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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Water-Nucleophilic Attack Mechanism for the Cu II (pyalk) 2 Water-Oxidation Catalyst

Here, we investigate the mechanism of water oxidation catalyzed by the Cu II (pyalk) 2 complex, combining density functional theory with experimental measurements of turnover frequencies, UV–visible spectra, H/D kinetic isotope effects (KIEs), electrochemical analysis, and synthesis of a derivative complex. We find that only in the cis form does Cu II (pyalk) 2 convert water to dioxygen. In a series of alternating chemical and electrochemical steps, the catalyst is activated to form a metal oxyl radical species that undergoes a water-nucleophilic attack defining the rate-limiting step of the reaction. The experimental H/D KIE (3.4) is in agreement with the calculated value (3.7), shown to be determined by deprotonation of the substrate nucleophile upon O–O bond formation. The reported mechanistic findings are particularly valuable for rational design of complexes inspired by Cu II (pyalk) 2 .

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

405 nm light microbicidal efficacy on Treponema pallidum spiked in ex vivo human platelets

Abstract Pathogen reduction technologies using chemicals and or UV light have been demonstrated to improve the safety of ex vivo platelets from infectious diseases. However, UV light exposure also may affect the treated products, depending on wavelength and exposure. Alternatively, visible spectra 405 nm violet-blue light has broad-spectrum microbicidal activity. Here we tested the effect of 405 nm light onTreponema pallidum, the bacterium that causes syphilis. We contaminated platelets stored in plasma with two treponemal concentrations (low and high titers) and treated an aliquot with 270 J/cm 2 dose (irradiance = 15 mW/cm 2 ) of 405 nm light while another aliquot remained untreated. Next, we inoculated intradermally an aliquot of both samples into rabbits. Rabbits inoculated with untreated samples developed syphilis while animals inoculated with light-treated samples did not. Thus, inactivation was demonstrated to the limit of detection of the bioassay. We estimated > 2 log 10 and > 4 log 10 reduction in the low and high dose studies, respectively. These results provide proof-of-concept that 405 nm light is effective in reducing syphilis risk in ex vivo platelets.

Science & Technology - Other Topics↗
DOE OSTI2025

A multivariate library of zirconia metal–organic frameworks with dissolved p -nitroaniline dipoles and concentration-dependent optical and dielectric response

In this work, we show how the combination of soluble non-polar and polar links allows for the preparation of multivariate metal–organic frameworks (MTV MOFs) that exhibit dipolar solid-solution behavior. We prepared a library of PIZOF-2 MOFs with varied concentrations of p -nitroaniline (PNA)-containing moiety embedded within the MTV links. This library forms a partial solid solution up to 30 mol% with input/output composition ratio of 0.536 ± 0.018. MOFs with x > 5 mol% PNA show concentration-dependent hypsochromic dipole–dipole coupling (H-coupling) in the solid-state UV-visible spectra. The MTV library also exhibits a dielectric relaxation event in the broadband dielectric spectra with activation enthalpies and entropies that vary with temperature and PNA content and follow linear Meyer–Neldel compensation relations.

Langlois, Kyle R. [Univ. of Central Florida, Orlan↗
DOE OSTI2016

The second– and third– order nonlinear optical properties and electronic transition of a NLO chromophore: A DFT study

It is well known that the practical applications of second-order and third-order nonlinear optical (NLO) materials have been reported in modern technology, such as optical data processing, transmission and storage, etc. In this respect, the linear and nonlinear optical parameters (the molecular static polarizability (α), and the first–order static hyperpolarizability (β{sub 0}), the second–order static hyperpolarizability (γ)), UV-vis spectra and HOMO and LUMO energies of 2-(1′-(4’’’-Methoxyphenyl)-5′-(thien-2″-yl)pyrrol-2′-yl)-1,3-benzothiazole were investigated by using the HSEh1PBE/6–311G(d,p) level of density functional theory. The UV–vis spectra were simulated using TD/HSEh1PBE/6– 311G(d,p) level, and the major contributions to the electronic transitions were obtained. The molecular hardness (η) and electronegativity (χ) parameters were also obtained by using molecular frontier orbital energies. The NLO parameters of the title compound were calculated, and obtained data were compared with that of para-Nitroaniline (pNA) which is a typical NLO material and the corresponding experimental data. Obtained data of the chromosphere display significant molecular second-and third-nonlinearity.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Optical and morphological characterizations of pyronin dye-poly (vinyl alcohol) thin films formed on glass substrates

Thin films of pyronin dye mixed with poly(vinyl alcohol) (PVA) on glass substrate were prepared by using spin-coating technique. The optical and morphological properties of the thin films were studied by UV-Vis., steady-state fluorescence spectroscopies and atomic force microscopy (AFM). The thin films on glass substrate were fabricated at various [PVA]/[dye] (P/D) ratios. Hence, the monomeric and H-aggregates thin films of pyronin dye mixed with PVA were formed as a function of the dye and PVA concentration. It was determined that while the monomeric thin films showed strong fluorescence, the formation of H-aggregates in the thin film caused to decreasing the fluorescence intensity. AFM studies demonstrated that the morphology of the thin film was drastically varied with changing the optical property of the thin film such as monomeric and H-aggregates thin films.

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

Atmospheric aerosols size distribution properties in winter and pre-monsoon over western Indian Thar Desert location

The first ever experimental results over Indian Thar Desert region concerning to height integrated aerosols size distribution function in particles size ranging between 0.09 to 2 µm such as, aerosols columnar size distribution (CSD), effective radius (R{sub eff}), integrated content of total aerosols (N{sub t}), columnar content of accumulation and coarse size aerosols particles concentration (N{sub a}) (size < 0.5 µm) and (N{sub c}) (size between 0.5 to 2 µm) have been described specifically during winter (a stable weather condition and intense anthropogenic pollution activity period) and pre-monsoon (intense dust storms of natural mineral aerosols as well as unstable atmospheric weather condition period) at Jaisalmer (26.90°N, 69.90°E, 220 m above surface level (asl)) located in central Thar desert vicinity of western Indian site. The CSD and various derived other aerosols size parameters are retrieved from their average spectral characteristics of Aerosol Optical Thickness (AOT) from UV to Infrared wavelength spectrum measured from Multi-Wavelength solar Radiometer (MWR). The natures of CSD are, in general, bio-modal character, instead of uniformly distributed character and power law distributions. The observed primary peaks in CSD plots are seen around about 10{sup 13} m{sup 2} μm{sup −1} at radius range 0.09-0.20 µm during both the seasons. But, in winter months, secondary peaks of relatively lower CSD values of 10{sup 10} to 10{sup 11} m{sup 2}/μm{sup −1} occur within a lower radius size range 0.4 to 0.6 µm. In contrast to this, while in dust dominated and hot season, the dominated secondary maxima of the higher CSD of about 10{sup 12} m{sup 2}μm{sup −3} is found of bigger aerosols size particles in a rage of 0.6 to 1.0 µm which is clearly demonstrating the characteristics of higher aerosols laden of bigger size aerosols in summer months relative to their prevailed lower aerosols loading of smaller size aerosols particles (0.4 to 0.6 µm) in cold months. Several other interesting features of changing nature of monthly spectral AOT, R{sub eff}, N{sub t}, N{sub a} and N{sub C} (particles/m{sup 2}) have been discussed in detail in this paper.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Charge transport mechanism analysis of Al/CdS:Sr{sup 2+}/ITO device under dark and light

In this study, we have synthesized CdS:Sr{sup 2+} by hydrothermal technique. Material property has been studied by X-ray diffraction (XRD), Scanning electron microscope (SEM) and UV-vis absorption spectroscopy. XRD data revealed that there are mixed phases of CdS and SrS in the synthesized sample. The optical band gap of the material was estimated as 3.15 eV from UV-vis data. The synthesized material has been applied in metal-semiconductor device and transport properties have been analyzed by measuring current–voltage characteristics under dark and light conditions at room temperature. Variation in different device parameters like ideality factor, barrier height and series resistance of Al/CdS:Sr{sup 2+}/ITO device were analyzed by using Cheung’s function.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Optical characterization of ZnO nanomaterial with praseodymium ions

ZnO nanomaterial with praseodymium ions was prepared by chemical synthesis method. The ZnO nanomaterial was characterized by XRD, SEM and TEM. Their absorption in UV-VIS/NIR regions was measured at room temperature. The experimental oscillator strengths were calculated from the areas under the absorption bands. Eight absorption bands have been observed. From these spectral data various energy interaction parameters like Slater–Condon, Lande, Racah, Nephelauxetic ratio and bonding parameters have been computed. Judd-Ofelt analysis has been carried out using the absorption spectra to evaluate the radiative properties for luminescent levels of the praseodymium ion and discussed. The observed nano particle size is 2nm.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Role of target-substrate distance on the growth of CuInSe{sub 2} thin films by pulsed laser ablation technique

CuInSe{sub 2} thin films have been deposited on corning glass substrates by pulsed laser ablation technique. The chamber pressure and substrate temperature was maintained at 1 × 10{sup −6} torr and 550°C respectively during deposition of the films. The influence of target to substrate (T-S) distance on the structural and optical properties of thin films have been investigated by grazing incidence x-ray diffraction, Raman spectroscopy, scanning electron microscope and UV-Vis-NIR spectroscopy. The study reveals that thin films crystallized in a chalcopyrite structure with highly preferential orientation along (112) plane. Optimum T-S distance has been attained for the growth of thin films with large grain size. An intense Raman peak at 174 cm{sup −1} corresponding to dominant A{sub 1} vibration mode is gradually shifted to smaller wavenumber with the increase in T-S distance. The optical bandgap energy of the films was evaluated and found to vary with the T-S distance. The bandgap tailing was observed to obey the Urbach rule and the Urbach energy was also calculated for the films. Scanning electron micrographs depicts uniform densely packed grains and EDAX studies revealed the elemental composition of CuInSe{sub 2} thin films.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Influence of N{sup +} ions on bandgap and electrical resistivity of TiN thin films

In the present work, nitrogen ions are embedded into Ti thin films (200 nm) using low energy ion beam implantation (70 keV) by varying ions fluence from 4×10{sup 15} ions/cm{sup 2} to 2×10{sup 16} ions/cm{sup 2}. For this, Ti films were grown using DC magnetron sputtering in Ar environment (power 200 W). TiN films were then characterized using versatile techniques for estimating the band gap and electrical resistivity. X-ray diffraction pattern shows shift in peaks towards higher angle with increase in nitrogen fluence that confirms the introduction of strain in Ti films. UV-Vis spectra show that band gap is reduced from 3.75 eV to 1.7 eV with increase in fluence from 4×10{sup 15} ions/cm{sup 2} to 2×10{sup 16} ions/cm{sup 2}. Furthermore, electrical resistivity also decreases from 2.67×10{sup −4} Ω.cm to 2.31×10{sup −4} Ωcm with nitrogen ion fluence. Based on these results, it can be inferred that ion implantation is an effective approach for uniform distribution of N ions in host matrix and tuning of optical and electrical properties.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Effect of silver on the shape of palladium nanoparticles

We report a facile route to prepare palladium-silver nanoparticles at considerably low temperature. First the controlled synthesis of palladium nanoparticles was performed via reduction of sodium tetrachloropalladate (II) in ethylene glycol in the presence of PVP(polyvinylpyrrolidone) as capping agent. The reaction was carried out at three different temperatures-80°C, 100°C and 120°C for one hour. Short reaction time and low synthesis temperature adds advantage to this method over others. Formed palladium nanoparticles were nearly spherical with the average particle size of 7.5±0.5 nm, 9.5±0.5 nm and 10.5±0.5 nm at 80°C, 100°C and 120°C respectively. Secondly, the palladium-silver nanoparticles were prepared by the simultaneous reduction of palladium and silver from their respective precursors in ethylene glycol at 100°C (optimized temperature). The shape and size distribution was studied by TEM (Transmission Electron Microscopy). The role of silver in transforming the shape of palladium nanoparticles from spherical to triangular has been discussed. Spherical symmetry of palladium nanoparticles is disturbed by the interaction of silver ions on the crystal facets of palladium nanoparticles. From UV-vis spectra, the absorption maxima of palladium nanoparticles at 205 nm and absorption maxima of palladium-silver nanoparticles at 272 nm revealed the partial evidence of their formation.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Post-annealing effect on optical absorbance of hydrothermally grown zinc oxide nanorods

In this study, the optical absorbance of zinc oxide (ZnO) nanorods was investigated. The ZnO thin film were deposited on indium tin oxide (ITO) layers using ultrasonic spray pyrolysis (USP) method and then grown by hydrothermal method. In order to improve the optical absorbance, the ZnO nanorods were then post-annealed for one hour at three different of temperatures, namely 250, 400, and 500 °C. The X-ray diffraction (XRD) spectra and FESEM images show that the ZnO nanorods have the hexagonal wurtzite crystal structure and the increasing of post-annealing temperature resulted in the increasing of crystallite size from 38.2 nm to 48.4 nm. The UV-vis spectra shows that all samples of ZnO nanorods exhibited the identical sharp absorption edge at 390 nm indicating that all samples have the same bandgap. The post-annealing process seemed to decrease the optical absorbance in the region of 300-550 nm and increase the optical absorbance in the region of 550-700 nm..

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2016

Kr photoionized plasma induced by intense extreme ultraviolet pulses

Irradiation of any gas with an intense EUV (extreme ultraviolet) radiation beam can result in creation of photoionized plasmas. The parameters of such plasmas can be significantly different when compared with those of the laser produced plasmas (LPP) or discharge plasmas. In this work, the photoionized plasmas were created in a krypton gas irradiated using an LPP EUV source operating at a 10 Hz repetition rate. The Kr gas was injected into the vacuum chamber synchronously with the EUV radiation pulses. The EUV beam was focused onto a Kr gas stream using an axisymmetrical ellipsoidal collector. The resulting low temperature Kr plasmas emitted electromagnetic radiation in the wide spectral range. The emission spectra were measured either in the EUV or an optical range. The EUV spectrum was dominated by emission lines originating from Kr III and Kr IV ions, and the UV/VIS spectra were composed from Kr II and Kr I lines. The spectral lines recorded in EUV, UV, and VIS ranges were used for the construction of Boltzmann plots to be used for the estimation of the electron temperature. It was shown that for the lowest Kr III and Kr IV levels, the local thermodynamic equilibrium (LTE) conditions were not fulfilled. The electron temperature was thus estimated based on Kr II and Kr I species where the partial LTE conditions could be expected.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Structural and optical characterization of In{sub 2}O{sub 3}/PANI nanocomposite prepared by in-situ polymerization

Polyaniline-indium oxide (In{sub 2}O{sub 3}/PANI) nanocomposite have been prepared by in-situ polymerization of aniline and as-synthesized In{sub 2}O{sub 3} nanoparticles. X-ray diffraction (XRD), Transmission electron microscopy (TEM), Fourier transformation infrared (FTIR) and UV/Vis spectroscopy techniques are used to investigate the structural and optical properties of In{sub 2}O{sub 3}/PANI nanocomposite. TEM analysis shows In{sub 2}O{sub 3} nanoparticles are embedded in PANI nanofibers. FTIR spectra show the good interactions between PANI nanofibers and In{sub 2}O{sub 3} nanoparticles. The band gap and electronic transitions in In{sub 2}O{sub 3}/PANI nanocomposite is determined by using UV/Vis spectra.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2017

Ligand manipulation of charge transfer excited state relaxation and spin crossover in [Fe(2,2′-bipyridine)2(CN)2]

We have used femtosecond resolution UV-visible and Kβ x-ray emission spectroscopy to characterize the electronic excited state dynamics of [Fe(bpy)2(CN)2], where bpy=2,2′-bipyridine, initiated by metal-to-ligand charge transfer (MLCT) excitation. The excited-state absorption in the transient UV-visible spectra, associated with the 2,2′-bipyridine radical anion, provides a robust marker for the MLCT excited state, while the transient Kβ x-ray emission spectra provide a clear measure of intermediate and high spin metal-centered excited states. From these measurements, we conclude that the MLCT state of [Fe(bpy)2(CN)2] undergoes ultrafast spin crossover to a metal-centered quintet excited state through a short lived metal-centered triplet transient species. These measurements of [Fe(bpy)2(CN)2] complement prior measurement performed on [Fe(bpy)3]2+ and [Fe(bpy)(CN)4]2− in dimethylsulfoxide solution and help complete the chemical series [Fe(bpy)N(CN)6–2N]2N-4, where N = 1–3. The measurements confirm that simple ligand modifications can significantly change the relaxation pathways and excited state lifetimes and support the further investigation of light harvesting and photocatalytic applications of 3d transition metal complexes.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Determination of Seven Organic Impurities in FD&C Yellow No. 6 by Ultra-High-Performance Liquid Chromatography

The U.S. Food and Drug Administration (FDA) batch certifies FD&C Yellow No. 6 (Y6) to ensure that the color additive meets requirements published in the Code of Federal Regulations (CFR), including specifications for seven organic manufacturing impurities consisting of two intermediates, a reaction by-product, an impurity originating from an intermediate, and three subsidiary colors. An ultra-high-performance liquid chromatography (UHPLC) method was developed and validated for determining seven organic impurities in Y6. For comparison, the currently used high-performance liquid chromatography (HPLC) method was also validated. The new UHPLC method uses a 1.7 µm particle size biphenyl column with aqueous ammonium formate and methanol as eluants. Analytes are identified by comparing their retention times and UV-visible spectra to those of reference standards. Calibration is performed in the presence of the dye matrix and analyte levels are determined from their peak areas. UHPLC and HPLC validation studies obtained linear calibration curves and excellent values for limits of detection, limits of quantitation, recovery, repeatability, and intermediate precision for all analytes. Survey analyses of 30 samples using the UHPLC and HPLC methods yielded results that were consistent within experimental error; however, the UHPLC method provided more accurate results for two analytes that coelute using the HPLC method. The UHPLC method satisfies the accuracy and precision requisites for routine certification of Y6. The UHPLC method is faster and generates less waste than the HPLC method while delivering better sensitivity, separation, and accuracy.

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

Collection: TD-DFT and EOM-CCSD Calculations for the GDB-9-Ex Dataset

We present two datasets that contain quantum chemical electronic structure calculations for organic molecules from the GDB-9-Ex dataset. The “GDB-9-Ex_TD-DFT-PBE0” dataset contains calculations performed using the time-dependent density functional theory (TD-DFT) first principles method, and the “GDB-9-Ex_EOMCCSD” dataset contains calculations performed using the equation-of-motion coupled cluster (EOM-CCSD) method. Both types of calculations were performed using the ORCA software and provided ultraviolet-visible spectra with a high level of accuracy.

Mehta, Kshitij [Oak Ridge National Laboratory (ORN↗