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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Versatile microbial communities rapidly assimilate ammonium hydroxide-treated plastic waste

Abstract Waste plastic presently accumulates in landfills or the environment. While natural microbial metabolisms can degrade plastic polymers, biodegradation of plastic is very slow. This study demonstrates that chemical deconstruction of polyethylene terephthalate (PET) with ammonium hydroxide can replace the rate limiting step (depolymerization) and by producing plastic-derived terephthalic acid and terephthalic acid monoamide. The deconstructed PET (DCPET) is neutralized with phosphoric acid prior to bioprocessing, resulting in a product containing biologically accessible nitrogen and phosphorus from the process reactants. Three microbial consortia obtained from compost and sediment degraded DCPET in ultrapure water and scavenged river water without addition of nutrients. No statistically significant difference was observed in growth rate compared to communities grown on DCPET in minimal culture medium. The consortia were dominated by Rhodococcus spp., Hydrogenophaga spp., and many lower abundance genera. All taxa were related to species known to degrade aromatic compounds. Microbial consortia are known to confer flexibility in processing diverse substrates. To highlight this, we also demonstrate that two microbial consortia can grow on similarly deconstructed polyesters, polyamides, and polyurethanes in water instead of medium. Our findings suggest that microbial communities may enable flexible bioprocessing of mixed plastic wastes when coupled with chemical deconstruction.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Soil Biogeochemistry

Depending upon type and pedogenic stage, soils are subject to biotic and abiotic interactions of complex nature depending on type, nature and specific properties. Soil biogeochemistry involves the study of elemental cycling as mediated by complex and inseparable interactions between the biotic (living) and abiotic (non-living) components of soils. Human activities have substantially altered biogeochemical cycling of several key elements including carbon, nitrogen, phosphorus, potassium, and other secondary and minor nutrients over the past few decades, which, in turn, had serious environmental consequences. The present chapter outlines the soil biogeochemical investigations conducted within Indian subcontinent in both natural ecosystems and managed agricultural systems and addresses the state-of-the-art in order to understand the undergoing biogeochemical reactions. Here, we sought to clarify complex interactions generally occurred during biogeochemical transformations of an element (or compound) of interest within the type-specific soil. Further, we emphasized the importance of advancing our understanding of feedback loops in soil biogeochemical processes as altered by anthropogenic perturbations in tropical and sub-tropical soils of India. Overall, this chapter is broadly focused on the nutrient cycling, which is followed by more specific topics like “soil microbiology,” “soil biodiversity,” and “soil biotechnology.”

Sihi, Debjani↗
DOE OSTI2023

Spin diffusion in the Phosphorus-31 NMR relaxation in a layered crystalline α-Sn(IV) phosphate contaminated by paramagnetic impurities

The study of a layered crystalline Sn(IV) phosphate by solid-state NMR has demonstrated that the 31 P T 1 relaxation of phosphate groups, dependent on spinning rate is completely controlled by the limited spin diffusion to paramagnetic ions found by EPR. The spin-diffusion constant, D(SD), was estimated as 2.04 10 –14 cm 2 s –1 . Finally, the conclusion was supported by the 31 P T 1 time measurements in zirconium phosphate 1–1, also showing paramagnetic ions and in diamagnetic compound (NH 4 ) 2 HPO 4 .

1H MAS NMR↗
DOE OSTI2020

Polydentate ligands and their complexes for molecular catalysis

Embodiments of the present disclosure relate generally to novel achiral and chiral sulfur-, nitrogen- and phosphorus-containing ligands, designated as NNS-type, P(O)NS-type, PNS-type, SNNS-type, SNNP(O)-type, or SNNP-type polydentate ligands and transition metal complexes of these ligands, including iridium complexes having PNS-type and NNS-type ligands. The catalysts derived from these ligands and transition metal complexes may be used in a wide range of catalytic reactions, including hydrogenation and transfer hydrogenation of unsaturated organic compounds, dehydrogenation of alcohols and boranes, various dehydrogenative couplings, chemoselective hydrogenation of α,β-unsaturated alcohols, and other catalytic transformations.

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

Visualizing Orbital Content of Electronic Bands in Anisotropic 2D Semiconducting ReSe 2

Many properties of layered materials change as they are thinned from their bulk forms down to single layers, with examples including indirect-to-direct band gap transition in 2H semiconducting transition metal dichalcogenides as well as thickness-dependent changes in the valence band structure in post-transition-metal monochalcogenides and black phosphorus. Here, we use angle-resolved photoemission spectroscopy to study the electronic band structure of monolayer ReSe 2 , a semiconductor with a distorted 1T structure and in-plane anisotropy. By changing the polarization of incoming photons, we demonstrate that for ReSe 2 , in contrast to the 2H materials, the out-of-plane transition metal dz2 and chalcogen pz orbitals do not contribute significantly to the top of the valence band, which explains the reported weak changes in the electronic structure of this compound as a function of layer number. We estimate a band gap of 1.7 eV in pristine ReSe 2 using scanning tunneling spectroscopy and explore the implications on the gap following surface doping with potassium. Additionally, a lower bound of 1.4 eV is estimated for the gap in the fully doped case, suggesting that doping-dependent many-body effects significantly affect the electronic properties of ReSe 2 . Our results, supported by density functional theory calculations, provide insight into the mechanisms behind polarization-dependent optical properties of rhenium dichalcogenides and highlight their place among two-dimensional crystals.

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

Nitrogen increases early‐stage and slows late‐stage decomposition across diverse grasslands

1. To evaluate how increased anthropogenic nutrient inputs alter carbon cycling in grasslands, we conducted a litter decomposition study across 20 temperate grasslands on three continents within the Nutrient Network, a globally distributed nutrient enrichment experiment 2. We determined the effects of addition of experimental nitrogen (N), phosphorus (P) and potassium plus micronutrient (K μ ) on decomposition of a common tree leaf litter in a long-term study (maximum of 7 years; exact deployment period varied across sites). The use of higher order decomposition models allowed us to distinguish between the effects of nutrients on early- versus late-stage decomposition. 3. Across continents, the addition of N (but not other nutrients) accelerated early-stage decomposition and slowed late-stage decomposition, increasing the slowly decomposing fraction by 28% and the overall litter mean residence time by 58%. 4. Synthesis. Using a novel, long-term cross-site experiment, we found widespread evidence that N enhances the early stages of above-ground plant litter decomposition across diverse and widespread temperate grassland sites but slows late-stage decomposition. These findings were corroborated by fitting the data to multiple decomposition models and have implications for N effects on soil organic matter formation. For example, following N enrichment, increased microbial processing of litter substrates early in decomposition could promote the production and transfer of low molecular weight compounds to soils and potentially enhance the stabilization of mineral-associated organic matter. By contrast, by slowing late-stage decomposition, N enrichment could promote particulate organic matter (POM) accumulation. Such hypotheses deserve further testing.

Nutrient Network (NutNet)↗
DOE OSTI2020

Elucidating Interfacial Stability between Lithium Metal Anode and Li Phosphorus Oxynitride via In Situ Electron Microscopy

Li phosphorus oxynitride (LiPON) is one of a very few solid electrolytes that have demonstrated high stability against Li metal and extended cyclability with high Coulombic efficiency for all solid-state batteries (ASSBs). However, theoretical calculations show that LiPON reacts with Li metal. Here, we utilize in situ electron microscopy to observe the dynamic evolutions at the LiPON–Li interface upon contacting and under biasing. We reveal that a thin interface layer (~60 nm) develops at the LiPON–Li interface upon contact. This layer is composed of conductive binary compounds that show a unique spatial distribution that warrants an electrochemical stability of the interface, serving as an effective passivation layer. Our results explicate the excellent cyclability of LiPON and reconcile the existing debates regarding the stability of the LiPON–Li interface, demonstrating that, though glassy solid electrolytes may not have a perfect initial electrochemical window with Li metal, they may excel in future applications for ASSBs.

25 ENERGY STORAGE↗
DOE OSTI2024

Magneto-optical response of the magnetic semiconductors EUCd 2 X 2 (X = P, As, SB)

n this study, we identify EuCd 2 X 2 (for X = P, As, Sb) as a series of magnetic semiconductors. We examine how the band gap of the series responds to X changing from phosphorus (P), to arsenic (As), and finally antimony (Sb). We characterize the samples using electronic transport and magnetization measurements. Based on infrared spectroscopy, we find that the band gap reduces progressively from 1.23 eV in EuCd 2 P 2 , to 0.77 eV in EuCd 2 As 2 , and finally 0.52 eV in EuCd 2 Sb 2 . In a magnetic field, all three systems show a strong response and their band gaps decrease at 4 K. This decrease is non-monotonic as we change X. It is strongest in the phosphorous compound and weakest in the antimony compound. For all the three compositions, EuCd 2 X 2 remains a semiconductor up to the highest magnetic field applied (16 T).

36 MATERIALS SCIENCE↗
DOE OSTI2024

Nutrient and moisture limitations reveal keystone metabolites linking rhizosphere metabolomes and microbiomes

Plants release a wealth of metabolites into the rhizosphere that can shape the composition and activity of microbial communities in response to environmental stress. The connection between rhizodeposition and rhizosphere microbiome succession has been suggested, particularly under environmental stress conditions, yet definitive evidence is scarce. In this study, we investigated the relationship between rhizosphere chemistry, microbiome dynamics, and abiotic stress in the bioenergy crop switchgrass grown in a marginal soil under nutrient-limited, moisture-limited, and nitrogen (N)-replete, phosphorus (P)-replete, and NP-replete conditions. We combined 16S rRNA amplicon sequencing and LC-MS/MS-based metabolomics to link rhizosphere microbial communities and metabolites. We identified significant changes in rhizosphere metabolite profiles in response to abiotic stress and linked them to changes in microbial communities using network analysis. N-limitation amplified the abundance of aromatic acids, pentoses, and their derivatives in the rhizosphere, and their enhanced availability was linked to the abundance of bacterial lineages from Acidobacteria, Verrucomicrobia, Planctomycetes, and Alphaproteobacteria. Conversely, N-amended conditions increased the availability of N-rich rhizosphere compounds, which coincided with proliferation of Actinobacteria. Treatments with contrasting N availability differed greatly in the abundance of potential keystone metabolites; serotonin and ectoine were particularly abundant in N-replete soils, while chlorogenic, cinnamic, and glucuronic acids were enriched in N-limited soils. Serotonin, the keystone metabolite we identified with the largest number of links to microbial taxa, significantly affected root architecture and growth of rhizosphere microorganisms, highlighting its potential to shape microbial community and mediate rhizosphere plant–microbe interactions.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Influence of hydrostatic pressure on hidden order, the Kondo lattice, and magnetism in URu 2 Si 2-x P x

Within the chemical substitution series URu 2 Si 2-x P x , there is an evolution in the ground-state behavior from hidden ordered (HO) for x ≲ 0.03, to Kondo lattice behavior with no ordering (NO) for 0.03 ≲ x ≲ 0.26, to antiferromagnetism (AFM-2) for 0.26 ≲ x ≲ 0.5 [A. Gallagher et al., Nat. Commun. 7, 10712 (2016); A. Gallagher et al., J. Phys.: Condens. Matter 29, 024004 (2016)]. To better understand what factors control this behavior, temperature-dependent electrical resistivity measurements are performed for this series under applied pressures P up to 20.5 kbar. Specimens in the HO x region show similarities to the parent compound, where HO transforms into antiferromagnetism (AFM-1) at a critical pressure (P c ). P c decreases with increasing x and collapses towards P = 0 near x ≈ 0.03, suggesting that AFM-1 occurs at ambient pressure for this concentration. No pressure-induced phase transitions are observed in the NO x region and the AFM-2 state is only weakly suppressed by P. Measurements further reveal that AFM-1 and AFM-2 are distinct from each other. Calculations of the wave functions using the tight-binding Hartree-Fock approximation are performed and show (i) that the radial probability distributions for the phosphorus ions are more tightly bound than those for the silicon and (ii) that the energy difference between the orbitals decreases with increasing x. The cumulative effect of these two factors is that Si → P substitution decreases the hybridization strength, which correlates with the weakening of HO. At large x, additional effects such as electrical charge tuning also play an important role in determining the ground-state

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2026

Phosphonium-Based Metal Halide Semiconductors: When a Single Atom Dictates Water and Thermal Stability

Phosphonium-based (R-P(R’) 3 + ) metal halide semiconductors (MHS) emerged recently as a promising family of materials offering enhanced water and thermal stability over conventional ammonium-based (R-NH 3 + ) MHS. Despite this performance, there is a lack of systematic studies that elucidate the origin of these features as well as the underlying optoelectronic properties. Here, we report here the synthesis of nine new 1D materials (L)PbX 3 (L= C4-P, C6-P, C6-N, P3-P, P4-P, X= I, Br), using custom made organic ligands, namely butyl(triethyl)phosphonium bromide (C4-P), hexyl(triethyl)phosphonium bromide (C6-P), benzyl(triethyl)phosphonium bromide (P3-P), benzyl(trimethyl)phosphonium bromide (P4-P), and hexyl(triethyl)ammonium bromide (C6-N). Most of the materials are water stable for over 21 months, while the assembly of the isostructural (C6-N)PbBr 3 and (C6-P)PbBr 3 allowed us to directly identify the impact of a single atom (phosphorus versus nitrogen), on water stability. Notably, the C6-P analog remains water stable for 21 months, whereas the C6-N analog dissolves in water. It was found that neither crystal packing nor the lack of hydrogen bond interactions with water is responsible for this record stability performance, challenging currently established claims on the 1 origin of water stability in MHS. All materials feature broad light emission at RT, with (P3-P)PbBr 3 exhibiting a PLQY of 22.0% ascribed to permanent traps, while electrochemical studies uncovered for the first time the redox properties and their strong potential for the sensing of per- and polyfluoroalkyl substances (PFAS) in water samples. Our work showcases the potential of these compounds for applications where thermal and water stability are interwoven, potentially rendering their (R-NH 3 + ) based counterparts obsolete.

PFAS sensing↗
DOE OSTI2025

Clarifying the trophic state concept to advance macroscale freshwater science and management

For over a century, ecologists have used the concept of trophic state (TS) to characterize an aquatic ecosystem's biological productivity. However, multiple TS classification schemes, each relying on a variety of measurable parameters as proxies for productivity, have emerged to meet use‐specific needs. Frequently, chlorophyll a, phosphorus, and Secchi depth are used to classify TS based on autotrophic production, whereas phosphorus, dissolved organic carbon, and true color are used to classify TS based on both autotrophic and heterotrophic production. Both classification approaches aim to characterize an ecosystem's function broadly, but with varying degrees of autotrophic and heterotrophic processes considered in those characterizations. Moreover, differing classification schemes can create inconsistent interpretations of ecosystem integrity. For example, the US Clean Water Act focuses exclusively on algal threats to water quality, framed in terms of eutrophication in response to nutrient loading. This usage lacks information about non‐algal threats to water quality, such as dystrophication in response to dissolved organic carbon loading. Consequently, the TS classification schemes used to identify eutrophication and dystrophication may refer to ecosystems similarly (e.g., oligotrophic and eutrophic), yet these categories are derived from different proxies. These inconsistencies in TS classification schemes may be compounded when interdisciplinary projects employ varied TS frameworks. Even with these shortcomings, TS can still be used to distill information on complex aquatic ecosystem function into a set of generalizable expectations. The usefulness of distilling complex information into a TS index is substantial such that usage inconsistencies should be explicitly addressed and resolved. To emphasize the consequences of diverging TS classification schemes, we present three case studies for which an improved understanding of the TS concept advances freshwater research, management efforts, and interdisciplinary collaboration. To increase clarity in TS, the aquatic sciences could benefit from including information about the proxy variables, ecosystem type, as well as the spatiotemporal domains used to classify TS. As the field of aquatic sciences expands and climatic irregularity increases, we highlight the importance of re‐evaluating fundamental concepts, such as TS, to ensure their compatibility with evolving science.

classification↗
DOE OSTI2024

Modeling prebiotic chemistries with quantum accuracy at classical costs

Molecular Dynamics (MD) simulations using classical force-fields are commonly employed in numerous scientific investigations. However, many natural processes involve bond breaking and quantum forces. This complexity is compounded by the presence of multiple competing length and timescales. For example, accurately modeling the thermodynamics and dynamics of a chemical reaction requires accounting for the concerted movements of numerous solvent molecules and ions with their own fast or slow timescales. While widely used static Density Functional Theory (DFT) calculations at 0 temperature can be beneficial for such investigations, they do not account for dynamics, and lack precision in describing the molecular environments. They particularly fail at correct, rigorous treatments of finite-temperature fluctuations, and thus generalization to experimentally relevant conditions. In PNAS Benayad et al develop a scalable, generalizable approach for designing Neural Network Potentials (NNPs) that can handle chemical reactivity in solvated systems with quantum accuracy at classical costs. Specifically, they study phosphoester bond formation and rupture, which is fundamentally relevant to the Phosphorus-Oxygen bond formation central to life, and especially for the RNA world hypothesis. The framework developed here has the potential to generalize to different chemical reactions of energy and biological relevance.

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

Tandem Electrocatalytic–Thermocatalytic Conversion of CO 2 to Aromatic Hydrocarbons

The reaction of CO 2 with H 2 O to produce aromatic hydrocarbons (benzene, toluene, ethylbenzene, and xylene isomers) (BTEX) represents a promising pathway for converting CO 2 to value-added liquid products. However, this reaction cannot be achieved in a single electrochemical or thermochemical process. This work utilizes tandem electrochemical-thermochemical reactors as a new paradigm by starting with CO 2 and H 2 O as the feed in a membrane electrode assembly (MEA) to produce C 2 H 4 , which subsequently undergoes thermochemical aromatization using a Gallium- and Phosphorus-modified zeolite ZSM-5 catalyst (Ga/ZSM-5/P) at ambient pressure to produce BTEX. The current study also demonstrates the potential advantage of the tandem strategy in mitigating negative effects of water by testing the tandem reactor system under different hydration conditions and by performing in-situ X-ray diffraction (XRD) and X-ray absorption (XAS) characterization of the aromatization catalysts. Finally, these results highlight the advantage of using the tandem process with the use of a water trap before the thermochemical reactor.

10 SYNTHETIC FUELS↗
DOE OSTI2020

Reviews and syntheses: Ironing out wrinkles in the soil phosphorus cycling paradigm

Soil phosphorus (P) management remains a critical challenge for agriculture worldwide, and yet we are still unable to predict soil P dynamics as confidently as that of carbon (C) or nitrogen (N). This is due to both the complexity of inorganic P (P i ) and organic P (P o ) cycling and the methodological constraints that have limited our ability to trace P dynamics in the soil–plant system. In this review, we describe the challenges for building parsimonious, accurate, and useful biogeochemical models that represent P dynamics and explore the potential of new techniques to usher P biogeochemistry research and modeling forward. We conclude that research efforts should focus on the following: (1) updating the McGill and Cole (1981) model of P o mineralization by clarifying the role and prevalence of biochemical and biological P o mineralization, which we suggest are not mutually exclusive and may co-occur along a continuum of P o substrate stoichiometry; (2) further understanding the dynamics of phytate, a six C compound that can regulate the poorly understood stoichiometry of soil P; (3) exploring the effects of C and P o saturation on P sorption and P o mineralization; and (4) resolving discrepancies between hypotheses about P cycling and the methods used to test these hypotheses.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Multimodal, microspectroscopic speciation of legacy phosphorus in two US mid-Atlantic agricultural soils

To understand phosphorus (P) mobility in agricultural soils and its potential environmental risk, it is essential to directly measure solid phase P speciation. Often, bulk P K-edge X-ray absorption near edge structure (XANES) spectroscopy followed by linear combination fitting (LCF) is utilized to determine the solid P phases in soil. However, this method may limit results to only a few major phases. Additionally, XANES spectra for different P species may have very similar features, leading to an over- or underestimate of their contribution to LCF. Here, an improved P speciation by pairing multimodal microbeam-X-ray fluorescence (µ-XRF) mapping coupled with µ-XANES (microbeam-X-ray absorption near edge structure) analysis to directly speciate major and minor P phases on the micron scale is provided. We combined maps of both tender (P, sulfur, aluminum, and silicon) and hard energy (calcium, iron [Fe], and manganese) elements to evaluate the elemental co-locations with P. To better account for uncertainty assigning XANES peaks to individual compounds, a more quantitative fingerprinting by “spectral feature analysis” was completed. With this analysis, an R-factor is reported for the fit. These results were compared to traditional LCF. Pre-edge fitting results revealed the presence of a two-component pre-edge feature for phosphate adsorbed to ferrihydrite. Additionally, phytate co-precipitated with ferrihydrite (Phytate-Fe-Cop) had a pre-edge feature, indicating direct association with Fe. Lastly, a unique P species associated with manganese oxide was identified in the soil via multimodal mapping and µ-XANES. These results allow for better prediction of P dissolution and mobility.

36 MATERIALS SCIENCE↗
DOE OSTI2025

The Effect of Core-Hole Shape on Attosecond Valence Electron Dynamics

Rapid X-ray ionization of a core electron is known to induce the attosecond motion of valence electrons; however, the effect of core-hole shape on the triggered dynamics remains relatively unknown. In this work, the sub-four fs response of prototypical functionalized/heterocyclic/polycyclic molecules was simulated using real-time time-dependent density functional theory (RT-TDDFT), a sudden approximation core-hole, and phenomenologically Auger–Meitner (AM) decay. These molecules included fluorobenzene, chlorobenzene, bromobenzene, phenol, thiophenol, pyridine, phosphorus, and azulene. It is observed that the valence electron dynamics are essentially independent of the core-hole created, provided that it is ionized from an inner-shell orbital and not an inner-valence orbital. This has broad implications for free-electron laser studies of X-ray pumped attosecond processes since the flexibility in edge allows for a wide range of experimental modalities, core-holes with longer AM lifetimes, and molecular targets.

aromatic compounds↗