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Au is Copper structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Au is bonded to twelve equivalent Au atoms to form a mixture of corner, edge, and face-sharing AuAu12 cuboctahedra. All Au–Au bond lengths are 2.95 Å.
Au(NO3)4NO2 crystallizes in the monoclinic P2_1/c space group. The structure is zero-dimensional and consists of two chebi:30328 molecules and two hydroxylamine, n-hydroxy- molecules.
Au(NO3)4H5O2H2O crystallizes in the monoclinic C2/c space group. The structure is zero-dimensional and consists of four chebi:30328 molecules, four molecular hydrogen;dihydrate molecules, and four water molecules.
Laser heating of chalcogenide glasses has successfully produced rotating lattice single crystals through a solid-solid transformation. To better understand the nature of complex, orientation-dependent lattice rotation, we designed heat profiles of the continuous wave laser by beam shaping, fabricated larger Sb2S3 crystal dots in Sb2S3 glass, and investigated the lattice rotation where the crystal could grow in all radial directions under a circular thermal gradient. The results show that the rate of lattice rotation is highly anisotropic and depends on crystallographic direction. The nature of this rotation is the same in crystals of different orientation relative to the surface. The growth directions that align with the slip planes show the highest rate of rotation and the rotation rate gradually decreases away from this direction. Additionally, the presence of multiple growth directions results in a complicated rotation system. We suggest that the growth front influences the density of dislocations introduced during growth under confinement and thus affects the lattice rotation rate in these crystals.
Plasmonic tip-sample junctions, at which the incident and scattered optical fields are localized and optimally enhanced, are often exploited to achieve ultrasensitive and highly spatially localized tip-enhanced Raman scattering (TERS). Recent work has demonstrated that the sensitivity and spatial resolution that are required to probe single molecules are attainable in such platforms. In this work, we observe and rationalize comparable TERS from few-layer WSe 2 single crystals exfoliated onto Au- and Cr-coated Si substrates, using a plasmonic TERS probe excited with a 638-nm laser. Our experimental observations are supported by finite-difference time-domain simulations that illustrate that the attainable field enhancement factors at the Au-Au and Au-Cr tip-sample nanojunctions are comparable in magnitude. Furthermore, through a combined experimental and theoretical analysis, we propose that besides Au/Ag, several metallic substrates may be used to record bright TERS spectral images.
LiTaO 3 crystals irradiated with 3 MeV and 1.162 GeV Au ions were studied by single crystal x-ray diffraction and Raman scattering measurements. The maximum lattice strains after 3 MeV Au ion irradiation to a fluence of 1.2 × 10 13 cm -2 were 1.2% and 0.6% along the c- and a-/b-axes, respectively. Two effects were observed in 1.162 GeV Au ion irradiated samples: (i) the (0006) and (1120) Bragg peaks were split into doublets, which suggested a subtle structural change due to slight modification of chemical composition; and (ii) the pre-damaged 1.2% lattice strain along the c-axis was relaxed to 0.9% after subsequent irradiation with 1.162 GeV Au ions, while relaxation along the a- or b-axis was not obvious. A distinct change in the Raman spectrum of the <0001> oriented LiTaO 3 crystals was observed after 1.162 GeV Au ion irradiation, but no obvious change was observed in the <1120> oriented samples or in 3 MeV Au ion irradiated samples. Strain and structural changes in crystalline LiTaO3, with or without pre-existing defects, upon ion irradiation are delineated in its responding to inelastic ionization and elastic nuclear collisions.
Abstract Noble metals supported on reducible oxides, like CoO x and TiO x , exhibit superior activity in many chemical reactions, but the origin of the increased activity is not well understood. To answer this question we studied thin films of CoO x supported on an Au(111) single crystal surface as a model for the CO oxidation reaction. We show that three reaction regimes exist in response to chemical and topographic restructuring of the CoO x catalyst as a function of reactant gas phase CO/O 2 stoichiometry and temperature. Under oxygen-lean conditions and moderate temperatures (≤150 °C), partially oxidized films (CoO x<1 ) containing Co 0 were found to be efficient catalysts. In contrast, stoichiometric CoO films containing only Co 2+ form carbonates in the presence of CO that poison the reaction below 300 °C. Under oxygen-rich conditions a more oxidized catalyst phase (CoO x>1 ) forms containing Co 3+ species that are effective in a wide temperature range. Resonant photoemission spectroscopy (ResPES) revealed the unique role of Co 3+ sites in catalyzing the CO oxidation. Density function theory (DFT) calculations provided deeper insights into the pathway and free energy barriers for the reactions on these oxide phases. These findings in this work highlight the versatility of catalysts and their evolution to form different active phases, both topological and chemically, in response to reaction conditions exposing a new paradigm in the catalyst structure during operation.
Slip line deformation of ordered and disordered Cu-Au intermetallic single crystals from microstrain and electron micrographic studies
Heterostructured, including heterophase, noble-metal nanomaterials have attracted much interest due to their promising applications in diverse fields. However, great challenges still remain in the rational synthesis of well-defined noble-metal heterophase nanostructures. Furthermore, we report the preparation of Pd nanoparticles with an unconventional hexagonal close-packed (2H type) phase, referred to as 2H-Pd nanoparticles, via a controlled phase transformation of amorphous Pd nanoparticles. Impressively, by using the 2H-Pd nanoparticles as seeds, Au nanomaterials with different crystal phases epitaxially grow on the specific exposed facets of the 2H-Pd, i.e., face-centered cubic (fcc) Au (fcc-Au) on the (002)h facets of 2H-Pd while 2H-Au on the other exposed facets, to achieve well-defined fcc-2H-fcc heterophase Pd@Au core–shell nanorods. Moreover, through such unique facet-directed crystal-phase-selective epitaxial growth, a series of unconventional fcc-2H-fcc heterophase core–shell nanostructures, including Pd@Ag, Pd@Pt, Pd@PtNi, and Pd@PtCo, have also been prepared. Impressively, the fcc-2H-fcc heterophase Pd@Au nanorods show excellent performance toward the electrochemical carbon dioxide reduction reaction (CO 2 RR) for production of carbon monoxide with Faradaic efficiencies of over 90% in an exceptionally wide applied potential window from –0.9 to –0.4 V (versus the reversible hydrogen electrode), which is among the best reported CO 2 RR catalysts in H-type electrochemical cells.
AuSn2 crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. Au is bonded to six Sn atoms to form a mixture of edge and corner-sharing AuSn6 octahedra. The corner-sharing octahedra tilt angles range from 48–66°. There are a spread of Au–Sn bond distances ranging from 2.79–2.89 Å. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded in a 3-coordinate geometry to three equivalent Au atoms. In the second Sn site, Sn is bonded in a 3-coordinate geometry to three equivalent Au atoms.
AuPb2 is Khatyrkite structured and crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. Au is bonded in a 10-coordinate geometry to two equivalent Au and eight equivalent Pb atoms. Both Au–Au bond lengths are 2.97 Å. All Au–Pb bond lengths are 3.15 Å. Pb is bonded in a 7-coordinate geometry to four equivalent Au and three equivalent Pb atoms. There are one shorter (3.34 Å) and two longer (3.52 Å) Pb–Pb bond lengths.
AuGa is Modderite structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Au is bonded in a 6-coordinate geometry to six equivalent Ga atoms. There are a spread of Au–Ga bond distances ranging from 2.66–2.79 Å. Ga is bonded in a 6-coordinate geometry to six equivalent Au atoms.
AuTl2 is Khatyrkite structured and crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. Au is bonded in a 10-coordinate geometry to two equivalent Au and eight equivalent Tl atoms. Both Au–Au bond lengths are 2.88 Å. All Au–Tl bond lengths are 3.17 Å. Tl is bonded in a 4-coordinate geometry to four equivalent Au atoms.
AuTl2 crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. Au is bonded to two equivalent Au and four equivalent Tl atoms to form distorted corner-sharing AuTl4Au2 octahedra. The corner-sharing octahedra tilt angles range from 0–43°. Both Au–Au bond lengths are 2.75 Å. All Au–Tl bond lengths are 2.97 Å. Tl is bonded in a distorted bent 150 degrees geometry to two equivalent Au atoms.
AuIn3 is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Au is bonded to twelve In atoms to form AuIn12 cuboctahedra that share corners with four equivalent AuIn12 cuboctahedra, edges with eight equivalent AuIn12 cuboctahedra, edges with sixteen equivalent InIn8Au4 cuboctahedra, faces with four equivalent AuIn12 cuboctahedra, and faces with eight equivalent InIn8Au4 cuboctahedra. There are four shorter (3.16 Å) and eight longer (3.30 Å) Au–In bond lengths. There are two inequivalent In sites. In the first In site, In is bonded to four equivalent Au and eight In atoms to form distorted InIn8Au4 cuboctahedra that share corners with twelve equivalent InIn8Au4 cuboctahedra, edges with eight equivalent AuIn12 cuboctahedra, edges with eight equivalent InIn8Au4 cuboctahedra, faces with four equivalent AuIn12 cuboctahedra, and faces with ten equivalent InIn8Au4 cuboctahedra. There are four shorter (3.16 Å) and four longer (3.30 Å) In–In bond lengths. In the second In site, In is bonded in a square co-planar geometry to four equivalent Au and eight equivalent In atoms.
Au2Al crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Au is bonded in a 10-coordinate geometry to five equivalent Al atoms. There are four shorter (2.76 Å) and one longer (3.09 Å) Au–Al bond lengths. Al is bonded in a 10-coordinate geometry to ten equivalent Au atoms.
AuAg3 is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Au is bonded to twelve Ag atoms to form AuAg12 cuboctahedra that share corners with four equivalent AuAg12 cuboctahedra, corners with eight equivalent AgAg8Au4 cuboctahedra, edges with eight equivalent AuAg12 cuboctahedra, edges with sixteen equivalent AgAg8Au4 cuboctahedra, faces with four equivalent AuAg12 cuboctahedra, and faces with fourteen AgAg8Au4 cuboctahedra. There are eight shorter (2.94 Å) and four longer (2.95 Å) Au–Ag bond lengths. There are two inequivalent Ag sites. In the first Ag site, Ag is bonded to four equivalent Au and eight Ag atoms to form distorted AgAg8Au4 cuboctahedra that share corners with twelve equivalent AgAg8Au4 cuboctahedra, edges with eight equivalent AuAg12 cuboctahedra, edges with sixteen AgAg8Au4 cuboctahedra, faces with four equivalent AuAg12 cuboctahedra, and faces with fourteen AgAg8Au4 cuboctahedra. There are four shorter (2.94 Å) and four longer (2.95 Å) Ag–Ag bond lengths. In the second Ag site, Ag is bonded to four equivalent Au and eight equivalent Ag atoms to form distorted AgAg8Au4 cuboctahedra that share corners with four equivalent AgAg8Au4 cuboctahedra, corners with eight equivalent AuAg12 cuboctahedra, edges with twenty-four AgAg8Au4 cuboctahedra, faces with six equivalent AuAg12 cuboctahedra, and faces with twelve AgAg8Au4 cuboctahedra.
AuGa3 is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Au is bonded to twelve Ga atoms to form AuGa12 cuboctahedra that share corners with four equivalent AuGa12 cuboctahedra, corners with twenty-four GaGa4Au4 cuboctahedra, edges with eight equivalent AuGa12 cuboctahedra, edges with eight equivalent GaGa4Au4 cuboctahedra, faces with four equivalent AuGa12 cuboctahedra, and faces with six equivalent GaGa8Au4 cuboctahedra. There are eight shorter (2.95 Å) and four longer (3.00 Å) Au–Ga bond lengths. There are two inequivalent Ga sites. In the first Ga site, Ga is bonded to four equivalent Au and four equivalent Ga atoms to form distorted GaGa4Au4 cuboctahedra that share corners with eight equivalent AuGa12 cuboctahedra, corners with sixteen GaGa4Au4 cuboctahedra, edges with four equivalent AuGa12 cuboctahedra, edges with sixteen GaGa4Au4 cuboctahedra, and faces with six equivalent GaGa4Au4 cuboctahedra. All Ga–Ga bond lengths are 2.95 Å. In the second Ga site, Ga is bonded to four equivalent Au and eight equivalent Ga atoms to form distorted GaGa8Au4 cuboctahedra that share corners with eight equivalent AuGa12 cuboctahedra, corners with twenty GaGa4Au4 cuboctahedra, edges with sixteen GaGa4Au4 cuboctahedra, faces with four equivalent GaGa8Au4 cuboctahedra, and faces with six equivalent AuGa12 cuboctahedra.