this work, we demonstrate the growth and phase stabilization of ultrawide bandgap polycrystalline rutile germanium dioxide (GeO2) thin films. GeO2 thin films were deposited using RF magnetron sputtering on r-plane sapphire (Al2O3) substrates. As-deposited films were x-ray amorphous. Postdeposition annealing was performed at temperatures between 650 and 950 °C in an oxygen or nitrogen ambient. Annealing at temperatures from 750 to 950 °C resulted in mixed-phase polycrystalline films containing tetragonal (rutile) GeO2, hexagonal (α-quartz) GeO2, and/or cubic (diamond) germanium (Ge). When nitrogen was used as the anneal ambient, mixed GeO2 phases were observed. In contrast, annealing in oxygen promoted stabilization of the r-GeO2 phase. Grazing angle x-ray diffraction showed a preferred orientation of (220) r-GeO2 for all crystallized films. The combination of O2 annealing and O2 flux during growth resulted in r-GeO2 films with highly preferential alignment. Using electron microscopy, we observed an interfacial layer of hexagonal-oriented GeO2 with epitaxial alignment to the (11¯02) Al2O3 substrate, which may help stabilize the top polycrystalline r-GeO2 film. 

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3. Developing a platform for Fresnel diffractive radiography with 1 μ m spatial resolution at the National Ignition Facility

   https://doi.org/10.1063/5.0101890  

   Schoelmerich, M. O.; Döppner, T.; Allen, C. H.; Divol, L.; Oliver, M.; Haden, D.; Biener, M.; Crippen, J.; Delora-Ellefson, J.; Ferguson, B.; et al (January 2023, Review of Scientific Instruments)

   An x-ray Fresnel diffractive radiography platform was designed for use at the National Ignition Facility. It will enable measurements of micron-scale changes in the density gradients across an interface between isochorically heated warm dense matter materials, the evolution of which is driven primarily through thermal conductivity and mutual diffusion. We use 4.75 keV Ti K-shell x-ray emission to heat a 1000 μm diameter plastic cylinder, with a central 30 μm diameter channel filled with liquid D2, up to 8 eV. This leads to a cylindrical implosion of the liquid D2 column, compressing it to ∼2.3 g/cm3. After pressure equilibration, the location of the D2/plastic interface remains steady for several nanoseconds, which enables us to track density gradient changes across the material interface with high precision. For radiography, we use Cu He-α x rays at 8.3 keV. Using a slit aperture of only 1 μm width increases the spatial coherence of the source, giving rise to significant diffraction features in the radiography signal, in addition to the refraction enhancement, which further increases its sensitivity to density scale length changes at the D2/plastic interface. 

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4. High spatial resolution direct conversion amorphous selenium X-ray detectors with monolithically integrated CMOS readout

   https://doi.org/10.1088/1748-0221/18/04/P04021  

   Han, Z.; Mukherjee, A.; Albert, A.; Rumaiz, A.K.; Harding, I.; Tate, M.W.; Gruner, S.M.; Thom-Levy, J.; Kuczewski, A.J.; Siddons, D.P.; et al (April 2023, Journal of Instrumentation)

   Abstract Recent progress in the field of micron-scale spatial resolution direct conversion X-ray detectors for high-energy synchrotron light sources serve applications ranging from nondestructive and noninvasive microscopy techniques which provide insight into the structure and morphology of crystals, to medical diagnostic measurement devices. Amorphous selenium ( a -Se) as a wide-bandgap thermally evaporated photoconductor exhibits ultra-low thermal generation rates for dark carriers and has been extensively used in X-ray medical imaging. Being an amorphous material, it can further be deposited over large areas at room temperatures and at substantially lower costs as compared to crystalline semiconductors. To address the demands for a high-energy and high spatial resolution X-ray detector for synchrotron light source applications, we have thermally evaporated a -Se on a Mixed-Mode Pixel Array Detector (MM-PAD) Application Specific Integrated Circuit (ASIC). The ASIC format consists of 128 × 128 square pixels each 150 μm on a side. A 200 μm a -Se layer was directly deposited on the ASIC followed by a metal top electrode. The completed detector assembly was tested with 45 kV Ag and 23 kV Cu X-ray tube sources. The detector fabrication, performances, Modulation Transfer Function (MTF) measurements, and simulations are reported. 

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5. Local structure of Sr ₂ CuO _3.3 , a 95 K cuprate superconductor without CuO ₂ planes

   https://doi.org/10.1073/pnas.1918890117  

   Conradson, Steven D.; Geballe, Theodore H.; Jin, Changqing; Cao, Lipeng; Baldinozzi, Gianguido; Jiang, Jack M.; Latimer, Matthew J.; Mueller, Oliver (February 2020, Proceedings of the National Academy of Sciences)

   The local structure of the highly “overdoped” 95 K superconductor Sr₂CuO_3.3determined by Cu K X-ray absorption fine structure (XAFS) at 62 K in magnetically oriented samples shows that 1) the magnetization is perpendicular to thecaxis; 2) at these levels of precision the Cu sublattice is tetragonal in agreement with the crystal structure; the O sublattice has 3) continuous -Cu-O- chains that orient perpendicular to an applied magnetic field; 4) approximately half-filled -Cu-O- chains that orient parallel to this field; 5) a substantial number of apical O vacancies; 6) O ions at some apical positions with expanded Cu-O distances; and 7) interstitial positions that imply highly displaced Sr ions. These results contradict the universally accepted features of cuprates that require intact CuO₂planes, magnetization along thecaxis, and a termination of the superconductivity when the excess charge on the CuO₂Cu ions exceeds 0.27. These radical differences in charge and structure demonstrate that this compound constitutes a separate class of Cu-O–based superconductors in which the superconductivity originates in a different, more complicated structural unit than CuO₂planes while retaining exceptionally high transition temperatures. 

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