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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Synchronous RNA conformational changes trigger ordered phase transitions in crystals

Time-resolved studies of biomacromolecular crystals have been limited to systems involving only minute conformational changes within the same lattice. Ligand-induced changes greater than several angstroms, however, are likely to result in solid-solid phase transitions, which require a detailed understanding of the mechanistic interplay between conformational and lattice transitions. Here we report the synchronous behavior of the adenine riboswitch aptamer RNA in crystal during ligand-triggered isothermal phase transitions. Direct visualization using polarized video microscopy and atomic force microscopy shows that the RNA molecules undergo cooperative rearrangements that maintain lattice order, whose cell parameters change distinctly as a function of time. The bulk lattice order throughout the transition is further supported by time-resolved diffraction data from crystals using an X-ray free electron laser. The synchronous molecular rearrangements in crystal provide the physical basis for studying large conformational changes using time-resolved crystallography and micro/nanocrystals.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Reactions of the ˙NO 3 radical with nuclear extraction ligands in alkane solution

Here, the reactivity of the nitrate radical (NO 3 ˙) with organophosphorus and amidic actinide and lanthanide complexing agents of interest to nuclear solvent extraction applications was measured, resulting in the first-ever reported bimolecular rate constants for this radicals’ reactions in dodecane solution. The order of reactivity for neutral organophosphorus compounds showed faster rate constants with increasing electron density on the phosphoryl phosphorus atom, indicating an increasing facility for electron abstraction reactions occurring in addition to H-atom abstraction from the ligand alkane chains. The only acidic organophosphorus compound investigated, HEH[EHP], showed low reactivity with the NO 3 ˙ radical, attributed to its dimerization in this non-polar solvent. Amide ligand reaction rates were faster than for organophosphorus molecules, suggesting more facile H-atom abstraction from carbonyl activated methylene and amyl groups. While all rate constants were slower than the diffusion-limited rate they were still rapid enough to result in significant oxidation of solvent extraction ligands in dodecane solution.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2026

Altered morphology and diffusivity of water confined in MXenes: Machine learning–accelerated computations combined with experiments

Nanoconfined water exhibits unique properties compared to bulk water due to limited quantities, frustrated hydrogen bonding, and surface interactions, which are fundamental for energy storage and transport applications. We integrate machine learning–accelerated ab initio molecular dynamics with x-ray diffraction (XRD) and inelastic neutron scattering (INS) to systematically analyze the thermodynamic and dynamic behavior of water confined between functionalized (-F, -O, and -OH) two-dimensional (2D) Ti 3 C 2 T x MXene layers. As water intercalates between layers, the interlayer spacing exhibits layer-dependent staging characteristics. The water polarization can be flipped by the count and morphology of intercalated molecules interacting with MXene surface groups, resulting in varying electrostatic potential profiles. On the basis of interfacial electrostatic potential, hydrogen bond lifetime, and molecular orientation, we establish a linear combination of exponential model describing water diffusivity. These computational insights align well with experimental x-ray and neutron measurements, suggesting strategies for tuning water morphology and transport by tailoring MXene surface chemistry and water content for electrochemical energy storage and nanofluidic applications.

Tang, Jiawei [Southeast Univ., Nanjing (China)] (O↗
DOE OSTI2022

All-optical nanoscopic spatial control of molecular reaction yields on nanoparticles

Molecular adsorbate reactions on nanoparticles play a fundamental role in areas such as nano-photocatalysis, atmospheric, and astrochemistry. They can be induced, enhanced, and controlled by field localization and enhancement on the nanoparticle surface. In particular, the ability to perform highly controlled near-field-mediated reactions is key to deepening our understanding of surface photoactivity on nanosystems. Here, using reaction nanoscopy, we experimentally demonstrate all-optical nanoscopic control of surface reaction yields by tailoring the near fields on nanoparticles with waveform-controlled linear and bicircular two-color laser pulses, respectively. We observe site-selective proton emission from the dissociative ionization of adsorbate molecules on Si O 2 nanoparticles as a function of the polarization and relative phase of the two-color pulses. The angularly resolved close-to-uniform mapping between the surface reaction yields and the measured ion momentum enables the observation and spatial control of molecular reactions on the nanoparticle surface with nanoscopic resolution. The experimental results are modeled and reproduced qualitatively by classical trajectory Monte Carlo simulations. Our work paves the way toward reliable all-optical control of photocatalytic chemical reactions on nanoscale surfaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2001

Comparison of satellite ozone observations in coincident air masses in early November 1994

Ozone observed by seven satellite instruments, the Atmospheric Trace Molecule Spectroscopy instrument (ATMOS), Stratospheric Aerosol and Gas Experiment (SAGE) II, Polar Ozone and Aerosol Measurement (POAM) II instrument, Halogen Occultation Experiment (HALOE), Microwave Limb Sounder (MLS), Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA), and Millimeter-wave Atmospheric Sounder (MAS), during early November 1994 is mapped in equivalent latitude/potential temperature (EqL/ theta )space to facilitate nearly global comparisons of measurements taken in similar air masses.

atmospheric↗
NASA NTRS2005

Progress in Insect-Inspired Optical Navigation Sensors

Progress has been made in continuing efforts to develop optical flight-control and navigation sensors for miniature robotic aircraft. The designs of these sensors are inspired by the designs and functions of the vision systems and brains of insects. Two types of sensors of particular interest are polarization compasses and ocellar horizon sensors. The basic principle of polarization compasses was described (but without using the term "polarization compass") in "Insect-Inspired Flight Control for Small Flying Robots" (NPO-30545), NASA Tech Briefs, Vol. 29, No. 1 (January 2005), page 61. To recapitulate: Bees use sky polarization patterns in ultraviolet (UV) light, caused by Rayleigh scattering of sunlight by atmospheric gas molecules, as direction references relative to the apparent position of the Sun. A robotic direction-finding technique based on this concept would be more robust in comparison with a technique based on the direction to the visible Sun because the UV polarization pattern is distributed across the entire sky and, hence, is redundant and can be extrapolated from a small region of clear sky in an elsewhere cloudy sky that hides the Sun.

Thakoor, Sarita↗
DOE OSTI2022

Computational Protocol to Evaluate Electron–Phonon Interactions Within Density Matrix Perturbation Theory

We present a computational protocol, based on density matrix perturbation theory, to obtain non-adiabatic, frequency-dependent electron–phonon self-energies for molecules and solids. Our approach enables the evaluation of electron–phonon interaction using hybrid functionals, for spin-polarized systems, and the computational overhead to include dynamical and non-adiabatic terms in the evaluation of electron–phonon self-energies is negligible. We discuss results for molecules, as well as pristine and defective solids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1978

Stabilization of He2(A(sup 3)Sigma(sub u)(+)) molecules in liquid helium by optical pumping for vacuum UV laser

A technique is disclosed for achieving large populations of metastable spin-aligned He2(a 3 Sigma u +) molecules in superfluid helium to obtain lasing in the vacuum ultraviolet wavelength regime around 0.0800 micron m by electronically exciting liquid (superfluid) helium with a comparatively low-current electron beam and spin aligning the metastable molecules by means of optical pumping with a modestly-powered (100mW) circularly-polarized continuous wave laser operating at, for example, 0.9096 or 0.4650 micron m. Once a high concentration of spin-aligned He2 (a 3 Sigma u +) is achieved with lifetimes of a few milliseconds, a strong microwave signal destroys the spin alignment and induces a quick collisional transition of He2 (a 3 Sigma u +) molecules to the a 1 Sigma u + state and thereby a lasing transition to the X 1 Sigma g + state.

Zmuidzinas, J. S.↗
DOE OSTI2020

Highly C2/C1-Selective Covalent Organic Frameworks Substituted with Azo Groups

A series of covalent organic frameworks substituted with azo groups (AzoCOFs) have been synthesized via imine condensation. The obtained frameworks show crystallinity and high stability. More importantly, the AzoCOFs exhibit exceptionally high ideal adsorption solution theory (IAST) selectivity in adsorption of C 2 H 2 (35–2891) over CH 4 at 273 K and 1 bar, owing to the favorable interactions between azo groups and acetylene molecules. The dependence of the gas adsorption property on pore size and polarity of the frameworks was also studied. Here, the triethylene glycol substituted Tg-AzoCOF shows the highest C 2 H 2 /CH 4 selectivity (IAST selectivity of 2891), which represents the highest reported for all porous materials. The AzoCOFs also exhibit high IAST adsorption selectivity of C 2 H 4 /CH 4 (11–20), C 2 H 6 /CH 4 (15–22), and CO 2 /CH 4 (12–37), which is comparable with most porous materials, thus showing their great potential in gas separation applications.

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

Nonane and Hexanol Adsorption in the Lamellar Phase of a Nonionic Surfactant: Molecular Simulations and Comparison to Ideal Adsorbed Solution Theory

Adsorption of n-nonane/1-hexanol (C9/C6OH) mixtures into the lamellar phase formed by a 50/50 w/w triethylene glycol mono-n-decyl ether (C10E3)/water system was studied using configurational-bias Monte Carlo simulations in the osmotic Gibbs ensemble. The interactions were described by the Shinoda–Devane–Klein coarse-grained force field. Prior simulations probing single-component adsorption indicated that C9 molecules preferentially load near the center of the bilayer increasing the bilayer thickness, whereas C6OH molecules are more likely to be found near the interface of the polar and non-polar moieties swelling the bilayer in the lateral dimension. Here, we extend this work to binary C9/C6OH adsorption to probe whether the difference in the spatial preferences may lead to a synergistic effect and enhanced loadings for the mixture. Comparing loading trends and the thermodynamics of binary adsorption to unary adsorption reveals that C9–C9 interactions lead to the largest enhancement, whereas C9–C6OH and C6OH–C6OH interactions are less favorable for this bilayer system. As a result, ideal adsorbed solution theory yields satisfactory predictions of the binary loading.

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

X-ray circular dichroism measured by cross-polarization x-ray transient grating

Measuring natural circular dichroism in the x-ray regime to extract stereochemical information from chiral molecules in solution remains a challenge. This is primarily due to technical limitations of the existing synchrotron sources, which hinder access to measurements of local chirality by exploiting core hole electronic transitions. In response to this challenge, we propose an alternative approach: utilizing XFEL-based cross-polarization x-ray transient grating (XTG). This method provides an indirect means to measure x-ray circular dichroism (XCD). Notably, our findings reveal that the signal emerges only once the excited cores have undergone dephasing through relaxation. XTG is now routinely measured in the XUV regime and has recently been made available for hard x-rays. Free electron lasers now offer polarization controls, and XTG can be extended to various polarization states for the two pump beams, making XCD measured by XTG feasible with the current state-of-the-art technology.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2020

Semiconducting Small Molecules as Active Materials for p-Type Accumulation Mode Organic Electrochemical Transistors

A series of semiconducting small molecules with bithiophene or bis-3,4-ethylenedioxythiophene cores are designed and synthesized. The molecules display stable reversible oxidation in solution and can be reversibly oxidized in the solid state with aqueous electrolyte when functionalized with polar triethylene glycol side chains. Evidence of promising ion injection properties observed with cyclic voltammetry is complemented by strong electrochromism probed by spectroelectrochemistry. Blending these molecules with high molecular weight polyethylene oxide (PEO) is found to improve both ion injection and thin film stability. The molecules and their corresponding PEO blends are investigated as active layers in organic electrochemical transistors (OECTs). For the most promising molecule:polymer blend (P4E4:PEO), p-type accumulation mode OECTs with µA drain currents, μS peak transconductances, and a µC* figure-of-merit value of 0.81 F V -1 cm -1 s -1 are obtained.

36 MATERIALS SCIENCE↗
NASA NTRS1986

Interstellar grain mantles

Interstellar molecular grain mantles are an important component of the interstellar dust inside dense molecular clouds as evidenced by the detection of absorption bands at 2.97, 3.08, 4.61, 6.0 and 6.8 microns. Mantles may also be the precursors of more complex grain mantles in the diffuse interstellar medium. The molecular composition of these icy grain mantles were calculated employing gas phase as well as grain surface reactions. The calculated mixtures consist mainly of the molecules H2O, H2CO, N2, CO, O2, H2O2, NH2, and their deuterated counterparts in varying ratios. The exact compositions depend strongly on the physical conditions in the gas phase. The absorption spectra of H2O with other molecules was studied in the laboratory. Optical constants were determined for a few selected mixtures. Extinction and polarization cross sections across the 3 micron ice band were calculated. A comparison with the observations towards BN shows that the low frequency wing observed on this feature is due to absorption by a mixture of H2O and other molecules rather than scattering by large, pure H2O ice grains.

Bregman, J.↗
DOE OSTI2025

Emergent Above-Gap Photoluminescence in Molecularly Engineered Hybrid Bilayer Crystals

Bilayer crystals, built by stacking two-dimensional (2D) covalent monolayers, give rise to coupled excitonic states whose properties are constrained by fixed lattice symmetry and orientation. Replacing one covalent monolayer with a 2D molecular crystal––held together by non-covalent forces––overcomes this limitation, as molecular functional groups afford tunable in-plane lattice geometry, intermolecular spacing, and interlayer coupling, providing a powerful knob for exciton engineering. Here, in this study, we report four-atom-thick hybrid bilayer crystals (HBCs) synthesized by directly growing single-crystalline PDI molecular crystal atop WS 2 monolayers, which exhibit a robust photoluminescence (PL) peak 120 meV above the WS 2 optical band gap alongside a belowgap emission. Both peaks display strong polarization anisotropy—nearing unity for the above-gap emission—and maintain a perfectly linear power-law dependence up to an excitation density of ~10 7 mW/cm 2 , indicative of coexisting localized and delocalized excitonic states. Substituting PDI with a PTCDA monolayer on WS 2 fully quenches PL, demonstrating molecular control over excitonic emission. Lattice scale ab initio GW and GW-BSE calculations reveal a significantly hybridized bilayer band structure in PDI/WS 2 that supports interlayer excitonic species both above and below the WS 2 gap with strong polarization anisotropy, in excellent agreement with experiment. Our work introduces a molecule-based bilayer platform for the bottom-up design and control of excitonic phenomena in atomically thin optoelectronic and quantum materials.

2D materials↗
DOE OSTI2021

Chiral-induced spin selectivity enables a room-temperature spin light-emitting diode

In traditional optoelectronic approaches, control over spin, charge, and light requires the use of both electrical and magnetic fields. In a spin-polarized light-emitting diode (spin-LED), charges are injected, and circularly polarized light is emitted from spin-polarized carrier pairs. Typically, the injection of carriers occurs with the application of an electric field, whereas spin polarization can be achieved using an applied magnetic field or polarized ferromagnetic contacts. We used chiral-induced spin selectivity (CISS) to produce spin-polarized carriers and demonstrate a spin-LED that operates at room temperature without magnetic fields or ferromagnetic contacts. The CISS layer consists of oriented, self-assembled small chiral molecules within a layered organic-inorganic metal-halide hybrid semiconductor framework. The spin-LED achieves ±2.6% circularly polarized electroluminescence at room temperature.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

The Nature of the Spin-Dependent Surface Chemical Bond

The final report summarizes advances in the use of spin polarized scanning tunneling microscopy to measure the electronic properties on individual organic molecules on magnetic substrates. These experiments led to a new and simple conceptual paradigm for understanding these magnet-molecule interfaces using ideas and models that have historically been applied to catalysis and surface chemistry. It further summarizes related advances in the scanning tunneling microscopy studies of molecules on topological insulator surfaces and the search for new spin liquid physics. These experiments were designed to push the boundaries of spintronics technology and quantum materials design.

36 MATERIALS SCIENCE↗
NASA NTRS1976

Investigation of structure-property relationships in systematic series of novel polymers

Solid state transitions in polymeric materials was associated with the onset of sub-molecular motions of the polymer chains. Although these were considered to be intramolecular in general, the local environment of the polymer molecule exerts a strong influence through, for example, the effects of crystallinity, polarity and diluents. The manner of specimen preparation and previous history also affect transitions. The transitions are considered to arise when sufficient free volume is available to permit the occurrence of these side chain and backbone reorientations. The glass transition is the principal transition of amorphous polymeric materials and is associated with the onset of long range segmental motion of the polymer backbone. The various types of shorter range motion occurring below the glass transition have been catalogued.

Gillham, J. K.↗