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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 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Probing axion-like particles at the Electron-Ion Collider

Abstract The Electron-Ion Collider (EIC), a forthcoming powerful high-luminosity facility, represents an exciting opportunity to explore new physics. In this article, we study the potential of the EIC to probe the coupling between axion-like particles (ALPs) and photons in coherent scattering. The ALPs can be produced via photon fusion and decay back to two photons inside the EIC detector. In a prompt-decay search, we find that the EIC can set the most stringent bound form a ≲ 20 GeV and probe the effective scales Λ ≲ 10 5 GeV. In a displaced-vertex search, which requires adopting an EM calorimeter technology that provides directionality, the EIC could probe ALPs withm a ≲ 1 GeV at effective scales Λ ≲ 10 7 GeV. Combining the two search strategies, the EIC can probe a significant portion of unexplored parameter space in the 0.2 a< 20 GeV mass range.

Physics↗
DOE OSTI2019

Computational modeling of curcumin-based fluorescent probe molecules

In recent years, a series of curcumin analogs have been designed as fluorescent probes for detecting and imaging Aβ peptide aggregates and reactive oxygen species (ROS) in Alzheimer’s disease (AD) brains. In order to gain a better understanding of the photophysical properties of these probe molecules, a systematical computational investigation was performed using the time-dependent density functional theory (TDDFT) calculations. Computed absorption and emission wavelengths well reproduced the spectral shifts among the curcumin analogs. In particular, for a recently proposed pair of probe molecules, CRANAD-5 and CRANAD-61, for sensing ROS in preclinical studies of AD brains, their emission wavelength difference was found to arise from a delocalization of the lowest unoccupied molecular orbital of CRANAD-61 from the curcuminoid backbone to the oxalate moiety. Altogether, this study reaffirms the value of employing TDDFT calculations to assist the design of new curcumin-based fluorescence probes for AD research.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Development of a New 4-Amino-1,8-Naphthalimide Derivative as a Fluorescent Probe for Monitoring the Divalent Copper Ion

This article presents the design and synthesis of a new variant of the 4-amino-1,8-naphthalimide fluorescent probe for monitoring the divalent copper ion, Cu{sup 2+}. The probe BRST, functionalized with two propionic carboxylic acid groups in its receptor moiety, demonstrated high selectivity and sensitivity for the detection of Cu{sup 2+} in competitive media of various metal ions in DMSO/HEPES buffer solution (1:1; pH 7.4), with a fluorescence quenching of 75.41%. Besides its good linearity with Cu{sup 2+}, the probe yielded commendable values of the association constant and the detection limit, 5.54 × 10{sup 5} M{sup –1} and 4.33 × 10{sup –9} M, respectively. The quenching of the fluorescence intensity of the sensor in the presence of Cu{sup 2+} ions is attributable to the strong paramagnetic nature of the Cu{sup 2+} ion. The fluorescence 'turn off' behavior of this simple and effective probe was successfully applied for the determination of Cu{sup 2+} levels in untreated water samples, with excellent recovery rates of 98–105.8%.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Development of a novel photoaffinity probe for labeling nocistatin receptor

Highlights: • Biotin-(AC{sub 5}){sub 2}-[Y{sup 6},azF{sup 14}]bNST is a novel nocistatin photoaffinity probe. • Biotin-(AC{sub 5}){sub 2}-[Y{sup 6},azF{sup 14}]bNST inhibits the tactile pain allodynia. • Biotin-(AC{sub 5}){sub 2}-[Y{sup 6},azF{sup 14}]bNST-binding proteins are observed at 58 and 64 kDa. Nocistatin (NST) is a neuropeptide produced from the same precursor protein of opioid peptide nociceptin/orphanin FQ, and it is involved in a broad range of central functions including pain transmission in the nervous system. However, the composition and structure of the receptor(s) for NST remain unclear. Here, we developed NST photoaffinity probe to identify NST receptor. The NST photoaffinity probe contains an azide moiety for the tagging of the binding protein as well as biotin for protein detection. Intrathecal administration of a NST photoaffinity probe, biotin-(AC{sub 5}){sub 2}-[Y{sup 6},azF{sup 14}]bNST, inhibited the nociceptin/orphanin FQ-evoked tactile pain allodynia in a manner similar to that of NST. The biotin-(AC{sub 5}){sub 2}-[Y{sup 6},azF{sup 14}]bNST-binding proteins were primarily localized in the gray matter of the spinal cord. After photo-crosslinking of the protein complex with biotin-(AC{sub 5}){sub 2}-[Y{sup 6},azF{sup 14}]bNST, two dominant binding protein bands were observed at 58 and 64 kDa. Thus, biotin-(AC{sub 5}){sub 2}-[Y{sup 6},azF{sup 14}]bNST has pharmacological activity and is useful for characterizing the NST receptor.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

Probing individual single atom electrocatalyst sites by advanced analytical scanning transmission electron microscopy

Single atom electrocatalysts (SAEs) are promising next-generation materials for promoting a variety of important reactions, such as the oxygen reduction, nitrogen reduction, and CO 2 reduction reactions. While bulk characterization techniques such as X-ray absorption spectroscopy and Mössbauer spectroscopy have significantly enhanced our understanding of these catalysts, direct probing of individual single metal atom sites at the atomic scale is necessary to understand local variations in the properties of these sites and accelerate design and synthesis of improved SAEs. Aberration-corrected scanning transmission electron microscopy (STEM) has become a powerful tool for providing this type of atomic-scale information about SAE metal sites. These sites are typically unstable under the electron beam, however, which, in combination with conventional acquisition methods and detectors, has limited the type and quantity of information obtainable by spectroscopic STEM techniques. Here, we map multiple individual SAE metal sites in a nitrogen-doped carbon containing atomically dispersed Fe and Re (FeReNC) at the atomic scale by direct electron detection electron energy-loss spectroscopy (EELS). Direct electron detection provides an improved signal-to-noise ratio over conventional scintillator-based detectors and enables detection and real space localization of weak signals. In addition, we demonstrate an automated method for identification of metal atom positions, placement of the probe on these sites, and simultaneous EELS and energy dispersive X-ray spectroscopic (EDS) signal acquisition. This simultaneous acquisition of EELS and EDS provides access to the composition and bonding of a wide range of SAE metal sites. In this study, focusing the probe directly on the metal sites also increases the relevant data acquisition rate by more than an order of magnitude over two-dimensional mapping, enabling improved statistical measurements of site properties. The versatility, sensitivity, and speed that these techniques provide enhances our ability to probe the local elemental and chemical environment of a large number of individual SAE metal site structures at the atomic scale, enabling an improved understanding of the variations in the local properties of these electrocatalysts to be gained. As a result, significantly increased information about individual metal sites will be available to future electrochemical studies through these techniques, accelerating the development of advanced SAEs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Determination of solute site occupancies within γ' precipitates in nickel-base superalloys via orientation-specific atom probe tomography

In this study, the analytical limitations in atom probe tomography such as resolving a desired set of atomic planes, for solving complex materials science problems, have been overcome by employing a well-developed unique and reproducible crystallographic technique, involving synergetic coupling of orientation microscopy with atom probe tomography. The crystallographic information in atom probe reconstructions has been utilized to determine the solute site occupancies in Ni-Al-Cr based superalloys accurately. The structural information in atom probe reveals that both Al and Cr occupy the same sub-lattice within the L1 2 -ordered g precipitates to form Ni 3 (Al,Cr) precipitates in a Ni-14Al-7Cr(at.%) alloy. Interestingly, the addition of Co, which is a solid solution strengthener, to a Ni-14Al-7Cr alloy results in the partial reversal of Al site occupancy within g precipitates to form (Ni,Al) 3 (Al,Cr,Co) precipitates. This unique evidence of reversal of Al site occupancy, resulting from the introduction of other solutes within the ordered structures, gives insights into the relative energetics of different sub-lattice sites when occupied by different solutes.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Probing the Solvation Shells of Lithium Ions in Glyme-Based Electrolytes

Glymes have been extensively studied as solvents for Li-battery electrolytes, most recently in equimolar mixtures with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), due to their ability to form stable solvates. However, directly quantifying free and coordinated glyme molecules in the liquid state has been challenging due to several experimental limitations. Here, in this work, new vibrational probes are demonstrated for studying the solvation structures of diglyme and triglyme in LiTFSI electrolytes. These IR probes make use of an amine group to report the solvation state of glymes at salt-to-solvent molar ratios ranging from 1:5 to 1:10. Characterization of the thermodynamic properties of the solvent exchange occurring in the first solvation shell of lithium ions (Li + ) showed an equilibrium constant for these probes close to unity at room temperature. This result demonstrates that the probes exhibit a similar solvation behavior to their glyme analogue. Concentration dependence studies also revealed a lack of significant amounts of contact ion pairs at the studied concentrations. Moreover, the first solvation shell of Li + appears to be formed by two partially chelating glyme molecules, establishing that even triglyme with multiple chelation sites does not fully coordinate the cation. Complementary molecular dynamics (MD) simulations agree with the experimental results and suggest that at these concentrations, TFSI – predominantly forms solvent-separated ion pairs. However, the simulations do not properly capture the partial solvation structure of the glyme molecules in the solvation shell of Li + as derived from the experiments.

electrolytes↗
DOE OSTI2017

Activity-Based Probes for Isoenzyme- and Site-Specific Functional Characterization of Glutathione S -Transferases

Glutathione S-transferases (GSTs) comprise a highly diverse family of phase II drug metabolizing enzymes whose shared function is the conjugation of reduced glutathione to various endo- and xenobiotics. Although the conglomerate activity of these enzymes can be measured by colorimetric assays, measurement of the individual contribution from specific isoforms and their contribution to the detoxification of xenobiotics in complex biological samples has not been possible. For this reason, we have developed two activity-based probes that characterize active glutathione transferases in mammalian tissues. The GST active site is comprised of a glutathione binding “G site” and a distinct substrate binding “H site”. Therefore, we developed (1) a glutathione-based photoaffinity probe (GSH-ABP) to target the “G site”, and (2) a probe designed to mimic a substrate molecule and show “H site” activity (GST-ABP). The GSH-ABP features a photoreactive moiety for UV-induced covalent binding to GSTs and glutathione-binding enzymes. The GST-ABP is a derivative of a known mechanism-based GST inhibitor that binds within the active site and inhibits GST activity. Validation of probe targets and “G” and “H” site specificity was carried out using a series of competitors in liver homogenates. Herein, we present robust tools for the novel characterization of enzyme- and active site-specific GST activity in mammalian model systems.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Estimating Soil Thermal Inertia Profiles From the Passive Equilibration of a Temperature Probe

Knowledge of the distribution of soil thermal properties is important for understanding subsurface hydrological and biogeochemical processes. This study describes and evaluates quick thermal profiling (QTP), a new measurement technique aimed at providing rapid, depth-resolved measurements of soil thermal inertia at numerous locations across the landscape. A cylindrical probe with temperature sensors at multiple depths is quickly inserted into the ground, and soil thermal inertia is estimated from how quickly the probe temperature equilibrates with the soil. To this end, a finite volume heat transfer model is used to generate temperature equilibration time series across combinations of controlling factors, and a gridded search inversion approach is applied to infer soil thermal inertia. Field tests in the Arctic indicate that QTP measurements have a minimum uncertainty of 0.14 J m −2 K −1 s −1/2 and covary with dual-probe heat pulse thermal analyzer measurements (concordance correlation coefficient = 0.56) with a root-mean-square error of 0.40 J m −2 K −1 s −1/2 . Besides demonstrating the value of QTP for estimating thermal inertia, this study identifies various sources of measurement uncertainty, particularly probe-soil contact resistance and frictional heating. Further, analysis of soil samples indicates that thermal inertia can be used to estimate thermal conductivity and dry bulk density in the studied area, although such inferences are highly site-specific. Overall, the QTP method holds promise to generate thermal inertia data products and to complement other characterization approaches for advancing understanding of soil properties across far more locations than is currently possible.

Lamb, J. R. [Lawrence Berkeley National Laboratory↗
DOE OSTI2024

Probing plexciton emission from 2D materials on gold nanotrenches

Probing strongly coupled quasiparticle excitations at their intrinsic length scales offers unique insights into their properties and facilitates the design of devices with novel functionalities. In this work, we investigate the formation and emission characteristics of plexcitons, arising from the interaction between surface plasmons in narrow gold nanotrenches and excitons in monolayer WSe 2 . We study this strong plasmon–exciton coupling in both the far-field and the near-field. Specifically, we observe a Rabi splitting in the far-field reflection spectra of about 80 meV under ambient conditions, consistent with our theoretical modeling. Using a custom-designed near-field probe, we find that plexciton emission originates predominantly from the lower-frequency branch, which we can directly probe and map its local field distribution. We precisely determine the plexciton's spatial extension, similar to the trench width, with nanometric precision by collecting spectra at controlled probe locations. Our work opens exciting prospects for nanoscale mapping and engineering of plexcitons in complex nanostructures with potential applications in nanophotonic devices, optoelectronics, and quantum electrodynamics in nanoscale cavities.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Learning neural representations for X-ray ptychography reconstruction with unknown probes

X-ray ptychography provides exceptional nanoscale resolution and is widely applied in materials science, biology, and nanotechnology. However, its full potential is constrained by the critical challenge of accurately reconstructing images when the illuminating probe is unknown. Conventional iterative methods and deep learning approaches are often suboptimal, particularly under the low-signal conditions inherent to low-dose and high-speed experiments. These limitations compromise reconstruction fidelity and restrict the broader adoption of the technique. In this work, we introduce the Ptychographic Implicit Neural Representation (PtyINR), a self-supervised framework that simultaneously addresses the object- and probe-recovery problem. By parameterizing both as continuous neural representations, PtyINR performs end-to-end reconstruction directly from raw diffraction patterns without requiring any pre-characterization of the probe. Extensive evaluations demonstrate that PtyINR achieves superior reconstruction quality on both simulated and experimental data, with remarkable robustness under challenging low-signal conditions. Furthermore, PtyINR offers a generalizable, physics-informed framework for addressing probe-dependent inverse problems, making it applicable to a wide range of computational microscopy problems.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Campanile Near-Field Probes Fabricated by Nanoimprint Lithography on the Facet of an Optical Fiber

One of the major challenges to the widespread adoption of plasmonic and nano-optical devices in real-life applications is the difficulty to mass-fabricate nano-optical antennas in parallel and reproducible fashion, and the capability to precisely place nanoantennas into devices with nanometer-scale precision. In this study, we present a solution to this challenge using the state-of-the-art ultraviolet nanoimprint lithography (UV-NIL) to fabricate functional optical transformers onto the core of an optical fiber in a single step, mimicking the 'campanile' near-field probes. Imprinted probes were fabricated using a custom-built imprinter tool with co-axial alignment capability with sub < 100 nm position accuracy, followed by a metallization step. Scanning electron micrographs confirm high imprint fidelity and precision with a thin residual layer to facilitate efficient optical coupling between the fiber and the imprinted optical transformer. The imprinted optical transformer probe was used in an actual NSOM measurement performing hyperspectral photoluminescence mapping of standard fluorescent beads. The calibration scans confirmed that imprinted probes enable sub-diffraction limited imaging with a spatial resolution consistent with the gap size. This novel nano-fabrication approach promises a low-cost, high-throughput, and reproducible manufacturing of advanced nano-optical devices.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Capturing relativistic wakefield structures in plasmas using ultrashort high-energy electrons as a probe

A new method capable of capturing coherent electric field structures propagating at nearly the speed of light in plasma with a time resolution as small as a few femtoseconds is proposed. This method uses a few femtoseconds long relativistic electron bunch to probe the wake produced in a plasma by an intense laser pulse or an ultra-short relativistic charged particle beam. As the probe bunch traverses the wake, its momentum is modulated by the electric field of the wake, leading to a density variation of the probe after free-space propagation. This variation of probe density produces a snapshot of the wake that can directly give many useful information of the wake structure and its evolution. Furthermore, this snapshot allows detailed mapping of the longitudinal and transverse components of the wakefield. We develop a theoretical model for field reconstruction and verify it using 3-dimensional particle-in-cell (PIC) simulations. This model can accurately reconstruct the wakefield structure in the linear regime, and it can also qualitatively map the major features of nonlinear wakes. As a result, the capturing of the injection in a nonlinear wake is demonstrated through 3D PIC simulations as an example of the application of this new method.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Probing the photochemistry of chemisorbed oxygen on TiO2(110) with Kr and other co-adsorbates

Weakly bound (physisorbed) atoms and molecules such as Ar, Kr, Xe, CO, CH4, CH3OH, CO2 and N2 are used to probe the photochemical interactions of O2 on rutile TiO2(110). UV irradiation of chemisorbed O2 along with the physisorbed probe species leads to photon-stimulated desorption (PSD) of Ar, Kr, CO, CH4 and N2. Without co-adsorbed O2, the PSD yields of the probe species are very low or not observed. No PSD was observed for CO2, N2O, CH3OH and the PSD yield for Xe is very low compared to the other probe atoms or molecules. The angular distribution of the photo-desorbing Kr, which is broad and cosine, is quite different from the O2 PSD angular distribution, which is sharply peaked along the surface normal. The Kr PSD yields increase with increasing coverage of Kr and of chemisorbed O2. We propose a mechanism for the observed phenomena where the chemisorbed O2 serves as photoactive center, excited via electronic excitations (electrons and/or holes) created in the TiO2 substrate by UV photon irradiation. The photo-excited O2 may transfer its energy to neighboring co-adsorbed atom or molecule resulting in desorption of the latter. Simple momentum transfer considerations suggest that heavier adsorbates (like Xe) and adsorbates with higher binding energy (like CO2) should desorb less efficiently according to the proposed mechanism. Various forms of chemisorbed O2 appeared photoactive in such stimulated desorption of Kr atoms: molecular anions (O22-, O2-), adatoms (Oa), and others. The observed phenomenon provides a new tool for study of photocatalysis.

photochemistry↗
DOE OSTI2016

Tracking reaction dynamics in solution by pump–probe X-ray absorption spectroscopy and X-ray liquidography (solution scattering)

Characterization of transient molecular structures formed during chemical and biological processes is essential for understanding their mechanisms and functions. Over the last decade, time-resolved X-ray liquidography (TRXL) and time-resolved X-ray absorption spectroscopy (TRXAS) have emerged as powerful techniques for molecular and electronic structural analysis of photoinduced reactions in the solution phase. Both techniques make use of a pump–probe scheme that consists of (1) an optical pump pulse to initiate a photoinduced process and (2) an X-ray probe pulse to monitor changes in the molecular structure as a function of time delay between pump and probe pulses. TRXL is sensitive to changes in the global molecular structure and therefore can be used to elucidate structural changes of reacting solute molecules as well as the collective response of solvent molecules. On the other hand, TRXAS can be used to probe changes in both local geometrical and electronic structures of specific X-ray-absorbing atoms due to the element-specific nature of core-level transitions. These techniques are complementary to each other and a combination of the two methods will enhance the capability of accurately obtaining structural changes induced by photoexcitation. Here we review the principles of TRXL and TRXAS and present recent application examples of the two methods for studying chemical and biological processes in solution. Furthermore, we briefly discuss the prospect of using X-ray free electron lasers for the two techniques, which will allow us to keep track of structural dynamics on femtosecond time scales in various solution-phase molecular reactions.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2016

Characterization of Fe 2+ ions in Fe,H/SSZ-13 zeolites: FTIR spectroscopy of CO and NO probe molecules

The IR spectra of adsorbed CO and NO probe molecules were used to characterize the coordination chemistry of Fe2+ ions in solution ion exchanged Fe,H/SSZ-13 zeolites. The effects of Fe ion exchange levels, as well the sample pre-treatment conditions on the adsorption of these probe molecules were investigated. The ion exchange levels (in the range of the study) did not affect significantly the IR spectra of either probe molecule, the IR features and their intensity ratios were very similar. Experiments with both probe molecules substantiated the presence of two distinct types of Fe2+ ions in cationic positions. We assign these two Fe2+ ions to two distinct cationic positions: Fe2+ in 6R and 8R positions. NO initially adsorbs preferentially onto Fe2+ sites in the 6R position, and then populates sites in the 8R. Fe2+ ions in the 8R positions require the interaction of more than one NO molecule to move them out from their adsorbate-free cationic positions. As soon as they move from their stable positions, they are able to bind to multiple NO molecules, and form mostly tri-nitrosyls. These tri-nitrosyls, however, are only stable in the presence of gas phase NO; under dynamic vacuum they lose one of the NO molecules from their coordination sphere and form stable di-nitrosyls. The adsorption of CO is much weaker on Fe2+ sites than that of NO, and requires cryogenic sample temperatures to initiate CO adsorption. Under the conditions applied in this study, only mono-carbonyl formation was observed. Reduction in H2 at 773 K increased the number of Fe2+ adsorption sites, primarily in the 8R locations. Oxidation by N2O, on the other hand, selectively reduced the adsorption of both CO and NO on the Fe2+ sites in 8R positions. Adsorbed oxygen left behind from the decomposition of N2O at 573 K readily reacted with CO to produce CO2 even at 150 K. The authors gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Program for the support of this work. The research described in this paper was performed in the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle.

coordination chemistry of Fe2+ ions↗
DOE OSTI2014

Quantification of thermal and contact resistances of scanning thermal probes

Scanning thermal probes are widely used for imaging temperature fields with nanoscale resolution, for studying near-field radiative heat transport and for locally heating samples. In all these applications, it is critical to know the thermal resistance to heat flow within the probe and the thermal contact resistance between the probe and the sample. Here, we present an approach for quantifying the aforementioned thermal resistances using picowatt resolution heat flow calorimeters. The measured contact resistance is found to be in good agreement with classical predictions for thermal contact resistance. The techniques developed here are critical for quantitatively probing heat flows at the nanoscale.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Diffusion studies on permeable nitroxyl spin probes through bilayer lipid membranes: A low frequency ESR study

Electron spin resonance (ESR) studies were carried out for permeable 2mM {sup 14}N-labeled deutrated 3 Methoxy carbonyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl (MC-PROXYL) in pure water and 1mM, 2mM, 3mM, 4mM concentration of 14N-labeled deutrated MC-PROXYL in 400mM concentration of liposomal solution by using a 300 MHz ESR spectrometer. The ESR parameters such as linewidth, hyperfine coupling constant, g-factor, partition parameter and permeability were reported for these samples. The line broadening was observed for the nitroxyl spin probe in the liposomal solution. The line broadening indicates that the high viscous nature of the liposomal solution. The partition parameter and permeability values indicate the maximum diffusion of nitroxyl spin probes in the bilayer lipid membranes at 2 mM concentration of nitroxyl radical. This study illustrates that ESR can be used to differentiate between the intra and extra- membrane water by loading the liposome vesicles with a lipid-permeable nitroxyl spin probe. From the ESR results, the spin probe concentration was optimized as 2mM in liposomal solution for ESR phantom studies/imaging, invivo and invitro experiments.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗