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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Reflectivity Around the Gold M-Edges of X-ray Reflector of the Soft X-Ray Telescope Onboard ASTRO-H

The X-ray astronomy satellite ASTRO-H are equipped with two equivalent soft X-ray telescopes (SXT-I and SXT-S) which cover the energy band 0.3-12 keV. The X-ray reflectors of the SXTs are coated with a gold monolayer by means of the replication technique. A series of gold M absorption edges in the 2-4 keV band causes complex structures in the energy response of the SXTs. In the same band, there are astrophysically important emission lines from Si, Ar and S. Since the SXS has unprecedentedly high spectral resolution, we have measured the reflectivity around the gold M-edges in an extremely fine energy pitch at the synchrotron radiation facility KEK PF BL11-B, with the 2 eV pitch in 2100 eV to 4100 eV band that covers the entire series of the absorption edges (M-I through M-V) at grazing incident angles to the reflectors of 0.5, 0.8, 1.0, 1.2, 1.4 degree, and with a finer pitch of 0.25 eV in the 2200 eV to 2350 eV band where the two deepest M-IV and M-V edges are included. In the resultant reflectivity curves, we have clearly identified the fine structures associated with all the M-edges. Using these data, we calculated atomic scattering factor f1 as a function of X-ray energy, with which we have built the mirror response function which can be applied to the Suzaku spectra. As a result, we have found that discrepancy of the spectral model to the Suzaku data of 4U1630-472 (a black hole transient) and the Crab nebula around the M-edges are significantly reduced from those with the official Suzaku response.

ASTRO-H↗
DOE OSTI2016

Highly active thermally stable nanoporous gold catalyst

In one embodiment, a system includes a nanoporous gold structure and a plurality of oxide particles deposited on the nanoporous gold structure; the oxide particles are characterized by a crystalline phase. In another embodiment, a method includes depositing oxide nanoparticles on a nanoporous gold support to form an active structure and functionalizing the deposited oxide nanoparticles.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Highly active thermally stable nanoporous gold catalyst

In one embodiment, a method includes depositing oxide nanoparticles on a nanoporous gold support to form an active structure and functionalizing the deposited oxide nanoparticles. In another embodiment, a system includes a nanoporous gold structure comprising a plurality of ligaments, and a plurality of oxide particles deposited on the nanoporous gold structure; the oxide particles are characterized by a crystalline phase.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Characterization of a Pixelated Cadmium Telluride Detector System Using a Polychromatic X-Ray Source and Gold Nanoparticle-Loaded Phantoms for Benchtop X-Ray Fluorescence Imaging

In this paper, the imaging dose and scan time have been considered as the two major constraints for routine benchtop x-ray fluorescence computed tomography (XFCT) imaging. One way to address this issue is to acquire x-ray fluorescence (XRF) signals in parallel through a 2D array of single-crystal detectors or a pixelated detector along with the cone-beam x-ray source. To identify a detector system suitable for this purpose, a commercially available, fully spectroscopic cadmium telluride (CdTe) pixelated detector, HEXITEC (High-Energy X-ray Imaging Technology), was tested under the experimental conditions optimized for benchtop XFCT imaging of gold nanoparticles (GNPs). Specifically, two different parallel-hole stainless steel collimators were fabricated and coupled with the detector for seamless integration into our existing benchtop cone-beam XFCT system. After the detector deployment, this benchtop XFCT system was used to detect XRF photons from GNP-loaded phantoms. A pixel-merging algorithm was introduced to enhance the sensitivity of XRF photon detection thereby minimizing the scan time. The effect of pixel-level charge sharing correction algorithms was investigated within the context of benchtop XFCT imaging. The detector energy resolution, in terms of the full width at half maximum (FWHM) values at different gold K-shell XRF energies, was also determined. Of the two charge sharing correction algorithms examined, the charge sharing addition gave better sensitivity than the charge sharing discrimination (csd). On the other hand, under the current experimental conditions, the energy resolution of the HEXITEC detector was the best with the csd and estimated to be 1.56 keV FWHM at 66-69 keV photon energy. Overall, despite some degradation of the detector energy resolution (compared with typical single crystal CdTe detectors), the HEXITEC detector enabled parallel data acquisition under the experimental conditions typical of benchtop XFCT imaging and operated well within our benchtop XFCT setup.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Spall strength and ejecta production of gold under explosively driven shock wave compression

Explosively driven shock wave experiments were conducted to characterize the spall strength and ejecta production of high-purity cast gold samples. The samples were from 0.75 to 1.84 mm thick and 30 mm in diameter. Peak stresses up to 44 GPa in gold were generated using PBX-9501 high explosive. Sample free surface and ejecta velocities were recorded using photonic Doppler velocimetry techniques. Lithium niobate pins were used to quantify the time dependence of the ejecta density and the total ejected mass. An optical framing camera for time-resolved imaging and a single-image x-ray radiograph were used for additional characterization. Free surface velocities exhibited a range of spall strengths from 1.7 to 2.4 GPa (mean: 2.0 ±0.3 GPa). The pullback signals were faint, minimal ringing was observed in the velocity records, and the spall layer continued to decelerate after first pull back. These results suggest finite tensile strength was present for some time after the initial void formation. Ejecta were observed for every sample with a roughened free surface, and the ejecta density increased with increased surface roughness, which was different in every experiment. The total ejected mass is consistent with the missing mass model.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Surfactant-Free Shape Control of Gold Nanoparticles Enabled by Unified Theoretical Framework of Nanocrystal Synthesis

Gold nanoparticles possess unique properties that are highly dependent on their shape and size. Synthetic methods that enable precise control over nanoparticle morphology currently require shape-directing agents such as surfactants or polymers that force growth in a particular direction by adsorbing to specific crystal facets. These auxiliary reagents passivate the nanoparticles' surface, and thus decrease their performance in applications like catalysis and surface-enhanced Raman scattering. In this work, a surfactant- and polymer-free approach to achieving high-performance gold nanoparticles is reported. A theoretical framework to elucidate the growth mechanism of nanoparticles in surfactant-free media is developed and it is applied to identify strategies for shape-controlled syntheses. Using the results of the analyses, a simple, green-chemistry synthesis of the four most commonly used morphologies: nanostars, nanospheres, nanorods, and nanoplates is designed. The nanoparticles synthesized by this method outperform analogous particles with surfactant and polymer coatings in both catalysis and surface-enhanced Raman scattering.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

Gold Catalysts Synthesized Using a Modified Incipient Wetness Impregnation Method for Propylene Epoxidation

Propylene epoxidation in the presence of oxygen and hydrogen were measured for a series of Au/TS-1 catalysts prepared by a modified incipient wetness impregnation (mIWI) method. This method enables precise control of the Au : Ti ratio in the Au/TS-1 catalysts. The optimized Au/TS-1 catalyst exhibited 12 % propylene conversion, 87 % PO selectivity, and 25 % hydrogen efficiency. The particle size of gold nanoparticles prepared by the modified IWI was between 2 and 3 nm, as demonstrated by XRD patterns, STEM images, and X-ray absorption spectroscopy at the Au L(3)edge. XPS spectra showed that the surface species on the catalysts were similar. UV-Vis spectra suggested that in the modified IWI method, the chlorine ligands in Au(Cl)(4)(-)were replaced by hydroxyl groups, which contributes to form small gold nanoparticles. Kinetic studies showed that the active sites of Au(mIWI)/TS-1 are similar to the Au(DP)/TS-1 prepared by deposition precipitation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Ligand synthesis and passivation for silver and large gold nanoparticles for single-particle-based sensing and spectroscopy

Here, silver and large gold nanoparticles are more efficient scatterers than smaller particles, which can be advantageous for a variety of single-particle-based sensing and spectroscopic applications. The increased susceptibility to surface oxidation and the larger surface area of these particles, however, present challenges to colloid stability and controllable bio-conjugation strategies. In this chapter, ligand syntheses and particle passivation procedures for yielding stable and bio-conjugatable colloids of silver and large gold nanoparticles are described.

36 MATERIALS SCIENCE↗
DOE OSTI2018

X-Ray Digital Radiography to Study Gold–Silver Nose Decorations from the Moche Tomb of the Lady of Cao

In the present study nose decorations from the tomb of the ‘Lady of Cao’, a mummified Moche woman dated around third–fourth century AD, were analyzed by a portable X-ray digital radiography (XDR) system. The Moche civilization flourished along the north coast of present-day Peru, between the Andes and the Pacific Ocean, approximately between 100 and 600 AD. The Moche were very sophisticated artisans and metal smiths, so that they are considered the finest producers of jewels and artifacts of the region. Their metalworking ability was impressively demonstrated by the excavations of the tomb of the ‘Lady of Cao’, discovered by Regulo Franco in 2005. More than 100 beautiful jewels were found in this tomb, among them about 40 nose decorations composed of a combination of gold and silver sheets. Radiographs of several of them were carried out, with the aim to evaluate the gold–silver joining process, to check the homogeneity of the alloy and to quantify the thickness of the sheets. The XDR system consisted of a mini X-ray tube and of a digital X-ray flat panel. The radiographic images of the nose decorations revealed details of the manufacturing process and of the Au–Ag junction.

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

Extraction of gold, mercury and lead on CL resin in HCl

The uptake behavior of 197 mHg, 194 Au and 212 Pb in HCl on CL resin (Triskem) was studied. The extraction of mercury and gold is high (D w > 5,000) at all concentrations of HCl, with a maximum extraction of gold at 4 M HCl (D w ~ 53,000) and maximum extraction of mercury at 0.01 M HCl (D w ~ 44,000). Lead has moderate uptake on CL resin (D w ~ 100) from lower concentrations of HCl (0.001 to 0.05 M) and no uptake on the resin in concentrations ≥ 0.4 M. The uptake kinetics are similar for all three isotopes with high weight distribution ratios (>1,000 for 197 mHg, 194 Au and > 100 for 212 Pb) in ~ 30 s and equilibrium established at ~ 5 min. A column study was performed to demonstrate that 197m Hg, 194 Au and 212 Pb could be retained on CL resin in dilute HCl and 212 Pb eluted in 1 M HCl with no detectable 197m Hg or 194 Au. Elution of 197 mHg and 194 Au was performed with concentrated HNO 3 , but with significant losses to the column, particularly for 194 Au.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2019

Gold grating assisted SPR based D-shaped single mode fiber for detection of liquid refractive index

In this paper, a surface plasmon resonance based D-shaped single mode fiber sensor with a gold grating over the polished fiber surface, is analyzed by finite element method for refractive index sensing. Benefitted from the localized surface plasmon resonance effect of gold grating, the proposed sensor achieves a reasonably good wavelength sensitivity of 7590 nm/RIU for the refractive index range varying from 1.34 to 1.38 and the corresponding resolution is 1.31 × 10{sup −5} RIU. Furthermore, the maximum amplitude sensitivity of the sensor is calculated to be 676.08 RIU{sup −1}. The good sensing performance, low cost and simple structure makes this sensor a potential candidate for application in the areas of food processing, environmental monitoring and biochemical analysis.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Photosensitive free-standing ultra-thin carbyne–gold films

In the article we introduce the experiment of the photostimulation effect in the tunneling conductivity of free-standing thin carbyne-gold films. We observe a sharp increase of the conductivity of hybrid film due to the electromagnetic exciting at the frequencies which are close to the plasmon resonance of gold nanoparticles. The use of carbyne threads as a stabilizing matrix makes it possible to obtain free-standing thin films that demonstrate a good structural stability. The tunnel current–voltage measurements demonstrate a strong dependence of the current value on the intensity of green laser radiation used to photostimulate thin C–Au in area of the measuring experiment.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Binding of gold(III) with silver(I) dipropyldithiocarbamate: supramolecular self-assembly (role of secondary Au…S and Ag…S bonds) and thermal behavior of the ionic-polymer complex ([Au(S{sub 2}CNPr{sub 2}){sub 2}][AgCl{sub 2}]){sub n}

The double ionic-polymer complex ([Au(S{sub 2}CNPr{sub 2}){sub 2}][AgCl{sub 2}]){sub n} (1) was prepared as an individual fixation form of gold(III) from NaCl solutions with silver(I) dipropyldithiocarbamate and was characterized by single-crystal X-ray diffraction and {sup 13}C magic-angle spinning (MAS) NMR spectroscopy. The structure of 1 comprises two nonequivalent centrosymmetric complex cations [Au(S{sub 2}CNPr{sub 2}){sub 2}]{sup +} (A and B) and the discrete linear anion [AgCl{sub 2}]{sup –}. Gold(III) cations are linked by pairs of unsymmetrical secondary Au…S bonds to form linear supramolecular chains (…A…B…)n. Neighboring cations are additionally linked by [AgCl{sub 2}]{sup –} anions via secondary Ag…S and Cl…S bonds, the anions being involved in the overall stabilization of the supramolecular structure. The cation–anion interactions lead to a distortion of the linear configuration of the [AgCl{sub 2}]{sup –} anion. The character of thermolysis of 1 accompanied by quantitative regeneration of bound Au and Ag was established by simultaneous thermal analysis.

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

Characteristics of Hydrogen Sensors Based on Thin Tin Dioxide Films Modified with Gold

Effect of hydrogen in the concentration range from 10 to 2000 ppm on the characteristics of sensors based on thin films of tin dioxide modified with gold (Au/SnO{sub 2}:Sb, Au) is studied in the thermo-cyclic mode at temperatures from 623 to 773 K and absolute humidity from 2.5 to 20 g/m{sup 3}. Experimental data are discussed using expressions obtained within the framework of a model that takes into account the presence of three types of adsorbed particles (O¯, OH, and OH¯) on the surface of SnO{sub 2} nanocrystals. The characteristics of the sensors based on thin Pt/Pd/SnO{sub 2}:Sb films (the first series) are compared with those of Au/SnO{sub 2}:Sb, Au films (the second series). It is found that the degree of dissociation of molecular hydrogen into atoms during adsorption on the sensor under interaction with Au particles on the SnO{sub 2} surface is 4 times greater than that under interaction with Pt/Pd particles. The degree of dissociation of H{sub 2}O molecules into hydrogen atoms and hydroxyl groups in pure moist air on the surface of the sensors of the second series is 1.6 times greater than that for the sensors of the first series. Thus, gold is a more effective stimulator of the dissociation of H{sub 2} and H{sub 2}O molecules than platinum and palladium. A formula is obtained that describes more accurately the dependence of the response of the sensors of both series to the effect of hydrogen on the concentration of this gas and on the temperature of the measuring devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Analysis of Chemical Bonding and Structural Network of Gold Silicide in Core–Shell Silicon Nanowire

The Au-catalyzed core–shell silicon nanowires (Si-NWs) were synthesized by chemical vapor deposition by using SiH{sub 4} and H{sub 2} precursor gases. The TEM and FTIR studies revealed that the Si-NWs consist of core silicon surrounded by a thick oxide sheath and Au distributed at the a-SiOx/Si interface. The x-ray photoelectron spectroscopy (XPS) was used to study the chemical composition and electronic environments of gold silicide in the a-SiO{sub x}/Si-NWs. The elemental analysis and chemical network of gold silicide of core–shell Si-NWs were explained on the basis of the random atomic distribution of Si, O and Au atoms. The Raman spectra and XRD peak reveal the crystalline core of Si-NWs. The individual contribution to the Au (4d) core orbital was deconvoluted to Au-Si-Au, Au-Si-O, Au-Au, Au-O-Au, Au-O-Si and Au=O/Au-O{sub 2} bonding structure. The analysis shows that the O linked with Si and Au has also contributed to growth of Si-NWs.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Gold(I) Cationization Promotes Ring Opening in Lysine-Containing Cyclic Peptides

A strategy to sequence lysine-containing cyclic peptides by MS{sup n} is presented. Doubly protonated cyclic peptides ions are transformed into gold (I) cationized peptide ions via cation switching ion/ion reaction. Gold(I) cationization facilitates the oxidation of neutral lysine residues in the gas phase, weakening the adjacent amide bond. Upon activation, facile cleavage N-terminal to the oxidized lysine residue provides a site-specific ring opening pathway that converts cyclic peptides into acyclic analogs. The ensuing ion contains a cyclic imine as the new N-terminus and an oxazolone, or structural equivalent, as the new C-terminus. Product ions are formed from subsequent fragmentation events of the linearized peptide ion. Such an approach simplifies MS/MS data interpretation as a series of fragment ions with common N- and C-termini are generated. Results are presented for two cyclic peptides, sunflower trypsin inhibitor and the model cyclic peptide, β-Loop. The power of this strategy lies in the ability to generate the oxidized peptide, which is easily identified via the loss of HAuNH{sub 3} from [M + Au]{sup +}. While some competitive processes are observed, the site of ring opening can be pinpointed to the lysine residue upon MS{sup 4} enabling the unambiguous sequencing of cyclic peptides. .

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2017

Mechanical properties of nanoporous gold in tension

We report results of the tensile properties of nanoporous gold (NPG) as a function of the density and average ligament diameter. As-dealloyed tensile samples were thermally treated to coarsen the length scale of the NPG structure while increasing the sample density resulting from thickness reductions. The behaviors of samples with mean ligament diameters ranging from 30 to 750 nm and corresponding densities ranging from 0.30 to 0.57 that of bulk gold were examined. Digital image analysis was used to obtain ligament size histograms that were fit to the Weibull distribution. The Young's modulus was found to obey a power law, but with an exponent larger than that predicted by Gibson-Ashby scaling. The fracture behavior showed a brittle-ductile transition as a function of increasing ligament size. For samples characterized by a mean ligament diameter less than ~ 220 nm, the tensile behavior was linear elastic to sample fracture while samples with larger scale ligaments showed macroscopic yielding prior to fracture. These results are interpreted within the framework of extreme value statistics.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Demonstration of gold nanorod systems for enhanced total efficiency: Experimental and numerical analysis

This study investigates the photothermal performance of gold nanorods engineered to exhibit longitudinal plasmon resonances at 695 nm, 780 nm, and 970 nm. The work combines synthesis, structural characterization, extinction measurements, numerical modeling, and controlled temperature experiments to quantify how nanorod geometry, resonance tuning, concentration, and chamber shape jointly influence heat generation. Transmission electron microscopy confirms that increasing nanorod aspect ratio systematically shifts the longitudinal plasmon peak toward the near-infrared region. Extinction measurements show strong agreement with theoretical predictions, validating the numerical model across two independent datasets. Three chamber geometries were tested under laser excitation at 640 nm, 808 nm, and 980 nm: an ascending stepped base, a flat base, and a descending stepped base. Without nanorods, the ascending geometry produced the highest efficiency due to enhanced natural convection. After introducing gold nanorods, all geometries exhibited substantial thermal enhancement, with total efficiencies exceeding 20%. The strongest improvement was obtained for nanorods resonant at 780 nm with a mass concentration of 4.6 mg/mL implemented on the descending stepped-base geometry. This performance resulted from the combined effect of spectral overlapping with the 808 nm laser, the highest nanorod concentration, and localized heat accumulation that intensified buoyancy-driven flow. The findings demonstrate that total efficiency is governed by a synergistic interplay between optical resonance, nanoparticle concentration, and macroscopic chamber design, revealing the system-level coupling between nanoscale plasmonic absorption and macroscale heat-transfer phenomena. The results provide a validated framework for tuning nanoscale plasmonic absorbers and optimizing thermal systems for applications requiring efficient light-to-heat conversion.

77 NANOSCIENCE AND NANOTECHNOLOGY↗