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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 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Convergent evolution of aerobic fermentation through divergent mechanisms acting on key shared glycolytic genes

As the tree of life becomes increasingly accessible to molecular investigations, describing mechanisms underlying evolutionary convergence and constraint will be crucial to understanding diversification. The lineage including the model yeast Saccharomyces cerevisiae evolved aerobic fermentation in part through an ancient whole genome duplication and retention of glycolytic genes. To evaluate glycolytic rates across diverse yeasts, we developed and deployed an extracellular acidification rates (ECAR) assay on 299 species that span more than 400 million years of evolution and identified a clade in the genus Saturnispora that convergently evolved aerobic fermentation. Through comparative genomics and transcriptomics, we found that several glycolytic genes had higher expression and novel cis-regulatory elements in aerobically fermenting Saturnispora species. When the transcription factor required for their activation was deleted in Saturnispora dispora, the mutants had reduced glycolytic rates and increased respiration. Intriguingly, many of the upregulated genes are orthologous to duplicated glycolytic genes in S. cerevisiae. These divergent genetic mechanisms affecting the same set of genes suggest that there are strong evolutionary constraints on how aerobic fermentation can arise.

Horianopoulos, Linda C. [Great Lakes Bioenergy Res↗
DOE OSTI2013

Reactive triblock polymers from tandem ring-opening polymerization for nanostructured vinyl thermosets

Multiply functional hydroxyl telechelic poly(cyclooctene-s-5-norbornene-2-methylene methacrylate) was synthesized by ring opening metathesis (co)polymerization of cis-cyclooctene and 5-norbornene-2-methylene methacrylate using the second generation Grubbs catalyst in combination with a symmetric chain transfer agent bearing hydroxyl functionality. The resulting hydroxyl-telechelic polymer was used as a macroinitiator for the ring opening transesterification polymerization of d,l-lactide to form reactive poly(lactide)-b-poly(cyclooctene-s-5-norbornene-2-methylene methacrylate)-b-poly(lactide) triblock polymers. Subsequently, the triblocks were crosslinked by free radical copolymerization with several vinyl monomers including styrene, divinylbenzene, methyl methacrylate, and ethyleneglycol dimethacrylate. Certain conditions led to optically transparent thermosets with mesoscale phase separation as evidenced by small angle X-ray scattering, differential scanning calorimetry and transmission electron microscopy. Disordered, bicontinuous structures with nanoscopic domains were generated in several cases, rendering the samples attractive for size-selective membrane applications.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Formation of 2- and 1-methyl-1,4-dihydronaphthalene isomers via the crossed beam reactions of phenyl radicals (C 6 H 5 ) with isoprene (CH 2 C(CH 3 )CHCH 2 ) and 1,3-pentadiene (CH 2 CHCHCHCH 3 )

Crossed molecular beam reactions were exploited to elucidate the chemical dynamics of the reactions of phenyl radicals with isoprene and with 1,3-pentadiene at a collision energy of 55 ± 4 kJ mol -1 . Both reactions were found to proceed via indirect scattering dynamics and involve the formation of a van-der-Waals complex in the entrance channel. The latter isomerized via the addition of the phenyl radical to the terminal C1/C4 carbon atoms through submerged barriers forming resonantly stabilized free radicals C 11 H 13 , which then underwent cis–trans isomerization followed by ring closure. The resulting bicyclic intermediates fragmented via unimolecular decomposition though the atomic hydrogen loss via tight exit transition states located 30 kJ mol -1 above the separated reactants in overall exoergic reactions forming 2- and 1-methyl-1,4-dihydronaphthalene isomers. The hydrogen atoms are emitted almost perpendicularly to the plane of the decomposing complex and almost parallel to the total angular momentum vector (‘sideways scattering’) which is in strong analogy to the phenyl–1,3-butadiene system studied earlier. RRKM calculations confirm that 2- and 1-methyl-1,4-dihydronaphthalene are the dominating reaction products formed at levels of 97% and 80% in the reactions of the phenyl radical with isoprene and 1,3-pentadiene, respectively. This barrier-less formation of methyl-substituted, hydrogenated PAH molecules further supports our understanding of the formation of aromatic molecules in extreme environments holding temperatures as low as 10 K.

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

Understanding the ionic liquid [NC 4111 ][NTf 2 ] from individual building blocks: an IR-spectroscopic study

This study explores the interactions underlying the IR spectra of the ionic liquid [NC 4111 ][NTf 2 ] and its deuterated isotopomer [d 9 -NC 4111 ][NTf 2 ] by first isolating the spectra of charged ionic building blocks using mass-selective CIVP spectroscopy and then following the evolution of these bands upon sequential assembly of the ionic constituents. The spectra of the (1,1) and (2,2) neutral ion pairs are recorded using superfluid helium droplets as well as a solid neon matrix, while those of the larger charged aggregates are again obtained with CIVP. In general, the cluster spectra are similar to that of the bulk, with the (2,2) system displaying the closest resemblance. Analysis of the polarization-dependent band intensities of the neutral ion pairs in liquid droplets as a function of external electric field yields dipole moments of the neutral aggregates. This information allows a coarse assessment of the packing structure of the neutral pairs to be antiparallel at 0.37 K, in contrast to the parallel arrangement found for the assembly of small, high-dipole neutral molecules with large rotational constants (e.g., HCN). The role of an extra anion or cation attached to both the (1,1) and the (2,2) ion pairs to form the charged clusters is discussed in the context of an additional remote, more unfavorable binding site intrinsic to the nature of the charged IL clusters and as such not anticipated in the bulk phase. Whereas for the anion itself only the lowest energy trans conformer was observed, the higher clusters showed an additional population of the cis conformer. Finally, the interactions are found to be consistent with a minimal role of hydrogen bonding.

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

Electrical conductivity in two mixed-valence liquids

In this work, two different room-temperature liquid systems were investigated, both of which conduct a DC electrical current without decomposition or net chemical transformation. DC electrical conductivity is possible in both cases because of the presence of two different oxidation states of a redox-active species. One system is a 1:1 molar mixture of n -butylferrocene (BuFc) and its cation bis(trifluoromethane)sulfonimide salt, [BuFc + ][NTf 2 - ], while the other is a 1:1 molar mixture of TEMPO and its cation bis(trifluoromethane)sulfonimide salt, [TEMPO + ][NTf 2 - ]. The TEMPO–[TEMPO + ][NTf 2 - ] system is notable in that it is an electrically conducting liquid in which the conductivity originates from an organic molecule in two different oxidation states, with no metals present. Single-crystal X-ray diffraction of [TEMPO + ][NTf 2 - ] revealed a complex structure with structurally different cation–anion interactions for cis - and trans [NTf 2 - ] conformers. The electron transfer self-exchange rate constant for BuFc/BuFc + in CD 3 CN was determined by 1 H NMR spectroscopy to be 5.4 × 10 6 M -1 s -1 . The rate constant allowed calculation of an estimated electrical conductivity of 7.6 × 10 -5 Ω -1 cm -1 for BuFc–[BuFc + ][NTf 2 - ], twice the measured value of 3.8 × 10 -5 Ω -1 cm -1 . Similarly, a previously reported self-exchange rate constant for TEMPO/TEMPO + in CH 3 CN led to an estimated conductivity of 1.3 × 10 -4 Ω -1 cm -1 for TEMPO–[TEMPO + ][NTf 2 - ], a factor of about 3 higher than the measured value of 4.3 × 10 -5 Ω -1 cm -1 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Facile solvolysis of a surprisingly twisted tertiary amide

In this study, a bicyclo[2.2.2]octane derivative containing both a tertiary amide and a methyl ester was shown crystallographically to adopt a conformation in which the amide is in the cis configuration, which is sterically disfavored, but electronically favored. The steric strain induces a significant torsion (15.9°) of the amide, thereby greatly increasing the solvolytic lability of the amide to the extent that we see competitive amide solvolysis in the presence of the normally more labile methyl ester also present in the molecule.

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

Ordering in bio-inorganic hybrid nanomaterials probed by in situ scanning transmission X-ray microscopy

Here, phospholipid bilayer coated Si nanowires are one-dimensional (1D) composites that provide versatile bio-nanoelectronic functionality via incorporation of a wide variety of biomolecules into the phospholipid matrix. The physiochemical behaviour of the phospholipid bilayer is strongly dependent on its structure and, as a consequence, substantial modelling and experimental efforts have been directed at the structural characterization of supported bilayers and unsupported phospholipid vesicles; nonetheless, the experimental studies conducted to date have exclusively involved volume-averaged techniques, which do not allow for the assignment of spatially resolved structural variations that could critically impact the performance of the 1D phospholipid-Si NW composites. In this manuscript, we use scanning transmission X-ray microscopy (STXM) to probe bond orientation and bilayer thickness as a function of position with a spatial resolution of ~30 nm for Δ9-cis 1,2-dioleoyl-sn-glycero-3-phosphocholine layers prepared Si NWs. When coupled with small angle X-ray scattering measurements, the STXM data reveal structural motifs of the Si NWs that give rise to multi-bilayer formation and enable assignment of the orientation of specific bonds known to affect the order and rigidity of phospholipid bilayers.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Efficient lipid extraction and quantification of fatty acids from algal biomass using accelerated solvent extraction (ASE)

Accelerated solvent extraction (ASE), a commercially available pressurized fluid extraction technique and conventional manual extraction were compared to identify the most effective chloroform–methanol extraction method for algal lipids. Using optimal ASE operating conditions (methanol/chloroform = 2 : 1 by vol, 100 °C, static time of 5 min, and four static cycles), the lipid contents of Chlorella vulgaris, C. sorokiniana, C. zofingiensis and Nannochloropsis gaditana were 27.5%, 25.8%, 15.2%, 29.8% of dry biomass, respectively. Here, the total fatty acid methyl ester (FAME) content of dry biomass from ASE extraction was found to be 1.3–2.7 fold higher than that from conventional manual extract from these species, demonstrating that ASE exhibited significant improvement for lipid and FAME recovery. Furthermore, ASE showed the capacity to extract all-cis-5,8,11,14,17-eicosapentaenoic acid (EPA) as 3.0% of dry biomass from Nannochloropsis gaditana suggesting that ASE has the potential to obtain polyunsaturated fatty acids (PUFAs) as well.

09 BIOMASS FUELS↗
DOE OSTI2016

Hydrogenation of levoglucosenone to renewable chemicals

Here, we have studied the hydrogenation of levoglucosenone (LGO) to dihydrolevoglucosenone (Cyrene), levoglucosanol (Lgol), and tetrahydrofurandimethanol (THFDM) and elucidated the reaction network over supported palladium catalysts. At low temperature (40 °C) over a Pd/Al 2 O 3 catalyst, LGO is selectively hydrogenated to Cyrene. At intermediate temperatures (100 °C) over a Pd/Al 2 O 3 catalyst, Cyrene is selectively hydrogenated to Lgol, with an excess of the exo-Lgol isomer produced over the endo-Lgol isomer. At higher temperatures (150 °C) over a bifunctional Pd/SiO 2 –Al 2 O 3 catalyst, Lgol is converted to THFDM in 58% selectivity, with 78% overall selectivity to 1,6-hexanediol precursors. The ratio of cis-THFDM relative to trans-THFDM is approximately 2.5, and this ratio is independent of the Lgol feed stereoisomer ratio. Finally, tetrahydropyran-2-methanol-5-ketone (THP2M5one) and tetrahydropyran-2-methanol-5-hydroxyl (THP2M5H) are side-products of Lgol hydrogenolysis, but neither of these species are precursors to THFDM.

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

Uranyl dication mediated photoswitching of a calix[4]pyrrole-based metal coordination cage

A set of self-assembled tri- and tetrapodal metal coordination cage structures ( cage-1 and cage-2 , respectively) constructed from the uranyl dication (UO 2 2+ ) and a dibenzoic acid functionalised cis -calix[4]pyrrole ( 1 ) are described. The inherent photochemical reactivity of the uranyl dication mediates the transformation of cage-1 to cage-2 via the activation of molecular oxygen here.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

An ab initio based full-dimensional potential energy surface for OH + O 2 ⮂ HO 3 and low-lying vibrational levels of HO 3

To offer an in-depth understanding of the HO 3 radical and its dissociation to OH + O 2 , a six-dimensional potential energy surface (PES) has been constructed by fitting 2087 energy points for the electronic ground state of HO 3 (X 2 A") using the permutation invariant polynomial-neural network (PIP-NN) approach. The energy points were calculated using an explicitly-correlated and Davidson-corrected multi-reference configuration interaction approach with the correlation-consistent polarized valence double zeta basis (MRCI( Q )-F12/VDZ-F12). On the PES, the trans -HO 3 isomer is found to be the global minimum, 33.0 cm -1 below the cis -HO 3 conformer, which is consistent with previous high-level theoretical investigations. The dissociation to the OH + O 2 asymptote from both conformers is shown to be barrierless. As a benchmark from a recently developed high-accuracy thermochemistry protocol, D 0 for trans -HO 3 is calculated to be 2.29 ± 0.36 kcal mol -1 , only slightly deeper than the value of 2.08 kcal mol -1 obtained using the PES, and in reasonable agreement with the experimentally estimated value of 2.93 ± 0.07 kcal mol -1 . Using this PES, low-lying vibrational energy levels of HO 3 are determined using an exact quantum Hamiltonian and compared with available experimental results.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Evaluation of Attractive Interactions in the Second Coordination Sphere of Iron Complexes Containing Pendant Amines

The interactions between pendant amines in the second coordination sphere and ligands in the first coordination sphere are important for understanding the structures and reactivity of complexes containing PR2NR'2 ligands, which have been shown to be highly active H2 oxidation/production catalysts. A series of [Fe(PPh2NBn2)2(X)(Y)]n+ complexes have been prepared and structurally characterized. These complexes have two different ligands with which the pendant amines of the diphosphine ligand can interact. The solid state structure of cis-Fe(PPh2NBn2)2Cl2 reveals that the six-membered rings adjacent to the P atoms are in a boat confirmation, resulting in close N•••P distances that suggests the P atoms have a greater affinity for the lone pair of electrons on the N atom than chloride ligands. Similarly, boat conformations are observed for both rings adjacent to the hydride ligands of trans-[HFe(PPh2NBn2)2(CH3CN)]+ and trans-HFe(PPh2NBn2)2Cl, resulting in short N•••H distances. Spectroscopic and computational studies of trans-[HFe(PPh2NBn2)2(CO)]+, trans-[HFe(PPh2NBn2)(PPh2NBn2H)(CO)]2+, and trans-[HFe(PPh2NBn2)2(H2)]+ indicate the complexes are more stable when the pendant amines in boat conformations are adjacent to the hydride ligand. These data suggest an attractor ordering of H- > CO > H2 > PR3 > Cl- ~ CH3CN. This work was supported by the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory (PNNL) is operated by Battelle for the U.S. DOE. Computations were performed using the Cascade supercomputer at the Environmental Molecular Sciences Laboratory, a National Scientific User Facility sponsored by the DOE’s Office of Biological and Environmental Research and located at PNNL.

Liao, Qian↗
DOE OSTI2019

Exploring the capabilities of optical pump X-ray probe NEXAFS spectroscopy to track photo-induced dynamics mediated by conical intersections

X-ray spectroscopy is gaining a growing interest in the scientific community, as it represents a versatile and powerful experimental toolbox for probing the dynamics of both core and valence electronic excitations, nuclear motions and material structure, with element and site specificity. Among the various X-ray based techniques, near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, which investigates the energy and probability of resonant core-to-valence transitions, has started to be applied to organic molecules: a recent UV-pump X-ray probe time-resolved NEXAFS experiment [Wolf et al., Nat. Commun., 2017, 8, 1] has shown the capability of the technique to provide information about the ultrafast internal conversion between the bright ππ* and the dark nπ* electronic states of the nucleobase thymine. In the present contribution we introduce an accurate theoretical approach for the simulation of NEXAFS spectra of organic molecules, employing azobenzene as a test case. The electronic structure calculations, which provide both energy levels and transition probabilities of core-to-valence excitations, were here performed with a high level multiconfigurational method, the restricted active space self consistent field (RASSCF/RASPT2). GS- and nπ*-NEXAFS spectra were obtained on the top of key molecular geometries (as the optimized cis, trans and conical intersection(s) structures) as well as along the fundamental isomerization coordinates (namely, symmetric and asymmetric bendings of the phenyl rings, and torsion around the central dihedral). We eventually characterize and explain the origin of the simulated signals, highlighting the specific signatures that make it possible to follow the excited state evolution from the nπ* Franck–Condon point, towards the conical intersection(s).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

The importance of intramolecular conductivity in three dimensional molecular solids

Recent years have seen tremendous progress towards understanding the relation between the molecular structure and function of organic field effect transistors. The metrics for organic field effect transistors, which are characterized by mobility and the on/off ratio, are known to be enhanced when the intermolecular interaction is strong and the intramolecular reorganization energy is low. While these requirements are adequate when describing organic field effect transistors with simple and planar aromatic molecular components, they are insufficient for complex building blocks, which have the potential to localize a carrier on the molecule. Here, we show that intramolecular conductivity can play a role in controlling device characteristics of organic field effect transistors made with macrocycle building blocks. We use two isomeric macrocyclic semiconductors that consist of perylene diimides linked with bithiophenes and find that the trans-linked macrocycle has a higher mobility than the cis-based device. Through a combination of single molecule junction conductance measurements of the components of the macrocycles, control experiments with acyclic counterparts to the macrocycles, and analyses of each of the materials using spectroscopy, electrochemistry, and density functional theory, we attribute the difference in electron mobility of the OFETs created with the two isomers to the difference in intramolecular conductivity of the two macrocycles.

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

Photophysics and ultrafast processes in rhenium( I ) diimine dicarbonyls

A series of nine Re( I ) diimine dicarbonyl complexes of the general molecular formula cis -[Re(N^N) 2 (CO) 2 ] + (N^N are various 2,2'-bipyridine (bpy) or 1,10-phenanthroline (phen) derivatives) were prepared and spectroscopically investigated.

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

Long-range coupling in cyclic silanes

We report the synthesis of a mixed methyl- and hydro-substituted cyclosilane (1) possessing cis/trans stereoisomerism. Each diastereomer of 1 possesses distinct symmetry elements (cis-1: Cs-symmetric; trans-1: C 2 -symmetric). Cyclosilane 1 is a model system to probe configuration- and conformation-dependent long-range proton–proton coupling. Here, extensive NMR spectroscopic characterization is reported, including one-dimensional 1 H NMR and 29 Si DEPT and INEPT+ spectra and two-dimensional 1 H– 29 Si and 1 H– 1 H correlated spectroscopy (HSQC, HMBC, COSY). On the basis of these experiments, molecular connectivity consistent with four-bond 1 H– 1 H coupling is confirmed.

36 MATERIALS SCIENCE↗