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Remote Activation of H–H Bonds by Platinum in Dilute Alloy Catalysts
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Missing Excitons: How Energy Transfer Competes with Free Charge Generation in Dilute-Donor/Acceptor Systems
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Development of 225 Ac Production from Low Isotopic Dilution 229 Th
The promise of 225 Ac targeted alpha therapies has been on the horizon for the last two decades. TerraPower Isotopes are uniquely suited to produce clinically relevant quantities of 225 Ac through the decay of 229 Th. Herein, a rapid processing scheme to isolate radionuclidic and radioisotopically pure 225 Ac in good yield (98%) produced from 229 Th that contains significant quantities of 228 Th activity is described. The characterization of each step of the process is presented along with the detailed characterization of the resulting 225 Ac isotopic starting material that will support the cancer research and development efforts.
Effect of Dilute Acetic Acid Hydrolysis on Xylooligosaccharide Production and the Inhibitory Effect of Cellulolytic Enzyme Lignin from Poplar
Acetic acid (AC) hydrolysis has been reported to prepare xylooligosaccharides (XOS) from poplar. However, the influence of AC hydrolysis on the lignin structure changes is not clear, which is important for the following enzymatic hydrolysis of poplar. Herein, AC was used to produce XOS, and cellulase adsorption on cellulolytic enzyme lignin (CEL) from AC-hydrolyzed poplar and its inhibitory effect on two commercial cellulase preparations were investigated. AC hydrolysis gave a XOS yield of 39.8% from poplar. After AC hydrolysis at 170 °C, the hydrophobicity and ζ-potential of CEL decreased to 2.3 L/g and 14.8 mV, respectively. The adsorption strength of CTec2 on CEL samples did not increase by AC hydrolysis, and the inhibitory effect of CEL on Celluclast 1.5L and β-glucosidase was observed, but not on CTec2. CEL samples improved the lytic polysaccharide monooxygenase (LPMO) activity of the enzymatic hydrolysis by CTec2. After CEL samples were added in enzymatic hydrolysis, the free filter paper activity of Celluclast 1.5L and β-G retained in the enzymatic hydrolysate decreased from 60.5 to 29.3–42.9%. The addition of CEL samples in enzymatic hydrolysis could not decrease the free filter paper activity of CTec2 retained in the enzymatic hydrolysate. In the enzymatic hydrolysis with CEL samples, higher glucose yields were obtained by CTec2 than those by Celluclast 1.5L and β-glucosidase. This work will help to understand the structure and inhibitory effects of AC-CELs and guide the development of AC hydrolysis for the production of XOS and monosaccharides from poplar.
Facilitating Hydrogen Dissociation over Dilute Nanoporous Ti–Cu Catalysts
The dissociation of H 2 is an essential elementary step in many industrial chemical transformations, typically requiring precious metals. Here, we report a hierarchical nanoporous Cu catalyst doped with small amounts of Ti (npTiCu) that increases the rate of H 2 –D 2 exchange by approximately one order of magnitude compared to the undoped nanoporous Cu (npCu) catalyst. The promotional effect of Ti was measured via steady-state H 2 –D 2 exchange reaction experiments under atmospheric pressure flow conditions in the temperature range of 300–573 K. Pretreatment with flowing H 2 is required for stable catalytic performance, and two temperatures, 523 and 673 K, were investigated. The experimentally determined H 2 –D 2 exchange rate is 5–7 times greater for npTiCu vs the undoped Cu material under optimized pretreatment and reaction temperatures. The H 2 pretreatment leads to full reduction of Cu oxide and partial reduction of surface Ti oxide species present in the as-prepared catalyst as demonstrated using in situ ambient pressure X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. The apparent activation energies and pre-exponential factors measured for H 2 –D 2 exchange are substantially different for Ti-doped vs undoped npCu catalysts. Density functional theory calculations suggest that isolated, metallic Ti atoms on the surface of the Cu host can act as the active surface sites for hydrogen recombination. Furthermore, the increase in the rate of exchange above that of pure Cu is caused primarily by a shift in the rate-determining step from dissociative adsorption on Cu to H/D atom recombination on Ti-doped Cu, with the corresponding decrease in activation entropy that it produces.
Mixed-valence state in the dilute-impurity regime of La-substituted SmB6
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Dilute carbon in H3S under pressure
Abstract Recently, room temperature superconductivity was measured in a carbonaceous sulfur hydride material whose identity remains unknown. Herein, first-principles calculations are performed to provide a chemical basis for structural candidates derived by doping H 3 S with low levels of carbon. Pressure stabilizes unusual bonding configurations about the carbon atoms, which can be six-fold coordinated as CH 6 entities within the cubic H 3 S framework, or four-fold coordinated as methane intercalated into the H-S lattice, with or without an additional hydrogen in the framework. The doping breaks degenerate bands, lowering the density of states at the Fermi level ( N F ), and localizing electrons in C-H bonds. Low levels of CH 4 doping do not increase N F to values as high as those calculated for $$Im\bar{3}m$$ I m 3 ¯ m -H 3 S, but they can yield a larger logarithmic average phonon frequency, and an electron–phonon coupling parameter comparable to that of R 3 m -H 3 S. The implications of carbon doping on the superconducting properties are discussed.
Nanocrystal synthesis, μfluidic sample dilution and direct extraction of single emission linewidths in continuous flow
We present a flow-based system coupled with an optical interferometry setup for the extraction of single nanocrystal properties.
Reply to the ‘Comment on “Migration-assisted, moisture gradient process for ultrafast, continuous CO 2 capture from dilute sources at ambient conditions”’ by J. Casado, Energy Environ. Sci. , 2022, 10.1039/D2EE00555G
Prajapati et al. developed a novel, robust, modular and industrially-scalable CO 2 capture process that utilizes a migration-assisted moisture gradient (MAMG) process.
Ion mobility and solvation complexes at liquid–solid interfaces in dilute, high concentration, and localized high concentration electrolytes
Evolution of a lithium cation solvation complex in low concentration electrolytes (LCEs), high concentration electrolytes (HCEs), and localized high concentration electrolytes (LHCEs) reveals competition of transport, desolvation, and deposition events.
Free-atom-like d states beyond the dilute limit of single-atom alloys
Through the use of high-throughput quantum-mechanical calculations, we uncover a diverse range of metal alloys and intermetallics with “free-atom-like” electronic states and discuss the potential implications for heterogeneous catalyst design.
The evolution of solvation symmetry and composition in Zn halide aqueous solutions from dilute to extreme concentrations
Valence-to-core X-ray emission spectroscopy is combined with electronic structure theory and molecular dynamics simulations to quantify contact ion pairing in Zn halide aqueous electrolytes.