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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 OSTI2025

Conformational Dynamics of Bacteriochlorophyll c in Chlorosomes from the bchQ Mutant of Chlorobaculum tepidum

In contrast to the common viewpoint that bacteriochlorophyll (BChl) motion is largely absent within the chlorosome assembly, physics-based modeling points to a crucial role of the nanoscale librational motion of the macrocycle for the transfer of excitons. To elucidate this motion experimentally, compositional uniformity and high sensitivity are required. We focused on uniformly 13 C labeled chlorosome preparations from the bchQ mutant Chlorobaculum tepidum with significantly enhanced structural homogeneity. The librational motion is characterized using Rotational Echo DOuble Resonance (REDOR), and in addition, the impact of temperature on specific functionalities within BChl molecules is studied with 1-dimensional and 2-dimensional dipolar and scalar-based MAS NMR measurements. Results show the gradual freezing of the tails and side chains of the BChls with decreasing temperature. However, the librational motion analyzed by measuring the 5C–H dipolar coupling strength obtained from REDOR data sets persists at different temperatures. REDOR simulations show a close match to the experimental dephasing frequency of oscillation for a dipolar coupling strength of 17.5 ± 0.5 kHz which is considerably less than the dipolar coupling strength of 22.7 kHz in the rigid limit. Following a two-site jump model, we arrive at an estimate for BChl libration sampling at an angle of θ = 48 ± 4°, corroborating that the macrocycle indeed experiences significant librational motion on a time scale that is short compared to the NMR measurement time. This finding is in full quantitative support of the dominant rotational motion exhibited by the BChl macrocycle estimated from early MD simulations.

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

Energy Barriers for H 2 Uptake and Release by Defects in Boron Nitride

Density functional theory simulations (DFT) have been used in combination with the climbing image nudged elastic band method (CI-NEB) to determine the energy barriers required to dissociate H 2 at four types of h-BN defects and evaluate the potential for reacted H species to hop to adjacent available sites. The defects were selected based on previous work in which ab initio thermodynamics was used to identify specific defects with optimal thermodynamics for reversible H 2 storage, that is, the defects would dissociate molecular H 2 while not binding H species too strongly so that hydrogen release is favorable. The four defects investigated are the N and B monovacancies, which only offer either B or N defective sites respectively, as well as larger cluster vacancy defects named 3V(1B2N) and hexagonal 6V(3B3N), which present a mixture of B and N defect sites available for H binding. While homogeneous H 2 dissociation by B and N monovacancies have energy barriers larger than 0.4 eV, we found that mixed BN terminated defects have energy barrier lower than 0.4 eV for H 2 dissociation. In particular, H 2 dissociation by the hexagonal 6V(3B3N) defect, exclusively made of Frustrated Lewis Pairs (FLPs), is almost barrierless. The energy barrier for subsequent H hopping to available adjacent B or N sites of the defect were also calculated. It was found that the hopping of H species generally involves high energy barriers ranging from 0.26 eV to 2.57 eV. In conclusion, this work completes previous thermodynamic theoretical investigations and provides a more comprehensive picture of H 2 reaction with defective h-BN for potential H 2 storage and recovery.

Sassi, Michel J. [Pacific Northwest National Labor↗
DOE OSTI2026

Adapted Cell Design for the Operando X‑Ray Absorption Study of a Structurally Evolving Cu Nanoparticle Ensemble during the CO2 Electroconversion to Multicarbon Products

An improved understanding of the materials that will sustain the future of energy production, storage, and delivery calls for better characterization tools. Operando characterization methods have thus become essential for investigating electrocatalytic materials. Without their resulting insights, the study of highly performing catalysts post-mortem cannot viably facilitate the further development of functional catalysts. Herein, we present an operando electrochemical cell designed for hard X-ray absorption spectroscopy (XAS) and specifically adapted to the study of an electrocatalytically active Cu nanoparticle ensemble. So far, this nanocatalyst has proven to pose quite a challenge to characterize due to its unique structural dynamics. Adopting a design comparable to the H-cell employed for all activity testing, we report the satisfactory translation of the active site formation into an XAS-compatible cell. The simultaneous collection of CO2-derived products during XAS characterization enabled the operando characterization of this CO2-reducing active structure. We report a Cu–Cu coordination number of the first scattering path higher than suggested in our previous studies, highlighting the importance of monitoring metastable nanoelectrocatalysts in operando. This study illustrates important caveats for the electrocatalysis community when considering the application of operando XAS. Our results highlight that the sample size, homogeneity, and stability determine how to interpret the measured signal. Considering these parameters carefully, the operando EXAFS results confirm the exceptional undercoordinated character of the Cu nanoparticle ensemble during CO2 reduction to C2+ products.

Louisia, Sheena↗
DOE OSTI2025

Sub-tesla On-Chip Nanomagnetic Metamaterial Platform for Angle-Resolved Photoemission Spectroscopy

Magnetically controlled states in quantum materials are central to their unique electronic and magnetic properties. However, direct momentum-resolved visualization of these states via angle-resolved photoemission spectroscopy (ARPES) has been hindered by the disruptive effect of magnetic fields on photoelectron trajectories. Here, we introduce an in situ method that is, in principle, capable of applying magnetic fields up to 1 T. This method uses substrates composed of nanomagnetic metamaterial arrays with alternating polarity. Such substrates can generate strong, homogeneous, and spatially confined fields applicable to samples with thicknesses up to the micron scale, enabling ARPES measurements under magnetic fields with minimal photoelectron trajectory distortion. Here, we demonstrate this minimal distortion with ARPES data taken on monolayer graphene. Our method paves the way for probing magnetic field-dependent electronic structures and studying field-tunable quantum phases with state-of-the-art energy-momentum resolutions.

Magnetic properties↗
DOE OSTI2026

Domain-Dependent Electronic Properties of 2D Copper Boride Synthesized from Reversible Subsurface Diffusion on Cu(111)

Emerging boron-based 2D materials hold properties with potential applications ranging from electronic devices to catalysis and energy storage. Using physical vapor deposition, 2D copper borides are formed on Cu(111) at elevated temperatures. However, the as-prepared surfaces often contain boron clusters that compromise structural homogeneity, and the dynamics of their formation is not yet fully understood. Through in situ low-energy electron microscopy (LEEM), Auger electron spectroscopy (AES), and scanning tunneling microscopy/spectroscopy (STM/STS), we show that cluster-free 2D CuB x is synthesized via reversible subsurface diffusion of boron atoms. The resolved regular atomic structure aligns with the previously calculated Cu 8 B 14 model. In a rare case, possibly due to surface strain and a change of orientation, a second domain of CuB x was observed with a pronounced change in electronic properties, yet electronic states remain delocalized in both domains. In conclusion, these findings demonstrate the sensitivity of electronic properties to domain structure and highlight a potential opportunity to tune 2D CuB x for diverse applications.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2026

Interference-Limited Absorption in Dense Molecular Nanolayers Near Reflecting Surfaces

We investigate linear resonant absorption by a dense ensemble of molecules confined to a sub-wavelength layer in two geometries: (i) a free-standing film in a homogeneous space and (ii) the same film placed at a controlled distance from a reflecting surface. In both cases, increasing the effective light–matter coupling (via molecular density/oscillator strength) produces a nonmonotonic response: absorption rises to an optimum and then decreases as the film becomes increasingly radiatively bright and reflective. Finite-difference time-domain simulations and analytical transfer-matrix calculations agree quantitatively and yield compact ridge conditions for the optimum. We interpret the trends using a scattering/port picture: the isolated film is a symmetric two-port system (reflection and transmission), which bounds single-sided resonant absorption to ≤50% in the ultrathin limit (reflecting transition saturation), whereas adding a mirror suppresses transmission and converts the structure into an effectively one-port absorber. In the mirror-backed geometry, interference can cancel reflection, and unity absorption is obtained at critical coupling, when radiative leakage is balanced by intrinsic molecular loss. These results clarify fundamental limits and design rules for collective absorption in dense molecular layers near dielectric or metallic boundaries.

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

Exfoliation of Cu-Containing Poly(triazine imide): From Three-Dimensional to Two-Dimensional Particle Morphology

Controlling the morphological parameters of extended covalent organic frameworks remains challenging and represents an important yet often elusive metric of consideration. Typically, carbon nitride materials possess local ordering but remain largely amorphous in terms of their long-range order and orientation. This study probes the synthesis of a crystalline carbon nitride, poly(triazine imide) lithium bromide which possesses an atomically-precise extended structure, and demonstrates its exfoliation into a two-dimensional hexagonal sheet-like morphology. Furthermore, a previously unreported carbon nitride material, poly(triazine imide) copper bromide, or PTI-CuBr, was developed through an additional flux-assisted cation-exchange process and is shown to retain its internal Cu cations during solvothermal exfoliation. Characterization by dynamic light scattering and high-angle annular dark-field scanning electron microscopy reveals the morphological changes and captures the high aspect ratio of the thin carbon nitride sheets with <10 nm thickness while maintaining hundreds of nm in width. Additional characterization by energy-dispersive spectroscopy and X-ray photoelectron spectroscopy confirms that the Cu:Br:N molar ratio was maintained within the extended layers throughout the exfoliation process. This top-down synthesis approach differs from typical methods that isolate thin sheets for subsequent metal−cation coordination and illustrates the importance of maintaining oxygen-free conditions to minimize copper clustering. Thus, this new approach is demonstrated to provide a consistent and more homogeneous occupancy of the PTI pore spaces throughout the carbon nitride framework.

Exfoliation↗
DOE OSTI2026

Protein Adhesion on Semi-Fluorinated Polystyrene Surfaces in Static and Dynamic Measurements

Reducing protein adhesion is a critical strategy in fouling-resistant material innovation, with broad applications spanning biomedical and healthcare devices, biosensors, industrial and environmental systems, and other important technological domains. Here, in this study, we elucidated protein adhesion behavior on polystyrene-based thin films by neutron reflectometry (NR) and quartz crystal microbalance with dissipation (QCM-D), using both lysozyme and bovine serum albumin (BSA) as model proteins. To this end, semifluorinated polystyrene thin films with gradient wettability and surface energy were fabricated through dry processing using plasma oxidation and gas-phase deposition. Although it is believed that a fully fluorinated alkyl chain offers extremely low surface energy, thus rejecting foulants, and has been used in many fouling-resistant surface designs, enhanced protein–surface interactions were observed consistently in NR and QCM-D results, due to the combined effects of surface morphology and chemistry. On the contrary, depositing shorter fluorinated silane onto a hydrophilic PS surface contributed to a more homogeneous nanoscale fluorine coating, resulting in less initial protein adsorption and improved surface recovery. Comparative analysis of proteins with different sizes on the nanopatterned semifluorinated surface revealed the influence of molecular characteristics on surface interactions. Lysozyme, being smaller and more compact, showed faster adsorption kinetics and higher surface coverage but largely reversible binding, whereas BSA, with its larger and more flexible structure, formed broader and more stable interfacial layers. This study fills the gap in understanding protein adhesion within the range of hydrophobicity (water contact angle ∼90°), as current strategies often associate with extreme hydrophilic and superhydrophobic surfaces due to hydration or low-surface-energy rejection mechanisms, respectively. It also provides in-depth insights into current combinatorial fouling-resistant surface design.

Yuan, Yue [Oak Ridge National Laboratory (ORNL), O↗
DOE OSTI2025

Crystallization Mechanisms of Poly(vinylidene Fluoride- co -chlorotrifluoroethylene): Nucleation Transitions, Growth Kinetics, and Microstructure Evolution

The crystallization kinetics of FK-800, a commercial semicrystalline copolymer of chlorotrifluoroethylene and vinylidene fluoride (poly(CTFE-co-VDF)), dictate its microstructure and functional performance. Crystallization occurs between the glass transition (T g ≈ 31 °C) and melting point (T m ≈ 110 °C), with grain boundaries playing a key role in applications such as memristors, where they regulate filament growth. This study integrates in situ atomic force microscopy (AFM), grazing-incidence wide-angle X-ray scattering (GIWAXS), and differential scanning calorimetry (DSC) to characterize nucleation, growth, and morphology across the full crystallization window. Hot-stage AFM reveals a transition from homogeneous to heterogeneous nucleation near 45 °C and a shift from reaction-limited to diffusion-limited growth above 60 °C. Kinetics are analyzed using Lauritzen–Hoffman, Turnbull–Fisher, and Avrami models to extract surface free energies and activation barriers. A multiscale modeling framework is developed in which nucleation densities and growth rates measured by AFM are used to reconstruct Avrami kinetics, which are then validated against coverage data, and extrapolated to predict bulk crystallization behavior observed by DSC. GIWAXS confirms a primarily flat-on chain orientation at all temperatures, linking orientation to domain morphology. This integrative approach quantitatively connects nanoscale crystallization dynamics with macroscopic phase evolution, establishing a quantitative framework for modeling crystallization across time, temperature, and length scales.

Crystallization↗
DOE OSTI2025

Understanding Viscoelasticity of an Entangled Silicone Copolymer via Coarse-Grained Molecular Dynamics Simulations

Entangled dynamics is important for understanding rheological properties of long-chain polymers. For entangled homopolymers, the classic tube-reptation model and its refinements have been successfully applied to quantify properties like diffusion coefficient and zero-rate viscosity. However, the application of such models to copolymers has been limited despite scientific and industrial importance. Here, we study the entangled melt dynamics of poly(dimethyl-co-diphenyl)siloxane random copolymer for a range of mean-composition-ratio ϕ of the diphenyl component via long-term molecular dynamics simulation with a recently developed coarse-grained model. We found that the segmental relaxation is heterogeneous at the monomeric level because of compositional fluctuations. However, at the chain-entanglement level and higher length scales, the viscoelastic response is homogeneous with compositional dependence only through the overall diphenyl fraction ϕ. The relaxation modulus of the entangled copolymer melt conforms to the Likhtman–McLeish model, and the viscosity predicted using our current coarse-grained parameters is in good quantitative agreement with experimental data.

Copolymers↗
DOE OSTI2026

Chemically Recyclable Analogs of Styrene–Butadiene Copolymers Enabling Perfectly Linear Ethylene–Styrene Materials with Random Phenyl Distribution

Copolymerization of cyclopentene (CP) and 4-phenylcyclopentene (4PCP) at a full range of comonomer feed ratios is reported using Ru-based ring-opening metathesis polymerization (ROMP) yielding homogeneous copolymers analogous to poly(styrene-ran-1,4-butadiene) and poly(ethylene-ran-styrene) copolymers following hydrogenation under mild conditions. In all cases, total monomer conversions of 86%–92% yielded copolymers with compositions within 4% of monomer feeds. Analysis of equilibrium copolymerization thermodynamics, rarely performed on two cycloolefin monomers with low ring strain energies, provides rational design strategies for negotiating two monomers with different equilibrium monomer concentrations. Inverse-gated decoupled 13 C NMR analysis of dyad sequences on the resulting copolymer microstructures concludes a near-random distribution of comonomer units. The copolymers produced from ROMP have number-average molar masses up to 60 kg mol –1 , moderate dispersities (1.5 ± 0.1), and high trans olefin content (86% ± 2%) while glass-transitions temperatures follow the Fox equation and span the full range between homopolymer extremities of PCP (−96 °C) and P4PCP (17 °C). Unlike most prevulcanized elastomers, these materials undergo facile chemical recycling to monomer, producing complete ring-closing metathesis depolymerization (RCMD) of the polymer back to the CP comonomers. Quantitative olefin hydrogenation produced perfectly linear polyethylene with 4%–16% of the backbone carbons containing a phenyl pendant, analogous to ES copolymers with up to 71.5% w/w styrene units but with random distribution of the aromatic pendants. Thermal properties of these materials are discussed, which span from semicrystalline to amorphous, and with T g values notably less than the reported ES copolymer analogs at similar compositions.

animal feed↗
DOE OSTI2024

Defect-Driven Configurational Entropy in the High-Entropy Oxide Li 1.5 MO 3-δ

Layered lithiated oxides are promising materials for next generation Li-ion battery cathode materials; however, instability during cycling results in poor performance over time compared to the high capacities theoretically possible with these materials. Here, in this paper, we report the characterizations of a Li 1.47 Mn 0.57 Al 0.13 Fe 0.095 Co 0.105 Ni 0.095 O 2.49 high-entropy layered oxide (HELO) with the Li 2 MO 3 structure where M = Mn, Al, Fe, Co, and Ni. Using electron microscopy and X-ray spectroscopy, we identify a homogeneous Li 2 MO 3 structure stabilized by the entropic contribution of oxygen vacancies. This defect-driven entropy would not be attainable in the LiMO 2 structure sometimes observed in similar materials as a secondary phase owing to the presence of fewer O sites and a 3+ oxidation state for the metal site; instead, a Li 2-γ MO 3-δ is produced. Beyond Li 2 MO 3 , this defect-driven entropy approach to stabilizing novel compositions and phases can be applied to a wide array of future cathode materials including spinel and rock salt structures.

25 ENERGY STORAGE↗
DOE OSTI2025

Modulating the Electronic Transport of 2D Sb2Te3 Nanoplates by Coinage Metal Intercalation

Thermoelectric materials are particularly relevant to the current energy infrastructure and demands of the 21st century, converting waste heat into usable electricity. The solution intercalation of zerovalent copper into Sb2Te3 nanoplates, a well-established thermoelectric material, is reported. The copper intercalant is homogeneously distributed throughout the nanoplates, confirmed by scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy. The copper composition was shown to be 6 at. % by X-ray photoelectron spectroscopy. Copper ordering within the van der Waals gaps of the nanoplates is confirmed by selected area electron diffraction. Fabrication and thermoelectric property measurements of single-crystal Sb2Te3 and Cu-Sb2Te3 nanoplate devices show effective modulation of electrical conductivity and Seebeck coefficient with Cu intercalation. X-ray photoelectron spectroscopic studies in the valence-band region reveal additional electronic states from copper that appear near the Fermi energy, postulated to act as electron acceptors, leading to modulation of the electronic transport properties.

2D nanoplates↗
DOE OSTI2025

Solvent Determines the Formation Pathway in Sol–Gel Synthesized Disordered Rock Salt Material for Lithium Ion Battery Application

The increasing demand for lithium-ion batteries with high capacity and cycling stability, in combination with the scarcity of cobalt and nickel, has led to significant efforts to develop new cathode materials based on earth-abundant transition metals. Mn- and Ti-based disordered rock salt (DRX) cathodes are promising candidates fulfilling these requirements. However, their large-scale fabrication can be energy- and time-intensive using traditional fabrication methods, e.g., solid-state synthesis. The present study showcases sol-gel synthesis as an alternative method with control over the crystallization pathway through solvent choice. Dimethylformamide (DMF) aids the homogenization of the transition metals during early crystallization stages and formation of Li2TiO3 and LiMn2O4 intermediates before the DRX phase is formed. In contrast, 2-methoxyethanol (2-ME) shows transition metal segregation and formation of an additional transition metal intermediate (Ti2MnO4) while not resulting in phase-pure DRX material after calcination. Coin cells prepared with DMF-material yield higher capacity and cycling stability compared with 2-ME material.

Kodalle, Tim↗
DOE OSTI2025

Pd–Methyl Bond Energy─Property Correlations, Noncorrelations, Machine Learning Models, and Application to Polymerization Catalysis

Metal–carbon bonds are a key intermediate in a variety of homogeneous organometallic transformations and often determine the critical thermodynamics and kinetics of catalytic processes. Surprisingly, the influence of different ligands on metal–carbon bond strengths has been largely overlooked. Here, in this study, we evaluated nearly 700 experimental Pd–methyl complexes by calculating their bond dissociation energies using density functional theory (DFT) and compared these bond strengths to several fundamental molecular properties, and this revealed several surprising correlations and noncorrelations. Most surprising was that several fundamental properties, such as the bond length, bond force constant, and bond electron density, have no correlation with bond strength, despite these correlations often holding for main-group compounds. We were indeed able to identify key ligand-dependent chemical features/descriptors that provided a highly accurate machine learning model and provided insight into the general factors that control the Pd–carbon bond strength, such as radical delocalization and nucleophilicity. Insights gained from the Pd–Me bond energy analysis were then applied to CO migratory insertion steps that are part of copolymerization reactions.

binding energy↗
DOE OSTI2026

Noncanonical folding of peptoid oligomers: Formation of a closed conformation in nonpolar solvent

Peptoids provide a versatile platform for foldamer design, yet their conformational behavior in low-dielectric media remains poorly understood. The structural characteristics of N-1-phenylethylglycine (Nspe) homo-oligomers were inves-tigated in chloroform, a solvent that mimics the interior of lipid bilayers, using nuclear magnetic resonance (NMR) spec-troscopy and molecular dynamics (MD) simulations. Nspe7 populated two distinct compact conformations, while Nspe10 adopted a single homogeneous conformation related to the previously reported Nspe9 threaded-loop structure. Integrated experimental and computational analysis reveals that these structures are stabilized by cooperative end-to-end intramo-lecular hydrogen bonding, cis-trans backbone isomerism, and hydrophobic side-chain shielding. The resulting structures minimize exposed polar surface area, demonstrating a closed conformation in the low-dielectric environment. These find-ings establish specific chain-length requirements for achieving well-defined closed conformations. This work provides insights into peptoid folding in nonpolar media, enabling rational design strategies for solvent-directed conformational switching systems.

Oh, Jinyoung↗
DOE OSTI2025

LiNi0.8Mn0.1Co0.1O2 Thin Films Prepared by Polymer-Assisted Deposition for the Study of Cathode-Electrolyte Interphases in Lithium-Ion Batteries

High-nickel layered oxide cathodes such as LiNi0.8Mn0.1Co0.1O2 (NMC811) are critical for next-generation lithium-ion batteries (LIBs) due to their superior energy density and reduced reliance on cobalt. However, many Ni-rich cathodes suffer from rapid capacity fade and structural instability originating from complex interfacial reactions at the cathode-electrolyte interface. Traditional composite electrodes exhibit degradation mechanisms that are challenging to quantitatively understand due to additives, including binders and carbon black. In this study, we demonstrate a new synthesis approach for binder- and additive-free NMC811 thin films using polymer-assisted deposition (PAD). PAD-NMC811 are model thin-film cathodes for investigating interfacial phenomena that can be obscured in composite cathodes. Structural and chemical characterization by X-ray diffraction, soft X-ray absorption spectroscopy, and atomic force microscopy show that PAD-NMC811 films possess high phase purity, crystallinity, chemical homogeneity, and morphological uniformity. Electrochemical analyses using cyclic voltammetry and galvanostatic cycling revealed electrochemical behavior consistent with that of composite electrodes, along with a moderate capacity fade indicative of cathode-electrolyte interphase (CEI) formation. Our findings illustrate the effectiveness of PAD synthesis of thin films tailored for detailed mechanistic studies, which offer critical insights into CEI evolution and cathode degradation pathways.

25 ENERGY STORAGE↗