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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

A nitrogen- and carbonyl-rich conjugated small-molecule organic cathode for high-performance sodium-ion batteries

Organic-based cathode materials have attracted considerable attention for sustainable Na-ion batteries due to their great promise to overcome the issues arising from the insertion of large Na + into the rigid structures of conventional transition-metal-containing inorganic electrodes. The structural flexibility as a result of weak intermolecular interactions and simple electron- and ion-storage mechanisms found in organic compounds ensure facile and reversible transport of Na ions. In order to address the general drawbacks of small-molecule organic electrodes such as material dissolution in commonly used organic electrolytes and poor electronic conductivity, we report the use of a nitrogen- and carbonyl-rich highly extended π-conjugated small molecule, hexaazatrianthranylene (HATA) embedded quinone (HATAQ), as a cathode for sodium-ion batteries. The unique hydrogen bonds between highly functionalized conjugated HATAQ molecules allow supramolecular graphite-like 2D layered arrangements in the solid state which help facilitate the structural stability during long-term cycling and promote charge transfer. The compound delivers a capacity as high as 460 mA h g -1 at 500 mA g -1 and an excellent capacity retention of 99% (~138 mA h g -1 ) after 5000 cycles at an extremely high rate of 60 A g -1 . The reaction kinetics and redox mechanism of the material have been elucidated by several characterization techniques together with density functional theory (DFT) studies. The insights gained in this work could pave the way for ultra-high-performance small-molecule organic cathodes for sustainable energy storage.

25 ENERGY STORAGE↗
DOE OSTI2024

Structural chemistry of penta- and hexanitrato thorium($\tiny{IV}$) complexes isolated using N–H donors

In this study, a series of fifteen tetravalent thorium phases were prepared. The compounds were isolated from acidic aqueous nitrate solutions using protonated nitrogen heterocycles of varying hydrogen-bond donation strength. Structural analysis via single crystal X-ray diffraction showed that the structures are built from pentanitrato, [Th(NO 3 ) 5 (H 2 O) 2 ] 1- , and hexanitrato, [Th(NO 3 ) 6 ] 2- , molecular units, with the latter being far more prevalent in the solid state. The vibrational properties of the compounds were examined using Raman and IR spectroscopy; the spectra are dominated by stretches characteristic of nitrate and the organic ions. The relative energetics of nitrate complexation was examined using electronic structure theory. These results confirmed that there are clear thermodynamic sinks for the penta- and hexanitrato structural units that were observed experimentally. Additionally, electrostatic surface potentials (ESPs) were calculated in an effort to better understand the counterion stabilization of the complexes. The ESP surfaces showed that the position of the water and nitrate molecules and the coordination geometry of the metal complex had a clear effect on the polarizability of the two structural motifs. Despite limited speciation of the Th–nitrate structural units, the compounds exhibit rich supramolecular chemistry resulting from hydrogen bonding of the Th complexes with the organic N–H donors and π–π stacking interactions from the protonated N-heterocycles.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Impact of peripheral alkyl chain length on mesocrystal assemblies of G2 dendrons

Unique sphere-packing mesophases such as Frank–Kasper (FK) phases have emerged from the viable design of intermolecular interactions in supramolecular assemblies. In this work, a series of C n -G2-CONH 2 dendrons possessing an identical core wedge are investigated to elucidate the impact of peripheral alkyl chain lengths (C n ) on the formation of the close-packed structures. The C 18 and C 14 dendrons, of which the contour lengths of the periphery L p are longer than the wedge length L w , assemble into a uniform sphere-packing phase such as body-centred cubic (BCC), whereas the C 8 dendron with short (L p < L w ) corona environment forms the FK A15 phase. Particularly in the intermediate C 12 and C 10 dendrons (L p ≈ L w ), cooling the samples from an isotropic state leads to cooling-rate-dependent phase behaviours. The C 12 dendron produces two structures of hexagonal columnar and sphere-packing phases (BCC and A15), while the C 10 dendron generates the A15 and σ phases by the fast- and slow-cooling processes, respectively. Our results show the impact of peripheral alkyl chain lengths on the formation of mesocrystal phases, where the energy landscape of the dendrons at L p /L w ≈ 1 must be more complex and delicate than those with either longer or shorter peripheral alkyl chains.

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

Nanocapsules of unprecedented internal volume seamed by calcium ions

The inception of an unprecedented class of voluminous Platonic solids displaying hierarchical geometry based on pyrogallol[4]arene moieties seamed by divalent calcium ion is described. Single-crystal X-ray structural determination has established the highly conserved geometry of two original Ca 2+ -seamed nanocapsules to be essentially cubic in shape with C-ethylpyrogallol[4]arene units located along the twelve edges of the cube which are then bridged by metallic polyatomic cations ([Ca 4 Cl] 7+ or [Ca(HCO 2 )Na 4 ] 5+ ) at the six cube faces. The accessible volume of the nanocapsules is ca. 3500 Å 3 and 2500 Å 3 and is completely isolated from the exterior of the capsules. These remarkable nanocapsule discoveries cast a spotlight on a marginalized area of synthetic materials chemistry and encourage future exploration of diversiform supramolecular assemblies, networks, and capsules built on calcium, with clear benefits deriving from the intrinsic biocompatibility of calcium. Finally, a proof-of-concept is demonstrated for fluorescent reporter encapsulation and sustained release from the calcium-seamed nanocapsules, suggesting their potential as delivery vehicles for drugs, nutrients, preservatives, or antioxidants.

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

Insights into water extraction and aggregation mechanisms of malonamide-alkane mixtures

Structure at the nanoscale in the organic phase of liquid–liquid extraction systems is often tied to separation performance. However, the weak interactions that drive extractant assembly lead to poorly defined structures that are challenging to identify. Here, in this work, we investigate the mechanism of water extraction for a malonamide extractant commonly applied to f-element separations. We measure extractant concentration fluctuations in the organic phase with small angle X-ray scattering (SAXS) before and after contact with water at fine increments of extractant concentration, finding no qualitative changes upon water uptake that might suggest significant nanoscopic reorganization of the solution. The critical composition for maximum fluctuation intensity is consistent with small water–extractant adducts. The extractant concentration dependence of water extraction is consistent with a power law close to unity in the low concentration regime, suggesting the formation of 1 : 1 water–extractant adducts as the primary extraction mechanism at low concentration. At higher extractant concentrations, the power law slope increases slightly, which we find is consistent with activity effects modeled using Flory–Huggins theory without introduction of additional extractant–water species. Molecular dynamics simulations are consistent with these findings. The decrease in interfacial tension with increasing extractant concentration shows a narrow plateau region, but it is not correlated with any change in fluctuation or water extraction trends, further suggesting no supramolecular organization such as reverse micellization. This study suggests that water extraction in this system is particularly simple: it relies on a single mechanism at all extractant concentrations, and only slightly enhances the concentration fluctuations characteristic of the dry binary extractant/diluent mixture.

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

Effect of heteroatom incorporation on electronic communication in metal chalcogenide nanoclusters

Metal chalcogenide nanoclusters (NC), specifically of type TM 6 E 8 (L) 6 (TM = transition metal, E = chalcogen, L = ligand) have garnered attention in recent years as promising catalysts and biosensors due to their remarkable electronic and magnetic properties, as well as their ability to undergo supramolecular assembly into 2D materials. Furthermore, the undercoordinated metal chalcogenide NCs have shown distinct surface reactivity, which is strongly dependent on the composition of the TM core. The differences in the reactivity of the undercoordinated species have been attributed to differences in ligand binding energies. Although ligand binding energies in homometallic NCs have been extensively studied, little is known about the effect of heteroatoms in the core on the strength of ligand binding in metal chalcogenide NCs. In this work, we provide new insights into this topic by examining the relative stability of [Co 6−x Fe x S 8 (PEt 3 ) 6 ] + (x = 0–6) NCs towards fragmentation using collision energy-resolved collision-induced dissociation (CID) experiments. We observe that the ligand binding energy gradually decreases until four Fe atoms are incorporated into the cluster core and then gradually increases until all the Co atoms are replaced with Fe. This experimental trend was compared with the results of density functional theory (DFT) calculations, which indicate drastic differences in the electronic communication between Co and Fe atoms in the TM core. By understanding the effect of heteroatom incorporation on ligand binding energy to the NC core, our work provides important insights into the effect of atom-by-atom substitution on the functional properties of tunable nanostructures.

Havenridge, Shana [Argonne National Laboratory (AN↗
DOE OSTI2025

An improved guess for the variational calculation of charge-transfer excitations in large systems

Ab initio quantum-chemical methods that perform well for computing the electronic ground state are not straightforwardly transferable to electronically excited states, particularly in large molecular systems. Wave function theory offers high accuracy, but is often prohibitively expensive. Methods based on time-dependent density functional theory (TD-DFT) are crucially sensitive to the chosen exchange-correlation functional (XCF) parameterization, and system-specific tuning protocols were therefore proposed to address the method's robustness. Methods based on the variational relaxation of the excited-state electron density showcased promising results for the calculation of charge-transfer excitations, but the complex shape of the electronic hypersurface makes convergence to a specific excited state much more difficult than for the ground state when standard variational techniques are applied. We address the latter aspect by providing suitable initial guesses, which we obtain by two separate constrained algorithms. Combined with the squared-gradient minimization algorithm for all-electrons relaxation in a freeze-and-release scheme (FRZ-SGM), we demonstrate that orbital-optimized density functional theory (OO-DFT) calculations can reliably converge to the charge-transfer states of interest even for large molecular systems. We test the FRZ-SGM method on a phenothiazine-anthraquinone CT excitation in a supramolecular Pd(II) coordination cage complex as a function of the cage conformation. This compound has been studied experimentally prior to our work. We compare this freeze-and-release scheme to two XCF reparameterizations, which were recently proposed as low-cost TD-DFT-based alternatives to variational methods. Two dye-semiconductor complexes, which were previously investigated in the context of photovoltaic applications, serve as a second example to investigate the convergence and stability of the FRZ-SGM approach. Our results demonstrate that FRZ-SGM provides reliable convergence for charge-transfer excited states and avoids variational collapse to lower-lying electronic states, whereas time-dependent DFT calculations with an adequate tuning procedure for the range-separation parameter provide a computationally efficient initial estimate of the corresponding energies, with a computational cost comparable to that of configuration-interaction singles (CIS) calculations.

Bogo, Nicola↗
DOE OSTI2025

Trinuclear gold chains and octanuclear copper gyrobifastigia stabilized using a fluorinated pyridyl ligand

The fluorinated pyridyl ligand [6-(CF 3 )-2-Py] − with gold( I ) affords trinuclear Au 3 assemblies that further organize into a supramolecular helical column through aurophilic interactions. Its chemistry with copper( I ) is even more remarkable, leading to an unprecedented octanuclear copper–pyridyl cluster complex featuring a central Cu 8 core with an approximate gyrobifastigium geometry. Solid powders of compounds {(6-(CF 3 )-2-Py)Au} 3 and {(6-(CF 3 )-2-Py)Cu} 8 exhibit intense photoluminescence at room temperature, displaying green and yellow colors to the naked eye, respectively. Here, the octanuclear copper complex is also an effective catalyst for azide–alkyne cycloaddition, producing triazoles. Detailed computational analyses confirm the preference for experimental geometries and provide insights into the observed luminescence.

Phan, Vo Quang Huy [University of Texas at Arlingt↗
DOE OSTI2021

r 2 SCAN-D4: Dispersion corrected meta-generalized gradient approximation for general chemical applications

We combine a regularized variant of the strongly constrained and appropriately normed semilocal density functional with the latest generation semi-classical London dispersion correction. The resulting density functional approximation r 2 SCAN-D4 has the speed of generalized gradient approximations while approaching the accuracy of hybrid functionals for general chemical applications. We demonstrate its numerical robustness in real-life settings and benchmark molecular geometries, general main group and organo-metallic thermochemistry, and non-covalent interactions in supramolecular complexes and molecular crystals. Main group and transition metal bond lengths have errors of just 0.8%, which is competitive with hybrid functionals for main group molecules and outperforms them for transition metal complexes. The weighted mean absolute deviation (WTMAD2) on the large GMTKN55 database of chemical properties is exceptionally small at 7.5 kcal/mol. This also holds for metal organic reactions with an MAD of 3.3 kcal/mol. The versatile applicability to organic and metal–organic systems transfers to condensed systems, where lattice energies of molecular crystals are within the chemical accuracy (errors <1 kcal/mol).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Structural and compositional complexities of hierarchical self-assembly: A hypergraph approach

Programmable self-assembly enables the construction of complex molecular, supramolecular, and crystalline architectures from well-designed building blocks. In this work, we introduce a hypergraph-based formalism, Blocks & Bonds (B&B), which generalizes classical chemical graph theory by incorporating directed and multicolored interactions, internal symmetries, and hierarchical organization. Within this framework, we develop the Structure Code (SC), a compact and versatile language for describing self-assembled architectures. We define a Kolmogorov-style structural complexity as the total information content of SC, obtained through its tokenization and Shannon information assignment. Complementing this encoding-based measure, we introduce a much simpler quantity, the compositional complexity, which depends only on the number and cumulative usage of block and bond types in the construction set. A central result of this work is a strong empirical correlation between the token-based structural complexity and the compositional complexity across all examined systems. Owing to this agreement, the compositional complexity emerges as the most practical and broadly applicable measure: it is easy to compute, requires no explicit encoding, and yet closely tracks the actual information content of structurally diverse architectures. Applications to molecular systems (ethylene glycol and glucose), DNA-origami lattices, and crystalline assemblies show that B&B hypergraphs provide a unified, scalable, and information-efficient representation of structural organization, naturally capturing symmetry, modularity, and stereochemistry. This framework establishes a quantitative foundation for complexity-aware classification and inverse design of programmable matter.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Photoelectron Spectroscopy and Structural Characterization of [EDTA·M(II)]2-·nH2O (M = Ni, Cu, Zn; n = 0-2) Complexes

We investigated microhydrated transition metal-EDTA dianion complexes [EDTA·M(II)]2-·nH2O (M = Ni, Cu, and Zn; n = 1, 2) using cryogenic photoelectron spectroscopy in conjunction with theoretical calculations. The measured spectra of [EDTA·Ni/Zn(II)]2-·nH2O closely resemble those of their corresponding bare dianions, with a systematic shift towards high electron binding energy side upon stepwise hydration and featuring a hexadentate metal-EDTA binding motif. In contrast, the spectra of hydrated [EDTA·Cu(II)]2- exhibit broadened first detachment bands, implying coexistence of multiple metal-ligand binding forms, as a consequence of the Jahn-Teller effect associated with its d9 electron arrangement. These findings showcase molecular-level insights into the structural adaptability of EDTA-based supramolecular assemblies comprising transition metal ions, water molecules, and multidentate ligand environments.

Ling, Zicheng↗
DOE OSTI2020

Crystallographic evidence of Watson–Crick connectivity in the base pair of anionic adenine with thymine

Utilizing an ionic liquid strategy, we report crystal structures of salts of free anionic nucleobases and base pairs previously studied only computationally and in the gas phase. Reaction of tetrabutylammonium ([N 4444 ] + ) or tetrabutylphosphonium ([P 4444 ] + ) hydroxide with adenine (HAd) and thymine (HThy) led to hydrated salts of deprotonated adenine, [N 4444 ][Ad]·2H 2 O, and thymine, [P 4444 ][Thy]·2H 2 O, as well as the double salt cocrystal, [P 4444 ] 2 [Ad][Thy]·3H 2 O·2HThy. The cocrystal includes the anionic [Ad-(HThy)] base pair which is a stable formation in the solid state that has previously not even been suggested. It exhibits Watson–Crick connectivity as found in DNA but which is unusual for the free neutral base pairs. The stability of the observed anionic bases and their supramolecular formations and hydrates has also been examined by electronic structure calculations, contributing to more insight into how base pairs can bind when a proton is removed and highlighting mechanisms of stabilization or chemical transformation in the DNA chains.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Evidence for long-term potentiation in phospholipid membranes

Biological supramolecular assemblies, such as phospholipid bilayer membranes, have been used to demonstrate signal processing via short-term synaptic plasticity (STP) in the form of paired pulse facilitation and depression, emulating the brain’s efficiency and flexible cognitive capabilities. However, STP memory in lipid bilayers is volatile and cannot be stored or accessed over relevant periods of time, a key requirement for learning. Using droplet interface bilayers (DIBs) composed of lipids, water and hexadecane, and an electrical stimulation training protocol featuring repetitive sinusoidal voltage cycling, we show that DIBs displaying memcapacitive properties can also exhibit persistent synaptic plasticity in the form of long-term potentiation (LTP) associated with capacitive energy storage in the phospholipid bilayer. The time scales for the physical changes associated with the LTP range between minutes and hours, and are substantially longer than previous STP studies, where stored energy dissipated after only a few seconds. STP behavior is the result of reversible changes in bilayer area and thickness. On the other hand, LTP is the result of additional molecular and structural changes to the zwitterionic lipid headgroups and the dielectric properties of the lipid bilayer that result from the buildup of an increasingly asymmetric charge distribution at the bilayer interfaces.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Architecture and functional regulation of a plant PSII-LHCII megacomplex

Photosystem II (PSII) splits water in oxygenic photosynthesis on Earth. The structure and function of the C 4 S 4 M 2 -type PSII-LHCII (light-harvesting complex II) megacomplexes from the wild-type and PsbR-deletion mutant plants are studied through electron microscopy (EM), structural mass spectrometry, and ultrafast fluorescence spectroscopy [time-resolved fluorescence (TRF)]. The cryo-EM structure of a type I C 4 S 4 M 2 megacomplex demonstrates that the three domains of PsbR bind to the stromal side of D1, D2, and CP43; associate with the single transmembrane helix of the redox active Cyt b 559 ; and stabilize the luminal extrinsic PsbP, respectively. This megacomplex, with PsbR and PsbY centered around the narrow interface between two dimeric PSII cores, provides the supramolecular structural basis that regulates the plastoquinone occupancy in Q B site, excitation energy transfer, and oxygen evolution. PSII-LHCII megacomplexes (types I and II) and LHC aggregation levels in Arabidopsis psbR mutant were also interrogated and compared to wild-type plants through EM and picosecond TRF.

Science & Technology - Other Topics↗
DOE OSTI2026

Unraveling design principles of protein landscapes in photosynthetic membranes in plant chloroplasts

The supramolecular organization of proteins within photosynthetic membranes is crucial for energy conversion in plants. Here, we introduce an analytical and computational pipeline that integrates high-resolution cryo–scanning electron microscopy, biochemical quantification, advanced Monte Carlo computer simulations, and statistical methods to elucidate the elusive protein landscapes of grana membranes in intact Arabidopsis leaves. Our integrated analysis challenges the prevailing view that particles on the exoplasmic fracture faces in freeze-fracture samples represent photosystem II exclusively. Instead, these particles also include cytochrome b 6 f complexes. Furthermore, our steric clash analysis demonstrates that stacked membranes contain a mixture of larger PSII supercomplexes (C 2 S 2 M 2 and C 2 S 2 ) in addition to a smaller complex (C 2 ). This suggests that in vivo PSII supercomplexes exist in an equilibrium distribution of differing sizes. Furthermore, we discovered that, although size exclusion effects govern the global protein arrangement, local packing exhibits orientational order indicative of lateral attractive protein-protein interactions.

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

Further Studies on Photocatalytic Water Decomposition

The initial ideas underlying this project were first developed during a sabbatical by RT as a Senior Fulbright Scholar in the laboratory of Professor Jean-Marie Lehn at the University of Strasbourg. Professor Lehn had recently been awarded the Nobel Prize for his work on Supramolecular Chemistry. The project, as it was originally proposed upon my return to Houston, involved using the excited state of an appropriate photocatalyst to bring about the bond-breaking (O-H) and bond making (O=O and H-H) steps involved in water decomposition.

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

Abbr. Final report: Self-assembled molecular containers as artificial water channels: towards biomimetic desalination membranes

Global water scarcity demands advances in desalination technologies that can deliver more fresh water with less energy. Current reverse osmosis membranes are fundamentally limited by a trade-off between how much water they can pass and how well they block salts. To address this challenge, we developed a bottom-up strategy to design and test artificial water channels that mimic the efficiency of biological proteins but are built from robust synthetic molecules. Over two years, we synthesized and evaluated more than twenty molecular channel candidates, including supramolecular macrocycles and nanographene pores with atomically precise structures. We showed that small chemical modifications allow direct control over pore size and chemistry, which in turn govern water permeability and salt rejection. In collaboration with university partners, we reported the first experimental demonstration of water transport through a nanographene pore, bridging a long-standing gap between simulation and experiment. Several of the artificial channels we developed achieved water–salt selectivity beyond conventional polymer membranes, highlighting their potential for next-generation desalination and precision separations.

36 MATERIALS SCIENCE↗