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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 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Chemical recycling of polymer composites induced by selective variable frequency microwave heating

Abstract The application of variable frequency microwave (VFM) heating to achieve rapid thermal depolymerization of polymer composites is reported for the first time. The thermal and chemical influence of composite additives on polymer decomposition has been studied for a set of chemically recyclable polymers, including polyphthalaldehyde, polypropylene carbonate, two polyhydroxyalkanoates, and nylon 6. Carbon‐based additives, specifically nanocarbon particles, were used as effective microwave absorbers to controllably degrade the surrounding polymer matrix into valuable, monomeric compounds. Depolymerization and byproduct confirmation were quantified by gel permeation chromatography and nuclear magnetic resonance spectroscopy. Synergistic effects can be leveraged from pre‐treating composite samples to further reduce the total microwave energy required to depolymerize composite samples. This study establishes the use of VFM heating for chemical recycling of polymer composites that can be leveraged toward a plastic circular economy.

Polymer Science↗
DOE OSTI2014

Interactions of amelogenin with phospholipids

Amelogenin protein has the potential to interact with other enamel matrix proteins, mineral, and cell surfaces. In this paper, we investigated the interactions of recombinant amelogenin rP172 with small unilamellar vesicles as model membranes, toward the goal of understanding the mechanisms of amelogenin–cell interactions during amelogenesis. Dynamic light scattering (DLS), fluorescence spectroscopy, circular dichroism (CD), and nuclear magnetic resonance (NMR) were used. In the presence of phospholipid vesicles, a blue shift in the Trp fluorescence emission maxima of rP172 was observed (~334 nm) and the Trp residues of rP172 were inaccessible to the aqueous quencher acrylamide. DLS studies indicated complexation of rP172 and phospholipids, although the possibility of fusion of phospholipids following amelogenin addition cannot be ruled out. NMR and CD studies revealed a disorder–order transition of rP172 in a model membrane environment. Strong fluorescence resonance energy transfer from Trp in rP172 to DNS-bound-phospholipid was observed, and fluorescence polarization studies indicated that rP172 interacted with the hydrophobic core region of model membranes. Finally, our data suggest that amelogenin has ability to interact with phospholipids and that such interactions may play key roles in enamel biomineralization as well as reported amelogenin signaling activities.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

A long‐lived Aβ oligomer resistant to fibrillization

Abstract The hydrophobic Aβ peptide is highly aggregation prone; it first forms soluble oligomers, which then convert into the amyloid fibrils found in the cerebral plaques of Alzheimer's disease. It is generally understood that as the peptide concentration of Aβ increases, the fibrillization process is accelerated, but we examine the limits on this phenomenon. We found that once a threshold concentration of Aβ is exceeded, a stable oligomer is formed at the expense of fibril formation. The suppression of fibril formation was observed by amyloid‐binding dye Thioflavin T and solution nuclear magnetic resonance (NMR). Small‐angle X‐ray scattering, size exclusion chromatography, and analytical ultracentrifugation demonstrated that Aβ peptides form a range of compact species, with a dimer being an early highly populated oligomer. Solution NMR allowed us to define the secondary structure of this Aβ dimer, which shows interlocking contacts between C‐terminal peptide strands. Thus, we present a novel Aβ oligomer that resists conversion to fibrils and remains stable for more than one year.

Nick, Mimi↗
DOE OSTI2018

Structural and metabolic responses of Staphylococcus aureus biofilms to hyperosmotic and antibiotic stress

Biofilms alter their metabolism in response to environmental stress. This study explores the effect of a hyperosmotic agent–antibiotic treatment on the metabolism of Staphylococcus aureus biofilms through the use of nuclear magnetic resonance (NMR) techniques. To determine the metabolic activity of S. aureus, we quantified the concentrations of metabolites in spent medium using high-resolution NMR spectroscopy. Biofilm porosity, thickness, biovolume, and relative diffusion coefficient depth profiles were obtained using NMR microimaging. Dissolved oxygen (DO) concentration was measured to determine the availability of oxygen within the biofilm. Under vancomycin-only treatment, the biofilm communities switched to anaerobic fermentation, as evidenced by high concentrations of formate, acetate, and lactate, and there was no detectable dissolved oxygen in the biofilm. Anaerobic conditions such as fermentation can signify that biofilm is combating antibiotic stress by developing resistance. In addition, we observed the highest consumption of pyruvate, the sole carbon source, under the vancomycin-only treatment. On the other hand, relative effective diffusion coefficients increased under vancomycin-only treatment but decreased under maltodextrin-only and combined treatments. No change was observed in either biofilm thickness or biovolume for biofilms treated with maltodextrin-only or in combination with vancomycin. This indicates that biofilm growth was halted during maltodextrin-only and combined treatments. Overall, we demonstrated that the metabolic activity of S. aureus biofilm is affected by hyperosmotic and antibiotic stress.

biofilm↗
DOE OSTI2024

Zeolite‐Based Catalysts for Conversion of Oxygenated Polymer Waste by Positron Annihilation

Positron Annihilation Lifetime Spectroscopy (PALS) has been employed to investigate the catalysts HZSM-5 and MESO−Y, which play a pivotal role in catalyzing and upgrading plastics, with a primary focus on oxygenated polymers, thereby transforming existing plastic materials into simpler, higher-quality value-added products. Here, in this study, PALS was systematically compared with other complementary analytical techniques. The research outcomes have successfully demonstrated the efficacy of PALS in elucidating the morphology and topology of zeolites at micro/meso-meter scales. The first experiment focuses on H-ZSM-5 zeolite subjected to treatments involving polyurethane and polypropylene. The second experiment delves into H-ZSM-5 zeolites with varying Si/Al ratios, both before and after conversion. The third experiment investigates Y zeolites that are surfactant templated to induce meso-porosity, examining their fresh state as well as their post-conversion condition. The PALS analysis was supplemented by BET (Brunauer-Emmett-Teller) analysis and NMR (Nuclear Magnetic Resonance) spectroscopies. Notably, PALS exhibits superior sensitivity, at the sub-nanometer scale, suggesting its potential as a preferred complementary method for catalysis studies. In conclusion, the integration of PALS into the repertoire of analytical tools enhances our understanding of catalyst behavior and catalytic processes, offering valuable insights for the advancement of plastic recycling and catalysis research.

32 - ENERGY CONSERVATION, CONSUMPTION, AND UTILIZA↗
DOE OSTI2018

In situ Stripline Electrochemical NMR for Batteries

Here, there exist some long outstanding technical challenges that continue to be of hindrance to fully harnessing the unique investigative advantages of nuclear magnetic resonance (NMR) spectroscopy in the in situ investigation of rechargeable battery chemistry. For instance, the conducting materials and circuitry necessary for an operational battery always deteriorate the coil–based NMR sensitivity when placed inside the coil, and the shape mismatch between them leads to low sample filling factors and even higher detection limits. We report herein a novel and successful adaptation of stripline NMR detection that integrates seamlessly the NMR detection with construction of an electro–chemical device in general (or a battery in particular) which leads to a technique with much higher detection sensitivity, higher sample filling factors, and which is particularly suitable for mass–limited samples.

25 ENERGY STORAGE↗
DOE OSTI2023

Phosphate‐functionalized Zirconium Metal–Organic Frameworks for Enhancing Lithium–Sulfur Battery Cycling

Abstract Lithium–sulfur batteries are promising candidates for next‐generation energy storage devices due to their outstanding theoretical energy density. However, they suffer from low sulfur utilization and poor cyclability, greatly limiting their practical implementation. Herein, we adopted a phosphate‐functionalized zirconium metal–organic framework (Zr‐MOF) as a sulfur host. With their porous structure, remarkable electrochemical stability, and synthetic versatility, Zr‐MOFs present great potential in preventing soluble polysulfides from leaching. Phosphate groups were introduced to the framework post‐synthetically since they have shown a strong affinity towards lithium polysulfides and an ability to facilitate Li ion transport. The successful incorporation of phosphate in MOF‐808 was demonstrated by a series of techniques including infrared spectroscopy, solid‐state nuclear magnetic resonance spectroscopy, and X‐ray pair distribution function analysis. When employed in batteries, phosphate‐functionalized Zr‐MOF (MOF‐808‐PO4) exhibits significantly enhanced sulfur utilization and ion diffusion compared to the parent framework, leading to higher capacity and rate capability. The improved capacity retention and inhibited self‐discharge rate also demonstrate effective polysulfide encapsulation utilizing MOF‐808‐PO4. Furthermore, we explored their potential towards high‐density batteries by examining the cycling performance at various sulfur loadings. Our approach to correlate structure with function using hybrid inorganic–organic materials offers new chemical design strategies for advancing battery materials.

Liu, Bingqian↗
DOE OSTI2025

The Role of Asparagine as a Gatekeeper Residue in the Selective Binding of Rare Earth Elements by Lanthanide‐Binding Peptides

Abstract Lanthanide‐binding tag (LBT) peptides selectively complex lanthanide cations (Ln 3+ ) in their binding pockets and are promising for lanthanide separation. However, designing LBTs that selectively target specific Ln 3+ cations remains a challenge due to limited molecular‐level understanding and control of interactions within the lanthanide‐binding pocket. In this study, we reveal that the N5 asparagine residue acts as a gatekeeper in the binding pocket, resulting in a 100‐fold selectivity for smaller Lu 3+ over larger La 3+ cations. Nuclear magnetic resonance spectroscopy and molecular dynamics simulations show that the N5 residue weakly binds to the larger La 3+ cation, permitting H 2 O molecules inside the pocket. For the smaller Lu 3+ cations, the N5 residue forms an inter‐arm hydrogen bond with the E14 glutamic acid residue, locking the Lu 3+ cation in the pocket and preventing H 2 O infiltration. Mutating the N5 asparagine to a D5 aspartic acid prevents such a hydrogen bond, eliminating the gatekeeping mechanism and precipitously reducing selectivity. The resulting binding affinity to Ln 3+ cations is non‐monotonic but generally increases with cation size. These results suggest a molecular design paradigm: the reduced affinity for larger lanthanides is due to open pocket conformations, while the selectivity of smaller Ln 3+ cations over larger ones is due to the gatekeeping hydrogen bond.

Chemistry↗
DOE OSTI2022

Hydrothermal synthesis of chiral carbon dots

Abstract Nanocolloids that are cumulatively referred to as nanocarbons, attracted significant attention during the last decade because of facile synthesis methods, water solubility, tunable photoluminescence, easy surface modification, and high biocompatibility. Among the latest development in this reserach area are chiral nanocarbons exemplified by chiral carbon dots (CDots). They are expected to have applications in sensing, catalysis, imaging, and nanomedicine. However, the current methods of CDots synthesis show often contradictory chemical/optical properties and structural information that required a systematic study with careful structural evaluation. Here, we investigate and optimize chiroptical activity and photoluminescence of L‐ and D‐ CDots obtained by hydrothermal carbonization of L‐ and D‐ cysteine, respectively. Nuclear magnetic resonance spectroscopy demonstrates that they are formed via gradual dehydrogenation and condensation reactions of the starting amino acid leading to particles with a wide spectrum of functional groups including aromatic cycles. We found that the chiroptical activity of CDots has an inverse correlation with the synthesis duration and temperature, whereas the photoluminescence intensity has a direct one, which is associated with degree of carbonization. Also, our studies show that the hydrothermal synthesis of cysteine in the presence of boric acid leads to the formation of CDots rather than boron nitride nanoparticles as was previously proposed in several reports. These results can be used to design chiral carbon‐based nanoparticles with optimal chemical, chiroptical, and photoluminescent properties.

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

Morphology-dependent stability of complex metal hydrides and their intermediates using first-principles calculations

Complex light metal hydrides are promising candidates for efficient, compact solid-state hydrogen storage. (De)hydrogenation of these materials often proceeds via multiple reaction intermediates, the energetics of which determine reversibility and kinetics. At the solid-state reaction front, molecular-level chemistry eventually drives the formation of bulk product phases. Therefore, a better understanding of realistic (de)hydrogenation behavior requires considering possible reaction products along all stages of morphological evolution, from molecular to bulk crystalline. Here, we use first-principles calculations to explore the interplay between intermediate morphology and reaction pathways. Employing representative complex metal hydride systems, we investigate the relative energetics of three distinct morphological stages that can be expressed by intermediates during solid-state reactions: i) dispersed molecules; ii) clustered molecular chains; and iii) condensed-phase crystals. Our results verify that the effective reaction energy landscape strongly depends on the morphological features and associated chemical environment, offering a possible explanation for observed discrepancies between X-ray diffraction and nuclear magnetic resonance measurements. Our theoretical understanding also provides physical and chemical insight into phase nucleation kinetics upon (de)hydrogenation of complex metal hydrides.

08 HYDROGEN↗
DOE OSTI2026

Structure and Dynamics of Imidazolium in an Ionic Liquid-PEGDA Iongel via IR, 2D-IR, and NMR Spectroscopy

Fourier transform infrared (FTIR) absorption spectroscopy, ultrafast two-dimensional infrared (2D-IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and density functional theory (DFT) calculations show that, in iongels composed of 1-ethyl-3-methylimidazolium bis(trifluoromethyl\-sulfonyl)imide ([C 2 C 1 Im][Tf 2 N]}) and cross-linked poly(ethylene glycol)diacrylate (cl-PEGDA), imidazolium cations solvate PEGDA chains in tight and loose complexes. H/D isotope substitution at the 2-position of the imidazolium ring simplifies the CH-stretching vibrational bands. Tight complexes are characterized by stronger, directional hydrogen bonding interactions between the 2-position of the imidazolium ring and the ethereal oxygens. The loose complexes resemble bulk ionic liquid (IL) non-specifically perturbed by the PEGDA chains.

ionic liquids, carbon dioxide, cross-linked PEGDA,↗
DOE OSTI2014

Reduction Mechanism of Fluoroethylene Carbonate for Stable Solid–Electrolyte Interphase Film on Silicon Anode

Fluoroethylene Carbonate (FEC) is an effective electrolyte additive which can significantly improve the cyclability of Si and other anode materials. However, the fundamental mechanism on this improvement is still not well understood. Based on the results obtained from 6Li Nuclear Magnetic Resonance and X-ray Photoelectron Scanning study, we propose a molecular level mechanism on how FEC affects the formation of solid electrolyte interphase (SEI) film: 1) FEC is reduced through the opening of the five member ring leading to the formation of lithium poly (vinyl carbonate), LiF and some dimmers; 2) The high tensile strength of the FEC-derived lithium poly (vinyl carbonate) enhances the stability of the SEI film. This mechanism has been verified by the results of electrochemical tests.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2018

Ethanol: A Promising Green Solvent for the Deconstruction of Lignocellulose

We present that growing energy demand and the need to reduce environmental impact, increase energy security, and rural economic development has encouraged the development of sustainable renewable fuels. Non-food lignocellulosic biomass is a suitable source for sustainable energy because the biomass feedstocks are low cost, abundant, and carbon neutral. Recent thermochemical conversion studies are frequently directed at converting biomass to high quality liquid fuel precursors or chemicals in a single step. Supercritical ethanol has been selected as a promising solvent medium to deconstruct lignocellulosic biomass since the ethanol has extraordinary solubility towards lignocellulosic biomass and can be resourced from cellulosic ethanol facilities. This review provides critical insight into both catalytic and non-catalytic strategies of lignocellulose deconstruction. In this context, the supercritical ethanol deconstruction pathways are thoroughly reviewed; gas chromatography coupled with mass spectrometry (GC-MS), one-dimensional and two-dimensional nuclear magnetic resonance spectrometry (NMR), and elemental analysis strategies towards liquid biomass deconstruction products are critically presented. Lastly, this review aims to provide readers a broad and accurate roadmap of this novel biomass to biofuel conversion techniques.

09 BIOMASS FUELS↗
DOE OSTI2021

Hybrid Chemo-Mechanical Plastics Recycling: Solvent-free, High-speed Reactive Extrusion of Low-Density Polyethylene

Low-Density Polyethylene (LDPE) is ubiquitous in the packaging industry due to its flexibility, toughness, and low cost. However, it is typically contaminated with other materials, seriously limiting options for mechanical recycling. Interest in chemical recycling techniques such as pyrolysis and hydrothermal liquefaction is growing, but most of these processes face technoeconomic challenges that have limited commercial deployment. We present a hybrid chemo-mechanical approach using reactive twin-screw extrusion (TSE) for tailoring the molecular weight and chain structure of reclaimed LDPE. Two types of zeolite catalysts at several loading levels were evaluated over a range of processing conditions. Structural, thermal, and rheological properties of the extruded samples were investigated and compared to virgin LDPE and LDPE extruded without the catalyst. A nuclear magnetic resonance spectroscopic technique was used to investigate changes in the structure of the polymer. LDPE extruded with microporous y-zeolite showed lower degradation temperature and increased short chain branching. Mesoporous MCM-41 also induced increased branching but had no effect on degradation temperature. The theoretical mechanical energy input for the chemical modification was calculated using process modeling. The demonstrated hybrid reactive extrusion process provides a potential low-cost, simple approach for repurposing LDPE-based flexible packaging as coatings and adhesives.

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

Hydrazine Energy Storage: Displacing N 2 H 4 from the Metal Coordination Sphere

Hydrogen carriers, such as hydrazine (N 2 H 4 ), may facilitate long duration energy storage, a vital component for resilient grids by enabling more renewable energy generation. Lanthanide coordination chemistry with N 2 H 4 as well as efforts to displace N 2 H 4 from the metal coordination sphere to develop an efficient catalytic production cycle were detailed. Modeling the equilibrium of different ligand coordination, it was predicted that strong sigma donor molecules would be required to displace N 2 H 4 . Monitoring competition experiments with nuclear magnetic resonance confirmed that trimethyl phosphine oxide, dimethylformamide, and dimethyl sulfoxide displaced N 2 H 4 in large or small lanthanide complexes.

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

Tuning the Properties of Lignin‐Derived Deep Eutectic Solvents for Biomass Processing

Lignin-derived deep eutectic solvents (DESs) have been investigated as sustainable green media for biomass processing. However, the properties and processability of DESs have not been fully understood with the chemical structures of their constituents for biomass fractionation. Here, in this article, the properties of the phenolic DESs are discussed with different numbers of functional groups, such as –OCH 3 and –CHO in their hydrogen bond donor (HBD) structures. The formation of DES is significantly related to the hydrogen bond between its constituents, identified by nuclear magnetic resonance (NMR) analysis and density functional theory calculation (DFT). Lower viscosity and net basicity of DES are achieved with fewer –OCH 3 on HBD structures, resulting in enhanced processability and fractionation efficiency. The thermal stability of the DES is also influenced by the –OCH 3 and –CHO of HBD, as indicated by its onset temperature. The recyclability of the phenolic DES is confirmed by the fractionation performance of the recycled DES. Understanding the structural impacts of DES constituents on the properties and performance is crucial for designing solvents in biorefinery applications.

Ryu, Jiae [State University of New York (SUNY), Sy↗
DOE OSTI2025

Biotransformation of Phenolics in Spent Liquor from Aqueous Ammonia Pretreatment

Spent liquors of biomass pretreatment provide a source for renewable chemical production. These liquors require treatment before being discharged; otherwise, they negatively impact the environment. Herein, spent liquors from aqueous ammonia pretreatment of poplar wood are characterized for phenolic content via liquid chromatography–mass spectrometry and nuclear magnetic resonance spectroscopy. The main phenolics are phenol, p-hydroxybenzamide (pHBAm), and p-hydroxybenzoic acid (pHBA), of which pHBAm and pHBA are produced from the ester-linked p-hydroxybenzoates in poplar wood. Phenol is produced from pHBA via decarboxylation. The potential biotransformation of the extracted phenolics into 2-pyrone-4,6-dicarboxylic acid (PDC) is assessed using an engineered strain of Novosphingobium aromaticivorans DSM12444 (PDC strain). Biotransformation of pHBAm to PDC is shown to be possible in the presence of pHBA, but not when pHBAm is the sole phenolic substrate, this is the first reported observation of N. aromaticivorans producing PDC from an aromatic amide. The phenol present is not transformed to PDC and does not inhibit PDC production. This study demonstrates that the phenolic amide in spent liquor from ammonia pretreatment can be valorized via biotransformation using N. aromaticivorans, which adds to the growing versatility of N. aromaticivorans as a microbial chassis for converting plant-derived compounds to useful products.

biomass↗