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1. Accurate Determination of the Quantity and Spatial Distribution of Counterions around a Spherical Macroion

   https://doi.org/10.1002/anie.202013806  

   Chen, Jiahui; Bera, Mrinal K.; Li, Hui; Yang, Yuqing; Sun, Xinyu; Luo, Jiancheng; Baughman, Jessi; Liu, Cheng; Yao, Xuesi; Chuang, Steven S. C.; et al (January 2021, Angewandte Chemie International Edition)

   Abstract The accurate distribution of countercations (Rb⁺and Sr²⁺) around a rigid, spherical, 2.9‐nm size polyoxometalate cluster, {Mo₁₃₂}⁴²⁻, is determined by anomalous small‐angle X‐ray scattering. Both Rb⁺and Sr²⁺ions lead to shorter diffuse lengths for {Mo₁₃₂} than prediction. Most Rb⁺ions are closely associated with {Mo₁₃₂} by staying near the skeleton of {Mo₁₃₂} or in the Stern layer, whereas more Sr²⁺ions loosely associate with {Mo₁₃₂} in the diffuse layer. The stronger affinity of Rb⁺ions towards {Mo₁₃₂} than that of Sr²⁺ions explains the anomalous lower critical coagulation concentration of {Mo₁₃₂} with Rb⁺compared to Sr²⁺. The anomalous behavior of {Mo₁₃₂} can be attributed to majority of negative charges being located at the inner surface of its cavity. The longer anion–cation distance weakens the Coulomb interaction, making the enthalpy change owing to the breakage of hydration layers of cations more important in regulating the counterion–{Mo₁₃₂} interaction. 

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2. Single Spot Rb‐Sr Isochron Dating of Biotite by LA‐MC‐ICP‐MS / MS

   https://doi.org/10.1111/ggr.12518  

   Cruz‐Uribe, Alicia M.; Craig, Grant; Garber, Joshua M.; Paul, Bence; Arkula, Cemil; Bouman, Claudia (July 2023, Geostandards and Geoanalytical Research)

   Laser ablation tandem mass spectrometry is a burgeoning field forin situRb‐Sr geochronology. Here, we determined simultaneous isotope ratios of⁸⁷Sr/⁸⁶Sr and⁸⁷Rb/⁸⁶Sr in metamorphic biotite from western Maine, using an ESL™ imageGEO™193 excimer laser ablation system coupled to a Thermo Scientific™ Neoma™ MC‐ICP‐MS/MS. Measurements were made on Faraday cups with Rb⁺at mass 87; Sr isotopes were reacted with SF₆gas and measured as SrF⁺at masses 103–107. Twenty‐two laser spots in biotite from a single sample yield a traditional Rb‐Sr isochron date of 289 ± 6 Ma. Time‐resolved signals reveal significant zoning in⁸⁷Sr/⁸⁶Sr and⁸⁷Rb/⁸⁶Sr within single spot analyses, which were used to construct single spot isochrons. Individual laser spots contain multiple isochronous subpopulations; some spots contain up to three distinct Rb‐Sr isochrons that are decoupled from variations in Rb/Sr. Thirty‐five isochron dates were determined using this sub‐spot approach, with⁸⁷Sr/⁸⁶Sr intercepts that systematically vary with Rb‐Sr date; two‐point isochrons were calculated for individual integrations (n= 780) based on these variable intercepts. Both methods yield age peaks at 303, 270 and 240 Ma. These data suggest that the Rb‐Sr system has the potential to record multiple heating, cooling or fluid‐alteration events spanning ~ 100 My within small domains in single biotite crystals. 

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3. Measurement-induced heating of a trapped ion

   https://doi.org/10.1088/1361-6455/ad838a  

   Rasmusson, A_J; Jung, Ilyoung; Schroer, Frank_G; Kyprianidis, Antonis; Richerme, Philip (October 2024, Journal of Physics B: Atomic, Molecular and Optical Physics)

   Abstract We experimentally study the heating of trapped atomic ions during measurement of their internal qubit states. During measurement, ions are projected into one of two basis states and discriminated by their state-dependent fluorescence. We observe that ions in the fluorescing state rapidly scatter photons and heat at a rate of $\dot{\overline{n}}\gtrsim 2\times {10}^4$quanta s⁻¹, which is orders of magnitude faster than typical anomalous ion heating rates. We introduce a quantum trajectory-based framework that accurately reproduces the experimental results and provides a unified description of ion heating for both continuous and discrete sources. 

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4. The Role of Lewis Acid Sites in γ‐Al ₂ O ₃ Oligomerization

   https://doi.org/10.1002/cphc.202300244  

   Breckner, Christian_J; Pham, Hien_N; Dempsey, Michael_G; Perez‐Ahuatl, Michelle_A; Kohl, Alyssa_C; Lytle, Corryn_N; Datye, Abhaya_K; Miller, Jeffrey_T (June 2023, ChemPhysChem)

   Abstract Olefin oligomerization by γ‐Al₂O₃has recently been reported, and it was suggested that Lewis acid sites are catalytic. The goal of this study is to determine the number of active sites per gram of alumina to confirm that Lewis acid sites are indeed catalytic. Addition of an inorganic Sr oxide base resulted in a linear decrease in the propylene oligomerization conversion at loadings up to 0.3 wt %; while, there is a >95 % loss in conversion above 1 wt % Sr. Additionally, there was a linear decrease in the intensity of the Lewis acid peaks of absorbed pyridine in the IR spectra with an increase in Sr loading, which correlates with the loss in propylene conversion, suggesting that Lewis acid sites are catalytic. Characterization of the Sr structure by XAS and STEM indicates that single Sr²⁺ions are bound to the γ‐Al₂O₃surface and poison one catalytic site per Sr ion. The maximum loading needed to poison all catalytic sites, assuming uniform surface coverage, was ∼0.4 wt % Sr, giving an acid site density of ∼0.2 sites per nm²of γ‐Al₂O₃, or approximately 3 % of the alumina surface. 

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5. Amorphous K–Co–Mo–S _x Chalcogel: A Synergy of Surface Sorption and Ion‐Exchange

   https://doi.org/10.1002/smll.202400679  

   Nie, Jing; Islam, Taohedul; Roy, Subrata Chandra; Li, Dien; Amin, Ruhul; Taylor‐Pashow, Kathryn; Zhu, Xianchun; Feng, Renfei; Chernikov, Roman; Pramanik, Avijit; et al (March 2024, Small)

   Abstract Chalcogel represents a unique class of meso‐ to macroporous nanomaterials that offer applications in energy and environmental pursuits. Here, the synthesis of an ion‐exchangeable amorphous chalcogel using a nominal composition of K₂CoMo₂S₁₀(KCMS) at room temperature is reported. Synchrotron X‐ray pair distribution function (PDF), X‐ray absorption near‐edge structure (XANES), and extended X‐ray absorption fine structure (EXAFS) reveal a plausible local structure of KCMS gel consisting of Mo⁵⁺₂and Mo⁴⁺₃clusters in the vicinity of di/polysulfides which are covalently linked by Co²⁺ions. The ionically bound K⁺ions remain in the percolating pores of the Co–Mo–S covalent network. XANES of Co K‐edge shows multiple electronic transitions, including quadrupole (1s→3d), shakedown (1s→4p + MLCT), and dipole allowed 1s→4p transitions. Remarkably, despite a lack of regular channels as in some crystalline solids, the amorphous KCMS gel shows ion‐exchange properties with UO₂²⁺ions. Additionally, it also presents surface sorption via [S∙∙∙∙UO₂²⁺] covalent interactions. Overall, this study underscores the synthesis of quaternary chalcogels incorporating alkali metals and their potential to advance separation science for cations and oxo‐cationic species by integrating a synergy of surface sorption and ion‐exchange. 

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