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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

FT-IR, Raman, and NMR Spectroscopy and DFT Theory of Glimepiride Molecule as a Sulfonylurea Compound

The glimepiride molecule was experimentally characterized using vibrational (FT-IR and laser-Raman) and NMR chemical shift spectroscopy. The molecule optimized structure, vibrational wavenumbers, and {sup 1}H and {sup 13}C NMR isotropic chemical shifts were theoretically obtained with the DFT/B3LYP method at a 6-311++G(d,p) basis set. The theoretical geometric parameters, vibrational wavenumbers, and NMR chemical shifts were found to be consistent with experimental data and similar spectral results in the literature.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2019

Energy diagram and stability range of families of soliton molecules in fibers

Following an analytically predicted energy diagram, we numerically investigate the behavior of a soliton molecule in terms of its energy with respect to the breathing factor and average-dispersion of dispersion managed optical fiber lines. We demonstrate the stable families of soliton molecules in anomalous, normal and zero average dispersion regimes. For normal average dispersion, it is showed that each stable family of SM is distributed over a lower and an upper branches. Further, the stability range is limited by a threshold value and a higher value of the breathing factor.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Reactions of concerted decomposition of cyclic molecules, as studied by the quantum chemistry methods and parabolic model

Reactions of concerted decomposition of cyclic molecules (Diels—Alder retro-reactions) were studied using quantum chemical modeling and the method of intersecting parabolas (M3IP model). According to results of quantum chemical calculations and topological analysis of transition states (TSs) of five concerted decomposition reactions of cyclic molecules, all TSs represent six-membered rings in which the bonds being cleaved are weak covalent ones. The presence of ring heteroatoms (N, O, or S) has a strong impact on the TS geometry and on the energy characteristics of the reactions. The M3IP model was used to process the experimental results to develop an algorithm for calculating the activation energies (E) of the reactions in question and the classical potential barriers to thermally neutral reaction (E{sub e}{sup 0}). Factors influencing the energies E were determined and assessed. These include the enthalpy of reaction, substituents, ring heteroatoms, the force constants of bonds, and the bond dissociation energies. A comparison of the activation energies E and the enthalpies of reaction ΔH obtained from the M3IP and density functional B3LYP/6-311++G** calculations revealed good agreement between them.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Study of the High Resolution Spectrum of the ν{sub 6}+ν{sub 10} Band of the {sup 13}C{sub 2}H{sub 4} Molecule

High resolution spectrum of the {sup 13}С{sub 2}H{sub 4} molecule recorded in the region of 1980–2080 cm{sup –1} with a resolution of 0.0025 cm{sup –1} using a Bruker IFS 120HR Fourier spectrometer is analyzed. As a result of solving the inverse spectroscopic problem, spectroscopic parameters of the vibrational state ( ν{sub 6} = ν{sub 10} = 1, B{sub 3u}) of the examined molecule are obtained for the first time that allows rotational energy levels to be reproduced with an accuracy close to the experimental one (a total of 677 rovibrational energies corresponding to 2300 transitions up to J{sup max} = 40 and K{sub a}{sup max}=15).

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2019

Photophysical Constants of the Tetraoxa[8]Circulene Molecule

The rate constants of photophysical processes (radiation rate constant, internal conversion rate constant, and quantum fluorescence yield) have been calculated for the tetraoxa[8]circulene molecule by the INDO/S, TDDFT, and CC2 methods. It is confirmed that the doubly degenerate triplet level Т{sub 2} and the level Т{sub 1} are located below the first singlet excited level S{sub 1}. According to the selection rules for the angular momentum, the spin-orbit interaction between the levels S{sub 1} and T{sub 1} (S{sub 1} and T{sub 2}) is equal to zero. Therefore, the internal conversion is the only nonradiative channel in this molecule. The results of calculations also demonstrate that values of the internal conversion rate constant and the quantum fluorescence yield obtained by the INDO/S method are incorrect.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Structure factors for tunneling ionization rates of diatomic molecules

Within the leading-order, single-active-electron, and frozen-nuclei approximation of the weak-field asymptotic theory, the rate of tunneling ionization of a molecule in an external static uniform electric field is determined by the structure factor for the highest occupied molecular orbital. We present the results of systematic calculations of structure factors for 40 homonuclear and heteronuclear diatomic molecules by the Hartree–Fock method using a numerical grid-based approach implemented in the program X2DHF.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Bell states and entanglement dynamics on two coupled quantum molecules

This work provides a complete description of entanglement properties between electrons inside coupled quantum molecules, nanoestructures which consist of two quantum dots. Each electron can tunnel between the two quantum dots inside the molecule, being also coupled by Coulomb interaction. First, it is shown that Bell states act as a natural basis for the description of this physical system, defining the characteristics of the energy spectrum and the eigenstates. Then, the entanglement properties of the eigenstates are discussed, shedding light on the roles of each physical parameters on experimental setup. Finally, a detailed analysis of the dynamics shows the path to generate states with a high degree of entanglement, as well as physical conditions associated with coherent oscillations between separable and Bell states.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Low-temperature phonoemissive tunneling rates in single molecule magnets

Tunneling between the two lowest energy levels of single molecule magnets with Ising type anisotropy, accompanied by the emission or absorption of phonons, is considered. Quantitatively accurate calculations of the rates for such tunneling are performed for a model Hamiltonian especially relevant to the best studied example, Fe{sub 8}. Two different methods are used: high-order perturbation theory in the spin–phonon interaction and the non-Ising-symmetric parts of the spin Hamiltonian, and a novel semiclassical approach based on spin-coherent-state-path-integral instantons. The methods are found to be in good quantitative agreement with other, and consistent with previous approaches to the problem. The implications of these results for magnetization of molecular solids of these molecules are discussed briefly.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Single-molecule imaging at high fluorophore concentrations by local activation of dye

Single-molecule fluorescence microscopy is a powerful approach to observe biomolecular interactions with high spatial and temporal resolution. Detecting fluorescent signals from individual, labeled proteins above high levels of background fluorescence remains challenging, however. For this reason, the concentrations of labeled proteins in in vitro assays are often kept low compared to their in vivo concentrations. Here, we present a new fluorescence imaging technique by which single fluorescent molecules can be observed in real time at high, physiologically relevant concentrations. The technique requires a protein and its macromolecular substrate to be labeled each with a different fluorophore. Then, making use of short-distance energy-transfer mechanisms, the fluorescence from only those proteins bound to their substrate are selectively activated. This approach is demonstrated by labeling a DNA substrate with an intercalating stain, exciting the stain, and using energy transfer from the stain to activate the fluorescence of only those labeled DNA-binding proteins bound to the DNA. Such an experimental design allowed us to observe the sequence-independent interaction of Cy5-labeled interferon-inducible protein 16 (IFI16) with DNA and the sliding via one-dimensional diffusion of Cy5-labeled adenovirus protease (pVIc-AVP) on DNA in the presence of a background of hundreds of nM Cy5 fluorophore.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

A simple-structured benzo[1,2-b:4,5-b’]dithiophene-based molecule as a third component enables organic solar cells with over 18.2% efficiency

In this study, research has shown that ternary strategy is an effective tool for improving the performance of organic solar cells (OSCs) and simple-structured small molecules with low-cost and wide bandgap which broadens the scope of the choice in third components recently attracted the attention of researchers. Herein, a small molecule with benzo[1,2-b:4,5-b’]dithiophene (BDT) core named BR-C12 which mixed well with PM6 has been designed and synthesized. Incorporating BR-C12 as third component into PM6:Y6, BR-C12 exhibits a complementary absorption with PM6 and Y6, promoted exciton dissociation and charge collection, reduced bimolecular recombination, resulting in more ordered molecular packing. The PM6:Y6:BR-C12 (1:1.2:0.1, weight ratio) OSC shows an improved power conversion efficiency (PCE) of 17.02% in comparison to host binary devises (16.42%). In addition, by employing BR-C12 as third component into PM6:L8-BO, the ternary device based on PM6:L8-BO:BR-C12 also achieves significant enhancement in device photovoltaic performance with a PCE of 18.26%. In addition, BR-C12-added ternary devices exhibit improved stability than binary ones. This work presents a method for constructing high-performance ternary OSCs and enriches the abundance of materials for the third components.

14 SOLAR ENERGY↗
DOE OSTI2023

Designer molecules of the synaptic organizer MDGA1 reveal 3D conformational control of biological function

MDGAs (MAM domain-containing glycosylphosphatidylinositol anchors) are synaptic cell surface molecules that regulate the formation of trans-synaptic bridges between neurexins (NRXNs) and neuroligins (NLGNs), which promote synaptic development. Mutations in MDGAs are implicated in various neuropsychiatric diseases. MDGAs bind NLGNs in cis on the postsynaptic membrane and physically block NLGNs from binding to NRXNs. In crystal structures, the six immunoglobulin (Ig) and single fibronectin III domains of MDGA1 reveal a striking compact, triangular shape, both alone and in complex with NLGNs. Whether this unusual domain arrangement is required for biological function or other arrangements occur with different functional outcomes is unknown. Here, we show that WT MDGA1 can adopt both compact and extended 3D conformations that bind NLGN2. Designer mutants targeting strategic molecular elbows in MDGA1 alter the distribution of 3D conformations while leaving the binding affinity between soluble ectodomains of MDGA1 and NLGN2 intact. In contrast, in a cellular context, these mutants result in unique combinations of functional consequences, including altered binding to NLGN2, decreased capacity to conceal NLGN2 from NRXN1β, and/or suppressed NLGN2-mediated inhibitory presynaptic differentiation, despite the mutations being located far from the MDGA1-NLGN2 interaction site. Thus, the 3D conformation of the entire MDGA1 ectodomain appears critical for its function, and its NLGN-binding site on Ig1-Ig2 is not independent of the rest of the molecule. As a result, global 3D conformational changes to the MDGA1 ectodomain via strategic elbows may form a molecular mechanism to regulate MDGA1 action within the synaptic cleft.

MDGAs↗
DOE OSTI2016

Experimental and numerical investigation of hydrate-guest molecule exchange kinetics

The 2012 Ignik Sikumi #1 Field Trial in Alaska was designed to test at field scale a methane hydrate production methodology that involves injecting carbon dioxide (CO 2 ) in situ to exchange with methane (CH 4 ) within a hydrate structure, thus releasing the methane for production. Since the completion of the field trial, experimental and numerical investigations have sought to better understand observations in terms of CH 4 production and changes to the hydrate bearing formation. Collectively, these insights may lead to more effective strategies for producing CH 4 from naturally occurring hydrates. This study presents results from a laboratory experiment performed at conditions experienced during the field trial (8.27 MPa and 275.15 K) to collect data relating to the CH 4 molecular exchange process. The experiment intentionally isolated the kinetic guest molecule exchange process from additional hydrate formation and mechanical changes to the hydrate bearing sand. Data were used to inform development of numerical models that were then used to fit key hydrate parameters (bound water saturation, kinetic formation constant, kinetic exchange constant, and preferential exchange weighting factors) and analyze experimental results. Results were in agreement with observations of preferential CO 2 /CH 4 guest molecule exchange at Ignik Sikumi #1 and from previous experimental studies while providing quantitative estimates of changing hydrate compositions. Additionally, simulations confirmed hydrate behavior and composition profiles otherwise indirectly evidenced by experimental results.

03 NATURAL GAS↗
DOE OSTI2015

The controllable assembly of nanorods, nanowires and microwires of a perylenediimide molecule with photoswitching property

By using an electron donor–acceptor molecule that consists of a perylenediimide (PDI) core bonded with two ferrocene (Fc) units, well-defined nanorods, nanowires and microwires of PDI-Fc were formed through simply adjusting the initial concentration of PDI-Fc in dichloromethane or CH{sub 2}Cl{sub 2}. Moreover, the two-ended devices based on individual microwire were fabricated. Highly reproducible and sensitive photo response characteristics were demonstrated in the microwire through controlling the white light on and off with different light intensities. The assembly strategy via complementary donors and acceptors is of significance for constructing photoconductive systems and developing novel functional devices. - Graphical abstract: The two-ended devices based on individual microwire were fabricated. Highly reproducible and sensitive photo response characteristics were observed by controlling the white light on and off with different light intensities. - Highlights: • An electron donor–acceptor molecule (PDI-Fc) was synthesized. • Well-defined nanorods, nanowires and microwires of PDI-Fc were formed. • The two-ended devices based on individual microwire were fabricated. • Highly reproducible and sensitive photo response characteristics were observed.

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

Synthesis of Zn-MOF incorporating titanium-hydrides as active sites binding H{sub 2} molecules

This paper describes the synthetic effort for a Zn-MOF imparting Ti-H as a preferential binding site potentially capturing H{sub 2} molecules via Kubas-type interaction. The formation mechanism of Ti-H innate to the final material was potentially demonstrated to follow a radical dissociation rather than a β-hydrogen elimination and a C-H reductive elimination. - Graphical abstract: This study details the synthesis and the formation mechanism of Zn-MOF adsorbent site-isolating TiH{sub 3} that can potentially capture H{sub 2} molecules via Kubas-binding mechanism. - Highlights: • OH-functionalized Zn-MOF was employed as a reactive template to site-isolate TiH{sub 3}. • This MOF was post-synthetically modified using a tetracyclohexyl titanium (IV). • This intermediate was hydrogenolyzed to change ligand from cyclohexyl to hydride. • Formation mechanism of TiH{sub 3} was investigated via two control GC–MS experiments. • Final Zn-MOF potentially site-isolating TiH{sub 3} species was used as a H{sub 2} adsorbent.

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

Conjugation of antioxidant molecule to PEGylated NPs for pH dependent drug release

Highlights: • Synthesis of Quercetin loaded PEGylated CdSe and PEGylated CdSe/CdS core/shell nanoparticles. • Quercetin quenches the fluorescence intensity of PEGylated nanoparticles. • Conjugation of Quercetin does not alter the spherical morphology of PEGylated nanoparticles. • Effect of pH environment on the optical properties of Quercetin loaded PEGylated nanoparticles. • In vitro release of Quercetin from PEGylated nanoparticles is pH and time dependent. - Abstract: This paper reports the encapsulation of antioxidant molecule Quercetin on PEG-diamine coated nanoparticles (NPs) by aqueous synthesis method to improve it's poor water solubility and stability. Two types of PEGylated NPs (PEGylated CdSe and PEGylated CdSe/CdS) have been used to conjugate Quercetin. The synthesis have been done using two different approaches, in first case organic solvent DMSO along with DI (De-Ionized) water have been used to dissolve Quercetin whereas during the second procedure DI water have been solely used to dissolve Quercetin. UV–vis absorption spectroscopy, TEM and IR results give the confirmation of conjugation of Quercetin to PEGylated NPs. Controlled release has been observed for both pH environments with a maximum release for CPD-I with 95.89% at pH 7.4 whereas at pH 5 CCPD-I shows maximum release i.e. 76.10%. The antioxidant activity results provide that the Quercetin molecules retain their antioxidant properties after conjugation with PEGylated NPs.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Semiempirical breakdown curves of C 2 N (+) and C 3 N (+) molecules; application to products branching ratios predictions of physical and chemical processes involving these adducts

Here, we constructed semiempirical breakdown curves (BDC) for C 2 N, C 3 N, C 2 N + and C 3 N + molecules. These BDC, which are energy dependent dissociation branching ratios (BR) curves, were used to predict products branching ratios for various processes leading to the formation of C 2 N (+) and C 3 N (+) excited adducts. These processes, of astrochemical interest, are neutral-neutral and ion-molecule reactions, dissociative recombination and charge transfer reactions with He + . Model predictions of BR are compared to the literature data and to reported values in the kinetic database for astrochemistry KIDA. With the new BR values, the C n N abundances in cold cores were simulated.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Exploring chemistry with single-molecule and -particle fluorescence microscopy

The evolution of single-molecule and -particle fluorescence microscopy imaging techniques for the investigation of chemical reactions yielded achievements at all fronts, from synthetic organic chemistry to materials science. The removal of ensemble averaging effects uncovers unique, otherwise hidden reaction intermediates, reactivity, and kinetics. Thus, new insights can be obtained even for well-explored chemical reactions and processes. The aim of this article is to serve as a guide and a source of inspiration for scientists who wish to develop single-molecule and -particle fluorescence microscopy to answer questions in chemistry. Here, we describe the current status of technical accomplishments in the field and point out technical and conceptual obstacles for overcoming in the near future, with focus on improvement of bench-scale synthetic reactions.

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

Ultra-Fast Electron Microscopic Imaging of Single Molecules With a Direct Electron Detection Camera and Noise Reduction

Time-resolved imaging of molecules and materials made of light elements is an emerging field of transmission electron microscopy (TEM), and the recent development of direct electron detection cameras, capable of taking as many as 1,600 fps, has potentially broadened the scope of the time-resolved TEM imaging in chemistry and nanotechnology. However, such a high frame rate reduces electron dose per frame, lowers the signal-to-noise ratio (SNR), and renders the molecular images practically invisible. Here, we examined image noise reduction to take the best advantage of fast cameras and concluded that the Chambolle total variation denoising algorithm is the method of choice, as illustrated for imaging of a molecule in the 1D hollow space of a carbon nanotube with ~1 ms time resolution. Through the systematic comparison of the performance of multiple denoising algorithms, we found that the Chambolle algorithm improves the SNR by more than an order of magnitude when applied to TEM images taken at a low electron dose as required for imaging at around 1,000 fps. Open-source code and a standalone application to apply Chambolle denoising to TEM images and video frames are available for download.

47 OTHER INSTRUMENTATION↗