Gold Lattice Research Articles

Goldene: An Anisotropic Metallic Monolayer with Remarkable Stability and Rigidity and Low Lattice Thermal Conductivity.

In a recent breakthrough in the field of two-dimensional (2D) nanomaterials, the first synthesis of a single-atom-thick gold lattice of goldene has been reported through an innovative wet chemical removal of Ti3C2 from the layered Ti3AuC2. Inspired by this advancement, in this communication and for the first time, a comprehensive first-principles investigation using a combination of density functional theory (DFT) and machine learning interatomic potential (MLIP) calculations has been conducted to delve into the stability, electronic, mechanical and thermal properties of the single-layer and free-standing goldene. The presented results confirm thermal stability at 700 K as well as remarkable dynamical stability of the stress-free and strained goldene monolayer. At the ground state, the elastic modulus and tensile strength of the goldene monolayer are predicted to be over 226 and 12 GPa, respectively. Through validated MLIP-based molecular dynamics calculations, it is found that at room temperature, the goldene nanosheet can exhibit anisotropic tensile strength over 9 GPa and a low lattice thermal conductivity around 10 ± 2 W/(m.K), respectively. We finally show that the native metallic nature of the goldene monolayer stays intact under large tensile strains. The combined insights from DFT and MLIP-based results provide a comprehensive understanding of the stability, mechanical, thermal and electronic properties of goldene nanosheets.

Study of quantum electron diffraction for the LISA test-mass charging

The future Laser Interferometer Space Antenna (LISA) for gravitational wave detection in space and the precursor LISA Pathfinder missions rely on metal test masses (TMs) playing the role of free-falling geodesic-reference and interferometer end mirrors. Charge deposited on the TMs by high-energy particles of galactic and solar origin couples with stray electric fields thus perturbing the free-falling geodesic motion. In previous works it has been shown that sub-keV electrons play a relevant role for TM charging. In particular, electrons with energies below 100 eV show a wave-like behavior when impacting on the gold coatings of the TMs and electrode-housing (EH), the capacitive position sensor/actuator that surrounds the TMs. We aim at studying the effects of quantum diffraction of electrons on LISA Pathfinder and LISA TMs and EH gold lattice. We calculate the quantum diffraction probability of electrons with energies < 100 eV impinging on gold lattice from different directions by using the methods of quantum mechanics. The effects of electron quantum diffraction on LISA TM charging are reported here for the first time. This work is also of interest for the second-generation LISA-like space interferometers and for all space missions whose performance relies on free-falling metal test masses.

Типоморфизм рентгеноструктурных характеристик золота (на примере россыпей и рудопроявлений Тимано-Североуральского региона)

The results of the study of native gold of the Timan-Northern Ural region using X-ray diffraction analysis (Debye-Scherrer diffractometric method, single crystal registration) have been presented. It was established that the structural characteristics of gold were different depending on the nature of gold-bearing objects. The structure of typical placer gold was an aggregate of randomly distributed microcrystallites. In this case, only solid annular lines of reflexes of the planes of the crystal lattice of gold were visible on the photodebagrams. The formation of this microcrystalline structure in gold was conditioned by exogenous mechanical deformations resulting from its occurrence in dynamic environments (water, wind activity, etc.).&#x0D; The structure of the autigenic gold of ore occurrences was characterized by a suboriented ordering of crystals (texturization). On the photodebagrams of this gold, intermittent dashed lines and nodes of reflections from the planes of the crystal lattice of the metal were observed. The frequency of occurrence of gold with this structure on primary ore objects varied from several units to several tens of percent. According to the authors, the findings of native gold with the structures of the ordering of its grains as part of accretions or aggregates of microcrystallites were a sign of the extreme proximity of this gold to its root source, which was important at predicting of gold content and searching for gold deposits.

A Laser Synthesis Route to Boron‐Doped Gold Nanoparticles Designed for X‐Ray Radiotherapy and Boron Neutron Capture Therapy Assisted by CT Imaging

AbstractNew multifunctional theranostic vectors allow the expansion of cancer therapeutic approaches toward scarcely investigated fields. One example is the combination of boron neutron capture therapy (BNCT) and X‐ray radiotherapy (XRT) for treating normal and XRT‐resistant hypoxic tumor regions and reduce recurrence. Of great relevance for BNCT is also the support of viable, rapid, safe, and reliable techniques for the localization and quantification of the radiosensitizers in the tissues. To address these challenges, polymer‐coated Au‐B nanoparticles (NPs) are obtained starting from a laser ablation in liquid process. Despite thermodynamic constraints, the two elements coexist by short‐range boron segregation in the gold lattice, as demonstrated experimentally and explained with the support of density functional theory calculations. Thus, the Au‐B NPs maintain a marked gold character such as biocompatibility, stability, and straightforward surface chemistry with thiolated compounds, desirable for the integration with agents capable of cell targeting and internalization. Overall, the Au‐B NPs exhibit the appropriate features for the investigation of combined BNCT and XRT, supported by the localization and quantification with X‐ray computed tomography imaging. Besides, the Au‐B nanotechnology tool is achievable without renouncing to reproducibility, environmental sustainability, and cost affordability thanks to the laser‐assisted synthetic pathway.

High Spectral Sensitivity of Strongly Coupled Hybrid Tamm-Plasmonic Resonances for Biosensing Application

In this study, the sensitivity to the refractive index changes of the ambient was studied on the uniform gold film (~50 nm) with a 1D photonic crystal (PC) from periodic five TiO2 (~110 nm)/SiO2 (~200 nm) bilayers and gold nano-bumps array produced by direct laser writing on the same sample. The optical signal sensitivity of hybrid plasmonic resonances was compared with traditional surface plasmon resonance (SPR) on a single gold layer. The influence of the strong coupling regime between Tamm plasmon polariton (TPP) and propagated plasmon polaritons in the hybrid plasmonic modes on the sensitivity of the optical was discussed. Recent studies have shown very high hybrid plasmonic mode sensitivity SHSPP ≈ 26,000 nm/RIU to the refractive index on the uniform gold layer; meanwhile, the introduction of gold lattice reduces the signal sensitivity, but increases the Q-factor of the plasmonic resonances. Despite this, the sensitivity to the ellipsometric parameters Ψ and Δ on the gold lattice was rather high due to the increased Q-factor of the resonances. The comparison of plasmonic resonance sensitivity to the refractive index changes of hybrid TPP-SPP mode on the uniform gold layer and traditional SPR have shown that hybrid plasmonic mode, due to a strong coupling effect, overcomes the SPR by about 27%.

Development of a longnoncodingRNA BC032469-dependent gold nanoparticle molecular beacon for the detection of gastric cancer cells.

Aim:Longnoncoding RNA(lncRNA) BC032469-dependent gold nanoparticle molecular beacons (AuNP-MB) were constructed for the detection of gastric cancer cells. Materials & methods: The AuNP-MBs were prepared according to well-established procedures based on the Au-S interaction between the gold lattice and thiol functionalized oligonucleotides. More importantly, the stability and targeting ability of AuNP-MB wereverified by a series of in vitro and in vivo experiments. Results: The lncRNA-dependent probes were successfully utilized for AuNP-MB-based intracellular imaging, with fluorescenceeffectively emitted in GC cells, but not in normal cells. Notably, such fluorescent emission was positively correlated with lncRNA BC032469 expression. Conclusion: The authors developed an effective fluorescent imaging probe for the recognition of gastric cancer cells.

Bio-directed synthesis of gold nanoparticles using Ananas comosus aqueous leaf extract and their photocatalytic activity for LDPE degradation

A bio-directed synthesis of gold nanoparticles (Au NPs) was developed via the reduction of hydrogen tetrachloroaurate (III) (HAuCl4·3H2O) solution by the aqueous leaf extract of Ananas comosus. The polyphenol stabilized Au NPs were characterized by UV–visible, Fourier transform infrared (FTIR), powder X-ray diffraction (PXRD)/selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (EDX) analyses. The HRTEM images revealed that Au NPs were well dispersed with spherical structures. The size ranges from 7.39 to 32.09 nm with average particle size of 18.85 ± 6.74 nm. The peaks of XRD analysis at (2θ) 37.96°, 44.06°, 64.54°, 77.50° and 81.73° were respectively assigned to (111), (200), (220), (311) and (222) planes of the face-centered cubic (fcc) lattice of gold. The photocatalytic potential of Au NPs was studied through the solid-phase degradation of low-density polyethylene (LDPE) film. The photoinduced degradation of LDPE@Au nanocomposite film was higher than that of the pure LDPE film. The weight loss of LDPE@Au (1.0 wt%) nanocomposite film steadily increased and reached 51.4 ± 4.8% in 240 h under solar light irradiation, compared to the photo-induced LDPE with only 8.6 ± 0.7%. However, LDPE film with 1.0% Au NPs gave a weight loss value of 4.72 ± 0.71 under the dark condition at the end of 240 h. Thus, LDPE film with 1.0% Au NPs showed a degradation efficiency of 90.8% under solar irradiation after 240 h. The sustainability of the nanoparticles was confirmed through reusability in the photocatalytic degradation reaction up to five consecutive cycles without substantial loss in its catalytic performance.

Synthesis and Two‐Dimensional Chiral Surface Self‐Assembly of a π‐Conjugated System with Three‐Fold Symmetry: Benzotri(7‐Azaindole)

AbstractThe synthesis of a novel expanded π‐conjugated system, namely benzotri(7‐azaindole), BTAI, is reported. Its C3h symmetry along with the integration of six complementary donor and acceptor N−H⋅⋅⋅N hydrogen bonds in the conjugated structure promote the 2D self‐assembly on Au(111) over extended areas. Besides, a perfect commensurability with the gold lattice endows the physisorbed molecular film with a remarkable stability. The structural features of BTAI result in two levels of surface chirality: Firstly, the molecules become chiral upon adsorption on the surface. Then, due to the favorable N−H⋅⋅⋅N hydrogen bond‐directed self‐assembly, along with the relative molecular rotation with respect to the substrate, supramolecular chirality manifests in two mirror enantiomorphous domains. Thus, the system undergoes spontaneous chiral resolution. LEED and STM assisted by theoretical simulations have been employed to characterize in detail these novel 2D conglomerates with relevant chiral properties for systems with C3h symmetry.

Synthesis and Two-Dimensional Chiral Surface Self-Assembly of a π-Conjugated System with Three-Fold Symmetry: Benzotri(7-Azaindole).

The synthesis of a novel expanded π-conjugated system, namely benzotri(7-azaindole), BTAI, is reported. Its C3h symmetry along with the integration of six complementary donor and acceptor N-H⋅⋅⋅N hydrogen bonds in the conjugated structure promote the 2D self-assembly on Au(111) over extended areas. Besides, a perfect commensurability with the gold lattice endows the physisorbed molecular film with a remarkable stability. The structural features of BTAI result in two levels of surface chirality: Firstly, the molecules become chiral upon adsorption on the surface. Then, due to the favorable N-H⋅⋅⋅N hydrogen bond-directed self-assembly, along with the relative molecular rotation with respect to the substrate, supramolecular chirality manifests in two mirror enantiomorphous domains. Thus, the system undergoes spontaneous chiral resolution. LEED and STM assisted by theoretical simulations have been employed to characterize in detail these novel 2D conglomerates with relevant chiral properties for systems with C3h symmetry.

Gold catalysts containing interstitial carbon atoms boost hydrogenation activity

Supported gold nanoparticles are emerging catalysts for heterogeneous catalytic reactions, including selective hydrogenation. The traditionally used supports such as silica do not favor the heterolytic dissociation of hydrogen on the surface of gold, thus limiting its hydrogenation activity. Here we use gold catalyst particles partially embedded in the pore walls of mesoporous carbon with carbon atoms occupying interstitial sites in the gold lattice. This catalyst allows improved electron transfer from carbon to gold and, when used for the chemoselective hydrogenation of 3-nitrostyrene, gives a three times higher turn-over frequency (TOF) than that for the well-established Au/TiO2 system. The d electron gain of Au is linearly related to the activation entropy and TOF. The catalyst is stable, and can be recycled ten times with negligible loss of both reaction rate and overall conversion. This strategy paves the way for optimizing noble metal catalysts to give an enhanced hydrogenation catalytic performance.

(Invited) Bimetallic Electrocatalysts for Electrochemical CO2 Reduction

Bimetallic nanoparticles (NPs) offer great flexibility to tailor the activity and selectivity in electrocatalytic conversion of carbon dioxide (CO2) to valuable chemicals. Here, we report on the electrocatalytic behavior of Au-Sn, Au-Ag and Au-Pb NPs, to highlight the effect of the intermetallic phase formation and the bimetallic composition in CO2 electroreduction.Firstly, a series of Au–Sn electrocatalysts with different intermetallic phases were obtained via tin incorporation into the gold lattice through gradual diffusion. Stoichiometric intermetallic phases were formed, and under optimal conditions, two high-value products formed with reasonable current density: formic acid in the liquid phase and syngas in the gas phase. Notably, the phase composition had a massive influence on both the activity and the product distribution. In situ Raman spectroelectrochemistry studies demonstrated that catalytic performance of the AuSn phase was superior to that its parent metals and other bimetallic counterparts.Secondly, the correlation between the electrocatalytic activity and the composition of Au-Ag alloy NPs was studied. The CO Faradaic efficiency (and thus the forming CO:H2 ratio) was changed linearly by controlling the Au:Ag ratio in the alloy. This trend was attributed to the changes in the electronic properties, as there was a monotonous shift in the Fermi level away from the vacuum level with increasing Au content. This shift correspondingly reduces the binding energy of the intermediates (*COOH and *CO), resulting in the gradually enhanced CO2-reduction activity.Finally, I will show results gained with Au-Pb electrodes, where the formation of methane (CH4) was demonstrated. Factors underpinning this unusual behavior were studied by both experimental and theoretical means.

Parametric optimization of visible wavelength gold lattice geometries for improved plasmon-enhanced fluorescence spectroscopy.

We report the exploitation of spectroplasmonics for innovations in optical transducer development, specifically in the well-established application of labeled fluorescent analytes known as fluorescence spectroscopy. Presented herein are comprehensive analyses of nanoscale plasmonic lattice feature geometries using finite-difference time-domain software to determine the largest surface electric ($E$E) field enhancement resulting from localized surface plasmon resonance for reducing the limit of detection of plasmon-enhanced fluorescence. This parametric optimization of the critical dimensions of the plasmon resonance of noble metal nanostructures will enable improved excitation and emission enhancement of fluorophores used in visible wavelength fluorescence spectroscopy.

Programmable assembly of gold nanoparticle nanoclusters and lattices.

Deterministic assembly of metallic nanoparticles (e.g. gold nanoparticles) into prescribed configurations has promising applications in many fields such as biosensing and drug delivery. DNA-directed bottom-up assembly has demonstrated unparalleled capability to precisely organize metallic nanoparticles into assemblies of designer configurations. However, the fabrication of assemblies comprising delicate nanoparticle arrangements, especially across large dimensions (e.g. micron size), has remained challenging. In this report, we have designed DNA origami hexagon tiles that are capable of assembling into higher-order networks of honeycomb arrays or tubes with dimensions up to several microns. The versatile addressability of the unit tile enables precise and periodic positioning of nanoparticles onto these higher-order DNA origami frame structures. Overall, we have constructed a series of 9 gold nanoparticle architectures with programmable configurations ranging from nanometer-sized clusters to micrometer-sized lattices. We believe these architectures shall hold great application potential in numerous biomedical fields.

Supported AuCu Alloy Nanoparticles for the Preferential Oxidation of CO (CO-PROX)

The insertion of copper into the gold lattice forming gold-copper (AuCu) nanoalloys enhances the gold catalytic performance in reactions such as CO oxidation. Here, we compared the catalytic performance of 6 nm AuCu nanoparticles (NPs) supported on SiO2 (AuCu_SiO2), a non-reducible oxide, and CeO2 (AuCu_CeO2), a reducible one, under preferential oxidation of CO (CO-PROX). Under reaction conditions, the support nature impacted in the stabilization of different species on the catalyst surface. The AuCu_CeO2 was both more active and more stable, which was associated with the ability of CeO2 to stabilize the AuCu alloy phase under reaction conditions.

MEA Recordings and Cell-Substrate Investigations with Plasmonic and Transparent, Tunable Holey Gold.

Microelectrode arrays are widely used in different fields such as neurobiology or biomedicine to read out electrical signals from cells or biomolecules. One way to improve microelectrode applications is the development of novel electrode materials with enhanced or additional functionality. In this study, we fabricated macroelectrodes and microelectrode arrays containing gold penetrated by nanohole arrays as a conductive layer. We used this holey gold to optically excite surface plasmon polaritons, which lead to a strong increase in transparency, an effect that is further enhanced by the plasmon's interaction with cell culture medium. By varying the nanohole diameter in finite-difference time domain simulations, we demonstrate that the transmission can be increased to above 70% with its peak at a wavelength depending on the holey gold's lattice constant. Further, we demonstrate that the novel transparent microelectrode arrays are as suitable for recording cellular electrical activity as standard devices. Moreover, we prove using spectral measurements and finite-difference time domain simulations that plasmonically induced transmission peaks of holey gold red-shift upon sensing medium or cells in close vicinity (<30 nm) to the substrate. Thus, we establish plasmonic and transparent holey gold as a tunable material suitable for cellular electrical recordings and biosensing applications.

Double-Lattice Magnetoplasmonic Structures Based on BIG and Perforated Gold Films

A method of manufacturing double-lattice magnetoplasmonic crystals with the structure (Au/BIG)2, in which the plasmon gold lattices are displaced relative to each other by half a period, has been presented. Gold films with thicknesses of about 40 nm have been formed by the ion-beam sputtering–deposition method, while the adhesive properties of the films allow the dimensional etching by a sharp-focused ion beam. It has been shown that the formation of the second plasmon lattice located on top of the 100 nm thick garnet layer allows the preserving of the periodicity of the first Au lattice. However, there is a significant influence of diffusion spreading on the lower lattice material, which leads to a decrease in its density. The dependence of the intensity magnetooptical effect in the geometry on the transmission as a function of the thickness of the upper lattice and presence of an additional layer of Ta2O5 has been studied.

N1s narrow spectrum study in AuN thin films

3d and 4d transition metals has not been considered to produce nitrides. In the last years different paper has been shown with the synthesis and characterization of the AuN. Amount of nitrogen concentration into gold lattice is the discussion nowadays, because obtain of gold nitride phases would carry to find application to this material. In this work, gold thin films has been produced by varying the nitrogen concentration at discharge moment, because it is known that mean free path make that particles obtain different energies, leading to have different components in the surface of the thin film. N1s narrow spectrum shown gold nitride, oxynitride and carbonitride into gold surface.

Luminescence color alteration induced by trapped solvent molecules in crystals of tetrahedral gold(i) complexes: near-unity luminescence mixed with thermally activated delayed fluorescence and phosphorescence.

The tetrahedral gold(i) complex [Au(LtBu)2]Cl 1Cl [LtBu = 1,2-bis[bis(4-tert-butylphenyl)phosphino]benzene], having eight tert-butyl (tBu) groups, was synthesized and characterized. Emission color alteration caused by solvent molecules captured in the crystal lattice of 1Cl was investigated. The recrystallization of 1Cl in mixed solvents of tetrahydrofuran, THF, and various alkanes afforded two single crystals: 1Cl·THF (1BG), presenting intense blue-green luminescence with an emission peak wavelength, λmax, = 507 nm and 1Cl·THF·0.5n-hexane·H2O (1OR), exhibiting weak orange luminescence with λmax = 625 nm. The emission quantum yields, ΦPL, of the two complexes were 0.95 and 0.06, respectively. X-ray structural analysis revealed that all the solvent molecules captured in the crystal were located inside the spaces surrounded by the tBu groups of the 1+ cation. Further, an n-hexane molecule in 1OR was found to be sandwiched between two 1+ cations via CH/π interactions. The structure of 1Cl in 1OR could be distorted by the n-hexane molecule incorporated in the crystal, leading to the red-shift of the emission peak wavelength and the low quantum efficiency of 1OR over that of 1BG. On the other hand, [Au(L)2]Cl [L = 1,2-bis(diphenylphosphino)benzene], having no peripheral tBu groups, was unable to incorporate the solvent molecules in the crystal by recrystallization from the mixed solvents, and thus, the crystal solely yielded intense blue light emission. The results revealed that the tBu groups of the peripheral phenyl units are essential for the luminescence color alteration caused by the incorporation of organic solvent molecules into the crystal lattice. Finally, studies on the emission spectra and quantum yields in the temperature range 77-293 K revealed that luminescence from both 1BG and 1OR was composed of phosphorescence and thermally activated delayed fluorescence.

Synthesis and Properties of Nanoscale Bismuth-Iron Garnet Films for Magnetoplasmonic Heterostructures

A method for the synthesis of symmetric magnetoplasmonic crystals with the plasmonic lattice of gold inserted into a magnetic dielectric is proposed. The successive application of ion-beam sputter deposition, rapid annealing, milling with a focused ion beam, and ion etching are shown to allow the plasmonic lattice of gold to be encapsulated by a polycrystalline Bi3Fe5O12 layer. Diffusion spreading, evaporation, and granulation do not significantly influence the grid’s geometry. These magnetoplasmonic crystals can be used as magnetic-optical sensors and have a high mechanical resistance.

Effect of Core Morphology on the Structural Asymmetry of Alkanethiol Monolayer-Protected Gold Nanoparticles

Gold nanoparticles (GNPs) are versatile materials suitable for various biological applications due to their tunable surface properties, but structure–function relationships between specific GNP components and GNP behavior are largely lacking. In this work, atomistic molecular dynamics simulations were used to study the influence of gold core morphology, size, and ligand length on the structure of uniformly nonpolar alkanethiol monolayer-protected GNPs in water. By use of a generalized system preparation workflow, three gold core models were selected for this study: (1) a uniformly spherical hollow gold core, (2) a spherical gold core cut from a bulk gold lattice, and (3) a faceted gold core obtained from variance-constrained semigrand-canonical simulations. Independent of the gold core morphology, we found that long alkanethiol ligands exhibit increased ligand order and form quasi-crystalline domains, or bundles, in which ligands orient in the same direction, leading to asymmetric monolayer structures. Fa...