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At least 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Sink or source? Insights into the behavior of copper and zinc in the sediment porewater of a constructed wetland by peepers

The H-02 free water surface constructed wetland has been applied to remove heavy metals, mainly copper (Cu) and zinc (Zn), from wastewater on the Savannah River Site (Aiken, SC, USA). More and more studies focus on the metal behavior between the sediment and the overlying water, which directly reflects the stability of metals after sedimentation in constructed wetlands. This study focused on the biogeochemical pathways in metal bioavailability and remobilization in the sediment after metals were removed from the overlying water. The dialysis sampling devices (peepers) were used to collect porewater samples from eight depths in the sediment for the measurement of Cu, Zn, dissolved organic carbon (DOC), and major anions (sulfate and chloride). Surface water samples were also collected for the measurement of Cu, Zn, DOC, and anions. Different temporal trends were observed for dissolved Cu between the surface and bottom waters, but not for dissolved Zn. There were no obvious changes in porewater metal concentrations with increasing depths in the sediment. Sediment served as a sink for Cu as only 3% of porewater samples showed higher labile Cu concentrations than the surface water during the entire year. Furthermore, sediment served as a source for Zn in summer and winter as 32% of porewater samples showed higher labile Zn concentrations than the surface water, and these samples were collected at all sediment depths. We think the seasonal changes in the behaviors of Cu and Zn were primarily controlled by the sulfur dynamics and the metal removal processes in the constructed wetland, as well as the different complexing chemistry between Cu and Zn. Also, our study supports that peeper is a powerful tool for studying the biogeochemistry of metals in the sediment.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Dynamic Metal–Support Interaction Dictates Cu Nanoparticle Sintering on Al 2 O 3 Surfaces

Nanoparticle sintering remains a critical challenge in heterogeneous catalysis. In this work, we present a unified deep potential (DP) model based on the Perdew–Burke–Ernzerhof approximation of density functional theory for Cu nanoparticles on three Al 2 O 3 surfaces (γ-Al 2 O 3 (100), γ-Al 2 O 3 (110), and α-Al 2 O 3 (0001)). Using DP-accelerated simulations, we reveal that the nanoparticle size-mobility relationship strongly depends on the supporting surface. The diffusion of nanoparticles on the two γ-Al 2 O 3 surfaces is almost independent of the size of the nanoparticle, while the diffusion on α-Al 2 O 3 (0001) decreases rapidly with increasing size. Interestingly, nanoparticles with fewer than 55 atoms diffuse several times faster on α-Al 2 O 3 (0001) than on γ-Al 2 O 3 (100) at 800 K while expected to be more sluggish based on their larger binding energy at 0 K. The diffusion on α-Al 2 O 3 (0001) is facilitated by dynamic metal–support interaction (MSI), where Al atoms move out of the surface plane to optimize contact with the nanoparticle and relax back to the plane as the nanoparticle moves away. In contrast, the MSI on γ-Al 2 O 3 (100) and on γ-Al 2 O 3 (110) is dominated by more stable and directional Cu–O bonds, consistent with the limited diffusion observed on these surfaces. Our extended MD simulations provide insight into the sintering processes, showing that the dispersity of the nanoparticles strongly influences the coalescence driven by nanoparticle diffusion. We observed that the coalescence of Cu 13 nanoparticles on α-Al 2 O 3 (0001) can occur in a short time (10 ns) at 800 K even with an initial internanoparticle distance increased to 3 nm, while the coalescence on the two γ-Al 2 O 3 surfaces are inhibited significantly by increasing the initial internanoparticle distance. These findings demonstrate that the dynamics of the supporting surface is crucial to understanding the sintering mechanism and offer guidance for designing sinter-resistant catalysts by engineering the support morphology.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Cu19Se11 by Materials Project

Cu19Se11 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are nineteen inequivalent Cu+1.16+ sites. In the first Cu+1.16+ site, Cu+1.16+ is bonded to four Se2- atoms to form corner-sharing CuSe4 trigonal pyramids. There are a spread of Cu–Se bond distances ranging from 2.38–2.55 Å. In the second Cu+1.16+ site, Cu+1.16+ is bonded to four Se2- atoms to form distorted corner-sharing CuSe4 tetrahedra. There are a spread of Cu–Se bond distances ranging from 2.35–2.63 Å. In the third Cu+1.16+ site, Cu+1.16+ is bonded in a 2-coordinate geometry to two equivalent Se2- atoms. There are one shorter (2.47 Å) and one longer (2.53 Å) Cu–Se bond lengths. In the fourth Cu+1.16+ site, Cu+1.16+ is bonded to four Se2- atoms to form distorted corner-sharing CuSe4 tetrahedra. There are a spread of Cu–Se bond distances ranging from 2.42–2.60 Å. In the fifth Cu+1.16+ site, Cu+1.16+ is bonded to one Cu+1.16+ and four Se2- atoms to form CuCuSe4 tetrahedra that share corners with nine CuSe4 tetrahedra and edges with three equivalent CuCu3Se4 tetrahedra. The Cu–Cu bond length is 2.51 Å. There are a spread of Cu–Se bond distances ranging from 2.41–2.54 Å. In the sixth Cu+1.16+ site, Cu+1.16+ is bonded in a 3-coordinate geometry to four Cu+1.16+ and six Se2- atoms. There are one shorter (2.50 Å) and two longer (2.51 Å) Cu–Cu bond lengths. There are a spread of Cu–Se bond distances ranging from 2.51–3.23 Å. In the seventh Cu+1.16+ site, Cu+1.16+ is bonded to three equivalent Cu+1.16+ and four Se2- atoms to form distorted CuCu3Se4 tetrahedra that share corners with three equivalent CuSe4 tetrahedra and edges with nine CuCuSe4 tetrahedra. There are a spread of Cu–Se bond distances ranging from 2.47–2.56 Å. In the eighth Cu+1.16+ site, Cu+1.16+ is bonded to four Se2- atoms to form corner-sharing CuSe4 tetrahedra. There are a spread of Cu–Se bond distances ranging from 2.42–2.49 Å. In the ninth Cu+1.16+ site, Cu+1.16+ is bonded to four Se2- atoms to form a mixture of corner and edge-sharing CuSe4 tetrahedra. There are a spread of Cu–Se bond distances ranging from 2.51–2.54 Å. In the tenth Cu+1.16+ site, Cu+1.16+ is bonded to four Se2- atoms to form a mixture of corner and edge-sharing CuSe4 tetrahedra. There are a spread of Cu–Se bond distances ranging from 2.45–2.51 Å. In the eleventh Cu+1.16+ site, Cu+1.16+ is bonded to four Se2- atoms to form a mixture of corner and edge-sharing CuSe4 tetrahedra. There are a spread of Cu–Se bond distances ranging from 2.35–2.53 Å. In the twelfth Cu+1.16+ site, Cu+1.16+ is bonded to four Se2- atoms to form a mixture of distorted corner and edge-sharing CuSe4 tetrahedra. There are a spread of Cu–Se bond distances ranging from 2.57–2.67 Å. In the thirteenth Cu+1.16+ site, Cu+1.16+ is bonded to four Se2- atoms to form a mixture of corner and edge-sharing CuSe4 tetrahedra. There are a spread of Cu–Se bond distances ranging from 2.41–2.57 Å. In the fourteenth Cu+1.16+ site, Cu+1.16+ is bonded to four Se2- atoms to form distorted corner-sharing CuSe4 tetrahedra. There are a spread of Cu–Se bond distances ranging from 2.56–2.66 Å. In the fifteenth Cu+1.16+ site, Cu+1.16+ is bonded to four Se2- atoms to form a mixture of corner and edge-sharing CuSe4 tetrahedra. There are a spread of Cu–Se bond distances ranging from 2.44–2.57 Å. In the sixteenth Cu+1.16+ site, Cu+1.16+ is bonded in a 3-coordinate geometry to three Se2- atoms. There are a spread of Cu–Se bond distances ranging from 2.69–2.90 Å. In the seventeenth Cu+1.16+ site, Cu+1.16+ is bonded in a distorted trigonal non-coplanar geometry to three equivalent Se2- atoms. There are one shorter (2.44 Å) and two longer (2.47 Å) Cu–Se bond lengths. In the eighteenth Cu+1.16+ site, Cu+1.16+ is bonded in a 2-coordinate geometry to three equivalent Se2- atoms. There are a spread of Cu–Se bond distances ranging from 2.65–3.03 Å. In the nineteenth Cu+1.16+ site, Cu+1.16+ is bonded in a 3-coordinate geometry to four Se2- atoms. There are a spread of Cu–Se bond distances ranging from 2.46–2.97 Å. There are eleven inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 8-coordinate geometry to eight Cu+1.16+ atoms. In the second Se2- site, Se2- is bonded to four Cu+1.16+ atoms to form corner-sharing SeCu4 trigonal pyramids. In the third Se2- site, Se2- is bonded in a distorted hexagonal planar geometry to six Cu+1.16+ atoms. In the fourth Se2- site, Se2- is bonded in a 4-coordinate geometry to four Cu+1.16+ atoms. In the fifth Se2- site, Se2- is bonded in a 5-coordinate geometry to seven Cu+1.16+ atoms. In the sixth Se2- site, Se2- is bonded in a 4-coordinate geometry to seven Cu+1.16+ atoms. In the seventh Se2- site, Se2- is bonded to four Cu+1.16+ atoms to form corner-sharing SeCu4 tetrahedra. In the eighth Se2- site, Se2- is bonded in a 7-coordinate geometry to seven Cu+1.16+ atoms. In the ninth Se2- site, Se2- is bonded in a body-centered cubic geometry to eight Cu+1.16+ atoms. In the tenth Se2- site, Se2- is bonded in a 7-coordinate geometry to eight Cu+1.16+ atoms. In the eleventh Se2- site, Se2- is bonded in a 3-coordinate geometry to ten Cu+1.16+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Deactivation of Cu-Exchanged Automotive-Emission NH 3 -SCR Catalysts Elucidated with Nanoscale Resolution Using Scanning Transmission X-ray Microscopy

To gain insight into the underlying mechanisms of catalyst durability for the selective catalytic reduction (SCR) of NO x with an ammonia reductant, we employed scanning transmission X-ray microscopy (STXM) to study Cu-exchanged zeolites with the CHA and MFI framework structures before and after simulated 135 000-mile aging. X-ray absorption near-edge structure (XANES) measurements were performed at the Al K- and Cu L-edges. The local environment of framework Al, the oxidation state of Cu, and geometric changes were analyzed, showing a multi-factor-induced catalytic deactivation. In Cu-exchanged MFI, a transformation of Cu II to Cu I and Cu x O y was observed. We also found a spatial correlation between extra-framework Al and deactivated Cu species near the surface of the zeolite as well as a weak positive correlation between the amount of CuI and tri-coordinated Al. By inspecting both Al and Cu in fresh and aged Cu-exchanged zeolites, we conclude that the importance of the preservation of isolated Cu II sites trumps that of Brønsted acid sites for NH 3 -SCR activity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Zr6Al7Cu16H3 by Materials Project

Zr6Cu16Al7H3 crystallizes in the orthorhombic Imm2 space group. The structure is three-dimensional. there are three inequivalent Zr sites. In the first Zr site, Zr is bonded in a 1-coordinate geometry to seven Cu, one Al, and two H atoms. There are a spread of Zr–Cu bond distances ranging from 2.91–2.95 Å. The Zr–Al bond length is 3.05 Å. There are one shorter (2.06 Å) and one longer (2.46 Å) Zr–H bond lengths. In the second Zr site, Zr is bonded in a distorted L-shaped geometry to six Cu and two equivalent H atoms. There are four shorter (2.88 Å) and two longer (2.92 Å) Zr–Cu bond lengths. Both Zr–H bond lengths are 2.11 Å. In the third Zr site, Zr is bonded in a single-bond geometry to eight Cu and one H atom. There are six shorter (2.92 Å) and two longer (2.95 Å) Zr–Cu bond lengths. The Zr–H bond length is 2.13 Å. There are eight inequivalent Cu sites. In the first Cu site, Cu is bonded in a 3-coordinate geometry to three Zr, six Cu, and three Al atoms. There are a spread of Cu–Cu bond distances ranging from 2.67–2.71 Å. All Cu–Al bond lengths are 2.45 Å. In the second Cu site, Cu is bonded in a 1-coordinate geometry to three Zr, six Cu, and four Al atoms. There are a spread of Cu–Cu bond distances ranging from 2.63–2.88 Å. There are one shorter (2.49 Å) and three longer (2.65 Å) Cu–Al bond lengths. In the third Cu site, Cu is bonded in a 7-coordinate geometry to three Zr, six Cu, and four Al atoms. There are a spread of Cu–Cu bond distances ranging from 2.64–2.87 Å. There are a spread of Cu–Al bond distances ranging from 2.48–2.65 Å. In the fourth Cu site, Cu is bonded in a 7-coordinate geometry to three Zr, six Cu, and four Al atoms. The Cu–Cu bond length is 2.69 Å. There are a spread of Cu–Al bond distances ranging from 2.49–2.64 Å. In the fifth Cu site, Cu is bonded in a 7-coordinate geometry to three Zr, six Cu, and four Al atoms. Both Cu–Cu bond lengths are 2.65 Å. There are a spread of Cu–Al bond distances ranging from 2.48–2.65 Å. In the sixth Cu site, Cu is bonded in a distorted single-bond geometry to five Cu, three Al, and one H atom. Both Cu–Cu bond lengths are 2.61 Å. There are two shorter (2.47 Å) and one longer (2.49 Å) Cu–Al bond lengths. The Cu–H bond length is 1.79 Å. In the seventh Cu site, Cu is bonded in a 3-coordinate geometry to three Zr, six Cu, and three Al atoms. The Cu–Cu bond length is 2.69 Å. There are one shorter (2.45 Å) and two longer (2.46 Å) Cu–Al bond lengths. In the eighth Cu site, Cu is bonded in a 3-coordinate geometry to three Zr, six Cu, and three Al atoms. The Cu–Cu bond length is 2.66 Å. There are two shorter (2.44 Å) and one longer (2.45 Å) Cu–Al bond lengths. There are four inequivalent Al sites. In the first Al site, Al is bonded in a 12-coordinate geometry to eight Cu atoms. In the second Al site, Al is bonded in a 12-coordinate geometry to eight Cu atoms. In the third Al site, Al is bonded to four equivalent Zr and eight Cu atoms to form distorted AlZr4Cu8 cuboctahedra that share corners with four equivalent HZr3Cu tetrahedra and edges with two equivalent HZr5 square pyramids. In the fourth Al site, Al is bonded in a body-centered cubic geometry to eight Cu atoms. There are two inequivalent H sites. In the first H site, H is bonded to five Zr atoms to form distorted HZr5 square pyramids that share edges with two equivalent AlZr4Cu8 cuboctahedra and edges with two equivalent HZr3Cu tetrahedra. In the second H site, H is bonded to three Zr and one Cu atom to form HZr3Cu tetrahedra that share corners with two equivalent AlZr4Cu8 cuboctahedra, a cornercorner with one HZr3Cu tetrahedra, and an edgeedge with one HZr5 square pyramid.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Mixed-Valent Copper Chalcogenides: Tuning Structures and Electronic Properties Using Multiple Anions

A series of mixed-anion copper chalcogenides have been prepared using solid-state methods including ACu 4.2 TeS 2 (A = K, Rb, Cs), which adopt the KCu 4 S 3 structure type. The mixedanion motif has an expanded sublattice, relative to KCu 4 S 3 , that can accommodate additional Cu atoms at its interstitial sites that are unoccupied in the parent structure. The variable temperature transport shows that the materials are p-type metals with carrier densities on the order of 10 21 cm -3 and room-temperature electrical conductivity as high as 4000 S cm -1 . Band structures calculated using density functional theory corroborate the experimental data and indicate that the interstitial Cu atoms lower the carrier concentration and increase the Fermi level of the materials. The layered structure has Te and S atoms occupying unique sites within the ACu 4.2 TeS 2 structure, where relatively hard S 2- anions prefer Wyckoff positions where they can form energetically favorable acid-base interactions with hard alkali cations. The phenomenon is observed in the related K 3 Cu 8 Te 2 S 4 system, which also has a fully ordered layered structure. Here, we believe that the report provides new chemical guidelines for targeting ordered multianion structures, as well as a unique method for tuning the electronic properties of metallic chalcogenides.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Electrochemical control over stoichiometry via cation intercalation into Chevrel-phase sulphides (Cu x Mo 6 S 8 , x = 1-3)

Herein this work presents a systematic investigation of the electrochemical intercalation of aqueous copper cations into the Chevrel phase (CP) Mo 6 S 8 and its effect on the host's electronic and structural characteristics as a function of stoichiometry. The electrochemical potentials at which copper intercalates into the CP Mo 6 S 8 host in 1 M CuSO 4 were identified for Cu x Mo 6 S 8 (x = 1–3) as 0.23 V, 0.11 V, and 0.055 V (vs. Cu/Cu 2+ ) for Cu 1 Mo 6 S 8 , Cu 2 Mo 6 S 8 , and Cu 3 Mo 6 S 8 , respectively, and correlated via ex situ PXRD to stoichiometric content. Potentials were also identified that yield non-stoichiometric phases with traceable Cu content-dependent structural changes. Ab initio DFT calculations were performed to probe thermodynamic stability of Cu x Mo 6 S 8 CP compositions and the metal-to-semiconductor transitions as a function of copper content. Lastly, we demonstrate that the SK-pre-edge intensity is a successful probe for intercalant content: as copper equivalents increase, so does charge transfer to the partially occupied S 3p orbitals, resulting in a decrease in the pre-edge intensity corresponding to the excitation of a S 1s-to-3p/Mo 4d hybridized orbital.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Progress and prospects for cuprate high temperature superconductors under pressure

Since the discovery of high temperature superconductivity in La 5–x Ba x Cu 5 O 5(3–y) at an unprecedented T c of 35K over 35 years ago, high pressure experiments have played a critical role in understanding cuprate superconductivity. Soon after its discovery, compression experiments on La 5–x Ba x Cu 5 O 5(3–y) revealed a large dT c /dP, motivating the study of ‘chemical pre-compression’ in the material that led to the 90K Superconductor YBa 2 Cu 3 O 7–y . Cuprate superconductors discovered subsequently exhibited a range of Tc from 30K-140K, including the commonly studied Bi, Tl, and Hg based families. Here, pressure has large effects on superconductivity in these materials, including raising T c in the Hg based cuprates from 140K to 164K at 30 GPa. Reviewing past experiments indicate that pressure dopes holes into the CuO 2 planes common to all cuprates. Further detailed high-pressure studies of these materials should deepen our understanding of cuprate superconductivity and the possibility of reaching still higher T c in cuprates.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Interpretable machine learning-guided design of Fe-based soft magnetic alloys

Here, we present a machine learning (ML) guided approach to predict saturation magnetization (𝑀 S ) and coercivity (𝐻 C ) in Fe-rich soft magnetic alloys, particularly Fe-Si-B systems. ML models trained on experimental data reveal that increasing Si and B content reduces 𝑀 S from 1.81 T (DFT ≈ 2.04 T) to ≈1.54 T (DFT ≈ 1.56T) in Fe-Si-B, which is attributed to decreased magnetic density and structural modifications. Experimental validation of ML predicted magnetic saturation on Fe-1Si-1B (2.09 T), Fe-5Si-5B (2.01 T), and Fe-10Si-10B (1.54 T) alloy compositions further supports our findings. These trends are consistent with density functional theory predictions, which link increased electronic disorder and band broadening to lower 𝑀 S values. Experimental validation on selected alloys confirms the predictive accuracy of the ML model, with good agreement across compositions. Beyond predictive accuracy, detailed uncertainty quantification and model interpretability including through feature importance and partial dependence analysis reveal that 𝑀 S is governed by a nonlinear interplay between Fe content and early transition metal ratios, while 𝐻 C is more sensitive to processing conditions such as ribbon thickness and thermal treatment windows. The ML framework was further applied to Fe-Si-B/Cr/Cu/Zr/Nb alloys in a pseudoquaternary compositional space, which shows comparable magnetic properties to NANOMET (Fe 84.8 ⁢Si 0.5 ⁢B 9.4 ⁢Cu 0.8⁢ P 3.5 ⁢C 1 ), FINEMET (Fe 73.5 ⁢Si 13.5 ⁢B 9 Cu 1 ⁢Nb 3 ), NANOPERM (Fe 88 ⁢Zr 7⁢ B 4 ⁢Cu 1 ), and HITPERM (Fe 44 ⁢Co 44 ⁢Zr 7⁢ B 4 ⁢Cu 1 . Our findings demonstrate the potential of the ML framework for accelerated search of high-performance soft magnetic materials.

density functional theory↗
DOE OSTI2023

Highly-Conductive and Durable SOFC Cathode-Side Contact Based on Reactively-Sintered Mn-Co Spinel

A cathode-side contact layer with well-matched coefficient of thermal expansion is needed to prevent cracking of solid oxide fuel cell stacks from thermal cycling during stack operations. An Mn 1.25 Co 1.75 O 4 (MCO) spinel layer synthesized via reactive sintering with a metal-containing precursor was proposed as a highly conductive and durable contact material. Compared to the interconnect/contact/cathode assemblies with the (La 0.80 Sr 0.20 ) 0.95 MnO 3-x and La(Mn 0.45 Co 0.35 Cu 0.2 )O 3 contacts, the assembly with the MCO contact exhibited the lowest area-specific resistance at 800 °C (8.2 mΩ·cm 2 ) during 2000-h cyclic exposure and was crack-free based on the cross-sectional examination, indicative of the superiority of the spinel contact over the perovskite counterparts.

Electrochemistry↗
NASA NTRS1990

Electrochemistry of cations in diopsidic melt - Determining diffusion rates and redox potentials from voltammetric curves

Results are presented on determinations of reduction potentials and their temperature dependence of selected ions in diopsidic melt, by using linear sweep voltammetry. Diffusion coefficients were measured for cations of Eu, Mn, Cr, and In. Enthalpies and entropies of reduction were determined for the cations V(V), Cr(3+), Mn(2+), Mn(3+), Fe(2+), Cu(2+), Mo(VI), Sn(IV), and Eu(3+). Reduction potentials were used to study the structural state of cations in the melt.

Colson, Russell O.↗
DOE OSTI2022

Nickel foam supported porous copper oxide catalysts with noble metal-like activity for aqueous phase reactions

Contiguous metal foams offer a multitude of advantages over conventional powders as supports for nanostructured heterogeneous catalysts; most critically a preformed 3-D porous framework ensuring full directional coverage of supported catalyst, and intrinsic ease of handling and recyclability. Nonetheless, metal foams remain comparatively underused in thermal catalysis compared to more conventional supports such as amorphous carbon, metal oxides, zeolites and more recently MOFs. Herein, we demonstrate a facile preparation of highly-reactive, robust, and easy to handle Ni foam-supported Cu-based metal catalysts. The highly sustainable synthesis requires no specialized equipment, no surfactants or additive redox reagents, uses water as solvent, and CuCl 2 (H 2 O) 2 as precursor. The resulting material seeds as well-separated micro-crystalline Cu 2 (OH) 3 Cl evenly covering the Ni foam. Calcination above 400 °C transforms the Cu 2 (OH) 3 Cl to highly porous CuO. All materials display promising activity towards the reduction of 4-nitrophenol and methyl orange. Notably, our leading CuO-based material displays 4-nitrophenol reduction activity comparable with very reactive precious-metal based systems. Furthermore, recyclability studies highlight the intrinsic ease of handling for the Ni foam support, and our results point to a very robust, highly recyclable catalyst system.

36 MATERIALS SCIENCE↗
DOE OSTI2020

The Activation of Hydrogen by First-Row Transition-Metal Complexes. Final Report

We have assigned the vibrational spectra of Os 1 and Os 2 complexes of propene, butene, and acetylene, and have used them for the assignment of the vibrational frequencies of surface alkenes and alkynes. We have measured the rates of H• transfer from (C 5 R 5 )Cr(CO) 3 H to olefins of many structural types, and have learned that even one substituent on the carbon to which the H• is transferred slows down the reaction considerably. We have shown that these Cr hydrides are useful catalysts for chain transfer during radical polymerization reactions. We have determined the strengths of several M–H bonds (in particular Cr–H ones), and have confirmed that the hydrides of first-row transition metals are particularly useful for generating radicals. We have used H• transfer to terminal methylenes to generate radicals that cyclize. We have shown that (C 5 R 5 )Cr(CO) 3 H can be regenerated under H 2 and is therefore catalytic, but that (P–P)V(CO) 4 H cannot be regenerated from H 2 and therefore can only be used stoichiometrically for radical generation. (The V-H bonds are weaker than the Cr–H ones, and the H• transfer to an olefin is therefore faster.) We have found that, under five atm of H 2 pressure, cobaloximes catalyze H• transfer; they efficiently remove an H• from cyclized radicals, and therefore can be used to catalyze the cycloisomerization of some olefins. We have explored the one- and two-electron oxidation of (Ph 3 P) 6 Cu 6 H 6 . One-electron oxidation (which is reversible) generates a cation radical, whereas two-electron oxidation generates loss of a hydride (i.e., two electrons and a proton). We have found that the hydricity of (Ph 3 P) 6 Cu 6 H 6 is between 36 and 50 kcal/mol. We have shown that uncongested organic radicals (i.e., TEMPO) can catalyze H• transfer from (C 5 R 5 )Cr(CO) 3 H to congested radicals like Ar 3 C•. We have examined the one-electron oxidation of [CpV(CO 3 H] – , and have inferred from the results that the reduction of alkyl iodides with [CpV(CO 3 H] – occurs by one-electron transfer. We have been able to use that reagent to catalyze radical cyclizations from H 2 and appropriate alkyl iodides.

08 HYDROGEN↗
DOE OSTI2026

Study of Key 57 Ni ⁢(𝑝,𝛾)⁢ 58 Cu Resonances to Understand 44 Ti Nucleosynthesis in Supernovae

An important validation of nucleosynthesis models of core-collapse supernovae is the comparison of radioisotope predictions to abundances inferred from observations of 𝛾 rays emitted in remnants. One such isotope, 44 Ti, is especially sensitive to the 57 Ni ⁢(𝑝,𝛾)⁢ 58 Cu reaction rate. Despite this importance, no experimentally constrained rate exists for this reaction. It is thus crucial to determine this rate. GRETINA ORRUBA: Dual Detectors for Experimental Structure Studies (GODDESS) was used along with the first use of the Enge split-pole spectrograph at Notre Dame to measure structure properties of 58 Cu via the 58 Ni ⁢( 3 He,𝑡)⁢ 58 Cu reaction. Here, the combined analysis of these complementary data sets allows for precise determination of 58 Cu level energies, and spins are constrained from analysis of the 𝛾-ray decay. 44 Ti yields were found to change by over 25% compared to previous estimates in model calculations using the new experimentally constrained reaction rate.

energy levels↗
NASA NTRS1994

Trans-Bis(acetato-0)bis(4-methylpyridine-N)copper(II)

The structure of trans-bis(acetato-O)bis (4-methylpyridine-N)copper(II), (Cu(C2H3O2)2(C6H7N)2), reported herein, represents a monomeric parent acetate complex with a distorted square-planar arrangement of acetate and 4-methylpyridine ligands around the Cu atom with the following distances and angles: Cu-N = 2.027(4) and Cu-O(1) = 1.950 (3) A; O(1)-Cu-N = 89.1 (2) and O(1)-Cu-N' = 90.0(2)deg. The Cu atom resides on a center of inversion. the most important dihedral angles are the angle between the 4-methylpyridine plane and the acetate plane (O(1), O(2), C(21), and C(22)), 78.2 deg, and the angle between the 4-methylpyridine ring and the coordination plane (Cu, N, O(1)), 31.6 deg.

Jedrzejas, Marek J.↗
DOE OSTI2021

Controlling Infrared Plasmon Resonances in Inverse-Spinel Cadmium Stannate Nanocrystals via Site-Selective Cation-Exchange Reactions

Doped metal oxide nanocrystals (NCs) exhibit tunable localized surface plasmon resonances (LSPRs) in the infrared spectral region. Compared to the binary oxides commonly studied, plasmonic NCs derived from ternary oxides remain far less explored primarily due to the difficulty of controlling NC phase-purity and stoichiometry. Here, we report the synthesis of inverse spinel-type cadmium stannate (Cd 2 SnO 4 ) NCs, for which cation-exchange reactions were developed to tailor their composition and LSPR properties. X-ray absorption spectroscopy studies revealed that the inequivalent tetrahedrally and octahedrally coordinated Cd 2+ can be selectively exchanged for Cu + and In 3+ ions, respectively, enabling broadband tunable LSPR and Cu-mediated cation-exchange with lanthanide ions that are otherwise difficult to incorporate. Here, our work paves the way for systematic compositional engineering to accelerate the design of complex metal oxide NCs with emerging plasmonic, electronic, and magnetic properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗