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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Coordination-Induced N–H Bond Weakening in a Molybdenum Pyrrolidine Complex: Isotopic Labeling Provides Insight into the Pathway for H 2 Evolution

The synthesis and characterization of a cationic molybdenum pyrrolidine complex is described that exhibits significant coordination-induced N–H bond weakening. Here, the N–H bond dissociation free energy (BDFE) of the coordinated pyrrolidine in [( Ph Tpy)(PPh 2 Me) 2 Mo(NH(pyrr))][BArF 24 ] ([1-NH(pyrr)] + ; PhTpy = 4'-Ph-2,2',6',2''-terpyridine, NH(pyrr) = pyrrolidine, ArF 24 = [C 6 H 3 -3,5-(CF 3 ) 2 ] 4 ) was determined to be between 41–51 kcal mol -1 by thermochemical analysis and supported by a density functional theory (DFT) computed value of 48 kcal mol -1 . The complex [1-NH(pyrr)] + underwent proton-coupled electron transfer (PCET) to 2,4,6-tri-tert-butylphenoxyl radical, as well as spontaneous H 2 evolution upon gentle heating to furnish the corresponding molybdenum pyrrolidide complex, [( Ph Tpy)(PPh 2 Me) 2 Mo(N(pyrr))][BArF 24 ] ([1-N(pyrr)] + ). Thermolysis of the deuterated isotopolog, [1-ND(pyrr)] + still produced H 2 with concomitant incorporation of the isotopic label into the pyrrolidide ligand in the product [(1-N(pyrr-d n )] + (n = 0–2), consistent with an H 2 evolution pathway involving intramolecular H–H bond formation followed by an intermolecular product-forming PCET step. These observations provide context for understanding H 2 evolution in the nonclassical ammine complex [( Ph Tpy)(PPh 2 Me) 2 Mo(NH 3 )][BArF 24 ] ([1-NH 3 ] + ) and are supported by DFT-computed reaction thermochemistry. Overall, these studies offer rare insight into the H 2 formation pathway in nonclassical amine complexes with N–H BDFEs below the thermodynamic threshold for H 2 evolution and inform the development of well-defined, thermody-namically potent PCET reagents.

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

Data for Roebuck et al. (2025), "Differences in dissolved organic matter composition between rivers and estuaries is conserved across freshwater and saltwater coastal regions"

Dissolved organic matter (DOM) in coastal surface waters influences local water quality and is an important component of biogeochemical cycling in coastal systems, but the processes that alter DOM composition along lower reaches of rivers and estuarine waters are poorly understood. Roebuck et al. (2025) leveraged a spatially distributed community sampling effort in coastal ecosystems across two regions to identify broad spatial drivers of surface water DOM composition and identify transferable trends between saltwater and freshwater coastal systems. Samples were collected by community members from 47 locations within the mid-Atlantic and Great Lakes coastal regions.This dataset includes:* A selection of commonly reported absorbance and fluorescence peaks normalized to dissolved organic carbon concentrations* Parallel factor output from the EC1 fluorescence datasets* A selection of commonly reported absorbance and fluorescence peaks * Spectral indices output from matlab script for absorbance and fluorescence datasets* CO2sys calculations of pH changes under varying temperatures and a constant salinity, DIC, and alkalinity concentrationAll data files are plain-text CSV (comma separated value) and no special software is required to read them.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

A combined experimental and modelling study of granite hydrothermal alteration

Geochemical reactions can induce significant changes of rock reservoir porosity and permeability via mineral dissolution and precipitation processes, affecting the long-term fluid behaviour within various geological systems. Here, the understanding and quantification of these reactions rely on field and experimental studies and on the predictions of reactive transport models. The present study was aimed at assessing the extent to which current geochemical models integrating available mineral dissolution/precipitation rate equations can reproduce the experimental data obtained from 4 to 17-day long hydrothermal alteration experiments of a muscovite-biotite granite and, thus, help provide an accurate description of the evolution of geothermal systems within granitic reservoirs. The experiments were conducted at a constant temperature of 180 °C and over an aqueous fluid pH range of 2 to 8.5, using both mixed-flow and static batch reactors. Modelled major element (K, Al, Si, Ca, and Mg) concentrations were generally in satisfactory agreement with the corresponding measured elemental fluxes – the differences between modelled and experimental values were generally within a factor of 5 – and the predicted identity and mass of formed secondary phases were consistent with the microscopic observations of the reacted solids. However, larger differences between measured and modelled element concentrations were observed when significant amounts of secondary phases formed, notably at pH 2 to 3, and for longer-term batch experiments. Much of this concentration difference stems from the underestimation of the amounts of Al-phases formed at acid to near-neutral pH. Although an idealized rock composition was considered, the observed mismatch between model calculations and experimental data can be attributed to inadequate mineral precipitation reaction rates and a poor description of reactive surface areas in existing geochemical modelling codes. More accurate quantification of precipitation kinetics, including nucleation and growth, and improved descriptions of the temporal change of mineral surface area would enhance the predictive capabilities of reactive transport models and benefit, particularly, the efforts aimed at increasing the sustainability of EGS reservoirs.

58 GEOSCIENCES↗
DOE OSTI2023

UniKP: a unified framework for the prediction of enzyme kinetic parameters

Prediction of enzyme kinetic parameters is essential for designing and optimizing enzymes for various biotechnological and industrial applications, but the limited performance of current prediction tools on diverse tasks hinders their practical applications. Here, we introduce UniKP, a unified framework based on pretrained language models for the prediction of enzyme kinetic parameters, including enzyme turnover number (k cat ), Michaelis constant (K m ), and catalytic efficiency (k cat / K m ), from protein sequences and substrate structures. A two-layer framework derived from UniKP (EF-UniKP) has also been proposed to allow robust k cat prediction in considering environmental factors, including pH and temperature. In addition, four representative re-weighting methods are systematically explored to successfully reduce the prediction error in high-value prediction tasks. We have demonstrated the application of UniKP and EF-UniKP in several enzyme discovery and directed evolution tasks, leading to the identification of new enzymes and enzyme mutants with higher activity. UniKP is a valuable tool for deciphering the mechanisms of enzyme kinetics and enables novel insights into enzyme engineering and their industrial applications.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1991

Dynamics of vegetation and soils of oak/saw palmetto scrub after fire: Observations from permanent transects

Ten permanent 15 m transects previously established in two oak/saw palmetto scrub stands burned in December 1986, while two transects remained unburned. Vegetation in the greater than 0.5 m and the less than 0.5 m layers on these transects was sampled at 6, 12, 18, 24, and 36 months postburn and determined structural features of the vegetation (height, percent bare ground, total cover). The vegetation data were analyzed from each sampling by height layer using detrended correspondence analysis ordination. Vegetation data for the greater than 0.5 m layer for the entire time sequence were combined and analyzed using detrended correspondence analysis ordination. Soils were sampled at 6, 12, 18, and 24 months postburn and analyzed for pH, conductivity, organic matter, exchangeable cations (Ca, Mg, K, Na), NO3-N, NH4-N, Al, available metals (Cu, Fe, Mn, Zn), and PO4-P. Shrub species recovered at different rates postfire with saw palmetto reestablishing cover greater than 0.5 m within one year, but the scrub oaks had not returned to preburn cover greater than 0.5 m in 3 years after the fire. These differences in growth rates resulted in dominance shifts after the fire with saw palmetto increasing relative to the scrub oaks. Overall changes in species richness were minor, although changes occurred in species richness by height layers due to different growth rates. Soils of well drained and poorly drained sites differed markedly. Soil responses to the fire appeared minor. Soil pH increased at 6 and 12 months postfire; calcium increased at 6 months postburn. Nitrate-nitrogen increased at 12 months postburn. Low values of conductivity, PO4-P, Mg, K, Na, and Fe at 12 months postburn may be related to heavy rainfall the preceding month. Seasonal variability in some soil parameters appeared to occur.

Schmalzer, Paul A.↗
NASA NTRS2020

The Effect of Europa and Enceladus Analog Seawater Composition on Isotopic Measurements of Volatile CO2

Science goals for icy ocean worlds missions include characterizing the chemical compositionof the surface and interior using remote sensing and in situ techniques. The next class of flightmass spectrometers for these missions will obtain compositional identifications and isotope ratiomeasurements of volatiles evolved from the ice surface (exosphere) and plumes. These massspectra will be combined with data from other flight instruments to infer the composition of theinterior from volatiles. To ensure accurate interpretation of these measurements, it is critical toverify whether the fundamental assumption that volatiles observed in icy ocean world exospheresor plumes will be a direct reflection of the sub-ice ocean. The present study evaluates whether isotopologues from an initial CO2 gas fractionate by interacting with seawater (brine) of varyingsalt composition and concentration. δ13CCO2 are affected by the pH of the brine and subsequentspeciation of {CO2}, where {CO2} represents the combination of CO2, H2CO3, HCO3-, and CO32-.{CO2} for low pH brines hypothesized for Europa will preferentially speciate as CO2. Analyzedδ13CCO2 for low pH brines are within error of the original δ13CCO2, demonstrating that volatile CO2in a low pH system will be a direct reflection of the original CO2. However, Europa’s radiativeenvironment and rapid depressurization due to plume ejection may impose fractionation effects.In contrast, high pH systems relevant to Enceladus or a more alkaline Europa are expected toform all carbonate species, while favoring speciation as HCO3-. High pH brines in theseexperiments include both an original CO2 gas and an isotopically distinct HCO3- (from NaHCO3salt). These alkaline experiments demonstrate that δ13CCO2 values are highly variable, and dependon the concentration of the dominant carbonate species, (Na)HCO3-. Mass balance estimatesindicate that measured δ13CCO2 is a thermodynamically predictable mixture of both carbonsources, suggesting that measurements of δ13C at Enceladus would directly reflect of the sourcesof CO2 and carbonate buffering in the ocean. δ18O measurements for CO2 interacting with KCland MgCl2 follow established models for δ18O-ionic strength. CO2 interacting with MgSO4,Na2SO4, and NaCl demonstrate an offset from established δ18O-ionic strength models dependingon the concentration of initial CO2. These results suggest that current predictive models for δ18Oin brines need to be resolved for changing concentrations of CO2

Ocean Worlds↗
DOE OSTI2025

Aerosol Thermodynamics (Aerosol Liquid Water Concentration and Aerosol pH) at S2 during CoURAGE

These data report aerosol liquid water content (ALWC) and aerosol pH for the S2 (Mt. Airy) site during CoURAGE for April - June 2025. The ISORROPIA-II aerosol thermodynamic equilibrium model was used to compute ALWC and pH. The model was run in forward mode, with solids formation disabled (metastable mode), according to Pye et al. (Atmospheric Chemistry and Physics, 2020). Information about the model can be found at https://www.epfl.ch/labs/lapi/models-and-software/isorropia/, and in Fountoukis and Nenes (Atmospheric Chemistry and Physics, 2007). Inputs to the model were: (1) measured Temperature and relative humidity, both from the DoE ARM “metwxt” data products at S2, (2) aerosol chemical composition from the ARM ACSM, and (3) gas-phase ammonia concentrations. For ISORROPIA-II, ambient RH values above 0.995 were input to the model as 0.995; therefore, caution should be exercised interpreting ALWC when RH was above 0.995. Aerosol composition or NH3(g) concentrations below the LOD were input into the model as 0.5*LOD. Model runs were only conducted for data points at 30-min resolution with all three inputs (meteorology, ACSM, and NH3). If any of the three model inputs were missing, aerosol thermodynamic outputs are flagged as -999. Similarly, aerosol thermodynamic outputs are flagged as -999 if measured NH3(g) and aerosol ammonium (NH4+) were simultaneously below the respective LODs. The ALWC includes liquid water from inorganic aerosol components, calculated directly by ISORROPIA-II, as well as liquid water from organics, estimated from the ACSM organics assuming a kappa value of 0.12 according to Guo et al. (Atmospheric Chemistry and Physics, 2015).

Aerosol Liquid Water Content↗
DOE OSTI2025

Upconversion of non-recycled MSW paper fractions into biochar via slow pyrolysis and life cycle analysis: Pathways to net negative GHG emission

This study presents an integrated and sustainable approach to valorizing non-recycled municipal solid waste (MSW), a heterogeneous and underutilized waste stream destined for landfilling, by converting it into valuable biochar resources. Specifically, we investigated the upcycling of nonrecycled paper waste based on compositional analysis into four major fractions: high cellulose, high lignin, high contamination, and high ash content papers. These fractions were then homogenized and subjected to slow pyrolysis. The high cellulose fraction (36.1 %) was the most abundant, and contained 66.7 % cellulose, while the high lignin fraction showed the highest lignin (12.1 %) and carbon content (44 %), resulting in highest energy value of 17.4 MJ kg −1 . Biochar yields ranged from 25.6 % to 35.6 %, with the high ash fraction producing the highest yield and alkalinity (pH ≈ 11.2) due to its higher mineral content. Elemental analysis revealed enhanced carbon content up to 76.9 % and reduced oxygen and hydrogen, confirming effective carbonization. The high lignin-derived biochar showed the highest aromatic carbon content (82.8 %) and greater structural stability, while contaminated and ash-rich fractions exhibited dense, low-porosity surfaces due to the presence of contaminants and minerals. Spectroscopic analysis revealed degradation of carbohydrates, disappearance of cellulose peaks and formation of aromatic and mineral derived phases. The scaled life cycle process yielded a global warming potential (GWP) of 119.3 kg CO 2 -eq per ton of dry paper waste, offset by soil carbon sequestration of − 556.41 kg CO 2 -eq, resulting in a net impact of − 427.36 kg CO 2 -eq. This represents a net carbon removal exceeding by ~186 % the emissions associated with landfilling paper waste with electricity generation.

09 BIOMASS FUELS↗
DOE OSTI2023

129 I, 99 Tc, And U Distribution Coefficients of Subsurface Sediments Collected from the Proposed Site of the Environmental Management Disposal Facility

Performance Assessment calculations were completed in 2020 to evaluate the Environmental Management Disposal Facility (EMDF), a proposed new low-level radioactive waste (LLW) disposal facility on the U.S. Department of Energy’s Oak Ridge Reservation (ORR). Among the large number of input parameters needed for such calculations, are distribution coefficients (K d values; radionuclide concentration solid:liquid ratio) that provide a measure of the tendency of radionuclides to bind to sediments. The objective of this study was to measure K d values of three radionuclides that may pose a disproportionately large amount of risk, U, 129 I and 99 Tc. The average I K d value for the 14 geological materials recovered from the proposed EMDF site was 37.8 mL/g and ranged from -1.8 to 140.9 mL/g. These values were consistent, but somewhat larger than previous measurements made with ORR sediments and were about an order of magnitude greater than those used in previous EMDF PA calculations. The median Tc K d value was 365.7 mL/g, much greater than previously reported using ORR geological materials. Five of the 14 tested geological materials sorbed large quantities of Tc, suggesting that the weakly sorbing Tc(VII) species had been reduced to the sparingly soluble Tc(IV) species. The five strongly sorbing sediments had apparent Tc solubility values of approximately <10 -8 mol/L. The median U K d value was 5,726 mL/g. All of the tested geological materials had large K d values, ranging from 625 to >10,208 mL/g. Among the sediment samples that exhibited strong U binding, the apparent solubility value was approximately <10 -9 mol/L. Based on sediment properties and general ORR geological considerations, it was proposed that much of the I and Tc retention could be attributed to the site materials exhibiting low pH (average pH = 4.94), low redox status, and/or the elevated levels of iron oxides, manganese oxides, and natural organic matter. Similarly, the extremely high U binding measured in these sediments may also be attributed to the low conditions of carbonates, which can complex and therefore solubilize uranyl in these tests due to the low pH, and also the relatively high concentrations of iron and organic coatings on these samples. An implication of this study is that the areas of the EMDF subsurface environment may have natural properties for attenuating I, Tc, and U movement, and potentially other radionuclides, thereby possibly reducing risk posed by burial of LLW at this site. This document is a revision of SRNL-STI-2021-00404, Revision 0 that includes new data describing U K d values and new I and Tc K d values for four Nolichucky sediments. These new results were integrated into the data presented in the original document.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS2004

Evaluation of a Multi-Parameter Sensor for Automated, Continuous Cell Culture Monitoring in Bioreactors

Compact and automated sensors are desired for assessing the health of cell cultures in biotechnology experiments in microgravity. Measurement of cell culture medium allows for the optirn.jzation of culture conditions on orbit to maximize cell growth and minimize unnecessary exchange of medium. While several discrete sensors exist to measure culture health, a multi-parameter sensor would simplify the experimental apparatus. One such sensor, the Paratrend 7, consists of three optical fibers for measuring pH, dissolved oxygen (p02), dissolved carbon dioxide (pC02) , and a thermocouple to measure temperature. The sensor bundle was designed for intra-arterial placement in clinical patients, and potentially can be used in NASA's Space Shuttle and International Space Station biotechnology program bioreactors. Methods: A Paratrend 7 sensor was placed at the outlet of a rotating-wall perfused vessel bioreactor system inoculated with BHK-21 (baby hamster kidney) cells. Cell culture medium (GTSF-2, composed of 40% minimum essential medium, 60% L-15 Leibovitz medium) was manually measured using a bench top blood gas analyzer (BGA, Ciba-Corning). Results: A Paratrend 7 sensor was used over a long-term (>120 day) cell culture experiment. The sensor was able to track changes in cell medium pH, p02, and pC02 due to the consumption of nutrients by the BHK-21. When compared to manually obtained BGA measurements, the sensor had good agreement for pH, p02, and pC02 with bias [and precision] of 0.02 [0.15], 1 mm Hg [18 mm Hg], and -4.0 mm Hg [8.0 mm Hg] respectively. The Paratrend oxygen sensor was recalibrated (offset) periodically due to drift. The bias for the raw (no offset or recalibration) oxygen measurements was 42 mm Hg [38 mm Hg]. The measured response (rise) time of the sensor was 20 +/- 4s for pH, 81 +/- 53s for pC02, 51 +/- 20s for p02. For long-term cell culture measurements, these response times are more than adequate. Based on these findings , the Paratrend sensor could offer automated, continuous monitoring of cell cultures with a temporal resolution of 1 minute, which is not attainable by sampling via handheld blood analyzer (i-STAT). Conclusion: The resulting bias and precision found in these cell culture-based studies is comparable to Paratrend sensor clinical results. Although the large error in p02 measurements (+/-18 mm Hg) may be acceptable for clinical applications, where Paratrend values are periodically adjusted to a BGA measurement, the O2 sensor in this bundle may not be reliable enough for the single-calibration requirement of sensors used in NASA's bioreactors. The pH and pC02 sensors in the bundle are reliable and stable over the measurement period, and can be used without recalibration to measure cell cultures in rn.jcrogravity biotechnology experiments. Future work will test additional Paratrend sensors to provide statistical assessment of sensor performance.

Pappas, D.↗
DOE OSTI2021

129 I and 99 Tc Distribution Coefficients of Subsurface Sediments Collected from the Proposed Site of the Environmental Manage Disposal Facility

Performance Assessment calculations are presently underway to evaluate the Environmental Management Disposal Facility (EMDF), a proposed new low-level radioactive waste (LLW) disposal facility on the U.S. Department of Energy’s Oak Ridge Reservation (ORR). Among the large number of input parameters needed for such calculations, are distribution coefficients (K d values; radionuclide concentration solid:liquid ratio) that provide a measure of the tendency of radionuclides to bind to sediments. The objective of this study was to measure K d values of two radionuclides that may pose a disproportionately large amount of risk, 129 I and 99 Tc. The average I K d value for the 10 geological materials recovered from the proposed EMDF site was 52.3 mL/g and ranged from 2.7 to 140.9 mL/g. These values were consistent, but somewhat larger than previous measurements made with ORR sediments and were about an order of magnitude greater than those used in previous EMDF PA calculations. The median Tc K d value was 807.2 mL/g, much greater than previously reported using ORR geological materials. Five of the ten tested geological materials sorbed large quantities of Tc, suggesting that the weakly sorbing Tc(VII) species had been reduced to the very strongly binding and sparingly soluble Tc(IV) species. The five strongly sorbing sediment had apparent solubility values of approximately <10 -8 mol/L. Based on sediment properties and general ORR geological considerations, it was proposed that much of the I and Tc sorption could be attributed to the low pH (average pH = 4.94), low redox status, and/or the elevated levels of iron oxides, manganese oxides, and natural organic matter. An implication of this study is that the areas of the EMDF subsurface environment may have natural properties for attenuating I and Tc movement, thereby potentially reducing risk posed by burial of LLW at this site.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1977

Light energy conservation processes in Halobacterium halobium cells

Proton pumping driven by light or by respiration generates an electrochemical potential difference across the membrane in Halobacterium halobium. The pH changes induced by light or by respiration in cell suspensions are complicated by proton flows associated with the functioning of the cellular energy transducers. A proton-per-ATP ratio of about 3 is calculated from simultaneous measurements of phosphorylation and the proton inflow. This value is compatible with the chemiosmotic coupling hypothesis. The time course of the light-induced changes in membrane potential indicates that light-driven pumping increases a dark pre-existing potential of about 130 mV only by a small amount (20 to 30 mV). The complex kinetic features of the membrane potential changes do not closely follow those of the pH changes, which suggests that flows of ions other than protons are involved. A qualitative model consistent with the available data is presented.

Bogomolni, R. A.↗
DOE OSTI2025

Acidities of MgO surface sites: implications for the formation mechanism of Mg(OH) 2

The hydroxylation of periclase (MgO) to brucite (Mg(OH) 2 ) is thought to be an important intermediate step when using MgO to capture CO 2 from the atmosphere. However, the mechanism of hydroxylation of MgO to form Mg(OH) 2 is poorly understood. In this work, we used atomic-scale density functional tight binding simulations coupled with the metadynamics rare event method to analyze the surface chemistry of MgO and the acid dissociation equilibrium constants (pK a ) of its surface sites. The method and parameters were validated by calculating the pK a for hydroxylation of the first shell water bound to aqueous Mg 2+ ion. The pK a value derived using a probabilistic method was 12.3, which is in fair agreement with the accepted value of 11.4, with the difference between them equal to a ∼5 kJ mol −1 error in the calculations. We then extended these pK a calculations to probe the hydroxylation reactions of the surface sites of the MgO(100)–water interface, arriving at pK a s of 5.4 to deprotonate terminal water molecules bound to the surface magnesium sites (η-OH 2 or 〉MgOH 2 ), and 13.9 to deprotonate hydroxylated bridging oxygen sites (μ 5 -oxo or 〉O). Hydroxide (OH − ) adsorption on the surface was also probed and found to be less thermodynamically favorable than deprotonation of the terminal water molecule. The plausibility of the computed pK a s was verified using an activity-based speciation model and compared to pH measurements of water equilibrated with MgO nanoparticles and single crystals. The model predicted a solution pH of 7.1 when surface sites buffered and the pH of 12.0 when MgO dissolution dominated. These are close to the experimental initial solution pHs of 7–7.5 and the long term pHs of ∼10.5. The similarity suggests that the calculated pK a values from the DFTB+/metadynamics simulations are plausible and that these methods can be a useful tool to probe reaction mechanisms involving covalent bonds.

Adapa, Sai Krishna Reddy [Oak Ridge National Labor↗
NASA NTRS1982

Intensity formulas for triplet bands

Previous work in this area is surveyed and the mathematics involved in determining the quantitative intensity measurements in triplet bands is presented. Explicit expressions for the intensity distribution in the branches of the 3 Sigma-3 Pi and 1 Sigma-3Pi bands valid for all values of the coupling constant Y of the 3 Pi terms are given. The intensity distribution calculated according to the formulas given is compared with measurements of PH, 3 Pi-3 Sigma. Good quantitative agreement is obtained.

Budo, A.↗
NASA NTRS1997

Atomic Physics with the Goddard High Resolution Spectrograph on the Hubble Space Telescope: Oscillator Strengths for Neutral Carbon - III

High quality spectra of interstellar absorption from C I toward beta(sup 1) S(sub co), rho O(sub ph) A, and chi O(sub ph) were obtained with the Goddard High Resolution Spectrograph on HST. Many weak lines were detected within the observed wavelength intervals: 1150-1200 A for beta(sup 1) S(sub co) and 1250-1290 A for rho O(sub ph) A and chi O(sub ph). Curve-of-growth analyses were performed in order to extract accurate column densities and Doppler parameters from lines with precise laboratory-based f-values. These column densities and b-values were used to obtain a self-consistent set of f-values for all the observed C I lines. A particularly important constraint was the need to reproduce data for more than one line of sight. For about 50% of the lines, the derived f-values differ appreciably from the values quoted by Morton.

Zsargo, J.↗
DOE OSTI2022

Remote Floating-Gate Field-Effect Transistor with 2-Dimensional Reduced Graphene Oxide Sensing Layer for Reliable Detection of SARS-CoV-2 Spike Proteins

Despite intensive research of nanomaterials-based field-effect transistors (FETs) as a rapid diagnostic tool, it remains to be seen for FET sensors to be used for clinical applications due to a lack of stability, reliability, reproducibility, and scalability for mass production. In this work, we propose a remote floating-gate (RFG) FET configuration to eliminate device-to-device variations of two-dimensional reduced graphene oxide (rGO) sensing surfaces and most of the instability at the solution interface. Also, critical mechanistic factors behind the electrochemical instability of rGO such as severe drift and hysteresis were identified through extensive studies on rGO–solution interfaces varied by rGO thickness, coverage, and reduction temperature. rGO surfaces in our RFGFET structure displayed a Nernstian response of 54 mV/pH (from pH 2 to 11) with a 90% yield (9 samples out of total 10), coefficient of variation (CV) < 3%, and a low drift rate of 2%, all of which were calculated from the absolute measurement values. As proof-of-concept, we demonstrated highly reliable, reproducible, and label-free detection of spike proteins of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in a saliva-relevant media with concentrations ranging from 500 fg/mL to 5 μg/mL, with an R 2 value of 0.984 and CV < 3%, and a guaranteed limit of detection at a few pg/mL. Taken together, this new platform may have an immense effect on positioning FET bioelectronics in a clinical setting for detecting SARS-CoV-2.

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

The [M 6 (S 2 C 2 Ph 2 ) 6 ] (M = Ni, Pd, Pt) Series: Multielectron Reservoirs That Sustain Ligand-Based Oxidations and Metal-Based Reductions

A complete [M 6 (S 2 C 2 R 2 ) 6 ] series (M = Ni (1), Pd (2), Pt (3); R = Ph), the rarest variety among homoleptic dithiolene transition-metal compounds, has been prepared by reaction between [M(S 2 C 2 Ph 2 ) 2 ] and a M 0 source. The platinum member of this set is the first of its type. Diffraction-quality crystals, grown with high reproducibility by evaporation from PhNO 2 solutions, reveal fully reduced [Ph 2 C 2 S 2 ] 2– dianions and an octahedral M 6 core that is reduced to C 2 symmetry by the fusion of a mononuclear D 2h [M(S 2 C 2 Ph 2 ) 2 ] fragment upon a C 4 -symmetric base. The [Ni 6 (S 2 C 2 Ph 2 ) 2 ] 1– monoanion, prepared by Cp* 2 Co reduction, shows only modest structural differences from its neutral counterpart. In CH 2 Cl 2 , 1 and 2 can undergo two reductions and an oxidation, while 3 sustains two reductions and two oxidations. In benzonitrile, 1 sustains three reversible oxidations at potentials that are shifted appreciably to less positive values. The cathodic processes are shown by density functional theory (DFT) calculations to involve an MO largely of metal–sulfur composition that has contributions throughout the C 4 -symmetric pentametallic base of the assembly, while the oxidations are largely ligand-based and confined to the monometallic [M(S 2 C 2 Ph 2 ) 2 ] cap. The absorption spectra are marked by multiple overlapping bands that produce a continuous, tapering absorption profile of unresolved shoulders and swells.

Ligands↗
DOE OSTI2023

Structure and Magnetic Properties of Homoleptic Trivalent Tris(alkyl)lanthanides

Six new solvent-free, homoleptic paramagnetic tris(alkyl)lanthanides Ln{C(SiHMe 2 ) 3 } 3 (1Ln) and Ln{C(SiHMe 2 ) 2 Ph} 3 (2Ln) (Ln = Gd, Dy, and Er) were synthesized to investigate the magnetic properties of 4f organometallic compounds stabilized by secondary Ln←H–Si and benzylic interactions. The unit cell of 1Gd contains one independent molecule (Z = 2), while 1Dy and 1Er crystallize with four independent isostructural molecules per unit cell (Z = 16). In all molecules, as in other 1Ln compounds, the three tris(dimethylsilyl)methyl ligands form a trigonal planar LnC 3 core, and six secondary interactions involving Ln←H–Si bonding in Ln{C(SiHMe 2 ) 3 } 3 form above and below the equatorial plane. Two and five crystallographically independent molecules of each 2Ln (2Gd, Z = 8; 2Dy, Z = 20) form with three π-coordinated phenyl groups in addition to either one or two secondary Ln←H–Si interactions per molecule. The packing of these midseries organolanthanide compounds contrasts the single crystallographically unique molecules in previously reported La{C(SiHMe 2 ) 3 } 3 (1La, Z = 2, Z' = 1) and La{C(SiHMe 2 ) 2 Ph} 3 (2La, Z = 2, Z' = 1/3). 2La doped with 2Dy can adopt the crystallographic structure of 2La, which promotes magnetic properties, namely a higher χ m T value at low temperatures as well as stronger magnetic anisotropy. The ac susceptibility data for 10% 2Dy doped into 2La suggests slow relaxation at low temperatures with a relaxation barrier of ~45 K. The computed saturated magnetization of 1Er (M ≈ 4.5 μ B ) and 1Dy (M ≈ 6 μ B ) matches the experimental values, while the computed value for 2Dy better matches the value measured for 2Dy diluted in 2La (M ≈ 5 μ B ). Gas-phase calculations predict that the ground-state and first excited-state multiplet separations are larger for 1Er than 2Er, while the ordering for dysprosium is 1Dy > 2Dy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗