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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Large orbital polarization in nickelate-cuprate heterostructures by dimensional control of oxygen coordination

Artificial heterostructures composed of dissimilar transition metal oxides provide unprecedented opportunities to create remarkable physical phenomena. Here, we report a means to deliberately control the orbital polarization in LaNiO 3 (LNO) through interfacing with SrCuO 2 (SCO), which has an infinite-layer structure for CuO 2 . Dimensional control of SCO results in a planar-type (P-SCO) to chain-type (C-SCO) structure transition depending on the SCO thickness. This transition is exploited to induce either a NiO 5 pyramidal or a NiO 6 octahedral structure at the SCO/LNO interface. Consequently, a large change in the Ni d orbital occupation up to similar to 30% is achieved in P-SCO/LNO superlattices, whereas the Ni e g orbital splitting is negligible in C-SCO/LNO superlattices. The engineered oxygen coordination triggers a metal-to-insulator transition in SCO/LNO superlattices. Our results demonstrate that interfacial oxygen coordination engineering provides an effective means to manipulate the orbital configuration and associated physical properties, paving a pathway towards the advancement of oxide electronics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Highly selective oxygen reduction to hydrogen peroxide on transition metal single atom coordination

Abstract Shifting electrochemical oxygen reduction towards 2e – pathway to hydrogen peroxide (H 2 O 2 ), instead of the traditional 4e – to water, becomes increasingly important as a green method for H 2 O 2 generation. Here, through a flexible control of oxygen reduction pathways on different transition metal single atom coordination in carbon nanotube, we discovered Fe-C-O as an efficient H 2 O 2 catalyst, with an unprecedented onset of 0.822 V versus reversible hydrogen electrode in 0.1 M KOH to deliver 0.1 mA cm −2 H 2 O 2 current, and a high H 2 O 2 selectivity of above 95% in both alkaline and neutral pH. A wide range tuning of 2e – /4e – ORR pathways was achieved via different metal centers or neighboring metalloid coordination. Density functional theory calculations indicate that the Fe-C-O motifs, in a sharp contrast to the well-known Fe-C-N for 4e – , are responsible for the H 2 O 2 pathway. This iron single atom catalyst demonstrated an effective water disinfection as a representative application.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Manipulating the oxygen reduction reaction pathway on Pt-coordinated motifs

Electrochemical oxygen reduction could proceed via either 4e - -pathway toward maximum chemical-to-electric energy conversion or 2e - -pathway toward onsite H 2 O 2 production. Bulk Pt catalysts are known as the best monometallic materials catalyzing O 2 -to-H 2 O conversion, however, controversies on the reduction product selectivity are noted for atomic dispersed Pt catalysts. Here, we prepare a series of carbon supported Pt single atom catalyst with varied neighboring dopants and Pt site densities to investigate the local coordination environment effect on branching oxygen reduction pathway. Manipulation of 2e - or 4e - reduction pathways is demonstrated through modification of the Pt coordination environment from Pt-C to Pt-N-C and Pt-S-C, giving rise to a controlled H 2 O 2 selectivity from 23.3% to 81.4% and a turnover frequency ratio of H 2 O 2 /H 2 O from 0.30 to 2.67 at 0.4 V versus reversible hydrogen electrode. Energetic analysis suggests both 2e - and 4e - pathways share a common intermediate of *OOH, Pt-C motif favors its dissociative reduction while Pt-S and Pt-N motifs prefer its direct protonation into H 2 O 2 . By taking the Pt-N-C catalyst as a stereotype, we further demonstrate that the maximum H 2 O 2 selectivity can be manipulated from 70 to 20% with increasing Pt site density, providing hints for regulating the stepwise oxygen reduction in different application scenarios.

36 MATERIALS SCIENCE↗
DOE OSTI2024

The elite haplotype OsGATA8 -H coordinates nitrogen uptake and productive tiller formation in rice

Excessive nitrogen promotes the formation of nonproductive tillers in rice, which decreases nitrogen use efficiency (NUE). Developing high-NUE rice cultivars through balancing nitrogen uptake and the formation of productive tillers remains a long-standing challenge, yet how these two processes are coordinated in rice remains elusive. Here we identify the transcription factor OsGATA8 as a key coordinator of nitrogen uptake and tiller formation in rice. OsGATA8 negatively regulates nitrogen uptake by repressing transcription of the ammonium transporter gene OsAMT3.2. Meanwhile, it promotes tiller formation by repressing the transcription of OsTCP19, a negative modulator of tillering. We identify OsGATA8-H as a high-NUE haplotype with enhanced nitrogen uptake and a higher proportion of productive tillers. The geographical distribution of OsGATA8-H and its frequency change in historical accessions suggest its adaption to the fertile soil. Overall, this study provides molecular and evolutionary insights into the regulation of NUE and facilitates the breeding of rice cultivars with higher NUE.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Coupled catalytic states and the role of metal coordination in Cas9

Controlling the activity of the CRISPR–Cas9 system is essential to its safe adoption for clinical and research applications. Although the conformational dynamics of Cas9 are known to control its enzymatic activity, details of how Cas9 influences the catalytic processes at both nuclease domains remain elusive. Here we report five cryo-electron microscopy structures of the active Acidothermus cellulolyticus Cas9 complex along the reaction path at 2.2–2.9 Å resolution. We observed that a large movement in one nuclease domain, triggered by the cognate DNA, results in noticeable changes in the active site of the other domain that is required for metal coordination and catalysis. Furthermore, the conformations synchronize the reaction intermediates, enabling coupled cutting of the two DNA strands. Consistent with the roles of conformations in organizing the active sites, adjustments to the metal-coordination residues lead to altered metal specificity of A. cellulolyticus Cas9 and commonly used Streptococcus pyogenes Cas9 in cells.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Theoretical prediction of coordination environments and stability constants of lanthanum lactate complexes in solution

Using Density Functional Theory calculations in combination with explicit solvent and a continuum solvent model, this work sets out to understand the coordination environment and relevant thermodynamics of La(III)-lactate complexes. Calculations focus on the coordination modes for the complexes and changes in Gibbs free energy for complexation in solution. These results confirm that the α-hydroxyl group should be protonated, or at least hydrogen bonded to a water molecule, upon successive addition of the lactate ligand to the La(III) center using Bader's Atoms-in Molecules (AIM) approach. In addition, we present a straightforward method for predicting stability constants at the semi-quantitative level for La(III)-lactate complexes in solution. Furthermore, the proposed method could be particularly useful for prediction of lanthanide complex formation in various biochemical, environmental, and nuclear separations processes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Enhanced adsorption of CO 2 at steps of ultrathin ZnO: the importance of Zn–O geometry and coordination

In this paper, the interaction between CO 2 and ultrathin ZnO supported on Au(111) has been studied using temperature programmed desorption (TPD) and density functional theory (DFT) calculations. We find that CO 2 binds weakly on the planar ZnO bilayer and trilayer surfaces, desorbing at T = 130 K. CO 2 binds more strongly at the steps formed between ZnO bilayers and trilayers, desorbing at T = 285–320 K depending upon the CO 2 exposure. The adsorption energies determined from DFT calculations for CO 2 on the ZnO planar surfaces and at the steps are ~5.8 and 19.0 kcal mol –1 , respectively, agreeing with the apparent activation energies of desorption (Ed) estimated based on the TPD peaks at the limit of low CO 2 exposures (7.7 and 19.5 kcal mol –1 , respectively). The DFT calculations further identify that the most stable adsorption configuration of CO 2 at the steps of ultrathin ZnO is facilitated by the geometry and coordination of the Zn cations and O anions near the step region. Specifically, the enhanced adsorption takes place via bonding of both the C and O atoms of the CO 2 molecule to the tri-fold coordinated O anions at the trilayer edge and to the neighboring Zn cations on the bilayer terrace, respectively, leading to CO 2 bending and formation of a carbonate-like species.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Evaluating the impacts of amino acids in the second and outer coordination spheres of Rh-bis(diphosphine) complexes for CO 2 hydrogenation

To explore the influence of a biologically inspired second and outer coordination sphere on Rh-bis(diphosphine) CO 2 hydrogenation catalysts, a series of five complexes were prepared by varying the substituents on the pendant amine in the P(Et) 2 CH 2 N R CH 2 P(Et) 2 ligands (P Et N R P Et ), where R consists of methyl ester modified amino acids, including three neutral (glycine methyl ester (GlyOMe), leucine methyl ester (LeuOMe), and phenylalanine methyl ester (PheOMe)), one acidic (aspartic acid dimethyl ester (AspOMe)) and one basic (histidine methyl ester (MeHisOMe)) amino acid esters. The turnover frequencies (TOFs) for CO 2 hydrogenation for each of these complexes were compared to those of the non-amino acid containing [Rh(depp) 2 ] + (depp) and [Rh(P Et N Me P Et ) 2 ] + (NMe) complexes. Each complex is catalytically active for CO 2 hydrogenation to formate under mild conditions in THF. Catalytic activity spanned a factor of four, with the most active species being the NMe catalyst, while the slowest were the GlyOMe and the AspOMe complexes. Finally, when compared to a similar set of catalysts with phenyl-substituted phosphorous groups, a clear contribution of the outer coordination sphere is seen for this family of CO 2 hydrogenation catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Coordination-supported organic polymers: mesoporous inorganic–organic materials with preferred stability

Here, a simple and versatile strategy, borrowing ideas from the chemistry of MOFs and COFs, is developed for the synthesis of coordination-supported organic polymers (COPs) via coordination between Al 3+ and 5-amino-8-hydroxyquinoline together with organic imine- or imide-based polycondensation. The COPs with high surface areas (up to 1123 m 2 g -1 ) and abundant mesopores (2.5 nm or 14 nm) possess good crystalline and porous structure after being soaked in boiling water.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

A coordination-based model for transition metal alloy nanoparticles

We present a simple approach for predicting the relative energies of bimetallic nanoparticles spanning a wide-ranging combinatorial space, using only the identity and nearest-neighbor coordination number of individual metal atoms as independent parameters. By performing straightforward metal atom adsorption calculations on surface slab models, we parameterize expressions for the energy of metal atoms as a function of their coordination number in 21 bimetallic pairings of fcc metals. Here, we rigorously establish the transferability of our model by predicting relative energies of a series of nanoparticles across a large number of morphologies, sizes, atomic compositions, and arrangements. The model is particularly accurate in predicting atomic rearrangements at or near the metal surfaces, which is essential for its potential applications when studying segregation phenomena or dynamic processes in heterogeneous catalysis. By rapidly forecasting site stabilities with atomic specificity across generic structural and compositional features, our model is able to reverse engineer thermodynamically feasible motifs of active sites in bimetallic nanoparticles through robust property ⇔ structure relations.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Combinatorial design of multimeric chelating peptoids for selective metal coordination

Current methods for metal chelation are generally based on multidentate organic ligands, which are generated through cumbersome multistep synthetic processes that lack flexibility for systematically varying metal-binding motifs. Octadentate ligands incorporating hydroxypyridinone or catecholamide binding moieties onto a spermine scaffold are known to display some of the highest affinities towards f-elements. Enhancing binding affinity for specific lanthanide or actinide ions however, necessitates ligand architectures that allow for modular and high throughput synthesis. Here we introduce a high-throughput combinatorial library of 16 tetrameric N -substituted glycine oligomers (peptoids) containing hydroxypyridinone or catecholamide chelating units linked via an ethylenediamine bridge and, for comparison, we also synthesized the corresponding mixed ligands derived from the spermine scaffold: 3,4,3-LI(1,2-HOPO) 2 (CAM) 2 and 3,4,3-LI(CAM) 2 (1,2-HOPO) 2 . Coordination-based luminescence studies were carried out with Eu 3+ and Tb 3+ to begin probing the properties of the new ligand architecture and revealed higher sensitization efficiency with the spermine scaffold as well as different spectroscopic features among the structural peptoid isomers. Solution thermodynamic properties of selected ligands revealed different coordination properties between the spermine and peptoid analogues with Eu 3+ stability constants log β 110 ranging from 28.88 ± 3.45 to 43.97 ± 0.49. The general synthetic strategy presented here paves the way for precision design of new specific and versatile ligands, with a variety of applications tailored towards the use of f-elements, including separations, optical device optimization, and pharmaceutical development.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Elucidating metal and ligand redox activities of a copper-benzoquinoid coordination polymer as the cathode for lithium-ion batteries

A novel redox-active quinone-based organic building block 1,4-dicyano-2,3,5,6-tetrahydroxybenzene (LH 4 ) has been synthesized and used as a bridging ligand to form a new 1D copper-benzoquinoid coordination polymer [CuL(DMF) 2 ] n . The compound is able to deliver an initial capacity as high as 268 mA h g -1 at 30 mA g -1 (~C/2.5) when used as the cathode in Li batteries. Ex situ XPS and FT-IR reveal the involvement of both Cu and organic moieties in the multi-electron redox reaction. Cu K-edge XANES and EXAFS measurements confirm the change in the oxidation state and coordination environment of Cu during the discharge–charge process. In situ generated metallic nanoparticles have been observed by TEM. The obtained mechanistic understanding of the metal–organic electrode materials for Li-based batteries may pave the way for the design of next-generation energy-storage systems.

25 ENERGY STORAGE↗
DOE OSTI2021

Ligand-coordinated Ir single-atom catalysts stabilized on oxide supports for ethylene hydrogenation and their evolution under a reductive atmosphere

In this work, we present a novel series of oxide-supported Ir-ligand single-atom catalysts (SACs) for ethylene hydrogenation. The SACs were created by a metal–ligand self-assembly strategy developed by our group, using one of two ligands, either 1,10-phenanthroline-5,6-dione (PDO) or 3,6-Di-2-pyridyl-1,2,4,5-tetrazine (DPTZ), on powder supports of either CeO 2 or MgO. Characterization by XAS, XPS, and CO adsorption proved that Ir exist principally as highly uniform, cationic single-atoms. Ir SACs show significantly higher durability and metal utilization efficiency than Ir nanoparticle (NP) catalysts during ethylene hydrogenation at 100 °C, as well as excellent stability, as no Ir aggregates were detected after >10 h reaction. The activity can be tuned by ligand and support effects: PDO and CeO 2 are superior to DPTZ and MgO, respectively. This tunability is attributed to differences in H 2 activation capability, which results from differences in support reducibility, electron density on Ir, and, potentially, the local coordination environment of Ir. The Ir SACs lose H 2 activation activity either under inert gas or under H 2 . Through XPS and in situ XAS studies, we attributed the former to the reversible loss of Ir hydride, which is the active species for H 2 activation, and the latter to irreversible over-hydrogenation and loss of Ir–O/N coordination. This work presents a new type of Ir hydrogenation SACs that are more durable, efficient, and tunable than supported Ir NPs, while more stable than homogeneous Ir complexes. It also offers fundamental understanding regarding ligand and support effects, as well as the evolution of Ir single-atoms under H 2 , instructing future design of stable, effective hydrogenation SACs.

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

Heavy chalcogenide-transition metal clusters as coordination polymer nodes

While metal–oxygen clusters are widely used as secondary building units in the construction of coordination polymers or metal–organic frameworks, multimetallic nodes with heavier chalcogenide atoms (S, Se, and Te) are comparatively untapped. The lower electronegativity of heavy chalcogenides means that transition metal clusters of these elements generally exhibit enhanced coupling, delocalization, and redox-flexibility. Leveraging these features in coordination polymers provides these materials with extraordinary properties in catalysis, conductivity, magnetism, and photoactivity. In this perspective, we summarize common transition metal heavy chalcogenide building blocks including polynuclear metal nodes with organothiolate/selenolate or anionic heavy chalcogenide atoms. Based on recent discoveries, we also outline potential challenges and opportunities for applications in this field.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Highly soluble copper(ι) iodide-based hybrid luminescent semiconductors containing molecular and one-dimensional coordinated anionic inorganic motifs

Copper(I) iodide-based inorganic–organic hybrid semiconductors are considered promising materials for various optoelectronic applications. Here, using imidazolium bridged benzotriazoles as multidentate ligands, we designed and synthesized a series of all-in-one (AIO)-type CuI hybrid materials that hold both ionic and coordinate bonds at the interface of organic and inorganic modules. Their structures range from 0D clusters to 2D extended networks built on various molecular (0D) and chain-like (1D) anionic inorganic motifs that are interconnected through cationic ligands via multiple Cu–N bonds. Benefiting from their unique bonding nature, these compounds exhibit high stability towards heat and moisture and can be well dissolved in polar aprotic solvents. They emit low-energy light spanning from yellow to red color (550–625 nm). Finally, the electronic structure, emission mechanism, and effect of different coordination modes on their photophysical properties were studied using both experimental and theoretical methods, which has provided insight into the structure–property relationship of these inorganic–organic semiconductors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Conformational dynamicity in a copper( ii ) coordination complex

The geometries of copper coordination complexes are intricately related to their electron transfer capabilities, but the role of dynamics in these processes are not fully understood. We have previously reported CuCl(dpa OMe ), a complex exhibiting conformational fluxionality in its Cu I state and rigidity upon oxidation to Cu II . Here, we report the synthesis and characterization of [CuCl(dpa SMe )] +/0 , a complex exhibiting relative rigidity in its CuI state and structural dynamics upon oxidation to Cu II . The dynamics of [CuCl(dpa SMe )] + were characterized via X-ray diffraction, cyclic voltammetry, and EPR spectroscopy, where temperature-dependent interconversion between trigonal bipyramidal and square pyramidal geometries is observed. Coupling these solid and solution-state characterization data enabled assignment of the coordination geometries involved. As a result, factors impacting these dynamics and their potential implications for electron transfer are discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗