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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

The radiation instability of thermally stable nanocrystalline platinum gold

Here, recent experimentally validated alloy design theories have demonstrated nanocrystalline binary alloys that are stable against thermally induced grain growth. An open question is whether such thermal stability also translates to stability under irradiation. In this study, we investigate the response to heavy ion irradiation of a nanocrystalline platinum gold alloy that is known to be thermally stable from previous studies. Heavy ion irradiation was conducted at both room temperature and elevated temperatures on films of nanocrystalline platinum and platinum gold. Using scanning/transmission electron microscopy equipped with energy-dispersive spectroscopy and automated crystallographic orientation mapping, we observe substantial grain growth in the irradiated area compared to the controlled area beyond the range of heavy ions, as well as compositional redistribution under these conditions, and discuss mechanisms underpinning this instability. These findings highlight that grain boundary stability against one external stimulus, such as heat, does not always translate into grain boundary stability under other stimuli, such as displacement damage.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Impact of Gold Thickness on Interfacial Evolution and Subsequent Embrittlement of Tin–Lead Solder Joints

Although gold remains a preferred surface finish for components used in high-reliability electronics, rapid developments in this area have left a gap in the fundamental understanding of solder joint gold (Au) embrittlement. Furthermore, as electronic designs scale down in size, the effect of Au content is not well understood on increasingly smaller solder interconnections. As a result, previous findings may have limited applicability. The current study focused on addressing these gaps by investigating the interfacial microstructure that evolves in 63Sn-37Pb solder joints as a function of Au layer thickness. Those findings were correlated to the mechanical performance of the solder joints. Increasing the initial Au concentration decreased the mechanical strength of a joint, but only to a limited degree. Kirkendall voids were the primary contributor to low-strength joints, while brittle fracture within the intermetallic compounds (IMC) layers is less of a factor. The Au embrittlement mechanism appears to be self-limiting, but only once mechanical integrity is degraded. Sufficient void evolution prevents continued diffusion from the remaining Au.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Gold nanocatalysts supported on heterostructured PbSO4-MCF mesoporous materials for CO oxidation

Metal oxides are commonly used as the supports of gold nanoparticles for catalytic CO oxidation, whereas metal salts are rarely considered suitable supports. In the present work, we developed a new kind of gold nanocatalyst supported on heterostructured PbSO4-MCF mesoporous materials that was prepared by an in situ growth method using dodecylbenzenesulfonate (SOBS) as a sulfonate precursor. It was found that an Au/PbSO4-MCF (SDBS) catalyst preheated at 300 degrees C showed high CO conversion below 100 degrees C. In addition, the stability of selected catalysts was studied as a function of time on stream. Because of the alteration of surface properties, these Au nanocatalysts were highly sinter-resistant. Published by Elsevier B.V.

Li, Lin↗
DOE OSTI2019

Architectural Stabilization of a Gold(III) Catalyst in Metal-Organic Frameworks

Unimolecular decomposition pathways are challenging to address in transition-metal catalysis and have previously not been suppressed via incorporation into a solid support. Two robust metal-organic frameworks (IRMOF-10 and bio-MOF-100) are used for the architectural stabilization of a structurally well-defined gold(III) catalyst. The inherent rigidity of these materials is utilized to preclude a unimolecular decomposition pathway—reductive elimination. Through this architectural stabilization strategy, decomposition of the incorporated gold(III) catalyst in the metal-organic frameworks is not observed; in contrast, the homogeneous analog is prone to decomposition in solution. Finally, stabilization of the catalyst in these metal-organic frameworks precludes leaching and enables recyclability, which is crucial for productive heterogeneous catalysis.

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

Pressed copper and gold-plated copper contacts at low temperatures – A review of thermal contact resistance

Cryogenic systems that utilize cryocoolers with conduction cooling for attaining temperatures of 4.2 K and below routinely employ mechanically pressed components of copper to form the heat conduction path. To help with the design of such systems, the present paper introduces thermal contact resistance data of pressed copper-copper and gold-plated copper-copper contacts from nearly twenty measurement programs that span across past fifty years. Relevant theoretical models of thermal contact resistance are briefly reviewed and compared with the experimental data. Gold-plated copper contacts display reasonable trend with the models, which may serve as a design reference for such contacts. A few measurement techniques are also summarized that enable quick characterization of thermal contacts at low temperatures.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Facile microwave synthesis of zirconium metal-organic framework thin films on gold and silicon and application to sensor functionalization

Zirconium-based metal-organic frameworks, including UiO-66 and related frameworks, have become the focus of considerable research in the area of chemical warfare agent (CWA) decontamination. However, little work has been reported exploring these metal-organic frameworks (MOFs) for CWA sensing applications. For many sensing approaches, the growth of high-quality thin films of the active material is required, and thin film growth methods must be compatible with complex device architectures. Several approaches to synthesize thin films of UiO-66 have been described but many of these existing methods are complex or time consuming. In this work, we describe the development of a simple and rapid microwave assisted synthesis of oriented UiO-66 thin films on unmodified silicon (Si) and gold (Au) substrates. Thin films of UiO-66 and UiO-66-NH 2 can be grown in as little as 2 min on gold substrates and 30 min on Si substrates. The film morphology and orientation are characterized and the effects of reaction time and temperature on thin film growth on Au are investigated. Both reaction time and temperature impact the overgrowth of protruding discrete crystallites in the thin film layer but, surprisingly, no strong correlation is observed between film thickness and reaction time or temperature. We also briefly describe the synthesis of Zr/Ce solid solution thin films of UiO-66 on Au and report the first synthesis of a solid solution thin film MOF. Finally, we demonstrate the utility of the microwave method for the facile functionalization of two sensor architectures, plasmonic nanohole arrays and microresonators, with UiO-66 thin films.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Sorafenib derivatives-functionalized gold nanoparticles confer protection against tumor angiogenesis and proliferation via suppression of EGFR and VEGFR-2

Sorafenib is a multi-kinase inhibitor that has been highlighted as a tumor suppressor due to its anti-proliferative and anti-angiogenic properties, whereas the clinical application of Sorafenib is restricted by the side effects it may cause. The past decade has witnessed the development of a series of sorafenib derivatives to improve the clinical performance of sorafenib. Gold nanoparticles (AuNPs) have been widely utilized in drug delivery systems due to their unique properties, including biocompatible nature, simple preparation, and easy surface modification. Herein, this study is aimed to investigate the anti-tumor effects of new sorafenib derivatives-capped gold nanoparticles (AuNPs-New Sor) in tumor formation and metastasis as well as the underlying mechanisms. Initially, new sorafenib derivatives were constructed and combined with AuNPs to form AuNPs-New Sor, and the properties of synthesized AuNPs-New Sor were identified in a mouse model of tumorigenesis. The effect of AuNPs-New Sor on tumor vascular normalization was investigated by assessing vascular permeability and perfusion rate. Next, we evaluated the effect of AuNPs-New Sor on migration and viability of tumor cells and human umbilical vein endothelial cells (HUVECs) as well as on HUVEC angiogenesis in vitro. A melanoma mouse model was further established for in vivo substantiation of the anti-tumor effect of AuNPs-New Sor. According to the results, AuNPs could deliver new sorafenib derivatives into tumor tissues and downregulate the expression of epidermal growth factor receptor (EGFR) and vascular endothelial growth factor receptor-2 (VEGFR-2), thereby suppressing tumor migration, EMT, and angiogenesis in vitro. In addition, AuNPs-New Sor displayed competitive anti-tumor activities in vivo. Taken together, AuNPs-New Sor may attenuate tumor development and angiogenesis through downregulation of EGFR and VEGFR-2.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Metallic Hydrogen in Atomically Precise Gold Nanoclusters

Hydrogen–metal interaction is the foundation of many technologies and processes, but how hydrogen behaves in atomically precise gold nanoclusters remains unknown even though they have been used in hydrogenation catalysis and water splitting. Herein, we investigate how hydrogen interacts with [Au25(SR)18]q clusters and mono-atom-doped bimetallic [M1Au24(SR)18]q clusters (M = Pt, Pd, Ag, Cu, Hg, or Cd) from first principles. We find that hydrogen behaves as a metal in these clusters and contributes its 1s electron to the superatomic free-electron count. This opposite behavior compared to that of the hydride in Cu and Ag clusters allows the small hydrogen to interstitially dope the gold clusters and tune their superatomic electronic structure. The doping energetics shows that when an eight-electron superatom is formed after H doping, the binding energy of H is much stronger, while binding of H with an already eight-electron superatom is much weaker. Indeed, frontier orbitals and the HOMO–LUMO gaps of [Au25H1(SR)18]0, [Au25H2(SR)18]+, [PtAu24H2(SR)18]0, [PdAu24H2(SR)18]0, [AgAu24H(SR)18]0, and [CuAu24H(SR)18]0 all have very similar features, because they are all eight-electron superatoms. By calculating the Gibbs free energies of hydrogen adsorption, we predict that PtAu24(SR)18, PdAu24(SR)18, and center-doped CuAu24(SR)18 can be good electrocatalysts for the hydrogen evolution reaction.

Hu, Guoxiang↗
DOE OSTI2015

Periodicity, Electronic Structures, and Bonding of Gold Tetrahalides [AuX4](-) (X = F, CI, Br, I, At, Uus)

Systematic theoretical and experimental investigations have been performed to understand the periodicity and electronic structures of trivalent-gold halides using gold tetrahalides [AuX4]⁻ anions (X = F, Cl, Br, I, At, Uus). The [AuX4]⁻ (X = Cl, Br, I) anions were produced in gas phase and their negative-ion photoelectron spectra were obtained, which exhibited rich and well-resolved spectral peaks. We calculated the adiabatic as well as vertical electron detachment energies using density functional methods with scalar and spin-orbit coupling relativistic effects. The simulated photoelectron spectra based on these calculations are in good agreement with the experimental spectra. Our results show that the trivalent Au(III) oxidation state becomes progressively less stable while Au(I) is preferred when the halides become heavier along the Period Table. This trend reveals that the oxidation state of metals in complexes can be manipulated through ligand design

Environmental Molecular Sciences Laboratory↗
DOE OSTI2018

Langmuir Films of n -Alkanethiol-Capped Gold Nanoparticles and n -Alkanes: Interfacial Mixing Scenarios Assessed by X-ray Reflectivity and Grazing Incidence Diffraction

A series of n-alkanes cospread with alkanethiol-stabilized gold nanoparticles (AuNP) were studied as Langmuir monolayers by synchrotron X-ray reflectivity and diffraction. Tetradecanethiol capped gold nanoparticles with core diameters close to 2 nm were used to make films at 20 °C, below the ligand order–disorder temperature. A variety of n-alkane chain lengths (Cn = C n H 2n+2 , where n = 12, 15 and 16) were tested to assess the interfacial assembly of nanoparticle films as a result of different mixing scenarios indicated in their surface pressure versus area isotherms. Synchrotron grazing incidence X-ray diffraction (GIXD) and reflectivity (XR) confirm that mixtures of n-alkane and AuNP exhibiting improved fluidity in their compression isotherm are indeed incorporating n-alkane into the AuNP ligand shell and stabilizing it at the air–water interface. The resulting films show a doubling of their correlation lengths and thus a significant improvement on their ordering, as well as increased lattice spacing that is dependent upon the n-alkane chain length. Mixtures that do not exhibit changes in their surface pressure vs area isotherm similarly show little change in the interfacial assembly of the nanoparticle films except to promote monolayer collapse and multilayer formation. Improvements to the film order are assigned to the initial formation of larger nanoparticle domains. Here, the nature of the chain length dependence and persistence of the n-alkane through compression suggest a favorable interaction with the nanoparticle ligand shell that results in the extension of methylene units of the longer alkanes beyond the thiol layer, which has implications for influencing nanoparticle interactions.

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

Dynamics of Electron–Phonon Coupling in Bicontinuous Nanoporous Gold

Here, the nanosize effect on electron–phonon interactions in free-electron noble metals has been a subject of intense discussion because of their important applications in physics, chemistry, and biomedicine. However, the interference from supports of dispersive nanoparticulate metals has led to controversial observations. We utilize freestanding, bicontinuous nanoporous gold (NPG) films to investigate electron–phonon interaction dynamics using ultrafast MeV electron diffraction. Compared to solid gold films, NPG shows faster electron–phonon interaction and thus noticeably higher electron–phonon coupling constant. The results demonstrate that surface states of electrons and phonons play an important role in electron–phonon coupling of nanostructured materials.

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

A Single Layer of MoS 2 Activates Gold for Room Temperature CO Oxidation on an Inert Silica Substrate

Here, we demonstrate the facile deposition of catalytically active stable Au nanoparticles on single-layer MoS 2 , on an inert oxide substrate (SiO 2 ). Unlike a gold surface, adsorption of CO on these gold particles proceeds even at room temperature. Subsequent exposure to oxygen leads to CO 2 formation and desorption along a reaction pathway described, in detail, by density functional theory. The barrier to CO oxidation, along this pathway, is less than 300 meV, corroborating the facile nature of the CO oxidation reactions in this system. X-ray photoelectron spectroscopy directly reveals that the carbon monoxide, adsorbed on Au nanoparticles on single-layer MoS 2 , can be repeatedly titrated off the substrate by exposure to oxygen. Comparison of computational results assuming a defect-laden and pristine MoS 2 substrate suggest that the pristine single-layer material may be superior in supporting this reaction.

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

Taking the Plunge: Nanoscale Chemical Imaging of Functionalized Gold Triangles in H2O via TERS

We demonstrate fast (0.25 s/pixel) nanoscale chemical imaging in aqueous solution via tip-enhanced Raman scattering (TERS), with sub-15 nm spatial resolution. The substrate consists of 4-mercaptobenzonitrile-functionalized monocrystalline gold triangular platelets immersed in H2O, which we map using a gold-coated AFM probe illuminated using a 633 nm laser source. We find that the recorded TERS images trace the enhanced local optical fields that are sustained towards the edges and corners of the triangles. In effect, we directly map local optical fields of a plasmonic substrate in aqueous solution through molecular TERS. Overall, our described platform and approach may generally be used for chemical and biological imaging, and potentially, to follow chemical transformations at solid-liquid interfaces through TERS.

Bhattarai, Ashish↗
DOE OSTI2021

Ion Mobility Spectrometry Characterization of the Intermediate Hydrogen-Containing Gold Cluster Au7(PPh3)7H52+

We employ ion mobility spectrometry and density functional theory to determine the structure of Au7(PPh3)7H52+ (PPh3 = triphenylphosphine) which was recently identified by high mass resolution mass spectrometry. Experimental ion-neutral collision cross sections represent the momentum transfer between the ionic clusters and gas molecules averaged over the relative thermal velocities of the colliding pair, thereby providing structural insights. Theoretical calculations indicate the geometry of Au7(PPh3)7H52+ is similar to Au7(PPh3)7+, with three hydrogen atoms bridging two gold atoms and two hydrogen atoms forming single Au–H bonds. Collision induced dissociation products observed during IMS experiments reveal that smaller hydrogen containing clusters may be produced through fragmentation of Au7(PPh3)7H52+. Our findings indicate that hydrogen containing species like Au7(PPh3)7H52+ act as intermediates in the formation of larger phosphine ligated gold clusters. These results advance the understanding and ability to control the mechanisms of size selective cluster formation which is necessary for scalable synthesis of clusters with tailored properties. This work was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. M.A.H. acknowledges support from the DOE Science Undergraduate Laboratory Internship (SULI) program. H.H. acknowledges support from the DOE Office of Workforce Development for Teachers and Scientist (WDTS) under the Visiting Faculty Program (VFP). The efforts of K.A.M. and B.H.C. were supported by the Defense Threat Reduction Agency (Grant No. HDTRA1-14-1-0023). The research was performed using EMSL, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle for DOE under Contract DE-AC05-76RL01830.

Ligare, Marshall R.↗
DOE OSTI2016

In Situ 3D Imaging of Catalysis Induced Strain in Gold Nanoparticles

Multielectron transfer processes are crucially important in energy and biological science but require favorable catalysts to achieve fast kinetics. Nanostructuring catalysts can dramatically improve their properties, which can be difficult to understand due to strain- and size-dependent thermodynamics, the influence of defects, and substrate-dependent activities. Here, we report three-dimensional (3D) imaging of single gold nanoparticles during catalysis of ascorbic acid decomposition using Bragg coherent diffractive imaging (BCDI). Local strains were measured in single nanoparticles and modeled using reactive molecular dynamics (RMD) simulations and finite element analysis (FEA) simulations. RMD reveals the pathway for local strain generation in the gold lattice: chemisorption of hydroxyl ions. FEA reveals that the RMD results are transferable to the nanocrystal sizes studied in the experiment. Our study probes the strain-activity connection and opens a powerful avenue for theoretical and experimental studies of nanocrystal catalysis.

Ulvestad, Andrew↗
DOE OSTI2018

Electrostatics Generated by a Supramolecular Capsule Stabilizes the Transition State for Carbon–Carbon Reductive Elimination from Gold(III) Complex

Tetrahedral assemblies of stoichiometry M 4 L 6 have been proven to catalyze a range of chemical reactions including the carbon-carbon reductive elimination reaction from transition metals such as gold. Here, we perform quantum chemical calculations of Gold(III) transition metal complexes in vacuum, and encapsulated in Ga 4 L 6 12- or Si 4 L 6 8- assemblies within both a reaction field continuum solvent and in an aqueous molecular environment with counterions, to rationalize the rate enhancements observed experimentally for the reductive elimination reaction. We find that the Ga 4 L 6 12- assembly lowers the energy barrier of the reaction compared to Si 4 L 6 8- , which is consistent with kinetic trends observed experimentally. We have determined that the primary factor for catalytic rate acceleration stems from the electrostatic environment emanating from the Ga 4 L 6 12- capsule as opposed to the water or counterions.

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

Isolation of a 300 kDa, Au -1400 Gold Compound, the Standard 3.6 nm Capstone to a Series of Plasmonic Nanocrystals Protected by Aliphatic-like Thiolates

Disclosed herein is a method to obtain the ~300 kDa gold–hexanethiolate compound, extracted from the Faradaurate series of smaller (3) and larger (1) homologues, thereby permitting the first measurement of its distinctive properties by methods including mass spectrometry, optical spectroscopy, electron microscopy, X-ray scattering, and diffraction. The results suggest a monocrystalline metallic core (free of twinning planes) of ~3.1 nm minimum dimension, which supports a clear plasmonic optical response, along with a diffuse exterior shell. An idealized model to account for this (and smaller) members of the series is proposed based on the completion of a convex core of regular truncated-octahedral (TO) morphology, that is, the TO (5,5) crystallite comprising 1289 sites. The diffuse layer may comprise the 240 S sites (thiolate sulfur headgroups) and 96 Au-adatom sites, giving a total composition (1385,240) and a molar mass of ~301.0 kDa (90.7% Au). The ~300 and ~400 kDa gold compounds contain Au ~1400 and Au ~2000 atoms, respectively.

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

Ultrafast Imaging of Surface Plasmons Propagating on a Gold Surface

We record time-resolved nonlinear photoemission electron microscopy (tr-PEEM) images of propagating surface plasmons (PSPs) launched from a lithographically patterned rectangular trench on a flat gold surface. Our tr-PEEM scheme involves a pair of identical, spatially separated, and interferometrically-locked femtosecond laser pulses. Power dependent PEEM images provide experimental evidence for a sequential coherent nonlinear photoemission process, in which one laser source creates a PSP polarization state through a linear interaction, and the second subsequently probes the prepared state via two photon photoemission. The recorded time-resolved movies of a PSP allow us to directly measure various properties of the surface-bound wave packet, including its carrier wavelength (785 nm) and group velocity (0.95c). In addition, tr-PEEM in concert with finite-difference time domain simulations together allow us to set a lower limit of 75 μm for the decay length of the PSP on a 100 nm thick gold film.

Environmental Molecular Sciences Laboratory↗