Au Clusters Research Articles

Fluorescent gold clusters for specific detection of SARS-CoV-2 nucleoprotein via fluorescence and electrochemical method

The promising fluorescent nature and functional properties of gold nanoclusters (AuNCs) enable their use as efficient sensor probes in various fields, particularly in healthcare diagnostics. Together with the effective fluorescence property, AuNCs also possess efficient electrocatalytic activity toward biosensing, thereby featuring the dual-functional (fluorescent and electrochemical) immunoprobe for sensing SARS-CoV-2 nucleoprotein. Density functional theory (DFT) calculations were carried out to assess the electronic structure arrangement of gold (III) chloride and bovine serum albumin (BSA) interactions with gold for efficient formation of Au clusters. Structural studies of coupled AuNCs show that antibodies with active sites for antigen binding are well conjugated on the surface of the gold nanoclusters. X-ray photoelectron and ultraviolet photoelectron spectral studies exhibited that the progression of the work function and ionization energy of nucleocapsid antibody conjugated AuNCs support antigen detection. The bio-affinitive nature of the AuNCs advances the mending of antibodies on their surface so as to increase the binding with epitopes of SARS-CoV-2 nucleoprotein. Antibody conjugated AuNCs based dual sensing system displayed an effective linear response with the lowest detection limit of about 20 pM and exhibited high responsiveness toward nucleoprotein detection. Thus, the dual practical sensing platform constructed from gold nanocluster-derived nanostructures offers new knowledge for additional examinations of COVID-19 detection.

Near-Neighbor Electron Orbital Coupling Effect of Single-Atomic-Layer Au Cluster Intercalated Bilayer 2H-TaS2 for Surface Enhanced Raman Scattering Sensing.

It is difficult to perfectly analyze the enhancement mechanism of two-dimensional (2D) materials and their combination with precious metals as surface enhanced Raman scattering (SERS) substrates using chemical enhancement mechanisms. Here, we propose a new mentality based on the coupling effect of neighboring electron orbitals to elucidate the electromagnetic field enhancement mechanism of single-atom-layer Au clusters embedded in double-layer 2H-TaS2 for SRES sensing. The insertion of Au atoms into the 2H-TaS2 interlayer was verified by XRD, AFM, and HRTEM, and a SERS signal enhancement of 2 orders of magnitude was obtained compared to the pure 2H-TaS2. XPS and micro-UV/vis-NIR spectra indicate that the outer electrons of neighboring Au and 2H-TaS2 overlap and migrate from Au to 2H-TaS2. First-principles calculations suggest strong electronic coupling between Au and 2H-TaS2. This study offers insights into SERS enhancement in nonprecious metal compounds and guides the development of new SERS substrates.

Improved Efficiency Droop of 370 nm UV LEDs with ITO/Au/ITO Structure

In this paper, a method of indium-tin oxide/Au/indium-tin oxide (IAI) structure as transparent conductive layers (TCLs) to improve the current spreading and suppress efficiency droop of ultraviolet light-emitting diodes (UV-LEDs) is investigated. The morphology and distribution of Au clusters formed by annealing are investigate by atomic force microscope and scanning electron microscope. Compared with the UV-LED without Au clusters, the forward voltage of UV-LED is reduced by 5.9% at 20 mA, light output power and wall plug efficiency increase by 64.2% and 84.2% at 300 mA for the UV-LED with IAI structure as the thickness of the Au interlayer is 1 nm. In addition, light emission distribution results show that by inserting Au interlayer, current distributes more uniform and the current spreading characteristics of UV-LED are improved. Ultimately, efficiency droop of the LED has been suppressed.

Atomic Precise Gold Nanoclusters: Toward the Customize Synthesis, Precision Medicine

AbstractWith the advantages of controllable atomic composition, unique molecular‐like properties, and excellent biocompatibility, atomic precision Au cluster is an ideal candidate for developing materials with customized biological functions to meet the needs of precision medicine. To achieve the rational design of functional materials through structural regulation at the atomic level, it is important to clarify the relationship between the structure and properties of Au clusters. With the development of synthesis methodology, a variety of structural regulation methods of Au clusters have been developed, providing new opportunities for structure–activity relationship establishment and precision medicine application. This review introduces the synthesis and structure regulation methods of atomic precision Au clusters, and the effects of structural regulation on the physicochemical properties are further described. At the same time, the applications of Au clusters in precision medicine, including the detection of biomolecules, functional imaging, and disease therapy are discussed, as well as the recent studies around their biosafety. At last, it also briefly summarizes the current problems and development directions. The present work provides potential theoretical guidance for the rational design of Au clusters with customized biological functions and is of great significance for broadening their applications in the field of precision medicine.

Interface-enhanced catalytic performance of TiO2-supported Cu and Au for dimethyl oxalate hydrogenation: A comparative microkinetic analysis

The electronic structures of Cu-TiO2 and Au-TiO2 and their catalytic behaviors in the hydrogenation of dimethyl oxalate (DMO) have been studied by the stochastic surface walking-global neural network potential method, density functional theory calculation, and microkinetic analysis. Calculated results indicate that metal clusters on the pristine and oxygen-deficient TiO2 are mostly coordinated to O2c ions, and the defective surface may provide additional oxygen vacancies for Cu6 and Au6 cluster anchoring. It turns out that the interfacial Ti5c and Cuδ+/Auδ- ions provide adsorption and hydrogenation sites for the reaction intermediates with unsaturated O and C atoms, respectively. The turnover frequency for DMO consumption is much higher on Cu-TiO2 than on Au-TiO2, Cu(111), and Cu(211) at 443.15 K and 20 bar of total pressure. Given the satisfactory methyl glycolate (MG) selectivity, the Cu-TiO2 catalyst has the potential to act as an excellent catalyst for the selective MG production.

A Biomimetic Nanoplatform with Improved Inflammatory Targeting Behavior for ROS Scavenging-Based Treatment of Ulcerative Colitis.

Ulcerative colitis (UC), a refractory disease, has become a global problem. Herein, a biomimetic nanoplatform (AU-LIP-CM) comprising Au cluster enzymes (AU)-loaded liposomes (AU-LIP) camouflaged with the fusion membrane (CM) consisting of neutrophil (NC) and red blood cell (RBC) membrane is designed for the treatment of UC. Briefly, revealed by second near-infrared (NIR-II) imaging through collection of fluorescence emitting >1200 nm from AU, the improved inflammatory targeting behavior contributed by CM cloaking, which inherits abilities of inflammatory targeting and immune escape from NC and RBC, respectively, promotes specific accumulation of AU within inflammatory intestines with up to ≈11.5 times higher than that of bare AU. Afterward, AU possessing superoxide dismutase- and catalase-like activities realizes high-efficiency scavenging of reactive oxygen species (ROS), leading to repair of intestinal barriers, regulation of the immune system, and modulation of gut microbiota, which surpass first-line UC drug. In addition, study of underlying therapeutic mechanism demonstrated that the treatment with AU-LIP-CM can alter the gene signature associated with response to ROS for UC mice to a profile similar to that of healthy mice, deciphering related signal pathways. The strategy developed here provides insights of learning from properties of natural bio-substances to empower biomimetic nanoplatform to confront diseases.

Hydride Locations and Planar σ‐Aromaticity in Hydrido‐Coinage‐Metal Clusters

AbstractThe atomic‐scale analysis of hydrides within metal clusters remains challenging due to the difficulties in performing spatially resolved characterization experiments. One important issue is understanding how hydrogens bond to metal atoms and their positions. The classification of hydride as either a ligand or doped metal is a difficult problem due to its different impacts on electronic structures of coinage metal (Cu, Ag, and Au) clusters. Here, geometric characteristics, stability and electronic properties of MnH (M=Cu, Ag and Au; n=2–9) clusters are investigated in detail. We find that structure transitions of CunH and AgnH occur at n=5, while all AunH are more inclined to planar configurations, where H atoms prefer to be located on the bridge positions of M−M regardless of different sizes and configurations. Among them, the planar M5H clusters have the same structural framework and higher stability than their neighbors. The AIMD simulations demonstrate that these three clusters still show excellent thermal stability at 700 K. The molecular orbitals and AdNDP analyses reveal that the M5H clusters exhibit three six‐center two‐electron σ bonds throughout whole structural spaces and conform to σ aromaticity rule, which are also further confirmed by the ELF, LOL and NICSzz‐scan analyses.

Controlled preparation of ordered dendritic nanoclusters at Au fractal biointerfaces

Owing to their ubiquitous use by natural systems, Au fractal structures by electrodeposition have been included in the design of new functional materials, yet a need exists for studying probe factors that influence the nature of materials produced in this process. In this investigation, we observe the presence of HCl results in a uniform structure of individual Au clusters. Also, the increase of deposition potential causes a decreasing size of Au cluster by accelerating the deposition process. Finally, as the deposition time becomes longer, significant increases occur in areas, densities, and fractal dimensions of individual Au clusters on the biointerface.

Designing of surface chemical enhanced Raman AgCu and AuCu clusters: Density functional theory

Designing of surface-enhanced Raman material with low cost and high enhancement ability become animportant research direction in the field of surface-enhanced Raman scattering. In this paper, the density functional theory calculations were utilized to investigated the Raman performances of stabled CuAg and CuAu clusters for 4-NBT probe molecule. Some suitable alloying designs in atomic level were found to reduce cost and enhance Raman signal of noble nanoparticles, such as, a small quantity introduction of Cu element into the tip of Ag nanoparticle surface and the core–shell structure. The designed Cu2Ag2, Cu1Ag12, Cu1Au12, Cu3Ag10, Cu3Au10, Cu14Ag9, Cu4Au9, Cu9Au4 and Cu10Au3 clusters exhibited enhanced Raman diffraction peak intensity beyond 11.0% compared to the 4-NBT molecule on the Ag4, Ag13 and Au13 clusters. This strategy could be applied to designing noble metal based surface-enhanced Raman materials with low cost and high enhancement ability by adjusting the atom site in atomic level.

Au Clusters Supported on Defect-Rich Ni-Ti Oxides Derived from Ultrafine Layered Double Hydroxides (LDHs) for CO Oxidation at Ambient Temperature

Ultrafine layered double hydroxides (LDHs) have abundant hydroxy groups at their edge sites, serving as anchor sites for metal NPs. Furthermore, transformation of ultrafine LDHs into mixed metal oxides (MMOs) generates abundant oxygen vacancies, which are advantageous for O2 activation during Au-catalyzed CO oxidation. We used ultrafine Ni-Ti LDHs with low crystallinity or Ni-Ti MMOs supported on SiO2 onto which Au NPs were deposited by deposition–precipitation (DP) and DP–urea (DPU). The catalytic activity of the Au catalysts was significantly affected by the preparation method, with the highest activity obtained by depositing Au onto LDH/SiO2 by DPU, followed by transformation of LDH to MMO (Au/Ni-Ti MMO/SiO2 (LDH-DPU)). The presence of Au on LDHs affected the transformation of LDHs into MMOs, resulting in LDH-DPU having the greatest number of oxygen vacancies in the TiO2 domain in MMOs. Consequently, the adsorbed or the lattice oxygen on the surface of LDH-DPU can be easily utilized for CO oxidation at low temperatures. Moreover, the catalytic activity of LDH-DPU increased with water vapor concentration up to 100% relative humidity at room temperature, suggesting the potential of Au/Ni-Ti MMO/SiO2 as an air purification catalyst.

Synthesis strategy of atomically dispersed Au clusters induced by NH3 on TS-1: Significantly improve the epoxidation activity of propylene

The epoxidation of propylene (C3H6) over TS-1 molecular sieve supported with nano-Au clusters by deposition–precipitation (DP) method has always been the focus of the catalytic field. A quantity of atomically dispersed Au clusters can be synthesized induced by NH3 as an assistant in the DP system. These smaller Au clusters show 14.3% C3H6 conversion, 91.7% propylene oxide (PO) selectivity, 10.6% H2 efficiency and 477.4 gPO·kgcat-1·h-1 PO productivity in the epoxidation reaction of C3H6. The interaction between NH3 and [AuCl4]- in aqueous solution is analyzed by means of experiments and Density Functional Theory (DFT), and it is concluded that at least 2 times of NH3 is needed to make Au precipitate completely. Similarly, the mechanism of C3H6 epoxidation catalyzed by Aun (n = 2, 3, 4) clusters in coordination with Ti sites is calculated with the help of DFT. It is believed that the in-situ formation of Ti-OOH structure at Ti sites through H2 and O2 is the key to initiate C3H6 epoxidation. The general rules of catalytic mechanism under different size of Au clusters are also analyzed.

Two-Step Electrochemical Au Nanoparticle Formation in Polyaniline.

In this work, we use a two-step cyclic electrochemical process to insert Au into polyaniline (PANI). It was suggested previously that this method would lead to the formation of atomic Au clusters with controlleds number of Au atoms without providing morphological proof. In each cycle, tetrachloroaurate anions (AuCl4-) are attached on the protonated imine sites of PANI, followed by a controlled reduction using cyclic voltammetry (CV). In contrast to previous work, we demonstrate that the reduction leads to the nucleation and growth of an Au nanoparticle (NP) whose density and size dispersion depend on the Au loading in PANI. Adding more deposition cycles increases the Au NP density and size. Transmission electron microscopy (TEM) and corresponding energy dispersive X-ray spectroscopy (EDS) indicate a homogeneous distribution of Au elements in the PANI matrix before CV reduction, while Au elements are aggregated and clearly localized in the NPs positions after CV reduction. We further use Rutherford backscattering spectrometry (RBS) to quantify the Au uptake in PANI. The Au distribution is verified to be initially homogeneous across the PANI layer whereas the increasing number of deposition cycles leads to a surface segregation of Au. We propose a two-step growth model based on our experimental results. Finally, we discuss the results with respect to the formation of atomic Au clusters reported previously using the same deposition method.

Electrochemical CO2 Reduction on Au Cluster-based Electrodes: Investigating the Role of Nafion Ionomer

The performance of electrocatalytic CO2 reduction (CO2RR) depends not only on the catalytic material but also on the neighbouring chemical environment around the active sites. The surrounding local environment can perturb the electronic properties of active sites and alter the adsorption/desorption behaviour of reactant/intermediate/product, thus changing CO2RR characteristics. Herein, we studied electrochemical reduction of CO2 onto supported atomically precise [Au9(PPh3)8](NO3)3 clusters and observed an unusual increase in catalytic activity over time. Additionally, electrochemical activation of the electrodes by applying a more negative potential was found to improve activity of the electrode. Investigations using UV–vis and X-ray absorption spectroscopy revealed that these observations may be attributed to the interaction of the Nafion ionomer with the catalytic Au9 clusters. These interactions may cause partial blocking of the Au9 active sites, and the prolonged application of negative potentials leads to favourable interface reconstructions. In addition, a method was developed to minimise the interaction between the Au9 clusters and Nafion ionomer by first depositing a layer of carbon black followed by dropcasting the active catalyst. Our study highlights that polymeric binders modulate the electronic properties of the electrocatalysts, which can change the product distribution during CO2 electrolysis.

Electron-rich Au nanocrystals/Co3O4 interface for enhanced electrochemical nitrate reduction into ammonia

Solar-driven electrochemical NO3– reduction reaction (NO3-RR) is a clean and sustainable strategy that can convert pollutant NO3– in wastewater to value-added NH3. In recent years, cobalt oxides-based catalysts have shown their intrinsic catalytic properties toward NO3-RR but still have room for improvement through catalyst design. Coupling metal oxides with noble metal has been demonstrated to improve electrochemical catalytic efficiency. Here, we use Au species to tune the surface structure of Co3O4 and improve the efficiency of NO3-RR to NH3. The obtained Au nanocrystals-Co3O4 catalyst exhibited an onset potential of 0.54 V vs RHE, NH3 yield rate of 27.86 µg/h·cm2, and Faradaic efficiency (FE) of 83.1% at 0.437 V vs RHE in an H-cell, which is much higher than Au small species (Au clusters or single atoms)-Co3O4 (15.12 µg/h·cm2) and pure Co3O4 (11.38 µg/h·cm2), respectively. Combined experiments with theory calculations, we attributed the enhanced performance of Au nanocrystals-Co3O4 to the reduced energy barrier of *NO hydrogenation to the *NHO and suppression of HER, which originated from the charge transfer from Au to Co3O4. Using an amorphous silicon triple-junction (a-Si TJ) as the solar cell and an anion exchange membrane electrolyzer (AME), an unassisted solar-driven NO3-RR to NH3 prototype was realized with a yield rate of 4.65 mg/h and FE of 92.1%.

Isomer-Selective Conversion of Au Clusters by Au(I) Thiolate Insertion

Isomer-selective conversion is a challenging goal in the rational design of Au clusters. Herein, we demonstrate the isomer-selective conversion of Au18(ScC6)14 (ScC6 = cyclohexanethiolate) into Au24(SR)x(ScC6)20-x in high yields by reactions with gold(I) thiolate (AuSR) complexes. Electrospray ionization mass spectrometry indicated that even numbers of AuSR units are inserted into Au18(SR)x(ScC6)14-x to generate Au24(SR)x(ScC6)20-x through intermediates Au20(SR)x(ScC6)16-x or Au22(SR)x(ScC6)18-x. These results suggest that the number of constituent atoms in surface Au(I)SR oligomers only increases, while the number of electrons in an Au core is maintained. UV-vis analysis revealed the generation of one of two Au24(SR)x(ScC6)20-x isomers in the reactions of Au18(ScC6)14 with AuSR complexes, in contrast to the formation of both isomers by reactions with thiols. When the structures of Au18(SR)14 are compared with those of the Au24(SR)20 isomers, the partial structure in the Au cores is preserved in the isomer-selective conversion with AuSR complexes, regardless of the structures of the thiolate moiety.

Revisiting the stable structures of gold clusters: Au n (n = 16–25) by artificial neural network potential

Identifying the stable structures of gold (Au) clusters is a huge challenge in cluster science. In this work, we have searched the ground-state structures of neutral Au n (n = 16–25) clusters using the potential of an artificial neural network (ANN) trained with density functional theory (DFT) data. Compared with the DFT data, the root mean square error of binding energy predicted by the ANN potential is about 8.66 meV/atom. Applying the ANN potential to search the ground-state structures by comprehensive genetic algorithm, we have found several new candidates of Au18, Au22, and Au23, which have not been previously reported. Au18 has a hollow cage structure, whereas Au22 and Au23 are flat cage structures. From the electronic analysis, we elucidate the stability mechanism of the newly found structures that are associated with the electronic shell closure of superatomic orbitals. Additonally, we also clarified how to clean a database to train an efficient ANN potential in detail. Overall, this work proves that applying machine learning to the description of atomic interactions can accelerate the search of ground-state structures of clusters and help to find new candidates for stable cluster structures.

Density Functional Theory Computation and Machine Learning Studies of Interaction between Au3 Clusters and 20 Natural Amino Acid Molecules.

The optimal adsorption sites and the binding energies of neutral Au3 clusters with 20 natural amino acids under the gas phase and water solvation were systematically investigated based on density functional theory (DFT) calculations. The calculation results showed that in the gas phase Au3 tends to bind with N atoms of amino groups in amino acids, except methionine, which tends to bind with Au3 through S atoms. Under water solvation, Au3 clusters tended to bind to N atoms of amino groups and N atoms of side chain amino groups in amino acids. However, methionine and cysteine bind more strongly to the gold atom through the S atom. Based on the binding energy data of Au3 clusters and 20 natural amino acids under water solvation calculated by DFT, a machine learning model (gradient boosted decision tree) was proposed to predict the optimal binding Gibbs free energy (ΔG) of the interaction between Au3 clusters and amino acids. The main factors affecting the strength of the interaction between Au3 and amino acids were uncovered by the feature importance analysis.

Mechanochemically activated Au/CeO2 for enhanced CO oxidation and COPrOx reaction

COPrOx reaction is one of the particularly appealing and cost-effective solutions for the selective oxidation of CO in hydrogen-rich gas streams to meet the stringent requirement of the current electrocatalysts employed in low-temperature fuel cells. Herein, we synthesized ultrasmall Au clusters supported on ceria by one-step solvent-free mechanochemical method. These catalysts exhibited higher activity for COPrOx and CO oxidation compared to the sample prepared by conventional incipient wetness impregnation. The unique Au-Ce interaction caused by impact and friction between the ball, vessel, and powders, greatly promotes the generation of positive charged Auδ+ active sites and, at the same time, the reducibility of the catalyst. Interestingly, an aging treatment of the ball-milled samples resulted in a significant superior performance of the catalytic activity. This enhancement has been attributed to a change in the oxidation state of Au between the fresh and the aged catalysts prepared by ball milling.

Unexpected Reactivity of Cationic-to-Cationic Thiolate Ligand-Exchange Reaction on Au25 Clusters.

Thiolate-protected molecular noble metal clusters have attracted significant attention due to their unique physicochemical properties, which make them applicable in diverse fields such as catalysis, sensing, and bioimaging. Ligand-exchange reactions are a crucial technique for synthesizing and functionalizing these clusters, as they allow for the introduction of new ligands onto the cluster surface, which can alter their properties. While numerous studies have investigated neutral-to-neutral, neutral-to-anionic, and neutral-to-cationic ligand-exchange reactions, the cationic-to-cationic ligand-exchange reaction has never been reported, making the study of such reactions intriguing. In this study, the cationic ligand-exchange reaction on Au25(4-PyET-CH3+)x(4-PyET)18-x (x ≈ 9) clusters, which contain both neutral and cationic ligands in nearly equivalent amounts, was investigated. Contrary to our expectation that the cationic-to-cationic ligand-exchange reaction would be suppressed due to Coulombic repulsion between the surface cationic ligands and incoming cationic ligands, the originally existing cationic ligand was selectively exchanged. The choice of counterions for cationic ligands played a crucial role in controlling the selectivity of ligand exchange. For instance, bulky and hydrophobic counterions such as PF6- can cause steric hindrance and reduce Coulombic repulsion, which promotes cationic-to-cationic ligand exchange. Conversely, counterions like Cl- can lead to neutral-to-cationic ligand exchange due to reduced steric hindrance and increased Coulombic repulsion between cationic ligands. These findings provide a novel method for tailoring the properties of molecular gold clusters through controlled ligand exchange without requiring the design of thiolate ligands with varying geometrical structures.

A Functionalized Heterogeneous Catalyst from Atomically Precise Pd1 Au8 Clusters Facilitates Carbon-Carbon Bond Construction.

It has become possible to establish a connection between homogeneous and heterogeneous catalysis with atomically precise metal clusters. Due to their defined coordination geometry, in this work, atomically precise Pd1 Au8 (PPh3 )8 2+ clusters are exploited to identify the crucial factor that can impact the catalytic efficiency for the Suzuki-Miyaura cross-coupling process and further gain valuable insight into the exclusive cooperative effect of the central Pd atom and the peripheral Au atoms of the Pd1 Au8 (PPh3 )8 2+ cluster on controlling the cross-coupling reaction. Specifically, a heterogeneous catalyst, namely Pd1 Au8 @Resin, is designed by exchanging positively charged Pd1 Au8 (PPh3 )8 2+ clusters into the porous resin, thereby not only facilitating catalyst recyclability when performed in a batch reactor, but also realizing time-on-stream performance for the Suzuki-Miyaura cross-coupling reaction carried out in a fixed-bed reactor. The integrated advantages of homogeneous complexes and heterogeneous catalysts are expected to advance the usability of atomically precise metal clusters as heterogeneous catalysts for important bond constructions in homogeneous systems.