Au Clusters Research Articles

Electron Injection via Interfacial Atomic Au Clusters Substantially Enhance the Visible‐Light‐Driven Photocatalytic H2 Production of the PF3T Enclosed TiO2 Nanocomposite

A hybrid composite of organic-inorganic semiconductor nanomaterials with atomic Au clusters at the interface decoration (denoted as PF3T@Au-TiO2 ) is developed for visible-light-driven H2 production via direct water splitting. With a strong electron coupling between the terthiophene groups, Au atoms and the oxygen atoms at the heterogeneous interface, significant electron injection from the PF3T to TiO2 occurs leading to a quantum leap in the H2 production yield (18578 µmol g-1 h-1 ) by ≈39% as compared to that of the composite without Au decoration (PF3T@TiO2 , 11321 µmol g-1 h-1 ). Compared to the pure PF3T, such a result is 43-fold improved and is the best performance among all the existing hybrid materials in similar configurations. With robust process control via industrially applicable methods, it is anticipated that the findings and proposed methodologies can accelerate the development of high-performance eco-friendly photocatalytic hydrogen production technologies.

The Molecular Mechanism of H2O2 Decomposition in a Reaction with an Au25(SCH3)12 Cluster

The reactions of neutral and anionic Au25(SCH3)12 clusters with one H2O2 molecule (mechanism I) and with its dimer (H2O2)2 (mechanism II) have been studied within the framework of the density functional theory (DFT). It has been established that all processes proceed with low activation barriers and a large gain in energy during the formation of products, and also that mechanisms I and II are interconnected. Based on the calculated data, the structure of gold clusters with the most probable active centers for further interaction with methane, which contain one or two O atoms, is proposed. In this case, clusters containing the O2 fragment can form not only in the reaction of the initial cluster Au25(SCH3)12 with hydrogen peroxide, but also with molecular oxygen, since the O2 adsorption energy is low and the process is close to equilibrium.

Non-linear optical behavior of gold and silver clusters adsorbed on 2,9-Dimethylquinacridone

In the present work, the adsorption of silver (Ag3) and gold (Au3) clusters on 2,9-Dimethylquinacridone (2,9-DMQA) was examined by using density functional theory. The variation of structural parameters was observed after the introduction of Ag3 and Au3 clusters. The interactions between the clusters and 2,9-DMQA induced variations in the structural parameters and electronic properties. The involvement of clusters in inducing the intramolecular charge transfer was confirmed by electrostatic potential surface and charge analysis. The electronic properties of the complex were studied by absorption and emission spectra. The adsorption of the Ag3 and Au3 clusters over the 2,9-DMQA leads to an enormous rise in the hyperpolarizability of the complexes. Thus, the Ag3 and Au3 clusters adsorbed 2,9-DMQA gave enhanced nonlinear optical activity.

Highly enhanced direct catalytic oxidation of cyclohexane to adipic acid with molecular oxygen: Dynamic collaboration between zeolite channel micro-environment and Au clusters

Adipic acid is a valuable chemical used to product Nylon-66, and one of the greenest ways to synthesize it is catalyzing the oxidation of cyclohexane by molecular oxygen in the absence of any other chemicals. However, it is challenging to convert cyclohexane effectively with high selectivity to adipic acid using the available catalysts. In response to the dilemma of achieving satisfactory conversion and selectivity at the same time, a remarkable Au@NaX catalyst is proposed using an improved in-situ crystallization method that exhibits Au clusters surrounded by X-zeolite channels. A 29.5% conversion of cyclohexane and an 85.6% selectivity to adipic acid can be obtained in a one-pot oxidation of cyclohexane at 140 °C, 20 bar O2, far exceeding most published results. Since determined by detailed characterizations and DFT calculations, the effective dynamic collaboration between Au clusters and zeolite inner micro-environment is the decisive role for superior catalytic performance. Specifically, the surrounding zeolite channel encourages the adsorption and activation of cyclohexane over the confined Au clusters, resulting in an unprecedented activity. The continuous oxidation of cyclohexanol and cyclohexanone to adipic acid is also vulnerable on the enclosed Au clusters, and the subsequent adipic acid can be further stabilized as a result of the strong interaction of –COOH with Na± in zeolite channels surrounding enclosed Au clusters. It prevents AA from poisoning active sites and generates a higher selectivity for the desired adipic acid. Our study highlighted the critical significance of the dynamic interaction between metal clusters and the zeolite channel microenvironment. It would shed light on the further high-performance catalysts designs for selective oxidation.

Shape-controlled preparation of nano gold (Au), Au clusters, and Au single atoms based on layered double hydroxide with closo-dodecaborate and their utilization for selective nitrobenzene reduction

Single-atom (SA) catalysts are superior in terms of catalytic activity, selectivity, and metal utilization. However, the complex preparation methods of SAs hinder their widespread application. Herein, layered double hydroxides (LDHs) with unique charge distributions were ingeniously combined with the dodecahydro-closo-dodecaborate anion [closo-B12H12]2−. We designed two different gold(Au) catalysts based on LDHs with closo-dodecaborate for the selective reduction of nitrobenzenes: composite dual-site Au SA/Au cluster catalysts (B12H12-MgAl-LDH-Au) were prepared using the anion exchangeability and spatial domain–limiting properties of LDH and the reducibility of [closo-B12H12]2−, and other Au nanoparticle catalysts (MgAl-LDH@B12H12@Au) were obtained using the reducibility of [closo-B12H12]2− immobilized on the LDH laminate. Up to 27 different nitrobenzene substrates can be selectively reduced to the corresponding azoxybenzenes (AOBs) with high efficiency at a wavelength of 450-nm radiation catalyzed by B12H12-MgAl-LDH-Au. However, large-size nanoparticles were more efficient in absorbing visible light energy. Therefore, 10 different AOB compounds were prepared using the MgAl-LDH@B12H12@Au system.

Super-Stretchable Resistive Strain Sensor Based on Ecoflex–Gold Nanocomposites

Superstretchable resistive strain sensors can reversibly undergo severe deformations in response to different mechanical stimuli, leading to a variation in their ohmic resistance. They are finding an increasing number of applications in wearable electronics, biomedical devices, and soft robotics. The development of fabrication process of reliable, highly sensitive, and biocompatible superstretchable strain sensors remains a challenge, especially in view of their integration with medical devices. Here, we demonstrate the fabrication of a high-strain resistive sensor based on Ecoflex elastomeric films and conductive Au clusters, obtained by supersonic cluster beam deposition. An extensive characterization of the electromechanical behavior of the sensor shows stable operation up to 4500 working cycles, with a maximum strain of 500% and a gauge factor of 124. Different mechanical stimuli, such as elongation and indentation, can be detected, and the easy coupling of the sensor with an inflatable balloon-type urinary catheter is demonstrated. Aiming at shedding light on the observed electromechanical mechanisms, the nanostructured morphology of the metal–polymer hybrid layer was investigated by low-vacuum scanning electron microscopy.

Highly Efficient Circularly Polarized Luminescence from Chiral Au13 Clusters Stabilized by Enantiopure Monodentate NHC Ligands.

Chiral Au nanoclusters have promising application prospects in chiral sensing, asymmetric catalysis, and chiroptics. However, enantiopure superatomic homogold clusters with crystallographic structures emitting bright circularly polarized luminescence (CPL) remain challenging. In this study, we designed chiral N-heterocyclic carbenes (NHCs), and for the first time enantioselectively synthesized a pair of monovalent cationic superatomic Au13 clusters. This new enantiomeric pair of clusters has a quasi-C2 symmetric core and exhibited CPL with an unprecedent solution-state quantum yield (QY) of 61 % among those of the atomically precise Au nanoclusters. DFT calculations provided insights into the circular dichroism behavior, and revealed the origin of CPL from superatomic Au clusters. This work opens a new avenue for developing novel homochiral nanoclusters using chiral NHC ligands and provides fundamental understanding of the origin of the chiroptics of metal clusters.

Highly Efficient Circularly Polarized Luminescence from Chiral Au13 Clusters Stabilized by Enantiopure Monodentate NHC Ligands

AbstractChiral Au nanoclusters have promising application prospects in chiral sensing, asymmetric catalysis, and chiroptics. However, enantiopure superatomic homogold clusters with crystallographic structures emitting bright circularly polarized luminescence (CPL) remain challenging. In this study, we designed chiral N‐heterocyclic carbenes (NHCs), and for the first time enantioselectively synthesized a pair of monovalent cationic superatomic Au13 clusters. This new enantiomeric pair of clusters has a quasi‐C2 symmetric core and exhibited CPL with an unprecedent solution‐state quantum yield (QY) of 61 % among those of the atomically precise Au nanoclusters. DFT calculations provided insights into the circular dichroism behavior, and revealed the origin of CPL from superatomic Au clusters. This work opens a new avenue for developing novel homochiral nanoclusters using chiral NHC ligands and provides fundamental understanding of the origin of the chiroptics of metal clusters.

Pterin interactions with gold clusters: A theoretical study

Gold (Au) nanoclusters (NCs) are novel materials with low cytotoxicity and high chemical stability. These properties are in high demand during the bioimaging. Moreover, the optical properties of gold clusters allow to use them as colorimetric and luminescent bionanosensors. Pterins are low molecular weight organic compounds, which are used in medicine as biomarkers of phenylketonuria, vitiligo, inflammation and immune system activation, cancer, COVID-19, etc. We have investigated the possibility of gold nanosensors usage to detect pterin (Ptr). Ptr-Aunq structures (n = 1–6; q = 0–2) Gibbs energy of complexation (Eb) have been obtained using density functional theory. The highest Eb was determined for the complexes of Au62+ and Au32+ in acidic and alkaline aqueous solution, respectively. The detection of pterin with gold clusters seems to be prospective using both colorimetric and fluorescent detection because of the intense S0→S1 transition in the absorption spectrum of the Au5+ complex. Raman detection of pterin should be performed at alkaline pH because of the dramatic changes in the spectrum of Ptr−1 upon the addition of Au clusters. We believe that these tunable changes of the pterin spectra due to Au clusters and nanoparticles attachment could be exploited in further studies on nanosensor design.

Au@MOFs used as peroxidase-like catalytic nanozyme for bacterial infected wound healing through bacterial membranes disruption and protein leakage promotion

Bacterial biofilms often hinder the healing of infected chronic wounds. Hence, it is significant to explore ways to destroy bacterial biofilms. In this work, a photothermal therapy strategy of designing Au clusters modified ZIF-8 MOFs (Au@ZIF-8) as peroxidase-like catalytic nanozyme was proposed for bacterial infected wound healing. Under near-infrared laser (NIR), the prepared Au@ZIF-8 present enhanced peroxidase-like activity and excellent photothermal response properties. Au@ZIF-8 achieved bacterial membrane disruption rate of 66.3% and MRSA clearance rate up to 97%. Au@ZIF-8 also catalyzed endogenous H2O2 to OH and achieved almost 97.4% healing rate in animal experiments. The prepared Au@ZIF-8 with peroxidase-like catalytic nanozyme properties has great potential in the treatment of infected diabetic wounds through bacterial membranes disruption and protein leakage promotion.

Planar σ-Aromaticity in Ga-Doped Au Clusters

Recently, the first example of Au-Ga clusters is synthesized and characterized, which can be described by the jellium model as a superatom with 8 valence electrons that come from the joint contribution of Au and Ga atoms, opening a whole new field for further research. Here, the structure features and stability of one Ga-doped Au cluster with magic number electrons (6 and 8) are analyzed in detail. Moreover, the valence electron fillings and chemical bonding of them are also further explored. It is found that Au3Ga and Au5Ga clusters present planar configurations, and they have higher stability than that of neighbor clusters. The AIMD simulations show that these two clusters still have a good thermal stability at 500 K. The molecular orbital analyses show that the Au3Ga and Au5Ga have three and one typical delocalization orbital throughout the whole planar spaces, respectively, following the planar σ-aromaticity rule. The ELF and LOL analyses are further performed, and the results are consistent with the molecular orbital analyses. The NICSzz-scan curves confirm that the Au3Ga is more aromatic than the Au5Ga, and the reason is that the former has more delocalized electrons than the latter. Our work opens up aromaticity studies in the Au-Ga clusters.

The effect of rutile TiO[formula omitted](110) surface on the physicochemical properties of subnanometer Au–Pd clusters: A DFT study

Bimetallic clusters are of particular interest in several applications due to the unique properties they exhibit as a result of the synergistic effect of their metals. In addition, the substrate can alter the structure and stability of these clusters by means of cluster–support interactions. In this work, we study the physicochemical properties of Au–Pd/TiO2(110) supported clusters via density functional theory (DFT) calculations. The effect of surface TiO2(110) on the structural and energetic properties of Au–Pd clusters is relevant. The cohesion energy depends on both metal–metal and metal–support interactions. Au and Au-rich bimetallic clusters change their gas phase configuration upon adsorption. Some clusters do not fit well on the surface, resulting in decreased stability. By contrast, pure Pd and Pd-rich bimetallic clusters have the highest adsorption energies and charge polarization due to the cluster–surface interaction. These clusters exhibit elongation in the metal–metal bonds and redshifts in their vibrations. The Bader charge analysis shows that Au–Pd clusters donate charge to the surface, thus becoming positively charged. Finally, the TiO2(110) surface induces stiffness in the clusters, since the supported clusters do not exhibit low-frequency vibrations like their gas-phase analogs.

Ultrasensitive detection and distinction of pollutants based on SERS assisted by machine learning algorithms

SERS as a promising sensing technique still faces challenges in the precise identification of trace-amount molecules due to the limitation of sensitivity and cleanliness of SERS substrate. Here, we report a precise and ultrasensitive identification of multiple pollutants via 3D clean cascade-enhanced nanosensor assisted by machine learning algorithms. This SERS substrate could achieve cascading electromagnetic energy with a remarkable enhancement factor as high as 8.35 × 109, which is attributed to the combination of micro-level polystyrene sphere (PS) porous array and nano-level Au-Ag clusters of this substrate. Benefitting from high cleanliness and ultra-sensitivity, multiple hazardous pollutants with similar geometry and Raman peaks at ultra-low concentration were successfully distinguished assisted by principal component analysis (PCA). As a result, this efficient and clean SERS substrate together with artificial intelligence could promote the application of SERS technology in the accurate identification of trace contaminants. Data AvailabilityData will be made available on request.

Advanced Catalyst for CO2 Photo-Reduction: From Controllable Product Selectivity by Architecture Engineering to Improving Charge Transfer Using Stabilized Au Clusters.

Despite enormous progress and improvement in photocatalytic CO2 reduction reaction (CO2 RR), the development of photocatalysts that suppress H2 evolution reaction (HER), during CO2 RR, remains still a challenge. Here, new insight is presented for controllable CO2 RR selectivity by tuning the architecture of the photocatalyst. Au/carbon nitride with planar structure (p Au/CN) showed high activity for HER with 87% selectivity. In contrast, the same composition with a yolk@shell structure (Y@S Au@CN) exhibited high selectivity of carbon products by suppressing the HER to 26% under visible light irradiation. Further improvement for CO2 RR activitywasachieved by a surface decoration of the yolk@shell structure with Au25 (PET)18 clusters as favorable electron acceptors, resulting in longer charge separation in Au@CN/Auc Y@S structure. Finally, by covering the structure with graphene layers, the designed catalyst maintained high photostability during light illumination and showed high photocatalytic efficiency. The optimized Au@CN/Auc /G Y@S structure displays high photocatalytic CO2 RR selectivity of 88%, where the CO and CH4 generations during 8h are 494 and 198µmol/gcat., respectively. This approach combining architecture engineering and composition modification provides a new strategy with improved activity and controllable selectivity toward targeting applications in energy conversion catalysis.

Structure and stability of Au, Au2 and Au8 cluster on Ni(111) supported h-BN sheet: Role of size and support towards oxygen bond activation

Atomic level heterogenous catalysis has been of importance for in-depth understanding and designing of novel catalytic material. Present work aims to investigate the chemical reactivity of Au, Au 2 and Au 8 cluster on hexagonal boron nitride nano sheet (h-BN) and its Ni(111) activated analogue using density functional theory (DFT). The average vertical separation of gold atom(s) from h-BN is significantly influenced by Ni(111) support. Oxygen molecule, which is the key reactant for any oxidation reaction, is considered as probe molecule to verify the reactivity. Contrary to the case of Au atom, which is the most reactive on free-standing h-BN, Au 2 and Au 8 clusters show higher reactivity on Ni supported h-BN. Thus the agglomeration of Au (Au–Au interaction) and Ni(111) support is important in controlling the reactivity and therefore, will play a key role to design Au based efficient catalyst for future. • On free-standing h-BNNS, Au atom and Au dimer favours on top B and N atoms, respectively. • With Ni (111) supported h-BNNS both Au and Au 2 favour on-top B atom. • On free-standing h-BNNS, Au elongates the O–O bond more than Au 2 and Au 8 . • On Ni (111) supported h-BNNS, the O–O bond elongation is maximum on Au 8 cluster. • The presence of Ni(111) support improves the catalytic activity by spin modulation of the B atoms of h-BNNS.

Dynamic catalysis of sub-nanometer metal clusters in oxygen dissociation

When the catalyst size decreases down to the nanometer or even sub-nanometer scale, their geometric and electronic structures are very different from the bulk materials. Especially, their structural dynamics can greatly affect catalytic performances. Herein, we report a theoretical study on oxygen dissociation on Ag19 cluster, a critical step of ethylene epoxidation, to investigate the effect of structural dynamics on the catalytic activity. Combining ab initio molecular dynamics (AIMD) and free energy calculation, we obtain the free energy profiles under different temperatures and find sudden drops in the reaction free energy and barrier at certain temperature ranges. The reaction entropy change shows a positive peak because of the different melting temperatures between initial and final states. Additionally, we further investigate the oxygen diffusion process on the Ag cluster and compare it with the Au and Cu clusters. We find that weak adsorption of oxygen on the silver cluster leads to its facile diffusion and thus reduces the melting temperature of the cluster, therefore facilitating partial oxidation under mild conditions.

Significantly reinforced thermoelectric performance in the novel 1T-Au6Se2 monolayer

Ultra-low lattice thermal conductivity has long been a requirement for the high thermoelectric properties of materials. In this work, the novel 1T-Au6Se2 monolayer was obtained by introducing Au6 clusters into the selenide monolayer, and its electrical and thermal transport characteristics are investigated using first-principles computations supplemented with semi-classical Boltzmann transport theory. The calculation shows that the 1T-Au6Se2 monolayer exhibits ultra-low lattice thermal conductivity and excellent thermoelectric properties owing to its low phonon frequency, group velocity, and extremely strong anharmonicity. Based on strain engineering from 0% to 2%, the lattice thermal conductivity further reduces by restricting the thermal transport on the premise of maintaining outstanding electrical transport properties in the p-type doped system. Thence, the value of ZT for the p-type system increases nearly by 70% compared with the non-stressed state at 700 K. Our investigation indicates the ultra-low thermal conductivity and high ZT of the 1T-Au6Se2 monolayer that might be prepared in the lab, providing new insights into enhancing the thermoelectric performance of the material in the future.

Gold cluster incorporated Rhenium disulfide: An efficient catalyst towards electrochemical and photoelectrochemical hydrogen evolution reaction

Rhenium disulfide (ReS2) is an emerging member of the transition metal dichalcogenide (TMD) family. It attracts recent research interest due to its tunable bandgap, weak interlayer coupling, and layer-independent optoelectronic properties. This work demonstrates a gold cluster incorporated ReS2 as a robust hydrogen evolution reaction (HER) catalyst. Au cluster is synthesized via the solid-state grinding method and mixed with ReS2 by mechanical mixing. The excellent catalytic activity of the ReS2-Au cluster is observed both in photoelectrochemical and electrochemical studies. Synergistic interaction between the Au cluster and ReS2 reinforces light absorption of the ReS2-Au cluster, especially within the visible region, and boosts the photoelectrochemical properties of the composite. The photoelectrochemical mechanism of the ReS2-Au cluster is investigated in detail using Mott-Schottky analysis. This work is anticipated to provide new insight into the photoelectrochemical properties of ReS2 and metal-cluster-sensitized TMD nanocomposites.

Partially Thiolated Au25 Cluster Anchored on Carbon Support via Noncovalent Ligand–Support Interactions: Active and Robust Catalyst for Aerobic Oxidation of Alcohols

Partially thiolated atomically precise Au cluster catalysts were developed by controlled calcination of presynthesized thiolate-protected Au clusters on a porous carbon support. X-ray absorption fine structure analysis, powder X-ray diffraction, and aberration-corrected high-angle annular dark field scanning transmission electron microscopy revealed that calcination of 1 wt % of Au25(SR)18 (RS = 2-phenylethanethiolate, 1-dodecanethiolate) on carbon at 450 °C for 8–12 h produced partially thiolated Au25 clusters Au25(SR)/C without sintering. The Au25(SR)/C catalyst exhibited comparable catalytic activity to that of the thiolate-free Au25 cluster Au25/C for benzyl alcohol oxidation, whereas Au25(SR)/C showed higher durability than Au25/C. These results suggested that the residual RS ligands were distributed at the interface between the clusters and the support and suppressed the diffusion of the clusters by multiple van der Waals interactions. Large kinetic isotope effects indicated that the hydride abstraction from the α-carbon of the alkoxide was the rate-determining step. The O2 pressure dependence on rate constants was comparable to that reported for negatively charged Au clusters stabilized by poly(N-vinyl-2-pyrrolidone). This comparison suggests that electron-rich Au atoms left behind by desorbed RS served as active sites, which was supported by density functional theory calculations on model clusters. The partially thiolated Au25 cluster catalysts oxidized various p-substituted benzyl alcohols and benzylic secondary alcohols, with turn-over numbers exceeding 1 × 104. This work demonstrates that partially ligated, atomically precise metal clusters anchored by noncovalent ligand–support interaction are promising model catalysts with both high activity and durability.

Gold Au(I)6 Clusters with Ligand‐Derived Atomic Steric Locking: Multifunctional Optoelectrical Properties and Quantum Coherence

AbstractAn atomically precise ultrasmall Au(I)6 nanocluster where the six gold atoms are complexed by three sterically interlocking stabilizing ligands is reported, allowing a unique combination of efficient third harmonic generation (THG), intense photoluminescence quantum yield (35%), ultrafast quantum coherence, and electron accepting properties. The reaction of 6‐(dibutylamino)‐1,3,5‐triazine‐2,4‐dithiol (TRZ) with HAuCl4 leads to complexation by thiolation. However, intriguingly, another reduction step is needed to form the centrosymmetric Au(I)6TRZ3 clusters with the multifunctional properties. Here, ascorbic acid is employed as a mild reducing agent, in contrast to the classic reducing agents, like NaBH4 and NaBH3CN, which often produce mixtures of clusters or gold nanoparticles. Such Au(I)6 nanocluster films produce very strong THG response, never observed for nanoclusters. The clusters also produce brilliant single and multiphoton luminescence with exceptional stability. Density functional theory calculations and femtosecond transient absorption studies suggest ultrafast ligand‐to‐metal charge transfer, quantum coherence with long decoherence time 200–300 fs, and fast propagation of excitation from the core to the surrounding solvent. Finally, novel electron‐accepting ground state properties allow p‐doping of 2D field‐effect transistor devices. Summarizing, the potential of ultrasmall sterically interlocked Au(I) clusters, i.e., complexes allowed by the new sequential reduction protocol, towards multifunctional devices, fast photoswitches, and quantum colloidal devices is shown.