Au Clusters Research Articles

Macroscopic Gold Cluster Helical Tendrils.

Handedness-controllable macroscopic helices are needed for understanding the chirality transfer through scales and design of high-performance devices. Bottom-up self-assembly rarely affords macroscopic helical superstructures because of accumulating disorder that is difficult to avoid during hierarchical self-assembly. Here, we demonstrate that tetragold Au4 clusters can assemble into macroscopic helices at the centimeter scale. Halogen-bond induces hierarchical self-assembly from nanotubes to aslant stacked nanotubes and finally to macrohelices. Sacrificial template synthesis via solvent-corrosion sufficiently removes the embedded 1,3,5-trifluoro-2,4,6-triiodobenzene to produce helical skeletons. Homochiral macroscopic tendrils are controllably synthesized by chiral halogen bonding donors, allowing high-fidelity chiral amplification. This work contributes to the development of macroscopic helical superstructures by hierarchical assembly.

Unraveling the Effects of Metal-Support Interaction on Nitrogen Reduction: A Theoretical Study in Au13/BiOCl.

Understanding the mechanism of the nitrogen reduction reaction (NRR) is essential for designing highly efficient catalysts. In this study, we investigated the effects of the metal-support interaction (MSI) on NRR using density functional theory. The simulations revealed that the MSI is weak in the Au13/BiOCl system, with charge accumulation and depletion primarily occurring within the Au13 cluster. By replacement of one Au atom with either a Ag or Pt atom, the MSI becomes stronger compared to that in the Au13/BiOCl system. The is because doping breaks the symmetry of the Au13 cluster, leading to charge accumulation and depletion at the interface. Specifically, this enhanced MSI reduces the energy barriers of the rate-determining step from 1.07 eV in the Au13/BiOCl system to 0.91 eV in Au12Ag/BiOCl and 0.87 eV in Au12Pt/BiOCl, respectively. Our study uncovers the critical role of MSI in the activity of NRR, providing theoretical insights for the development of highly efficient NRR catalysts.

Unlocking the Photoluminescence and Photostability of Au11 Clusters through Pt-Mediated Band-Gap Engineering.

Au nanoclusters often demonstrate useful optical properties such as visible/near-infrared photoluminescence, in addition to remarkable thermodynamic stability owing to their superatomic behavior. The smallest of the 8e- superatomic Au nanoclusters, Au11, has limited applications due to its lack of luminescence and relatively low stability. In this work, we investigate the introduction of a single Pt dopant to the center of a halide- and triphenylphosphine-ligated Au11 nanocluster, affording a cluster with a proposed molecular formula PtAu10(PPh3)7Br3. Electrochemical and spectroscopic analysis reveal an expansion of the HOMO-LUMO gap due to the Pt dopant, as well as relatively strong near-infrared (NIR) photoluminescence which is atypical for an M11 cluster (λmax = 700 nm, Φ = 1.88 %). The Pt dopant additionally boosted photostability; more than tenfold. Lastly, we demonstrate the application of the PtAu10 cluster's NIR photoluminescence in the detection of the nitroaromatic compound 2,4-dinitrotoluene, with a limit-of-detection of 9.52 μM (1.74 ppm). The notable ability of a single central Pt dopant to unlock photoluminescence in a non-luminescent nanocluster highlights the advantages of heterometal doping in the tuning of both the optical and thermodynamic properties of Au nanoclusters.

Photocatalytic Hydroxylation and Oxidative Coupling Reactions Mediated by Multinuclear Au(I) Supramolecular Clusters.

Polynuclear Au(I) cluster photocatalysts, known for their high activity and stability, hold substantial potential in organic synthetic chemistry. This study synthesized two Au(I) supramolecular cluster catalysts with different nuclearities: a tetranuclear cluster, C1 ([(dppmAu2)2L1] • PF6 -), and a hexadecanuclear cluster, C2 [(dppmAu2)6(Au4)(L1)4] • 4PF6 -, through a multicomponent stepwise self-assembly approach. Both cluster structures feature aurophilicity interaction motifs that endow them with exceptional photocatalytic performance, exhibiting optical band gaps of 2.27 eV and 2.41 eV, respectively. Upon photoexcitation, these clusters efficiently generate reactive oxygen species, significantly enhancing their photocatalytic efficacy for the oxidative hydroxylation of phenylboronic acids and oxidative coupling of benzylamines under mild conditions. Catalytic efficiencies exceeding 90 % were achieved. Turnover frequencies for C2 and C1 were measured at 52.045 h-1 and 6.030 h-1, respectively, representing the highest efficiencies reported for photocatalysts to date. Compared to C1, C2 exhibited superior photocatalytic activity, attributed to its higher photoelectric sensitivity and greater exposure of active metal sites. Using a combination of experimental data and density functional theory calculations, the plausible mechanisms were proposed for two photocatalytic reactions. This study demonstrates that the use of multicomponent cooperative self-assembly strategy to synthesize high-nuclearity Au(I) clusters offers innovative pathways for the development of efficient, green, light-driven organic synthesis.

Photocatalytic Hydroxylation and Oxidative Coupling Reactions Mediated by Multinuclear Au(I) Supramolecular Clusters

AbstractPolynuclear Au(I) cluster photocatalysts, known for their high activity and stability, hold substantial potential in organic synthetic chemistry. This study synthesized two Au(I) supramolecular cluster catalysts with different nuclearities: a tetranuclear cluster, C1 ([(dppmAu2)2L1] • PF6−), and a hexadecanuclear cluster, C2 [(dppmAu2)6(Au4)(L1)4] • 4PF6−, through a multicomponent stepwise self‐assembly approach. Both cluster structures feature aurophilicity interaction motifs that endow them with exceptional photocatalytic performance, exhibiting optical band gaps of 2.27 eV and 2.41 eV, respectively. Upon photoexcitation, these clusters efficiently generate reactive oxygen species, significantly enhancing their photocatalytic efficacy for the oxidative hydroxylation of phenylboronic acids and oxidative coupling of benzylamines under mild conditions. Catalytic efficiencies exceeding 90 % were achieved. Turnover frequencies for C2 and C1 were measured at 52.045 h−1 and 6.030 h−1, respectively, representing the highest efficiencies reported for photocatalysts to date. Compared to C1, C2 exhibited superior photocatalytic activity, attributed to its higher photoelectric sensitivity and greater exposure of active metal sites. Using a combination of experimental data and density functional theory calculations, the plausible mechanisms were proposed for two photocatalytic reactions. This study demonstrates that the use of multicomponent cooperative self‐assembly strategy to synthesize high‐nuclearity Au(I) clusters offers innovative pathways for the development of efficient, green, light‐driven organic synthesis.

Strong Metal-Support Interaction Facilitates the Separation of Electron-Hole Pairs at Au13/BiOCl Interface: Insight from Quantum Dynamics.

Focusing on Au13/BiOCl, we investigated the effects of the metal-support interaction (MSI) on the photogenerated charge carrier separation using nonadiabatic molecular dynamic simulations combined with time-domain density functional theory. Our results show that the time scales of electron transfer from the Au13 cluster to BiOCl are distinct depending on the intensity of MSI. Oxygen vacancy (OV) can enhance the interaction between the Au13 cluster and BiOCl, leading to a stronger nonadiabatic (NA) coupling in Au13/BiOCl with an OV system compared to that in a pristine Au13/BiOCl system. The time scale of electron transfer in Au13/BiOCl with the OV system is reduced by a factor of 1.65 compared to that of the pristine Au13/BiOCl system. Our study suggests that the electron transfer can be facilitated by enhancing the MSI and provides valuable principles for the design of high-performance photocatalysts.

Fusion features of monocomponent parts in Janus-like nanoscale clusters under impacts of low- and ultra-low-energy Ar13 and Ar projectiles

ABSTRACT Molecular dynamics simulation of metastable Janus-like Ni–Al, Cu–Bi, and Cu–Au clusters with 195 atoms of each component is performed for 200 ps after impacts of Ar13 and Ar ions with different cases of initial energies from 25 to 300 eV. The boiling state of the components is achieved either at a high negative heat of mixing (Al, Ni–Al) or at a low boiling point of at least one of the components (Bi, Cu–Bi), provided that the Ar13 projectiles have the initial energy from 200 eV. In other cases, the Ni–Al cluster is also in a molten state, while the Cu–Bi cluster, as well as the Cu–Au cluster in all impact cases, may be in a molten state or have an atomic structure of varying degrees of the regularity of one/both component(s). The molten clusters form spatial core–shell distributions of the components, while in other cases different degrees and forms of their overlapping and eccentricity are possible during the time of simulation.

Surmounting the instability of atomically precise metal nanoclusters towards boosted photoredox organic transformation.

Atomically precise metal nanoclusters (NCs) have recently been recognized as an emerging sector of metal nanomaterials but suffer from light-induced poor stability, giving rise to the detrimental self-transformation into metal nanocrystals (NYs), losing the photosensitization effect and ultimately retarding their widespread applications in photoredox catalysis. Are metal NCs definitely superior to metal NYs in heterogeneous photocatalysis in terms of structural merits? To unlock this mystery, herein, we conceptually demonstrate how to rationally manipulate the instability of metal NCs to construct high-efficiency artificial photosystems and examine how the metal NYs self-transformed from metal NCs influence charge transfer in photoredox selective organic transformation. To our surprise, the results indicate that the Schottky-type electron-trapping ability of Au NYs surpasses the photosensitization effect of glutathione (GSH)-protected Au clusters [Au25(GSH)18 NCs] in mediating charge separation and enhancing photoactivities towards selective photoreduction of aromatic nitro compounds to amino derivatives and photocatalytic oxidation of aromatic alcohols to aldehydes under visible light irradiation. This work strategically provides new insights into the inherent instability of metal NCs utilized for photocatalysis and reinforces our fundamental understanding on metal NC-based artificial photosystems for solar energy conversion.

Heterogeneous Catalysis of Molecular‐Like Au8M(PPh3)8n+ Clusters Cultivated in Mesoporous SBA‐15

AbstractIt is a dream of researchers to be able to tailor the catalytic performances by adjusting heterogeneous catalysts at the atomic level. Atomically precise metal clusters provide us with the possibility to achieve this challenge. Here, we design a push‐and‐pull synthesis strategy coupled with TiOx coating to prepare the heterogeneous catalysts denoted as TiOx/Au8M@SBA via cultivating atomically precise Au8M(PPh3)8n+ (M=Pd, Pt or Au; n=2 for Pd/Pt and 3 for Au) clusters in mesoporous molecular sieve. The catalysts are made up of the three functional units, which include Au8M(PPh3)8n+ clusters that can act as the active sites, the pore environment of the SBA‐15 that can announce a catalysis show for the clusters with precise number of atoms maintained during the chemical reactions, and the TiOx coating that can further inhibit the migration of the clusters under reaction conditions. The selective hydrogenation of acetylene performed in the fixed‐bed reactor taken, for example, we learn how the atom‐by‐atom tailoring of a heterogeneous catalyst can switch on elusive heterogeneous mechanisms with cluster catalysis. This work sheds light on the fundamental insight into catalysis origin of heterogeneous catalysts and achieves a distinguished level of detail for cluster catalysis.

Heterogeneous Catalysis of Molecular-Like Au8M(PPh3)8 n+ Clusters Cultivated in Mesoporous SBA-15.

It is a dream of researchers to be able to tailor the catalytic performances by adjusting heterogeneous catalysts at the atomic level. Atomically precise metal clusters provide us with the possibility to achieve this challenge. Here, we design a push-and-pull synthesis strategy coupled with TiOx coating to prepare the heterogeneous catalysts denoted as TiOx/Au8M@SBA via cultivating atomically precise Au8M(PPh3)8 n+ (M=Pd, Pt or Au; n=2 for Pd/Pt and 3 for Au) clusters in mesoporous molecular sieve. The catalysts are made up of the three functional units, which include Au8M(PPh3)8 n+ clusters that can act as the active sites, the pore environment of the SBA-15 that can announce a catalysis show for the clusters with precise number of atoms maintained during the chemical reactions, and the TiOx coating that can further inhibit the migration of the clusters under reaction conditions. The selective hydrogenation of acetylene performed in the fixed-bed reactor taken, for example, we learn how the atom-by-atom tailoring of a heterogeneous catalyst can switch on elusive heterogeneous mechanisms with cluster catalysis. This work sheds light on the fundamental insight into catalysis origin of heterogeneous catalysts and achieves a distinguished level of detail for cluster catalysis.

Search for Thiol‐Protected Gold Clusters Doped with Different Elements Using Dendrimers

AbstractThe synthesis of thiol‐protected Au clusters MAu24(SR)18 containing different elements (M: different element, SR: thiol ligand) generally requires various steps. Therefore, the finding of a new MAu24(SR)18 cluster is not easy though it is necessary to take a great deal of effort to consider the synthesis. In this study, MAu24(SR)18 is searched for and attempted cluster synthesis using a dendrimer‐template method. It is also found that this method may be useful for exploring and discovering new clusters.

Enhancement of Selective Catalytic Oxidation of Lignin β-O-4 Bond via Orbital Modulation and Surface Lattice Reconstruction.

The orbital modulation and surface lattice reconstruction represent an effective strategy to regulate the interaction between catalyst interface sites and intermediates, thereby enhancing catalytic activity and selectivity. In this study, the crystal surface of Au-K/CeO2 catalyst can undergo reversible transformation by tuning the coordination environment of Ce, which enables the activation of the Cβ-H bond and the oxidative cleavage of the Cβ-O and Cα-Cβ bonds, leading to the cleavage of 2-phenoxy-1-phenylethanol. The t2g orbitals of Au 5d hybridize with the 2p orbitals of lattice oxygen in CeO2 via π-coordination, modulating the coordination environment of Ce 4 f and reconstructing the lattice oxygen in the CeO2 framework, as well as increasing the oxygen vacancies. The interface sites formed by the synergy between Au clusters in the reconstructed Ce-OL1-Au structure and doped K play dual roles. On the one hand, it activates the Cβ-H bond, facilitating the enolization of the pre-oxidized 2-phenoxy-1-phenylethanone. On the other hand, through single-electron transfer involving Ce3+ 4f1 and the adsorption by oxygen vacancies, it enhances the oxidative cleavage of the Cβ-O and Cα-Cβ bonds. This study elucidates the complex mechanistic roles of the structure and properties of Au-K/CeO2 catalyst in the selective catalytic oxidation of lignin β-O-4 bond.

Preparation and Catalytic Properties of Gold Single-Atom and Cluster Catalysts Utilizing Nanoparticulate Mg-Al Layered Double Hydroxides.

Au single atoms and clusters were stabilized on Mg-Al layered double hydroxide nanoparticles (LDH NPs), and the obtained Au@LDH NPs were supported on SiO2 and CeO2. After hydrogen reduction, Au single atoms were found together with Au clusters on LDH/SiO2. In contrast to Au single-atom catalysts which are deposited in metal vacancies of oxide supports, the LDH NPs stabilize very small Au species despite the absence of metal vacancies. The obtained Au(0)@LDH/SiO2 catalyzed aerobic oxidation of alcohols, and Au single atoms maintained after the reaction. Given that only Au NPs were observed on bulk LDH, the abundant surface OH group of LDH NPs would contribute to stabilize Au, resulting in higher activity than Au/LDH-bulk. After calcination to transform LDH to mixed metal oxide (MMO), the obtained Au(0)@MMO/SiO2 also exhibited high catalytic activity. Moreover, Au(0)@LDH/CeO2 exhibited higher activity and excellent selectivity for hydrogenation of 4-nitrostyrene to 4-aminostyrene than conventional Au catalysts such as Au/CeO2 and Au/TiO2. We demonstrated that Au size can be minimized using LDH NPs, exhibiting high catalytic performance. The basic surface OH groups of LDH would be also beneficial for deprotonation of alcohols and heterolytic dissociation of H2 in the catalytic reactions.

Investigation of the adsorption behaviors of novel Au3 cluster decorated arsenene nanosheets towards thiophene and methanethiol detection: A DFT study

Investigation of the adsorption behaviors of novel Au3 cluster decorated arsenene nanosheets towards thiophene and methanethiol detection: A DFT study

Revisiting the global minimum of Au10 clusters.

This study employs high-level quantum chemical calculations to determine the global minimum structure of Au10 clusters definitively. Contrary to previous reports, coupled-cluster singles and doubles with perturbative triples [CCSD(T)] calculations with sizable quadruple-ζ basis sets incorporating the spin-orbit (SO) effect reveal that the planar 10.b structure is the true global minimum for Au10, not the three-dimensional 10.a structure. Two-component spin-orbit density functional theory calculations demonstrate that the SO effect is minimal for most Au10 isomers, except for the 10.f structure. A straightforward diagnostic tool is proposed for identifying Au cluster structures with strong spin-orbit coupling based on 6p orbital occupation. The calculated IR spectra based on Boltzmann averaging the six Au10 isomers show good agreement with recent experimental spectra although minor discrepancies are noted potentially due to interactions with Kr. The results suggest that the transition point to non-planar global minimum structures for Au clusters lies beyond Au10 but is nearby.

Unraveling the Synergy of Au and Polar MgO(111) Surface in Photothermal Catalytic Oxidative Coupling of Methane

AbstractDirect and selective catalytic oxidative coupling of methane (OCM) into high‐carbon products is a great challenge in C1 chemistry. Herein, the successful fabrication of a series of Au clusters loaded on different MgO facets of (111), (110), and (100) is reported. This work demonstrates the Au‐loaded MgO(111) (denoted as Au/MgO(111)) shows the highest C2H6 yield of 12733.4 µmol g−1 h−1 and selectivity of 90.4%, which is 2.46 times higher than that of Au/MgO(110) (5171.4 µmol g−1 h−1) and 25.14 times higher than that of Au/MgO(100) (506.4 µmol g−1 h−1). Moreover, the high activity of Au/MgO(111) can be well maintained over 100 h. Detailed in situ experiments and theoretical calculation reveal such great performance can be attributed to 1) the strong electronic affinity of the surface oxygen species on polar MgO(111) and CH4with the lowest adsorption energy of −0.82 eV; 2) the Au/MgO(111) shows the lowest ΔERDS of 0.53 eV in the rate‐deterime step of OCM that comes in activating the second CH4 molecule; 3) the Au can act as a hole acceptor under light irradiation and adsorb *CH3 with a strong d‐σ hybridization, resulting in an increased C2H6 selectivity.

Enhanced performance of a promising Au/TMDC heterostructure composed of MoTe2 nanosheets decorated with Au5 clusters: A DFT study

Enhanced performance of a promising Au/TMDC heterostructure composed of MoTe2 nanosheets decorated with Au5 clusters: A DFT study

DFT study of the structures and electronic properties of Au cluster– and Pt cluster–functionalized BC3 nanosheets and their effects on sensing and adsorption of volatile organic compounds

DFT study of the structures and electronic properties of Au cluster– and Pt cluster–functionalized BC3 nanosheets and their effects on sensing and adsorption of volatile organic compounds

Resistance of a PdAu12(8e) Core to Growth in Collision-Induced Sequential Reductive Elimination of (C≡CR)2 from [PdAu24(C≡CR)18]2.

Previous studies have reported that [PdAu24(PAF)18]2- (PAF = 3,5-(CF3)2C6H3C≡C) with an icosahedral superatomic PdAu12(8e) core underwent collision-induced sequential reductive elimination (CISRE) of 1,3-diyne (PAF)2 ( J. Phys. Chem. C 2020, 124, 19119). The most likely scenario after the CISRE of (PAF)2 is the growth of the PdAu12(8e) core via the fusion of the Au(0) atoms produced from the Au2(PAF)3 units on the core surface. Contrary to expectation, anion photoelectron spectroscopy and theoretical calculations regarding the CISRE products [PdAu24(PAF)18-2n]2- (n = 1-6) revealed that the electronically closed PdAu12(8e) core does not grow to a single superatom with (8 + 2n)e but assembles with Au2(2e) units. Characterization of the CISRE products of other alkynyl-protected Au clusters suggested that even the non-superatomic Au17(8e) core was resistant to growth due probably to rigidification by PA ligands. We propose that there is a kinetic bottleneck in the growth process of protected Au clusters at the stage where they are electronically closed and/or lose their structural fluxionality by ligation.

C60 Fullerene-Induced Reduction of Metal Ions: Synthesis of C60-Metal Cluster Heterostructures with High Electrocatalytic Hydrogen-Evolution Performance.

Metal clusters, due to their small dimensions, contain a high proportion of surface atoms, thus possessing a significantly improved catalytic activity compared with their bulk counterparts and nanoparticles. Defective and modified carbon supports are effective in stabilizing metal clusters, however, the synthesis of isolated metal clusters still requires multiple steps and harsh conditions. Herein, we develop a C60 fullerene-driven spontaneous metal deposition process, where C60 serves as both a reductant and an anchor, to achieve uniform metal (Rh, Ir, Pt, Pd, Au and Ru) clusters without the need for any defects or functional groups on C60. Density functional theory calculations reveal that C60 possesses multiple strong metal adsorption sites, which favors stable and uniform deposition of metal atoms. In addition, owing to the electron-withdrawing properties of C60, the electronic structures of metal clusters are effectively regulated, not only optimizing the adsorption behavior of reaction intermediates but also accelerating the kinetics of hydrogen evolution reaction. The synthesized Ru/C60-300 exhibits remarkable performance for hydrogen evolution in an alkaline condition. This study demonstrates a facile and efficient method for synthesizing effective fullerene-supported metal cluster catalysts without any pretreatment and additional reducing agent.