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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Iron-iminopyridine complexes as charge carriers for non-aqueous redox flow battery applications

Non-aqueous redox flow batteries (RFBs) have been gaining increased attention in the energy storage arena. Some of their attractive features include the promise for high energy densities, wider voltage windows compared to aqueous systems, as well as wider operating temperature ranges. One of the major challenges in the development of these systems is the lack of electroactive materials that can undergo reversible redox events within the larger potential window of organic solvents. In this paper, we present the design, synthesis, and measurement of electrochemical properties of some iron-based imine- and iminopyridine complexes as promising candidates for RFB applications. Synthesized complexes afforded three reversible redox couples over a ~3 V range. The redox events were also computationally explored and are in good agreement with experimental data. Theoretical calculations show that the redox event at the positive potential can be characterized as metal-centered event corresponding to Fe 3+ → Fe 2+ reduction, while the two redox events at negative potentials are associated with the consecutive reductions of iminopyridine or diimine moieties. This work has led to the identification of a promising anolyte material, [tris(imino)pyridine)Fe][OTf] 2 (1), which is soluble in acetonitrile and is synthesized in two simple steps. This species shows outstanding performance when cycled between 1.0 V and 2.35 V, with 93% coulombic efficiency, 84% energy efficiency, and a capacity decay rate of 0.61% per cycle at 5 mA cm –2 . Further modifications to this kind of charge carrier may lead to the development of high energy density materials for grid scale energy storage applications.

25 ENERGY STORAGE↗
DOE OSTI2020

Anion and cation co-doping of Na 4 SnS 4 as sodium superionic conductors

Na based all-solid-state batteries are one of the most promising candidates for large-scale electrochemical energy storage owing to their low cost and outstanding safety properties. The key enabler of this technology is solid electrolyte with sufficiently high ionic conductivity at room temperature. In this work, the design, synthesis, characterization and testing of a series of novel fast Na-ion conductors, Na 4-x-y Sn 1-x A x S 4-y X y with aliovalent cation (P 5+ /Sb 5+ ) and anion substitutions (Cl - /Br - ) of the parent compound Na 4 SnS 4 are reported. The doped samples crystalize in a new phase with space group I4 1 /acd and show ionic conductivities that are one to four orders of magnitude higher than that of undoped Na 4 SnS 4 . R. t. conductivity of 0.64 mS cm -1 is achieved in Na 3.7 Sn 0.8 Sb 0.2 S 3.9 Cl 0.1 with a low activation energy of 0.26 eV. Furthermore, Rietveld refinement against high resolution synchrotron X-ray powder diffraction data reveals that the distribution of the doping ions and the resulted Na vacancies are underlying cause of the enhanced conductivity.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Access to Advanced Functional Materials through Postmodification of Biomimetic Assemblies via Click Chemistry

The design, synthesis, and fabrication of functional nanomaterials with specific properties remain a long-standing goal for many scientific fields. The self-assembly of sequence-defined biomimetic synthetic polymers presents a fundamental strategy to explore the chemical space beyond biological systems to create advanced nanomaterials. Moreover, subsequent chemical modification of existing nanostructures is a unique approach for accessing increasingly complex nanostructures and introducing functionalities. Of these modifications, covalent conjugation chemistries, such as the click reactions, have been the cornerstone for chemists and materials scientists. Herein, we highlight some recent advances that have successfully employed click chemistries for the postmodification of assembled one-dimensional (1D) and two-dimensional (2D) nanostructures to achieve applications in molecular recognition, mineralization, and optoelectronics. Specifically, biomimetic nanomaterials assembled from sequence-defined macromolecules such as peptides and peptoids are described.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Deepening the LUMO: Brominated Naphthalene Diimide Electron Transport Layers for Low-Hysteresis Perovskite Solar Cells

Precise energy level alignment at the interfaces between the charge transport layers, active layer, and electrodes plays a key role in maximizing photovoltaic performance and operational stability in perovskite solar cells (PSCs). Organic electron transport layers (ETLs) have received little attention compared to their inorganic counterparts but offer the unique advantage of facile functionalization for fine-tuning of electronic properties. Here, we report the design, synthesis, and characterization of two benzyl-phosphonic acid (BnPA)-functionalized naphthalene diimide (NDI) derivatives, NDI-(BnPA) 2 and Br 2 -NDI-(BnPA) 2 as organic ETLs for PSCs in an n-i-p device configuration. Bromination of the NDI core at the 4,9-positions deepens the lowest unoccupied molecular orbital (LUMO) in Br 2 -NDI-(BnPA) 2 by 0.29 eV, enabling improved energy alignment with the conduction band minimum of the perovskite. Devices incorporating Br 2 -NDI-(BnPA) 2 demonstrated enhanced short-circuit current density (JSC), reduced hysteresis, and a maximum power conversion efficiency of 13.67%, compared to 13.20% for the unsubstituted NDI-(BnPA) 2 analog. The deeper LUMO of Br 2 -NDI-(BnPA) 2 is hypothesized to facilitate more efficient electron extraction, suppress interfacial charge accumulation, and reduce field-driven ion migration, collectively contributing to the observed reduction in hysteresis. These results highlight the effectiveness of combining molecular-level LUMO tuning with robust interfacial anchoring to advance the performance and durability of organic ETLs in PSCs.

Deposition↗
DOE OSTI2016

Selective Carbon Dioxide Adsorption by Two Robust Microporous Coordination Polymers

In the present work we report the design, synthesis, crystal structure determination, and adsorption properties of two new cadmium-based porous coordination polymers, [Cd(pda) 0.5 (spiro-4-py) 0.5 (HCOO)]•2H 2 O•DMF (compound 1, pda = p-phenylenediacetate, spiro- 4-py = (2,2’,7,7’-tetra(pyridin-4-yl)-9,9’-spirobi[fluorene], DMF = N,N’-dimethylformamide) and [Cd 2 (pda)(spiro-4-py)(CH 3 COO) 2 ]•DMA (compound 2, DMA = N,N’-dimethylacetamide) with similar structures. The coordination between cadmium and two organic linkers, pda and spiro-4-py, has yielded two-dimensional frameworks with rhombic openings. Stacking of these two-dimensional networks does not block the openings but rather results in permanent porosity with one-dimensional channels in the final structures. The permanent porosity of these compounds is confirmed by gas adsorption measurements. Compounds 1 and 2 have BET (Brunauer-Emmett-Teller) surface areas of 687 and 584 m 2 /g, respectively. Both compounds show favorable adsorption towards carbon dioxide over other light gases such as nitrogen, oxygen, and carbon monoxide. IAST (Ideal adsorbed solution theory) is employed to predict the adsorption selectivity of binary gas mixtures. Though compounds 1 and 2 possess similar structures, differences are observed in their gas adsorption behaviors, which can be attributed to their different terminal ligands of formate and acetate, respectively. Strikingly, both compounds show exceptionally high stability in aqueous media with a wide pH range, a characteristic that is highly desirable for gas separation-related applications. The robustness of these structures suggests that the use of hydrophobic spiro based multipyridine ligands can lead to water stable frameworks built on late-transition metals that are otherwise sensitive to moisture.

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

Correction to Selective Carbon Dioxide Adsorption by Two Robust Microporous Coordination Polymers

In the present work we report the design, synthesis, crystal structure determination, and adsorption properties of two new cadmium-based porous coordination polymers, [Cd(pda)0.5(spiro-4-py)0.5(HCOO)]•2H2O•DMF (compound 1, pda = p-phenylenediacetate, spiro- 4-py = (2,2’,7,7’-tetra(pyridin-4-yl)-9,9’-spirobi[fluorene], DMF = N,N’-dimethylformamide) and [Cd2(pda)(spiro-4-py)(CH3COO)2]•DMA (compound 2, DMA = N,N’-dimethylacetamide) with similar structures. The coordination between cadmium and two organic linkers, pda and spiro-4-py, has yielded two-dimensional frameworks with rhombic openings. Stacking of these two-dimensional networks does not block the openings but rather results in permanent porosity with one-dimensional channels in the final structures. The permanent porosity of these compounds is confirmed by gas adsorption measurements. Compounds 1 and 2 have BET (Brunauer-Emmett-Teller) surface areas of 687 and 584 m 2 /g, respectively. Both compounds show favorable adsorption towards carbon dioxide over other light gases such as nitrogen, oxygen, and carbon monoxide. IAST (Ideal adsorbed solution theory) is employed to predict the adsorption selectivity of binary gas mixtures. Though compounds 1 and 2 possess similar structures, differences are observed in their gas adsorption behaviors, which can be attributed to their different terminal ligands of formate and acetate, respectively. Strikingly, both compounds show exceptionally high stability in aqueous media with a wide pH range, a characteristic that is highly desirable for gas separation-related applications. The robustness of these structures suggests that the use of hydrophobic spiro based multipyridine ligands can lead to water stable frameworks built on late-transition metals that are otherwise sensitive to moisture.

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

Design and Development of Highly Potent HIV-1 Protease Inhibitors with a Crown-Like Oxotricyclic Core as the P2-Ligand To Combat Multidrug-Resistant HIV Variants

Design, synthesis, and evaluation of a new class of exceptionally potent HIV-1 protease inhibitors are reported. Inhibitor 5 displayed superior antiviral activity and drug-resistance profiles. In fact, this inhibitor showed several orders of magnitude improved antiviral activity over the FDA approved drug darunavir. This inhibitor incorporates an unprecedented 6–5–5 ring-fused crown-like tetrahydropyranofuran as the P2 ligand and an aminobenzothiazole as the P2' ligand with the (R)-hydroxyethylsulfonamide isostere. The crown-like P2 ligand for this inhibitor has been synthesized efficiently in an optically active form using a chiral Diels–Alder catalyst providing a key intermediate in high enantiomeric purity. Furthermore, two high resolution X-ray structures of inhibitor-bound HIV-1 protease revealed extensive interactions with the backbone atoms of HIV-1 protease and provided molecular insight into the binding properties of these new inhibitors.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

High-Affinity Peptidomimetic Inhibitors of the DCN1-UBC12 Protein–Protein Interaction

Cullin-RING ligases (CRLs) regulate the turnover of approximately 20% of the proteins in mammalian cells and are emerging therapeutic targets in human diseases. The activation of CRLs requires the neddylation of their cullin subunit, which is controlled by an activation complex consisting of Cullin-RBX1-UBC12-NEDD8-DCN1. In this paper, we describe the design, synthesis, and evaluation of peptidomimetics targeting the DCN1-UBC12 protein–protein interaction. Starting from a 12-residue UBC12 peptide, we have successfully obtained a series of peptidomimetic compounds that bind to DCN1 protein with KD values of <10 nM. Determination of a cocrystal structure of a potent peptidomimetic inhibitor complexed with DCN1 provides the structural basis for their high-affinity interaction. Cellular investigation of one potent DCN1 inhibitor, compound 36 (DI-404), reveals that it effectively and selectively inhibits the neddylation of cullin 3 over other cullin members. Further optimization of DI-404 may yield a new class of therapeutics for the treatment of human diseases in which cullin 3 CRL plays a key role.

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

Discovery of Potent and Selective Allosteric Inhibitors of Protein Arginine Methyltransferase 3 (PRMT3)

PRMT3 catalyzes the asymmetric dimethylation of arginine residues of various proteins. It is crucial for maturation of ribosomes and has been implicated in several diseases. We recently disclosed a highly potent, selective, and cell-active allosteric inhibitor of PRMT3, compound 4. Here, we report comprehensive structure–activity relationship studies that target the allosteric binding site of PRMT3. We conducted design, synthesis, and evaluation of novel compounds in biochemical, selectivity, and cellular assays that culminated in the discovery of 4 and other highly potent (IC 50 values: ~10–36 nM), selective, and cell-active allosteric inhibitors of PRMT3 (compounds 29, 30, 36, and 37). In addition, we generated compounds that are very close analogs of these potent inhibitors but displayed drastically reduced potency as negative controls (compounds 49–51). These inhibitors and negative controls are valuable chemical tools for the biomedical community to further investigate biological functions and disease associations of PRMT3.

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

Discovery of QCA570 as an Exceptionally Potent and Efficacious Proteolysis Targeting Chimera (PROTAC) Degrader of the Bromodomain and Extra-Terminal (BET) Proteins Capable of Inducing Complete and Durable Tumor Regression

Proteins of the bromodomain and extra-terminal (BET) family are epigenetics “readers” and promising therapeutic targets for cancer and other human diseases. We describe herein a structure-guided design of [1,4]oxazepines as a new class of BET inhibitors and our subsequent design, synthesis, and evaluation of proteolysis-targeting chimeric (PROTAC) small-molecule BET degraders. Our efforts have led to the discovery of extremely potent BET degraders, exemplified by QCA570, which effectively induces degradation of BET proteins and inhibits cell growth in human acute leukemia cell lines even at low picomolar concentrations. We report QCA570 achieves complete and durable tumor regression in leukemia xenograft models in mice at well-tolerated dose-schedules. QCA570 is the most potent and efficacious BET degrader reported to date.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Structure-Based Discovery of M-89 as a Highly Potent Inhibitor of the Menin-Mixed Lineage Leukemia (Menin-MLL) Protein–Protein Interaction

Inhibition of the menin-mixed lineage leukemia (MLL) protein–protein interaction is a promising new therapeutic strategy for the treatment of acute leukemia carrying MLL fusion (MLL leukemia). We describe herein our structure-based design, synthesis, and evaluation of a new class of small-molecule inhibitors of the menin-MLL interaction (hereafter called menin inhibitors). Our efforts have resulted in the discovery of highly potent menin inhibitors, as exemplified by compound 42 (M-89). M-89 binds to menin with a K d value of 1.4 nM and effectively engages cellular menin protein at low nanomolar concentrations. M-89 inhibits cell growth in the MV4;11 and MOLM-13 leukemia cell lines carrying MLL fusion with IC 50 values of 25 and 55 nM, respectively, and demonstrates >100-fold selectivity over the HL-60 leukemia cell line lacking MLL fusion. The determination of a co-crystal structure of M-89 in a complex with menin provides the structural basis for their high-affinity interaction. Overall, we conclude that further optimization of M-89 may lead to a new class of therapy for the treatment of MLL leukemia.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2025

Single-Molecule Conductance through Hybrid Radially and Linearly π-Conjugated Macromolecules Reveals an Unusual Intramolecular π-Interaction

We describe the design, synthesis, and single-molecule junction conductance of π-electron molecules bearing both radial and linear π-conjugation pathways, whereby cycloparaphenylene (CPP) radial cores are π-extended linearly with aryl alkyne substituents as models for previously reported CPP-arylene ethynylene conjugated polymers. Although radially and linearly conjugated molecules have been studied previously in isolation as junction-bridging molecular electronic units, this is the first study to examine molecules where both topologies are operative. Our results reveal that the presence of radial CPP components within the junction-spanning pathway leads to a reduction in the conductance of the backbone compared to model linear phenyl substituents. Through tight-binding and DFT-based calculations, we attribute this conductance change to intramolecular van der Waals (vdW) interactions between the CPP ring and the junction-spanning arylene-ethynylene molecular backbone. These interactions induce changes in the dihedral angles of the backbone, leading to a reduced overlap of π orbitals within the molecular junction.

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

Anomalous Shape Evolution of Ag 2 O 2 Nanocrystals Modulated by Surface Adsorbates during Electron Beam Etching

An understanding of nanocrystal shape evolution is significant for the design, synthesis, and applications of nanocrystals with surface-enhanced properties such as catalysis or plasmonics. Surface adsorbates that are selectively attached to certain facets may strongly affect the atomic pathways of nanocrystal shape development. However, it is a great challenge to directly observe such dynamic processes in situ with a high spatial resolution. In this work, we report the anomalous shape evolution of Ag 2 O 2 nanocrystals modulated by the surface adsorbates of Ag clusters during electron beam etching, which is revealed through in situ transmission electron microscopy (TEM). In contrast to the Ag 2 O 2 nanocrystals without adsorbates, which display the near-equilibrium shape throughout the etching process, Ag 2 O 2 nanocrystals with Ag surface adsorbates show distinct facet development during etching by electron beam irradiation. Three stages of shape changes are observed: a sphere-to-a cube transformation, side etching of a cuboid, and bottom etching underneath the surface adsorbates. We find that the Ag adsorbates modify the Ag 2 O 2 nanocrystal surface configuration by selectively capping the junction between two neighboring facets. They prevent the edge atoms from being etched away and block the diffusion path of surface atoms. Finally, our findings provide critical insights into the modulatory function of surface adsorbates on the shape control of nanocrystals.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Revealing the Role of Phase Structures of Bimetallic Nanocatalysts in the Oxygen Reduction Reaction

The ability to tune the atomic-level structure of alloy nanoparticles (NPs) is necessary for the design and preparation of active and stable catalysts for fuel cell reactions such as the oxygen reduction reaction (ORR), which is highly sensitive to the structure of the catalysts. We report here structurally tunable PdCu nanoparticle catalysts for the ORR obtained by varying the thermochemical treatment parameters. The phase type and the atomic structure of the nanoalloy catalysts strongly depend on the thermochemical treatment temperature and atmosphere, especially at low temperatures. While PdCu nanoalloys feature both body-centered cubic (bcc) and face-centered cubic (fcc) phase structures, a pure fcc structure, prepared by unusually low thermochemical treatment temperature, showed the highest catalytic activity for ORR. This was evidenced by a mass activity of eight times higher than that of commercial Pd catalyst. This activity enhancement was shown to be linked to the nanostructural tuning between fcc and bcc structures, as supported by systematic characterization using X-ray diffraction coupled with pair distribution function analysis. The impact of phase structure on the catalytic properties of the nanocatalyst is further substantiated by computational modeling based on density functional theory. Our results provide a fresh insight into the nanostructure-activity correlation at the atomic scale, which has significant implications for the design, synthesis, and processing of highly-active nanoalloy catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Extremely Bright, Near-IR Emitting Spontaneously Blinking Fluorophores Enable Ratiometric Multicolor Nanoscopy in Live Cells

New bright, photostable, emission-orthogonal fluorophores that blink without toxic additives are needed to enable multicolor, live-cell, single-molecule localization microscopy (SMLM). Here we report the design, synthesis, and biological evaluation of Yale676sb, a photostable, near-IR-emitting fluorophore that achieves these goals in the context of an exceptional quantum yield (0.59). When used alongside HMSiR, Yale676sb enables simultaneous, live-cell, two-color SMLM of two intracellular organelles (ER + mitochondria) with only a single laser and no chemical additives.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

C10-Benzoate Esters of Anhydrotetracycline Inhibit Tetracycline Destructases and Recover Tetracycline Antibacterial Activity

Tetracyclines (TCs) are an important class of antibiotics threatened by enzymatic inactivation. These tetracycline-inactivating enzymes, also known as tetracycline destructases (TDases), are a subfamily of class A flavin monooxygenases (FMOs) that catalyze hydroxyl group transfer and oxygen insertion (Baeyer–Villiger type) reactions on TC substrate scaffolds. Semisynthetic modification of TCs (e.g., tigecycline, omadacycline, eravacycline, and sarecycline) has proven effective in evading certain resistance mechanisms, such as ribosomal protection and efflux, but does not protect against TDase-mediated resistance. Here, we report the design, synthesis, and evaluation of a new series of 22 semisynthetic TDase inhibitors that explore D-ring substitution of anhydrotetracycline (aTC) including 14 C10-benzoate ester and eight C9-benzamides. Overall, the C10-benzoate esters displayed enhanced bioactivity and water solubility compared to the corresponding C9-benzamides featuring the same heterocyclic aryl side chains. The C10-benzoate ester derivatives of aTC were prepared in a high-yield one-step synthesis without the need for protecting groups. The C10-esters are water-soluble, stable toward hydrolysis, and display dose-dependent rescue of tetracycline antibiotic activity in E. coli expressing two types of tetracycline destructases, represented by TetX7 (Type 1) and Tet50 (Type 2). The best inhibitors recovered tetracycline antibiotic activity at concentrations as low as 2 μM, producing synergistic scores <0.5 in the fractional inhibitory concentration index (FICI) against TDase-expressing strains of E. coli and clinical P. aeruginosa. The C10-benzoate ester derivatives of aTC reported here are promising new leads for the development of tetracycline drug combination therapies to overcome TDase-mediated antibiotic resistance.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

Indolo[2,3- b ]quinoxaline as a Low Reduction Potential and High Stability Anolyte Scaffold for Nonaqueous Redox Flow Batteries

Redox flow batteries (RFBs) are a promising stationary energy storage technology for leveling power supply from intermittent renewable energy sources with demand. A central objective for the development of practical, scalable RFBs is to identify affordable and high-performance redox-active molecules as storage materials. Herein, we report the design, synthesis, and evaluation of a new organic scaffold, indolo[2,3-b]quinoxaline, for highly stable, low-reduction potential, and high-solubility anolytes for nonaqueous redox flow batteries (NARFBs). The mixture of 2- and 3-(tert-butyl)-6-(2-methoxyethyl)-6H-indolo[2,3-b]quinoxaline exhibits a low reduction potential (-2.01 V vs Fc/Fc + ), high solubility (>2.7 M in acetonitrile), and remarkable stability (99.86% capacity retention over 49.5 h (202 cycles) of H-cell cycling). This anolyte was paired with N-(2-(2-methoxyethoxy)-ethyl)phenothiazine (MEEPT) to achieve a 2.3 V all-organic NARFB exhibiting 95.8% capacity retention over 75.1 h (120 cycles) of cycling.

25 ENERGY STORAGE↗
DOE OSTI2026

Optimized Photoemission from Organic Molecules in 2D Layered Halide Perovskites

In recent years, hybrid organic−inorganic metal halides have been at the forefront of materials research. Typically, the functional (e.g., optoelectronic) properties of hybrid halides are derived from the inorganic structural part, whereas the organic structural units can add extra advantages in terms of stability, rigidity, and processability. Here, we report the design, synthesis, and characterization of two new hybrid materials in which the outstanding photophysical properties originate from the organic structural part. The new compounds, (C 15 H 16 N) 2 CdCl 4 and ((Br)C 15 H 15 N) 2 CdCl 4 , have 2D layered Ruddlesden−Poppertype perovskite structures. These hybrids are blue-white light emitters just like their corresponding pure organic salts, but with much improved emission efficiencies. Optical spectroscopy and density functional theory (DFT) studies confirm that photoemission comes from the trans-stilbene organic cations. The photoluminescence quantum yield (PLQY) values of these new materials are among the highest known, 50.83% and 26.60% for (C 15 H 16 N) 2 CdCl 4 and ((Br)C 15 H 15 N) 2 CdCl 4 , respectively. This is up to a 5-fold increase as compared to the light emission efficiency of the precursor salt C 15 H 16 NCl (PLQY of 10.33%). Alongside their outstanding optical properties, their environmental and thermal stability allow their consideration for potential practical applications such as radiation detection. This work shows that hybrid metal halides can be compositionally and structurally engineered to have highly efficient photoemission originating from the organic components for fast scintillation applications.

Halogens↗