Single Gold Atom Research Articles

Single active Au1O5 clusters for metabolism-inspired sepsis management through immune regulation

Artificial enzymes with reprogrammed and augmented catalytic activities hold significant potential in biomedicine. However, common issues with biocatalysts are the presence of numerous inactive site atoms, leading to inefficiencies in their catalytic processes. To leverage the full potential of active catalytic sites, we aim to minimize the biocatalyst structure, transitioning from nanoparticles or polymetallic atomic clusters down to singular-active-unit molecules. In this context, we have developed a unique single active-site cluster molecule, Au1-O5-Na9-(OH)4 (AuO) clusters, comprising a single gold atom, five oxygen atoms, and a protective layer, where Au-O acts as a singular-active site displaying elevated catalytic activities without inefficiencies associated with biocatalytic reactions. AuO clusters demonstrate activities reminiscent of nicotinamide adenine dinucleotide oxidase (NOX), glutathione peroxidase (GPx), and urease, among other oxidoreductase functions, through optimal utilization of atoms. Clusters are instrumental in enhancing the redox balance, mitigating inflammation, and averting inflammation-induced cellular apoptosis, thereby preserving immune balance in sepsis. These mechanisms are crucial in sepsis pathogenesis. Demonstrating GPx-like and NOX-like capabilities, the AuO clusters have shown remarkable effectiveness against lipopolysaccharide-induced and cecum ligation puncture-induced multiorgan damage, underscoring their substantial promise for sepsis management.

Enhanced photocatalytic CO2 reduction via single-atom Au anchored on ZnIn2S4 nanosheets

In this study, we systematically investigated the effect of single-atom gold (Au) loaded on ZnIn2S4 nanosheets on the photocatalytic reduction of carbon dioxide (CO2). Utilizing a photodeposition method, we successfully dispersed single-atom Au uniformly on the surface of ZnIn2S4 nanosheets. Under simulated sunlight irradiation, the Au-loaded catalyst demonstrated a higher yield and selectivity in the CO2 reduction reaction compared to the pure ZnIn2S4 nanosheets. Surface photovoltage testing revealed that the addition of Au significantly enhanced the separation efficiency of photo-generated charge carriers, thereby improving the photocatalytic efficiency. Density functional theory calculations indicated that the loading of single-atom Au reduced the reaction energy barrier from CO2 to CO, enhancing the selectivity of photocatalytic CO2 reduction. This research not only developed an efficient catalyst for CO2 reduction but also provided deep insights into the mechanism of single-atom catalysts in the photocatalytic CO2 reduction process through extensive experimental and theoretical analysis.

Engineering the Electronic Interaction Between Single Au Atoms and CoN Through Nitrogen‐Coordination Bonding as an Efficient Bifunctional Electrocatalyst for Rechargeable Zn–Air Batteries

AbstractSingle‐atom catalysts hold significance in the field of electrocatalysis. In this study, cobalt nitride (CoN), known for its semiconductor characteristics, is selected as the substrate, on which single gold (Au) atoms are loaded, to synthesize the catalyst Au SAC CoN@NF with Au single atoms anchored on CoN catalysts and grown on nickel foam. The introduction of single Au atoms results in an exceptional double‐layer capacitance (1425.7 mF cm−2), which offers immense possibilities for the applications of zinc–air batteries based on Au SAC CoN@NF. The zinc–air batteries demonstrated remarkable performance metrics, including a power density of 161.94 mW cm−2, a specific capacity of 813.80 mAh g−1, and a cycling stability of more than 260 h at 10 mA cm−2. In addition, these batteries show an outstanding round‐trip efficiency of 65.1%. Density functional theory calculations reveal that Au SAC CoN@NF can optimize the adsorption energies of intermediates for oxygen evolution reaction and promote single Au atoms in transporting electrons to the OH− species at an Au–N active site for oxygen reduction reaction. The proposed electronic metal‐support interaction strategy offers fresh insights for designing single‐atom catalysts to enhance electrocatalysis efficiency, thereby expanding the practical application prospects of zinc–air batteries.

On-Surface Synthesis of Non-Benzenoid Nanographenes Embedding Azulene and Stone-Wales Topologies.

The incorporation of non-benzenoid motifs in graphene nanostructures significantly impacts their properties, making them attractive for applications in carbon-based electronics. However, understanding how specific non-benzenoid structures influence their properties remains limited, and further investigations are needed to fully comprehend their implications. Here, we report an on-surface synthetic strategy toward fabricating non-benzenoid nanographenes containing different combinations of pentagonal and heptagonal rings. Their structure and electronic properties were investigated via scanning tunneling microscopy and spectroscopy, complemented by computational investigations. After thermal activation of the precursor P on the Au(111) surface, we detected two major nanographene products. Nanographene Aa-a embeds two azulene units formed through oxidative ring-closure of methyl substituents, while Aa-s contains one azulene unit and one Stone-Wales defect, formed by the combination of oxidative ring-closure and skeletal ring-rearrangement reactions. Aa-a exhibits an antiferromagnetic ground state with the highest magnetic exchange coupling reported up to date for a non-benzenoid containing nanographene, coexisting with side-products with closed shell configurations resulted from the combination of ring-closure and ring-rearragement reactions (Ba-a , Ba-s , Bs-a and Bs-s ). Our results provide insights into the single gold atom assisted synthesis of novel NGs containing non-benzenoid motifs and their tailored electronic/magnetic properties.

On‐Surface Synthesis of Non‐Benzenoid Nanographenes Embedding Azulene and Stone‐Wales Topologies

AbstractThe incorporation of non‐benzenoid motifs in graphene nanostructures significantly impacts their properties, making them attractive for applications in carbon‐based electronics. However, understanding how specific non‐benzenoid structures influence their properties remains limited, and further investigations are needed to fully comprehend their implications. Here, we report an on‐surface synthetic strategy toward fabricating non‐benzenoid nanographenes containing different combinations of pentagonal and heptagonal rings. Their structure and electronic properties were investigated via scanning tunneling microscopy and spectroscopy, complemented by computational investigations. After thermal activation of the precursor P on the Au(111) surface, we detected two major nanographene products. Nanographene Aa−a embeds two azulene units formed through oxidative ring‐closure of methyl substituents, while Aa−s contains one azulene unit and one Stone‐Wales defect, formed by the combination of oxidative ring‐closure and skeletal ring‐rearrangement reactions. Aa−a exhibits an antiferromagnetic ground state with the highest magnetic exchange coupling reported up to date for a non‐benzenoid containing nanographene, coexisting with side‐products with closed shell configurations resulted from the combination of ring‐closure and ring‐rearragement reactions (Ba−a, Ba−s, Bs‐a and Bs−s). Our results provide insights into the single gold atom assisted synthesis of novel NGs containing non‐benzenoid motifs and their tailored electronic/magnetic properties.

Dehydrogenative Coupling of Organosilanes with Alcohols by a Single-Atom Gold(I) Catalyst

Dehydrogenative Coupling of Organosilanes with Alcohols by a Single-Atom Gold(I) Catalyst

On-Surface Synthesis of a Radical 2D Supramolecular Organic Framework.

The design of supramolecular organic radical cages and frameworks is one of the main challenges in supramolecular chemistry. Their interesting material properties and wide applications make them very promising for (photo)redox catalysis, sensors, or host-guest spin-spin interactions. However, the high reactivity of radical organic systems makes the design of such supramolecular radical assemblies challenging. Here, we report the on-surface synthesis of a purely organic supramolecular radical framework on Au(111), by combining supramolecular and on-surface chemistry. We employ a tripodal precursor, functionalized with 7-azaindole groups that, catalyzed by a single gold atom on the surface, forms a radical molecular product constituted by a π-extended fluoradene-based radical core. The radical products self-assemble through hydrogen bonding, leading to extended 2D domains ordered in a Kagome-honeycomb lattice. This approach demonstrates the potential of on-surface synthesis for developing 2D supramolecular radical organic chemistry.

Experimental and theoretical evidence for unprecedented strong interactions of gold atoms with boron on boron/sulfur-doped carbon surfaces.

The 16e square-planar bis-thiolato-Au(iii) complexes [AuIII(1,2-dicarba-closo-dodecarborane-1,2-dithiolato)2][NBu4] (Au-1) and [AuIII(4-methyl-1,2-benzenedithiolato)2][NBu4] (Au-2) have been synthesized and fully characterized. Au-1 and Au-2 were encapsulated in the symmetrical triblock copolymer poloxamer (Pluronic®) P123 containing blocks of poly(ethylene oxide) and poly(propylene oxide), giving micelles AuMs-1 and AuMs-2. High electron flux in scanning transmission electron microscopy (STEM) was used to generate single gold atoms and gold nanocrystals on B/S-doped graphitic surfaces, or S-doped amorphous carbon surfaces from AuMs-1 and AuMs-2, respectively. Electron energy loss spectroscopy (EELS) data suggested strong interactions of gold atoms/nanocrystals with boron in the B/S-doped graphitic matrix. Density-functional theory (DFT) calculations, also supported the experimental findings, pointing towards strong Au-B bonds, depending on the charge on the Au-(B-graphene) fragment and the presence of further defects in the graphene lattice.

Synergistic sensitization effects of single-atom gold and cerium dopants on mesoporous SnO2 nanospheres for enhanced volatile sulfur compound sensing

A concept of synergistic sensitization effects involving single-atom Au and Ce dopants on mesoporous SnO2 nanospheres is proposed for ultrasensitive and real-time monitoring of ppb-level volatile sulfur compounds.

Linear-Structure Single-Atom Gold(I) Catalyst for Dehydrogenative Coupling of Organosilanes with Alcohols.

A strategy for the synthesis of a gold-based single-atom catalyst (SAC) via a one-step room temperature reduction of Au(III) salt and stabilization of Au(I) ions on nitrile-functionalized graphene (cyanographene; G-CN) is described. The graphene-supported G(CN)-Au catalyst exhibits a unique linear structure of the Au(I) active sites promoting a multistep mode of action in dehydrogenative coupling of organosilanes with alcohols under mild reaction conditions as proven by advanced XPS, XAFS, XANES, and EPR techniques along with DFT calculations. The linear structure being perfectly accessible toward the reactant molecules and the cyanographene-induced charge transfer resulting in the exclusive Au(I) valence state contribute to the superior efficiency of the emerging two-dimensional SAC. The developed G(CN)-Au SAC, despite its low metal loading (ca. 0.6 wt %), appear to be the most efficient catalyst for Si-H bond activation with a turnover frequency of up to 139,494 h-1 and high selectivities, significantly overcoming all reported homogeneous gold catalysts. Moreover, it can be easily prepared in a multigram batch scale, is recyclable, and works well toward more than 40 organosilanes. This work opens the door for applications of SACs with a linear structure of the active site for advanced catalytic applications.

Tip-activated single-atom catalysis: CO oxidation on Au adatom on oxidized rutile TiO2 surface.

Single-atom catalysis of carbon monoxide oxidation on metal-oxide surfaces is crucial for greenhouse recycling, automotive catalysis, and beyond, but reports of the atomic-scale mechanism are still scarce. Here, using scanning probe microscopy, we show that charging single gold atoms on oxidized rutile titanium dioxide surface, both positively and negatively, considerably promotes adsorption of carbon monoxide. No carbon monoxide adsorption is observed on neutral gold atoms. Two different carbon monoxide adsorption geometries on gold atoms are identified. We demonstrate full control over the redox state of adsorbed gold single atoms, carbon monoxide adsorption geometry, and carbon monoxide adsorption/desorption by the atomic force microscopy tip. On charged gold atoms, we activate Eley-Rideal oxidation reaction between carbon monoxide and a neighboring oxygen adatom by the tip. Our results provide unprecedented insights into carbon monoxide adsorption and suggest that the gold dual activity for carbon monoxide oxidation after electron or hole attachment is also the key ingredient in photocatalysis under realistic conditions.

Stability of Single Gold Atoms on Defective and Doped Diamond Surfaces.

Polycrystalline boron-doped diamond (BDD) is widely used as a working electrode material in electrochemistry, and its properties, such as its stability, make it an appealing support material for nanostructures in electrocatalytic applications. Recent experiments have shown that electrodeposition can lead to the creation of stable small nanoclusters and even single gold adatoms on the BDD surfaces. We investigate the adsorption energy and kinetic stability of single gold atoms adsorbed onto an atomistic model of BDD surfaces by using density functional theory. The surface model is constructed using hybrid quantum mechanics/molecular mechanics embedding techniques and is based on an oxygen-terminated diamond (110) surface. We use the hybrid quantum mechanics/molecular mechanics method to assess the ability of different density functional approximations to predict the adsorption structure, energy, and barrier for diffusion on pristine and defective surfaces. We find that surface defects (vacancies and surface dopants) strongly anchor adatoms on vacancy sites. We further investigated the thermal stability of gold adatoms, which reveals high barriers associated with lateral diffusion away from the vacancy site. The result provides an explanation for the high stability of experimentally imaged single gold adatoms on BDD and a starting point to investigate the early stages of nucleation during metal surface deposition.

Experimental and simulation studies of bioinspired Au-enhanced copper single atom catalysts towards real-time expeditious dopamine sensing on human neuronal cell

Single atom catalysts (SACs) becoming important participants in biosensing owing to their characteristics such as dispersed metal active sites, signal amplification, and acceptable sensitivity and selectivity toward distinct biomolecules. A recent advancement is the extension of SACs to form dual-metal single atom catalysts with high metal loading and flexible active sites, thus enhancing the electrochemical activity and biosensing ability. This study reports carbon-supported dual-metal single atoms, bioinspired from barnacle shell-extracted chitosan, for electrochemically detecting dopamine in real-time cellular environments and biofluids. Single copper and gold atoms anchored on bioinspired chitosan-extracted carbon (CuAu SACs/BC) based electrode was fabricated and used for the selective and sensitive detection of nanomolar dopamine in biological and cellular environments. Density functional theory calculations revealed that dopamine is predominantly sensed by single Cu atoms, together with the signal enhancement by single Au atoms. Collectively, the CuAu SACs/BC-based detection platform enabled real-time dopamine detection in neuronal cells upon triggering by a precursor with good biocompatibility and nanomolar sensitivity in male, female geriatric plasma. Thus, this study demonstrated the effective utilization of bioinspired carbon with dual-metal single atom catalysts to develop promising real-time electrochemical biosensors.

Unusual Scaffold Rearrangement in Polyaromatic Hydrocarbons Driven by Concerted Action of Single Gold Atoms on a Gold Surface

AbstractChemical transformation of polyaromatic hydrocarbon (PAH) molecules following different reaction strategies has always been the focus of organic synthesis. In this work, we report the synthesis of a PAH molecule, formation of which consists of an unusual C−C bond cleavage accompanied by a complex π‐conjugated molecular scaffold rearrangement. We demonstrate that the complex chemical transformation is steered by concerted motion of individual Au0 gold atoms on a supporting Au(111) surface. This observation underpins the importance of single‐atom catalysis mediated by adatoms in on‐surface synthesis as well as catalytic activity of single Au0 atoms facilitating cleavage of covalent carbon bonds.

Unusual Scaffold Rearrangement in Polyaromatic Hydrocarbons Driven by Concerted Action of Single Gold Atoms on a Gold Surface.

Chemical transformation of polyaromatic hydrocarbon (PAH) molecules following different reaction strategies has always been the focus of organic synthesis. In this work, we report the synthesis of a PAH molecule, formation of which consists of an unusual C-C bond cleavage accompanied by a complex π-conjugated molecular scaffold rearrangement. We demonstrate that the complex chemical transformation is steered by concerted motion of individual Au0 gold atoms on a supporting Au(111) surface. This observation underpins the importance of single-atom catalysis mediated by adatoms in on-surface synthesis as well as catalytic activity of single Au0 atoms facilitating cleavage of covalent carbon bonds.

Selective Activation of Aromatic C-H Bonds Catalyzed by Single Gold Atoms at Room Temperature.

Selective activation and controlled functionalization of C-H bonds in organic molecules is one of the most desirable processes in synthetic chemistry. Despite progress in heterogeneous catalysis using metal surfaces, this goal remains challenging due to the stability of C-H bonds and their ubiquity in precursor molecules, hampering regioselectivity. Here, we examine the interaction between 9,10-dicyanoanthracene (DCA) molecules and Au adatoms on a Ag(111) surface at room temperature (RT). Characterization via low-temperature scanning tunneling microscopy, spectroscopy, and noncontact atomic force microscopy, supported by theoretical calculations, revealed the formation of organometallic DCA-Au-DCA dimers, where C atoms at the ends of the anthracene moieties are bonded covalently to single Au atoms. The formation of this organometallic compound is initiated by a regioselective cleaving of C-H bonds at RT. Hybrid quantum mechanics/molecular mechanics calculations show that this regioselective C-H bond cleaving is enabled by an intermediate metal-organic complex which significantly reduces the dissociation barrier of a specific C-H bond. Harnessing the catalytic activity of single metal atoms, this regioselective on-surface C-H activation reaction at RT offers promising routes for future synthesis of functional organic and organometallic materials.

Discerning the Contributions of Gold Species in Butadiene Hydrogenation: From Single Atoms to Nanoparticles.

Identification of the roles of different active sites is vital for the rational design of catalysts. We present a cutting-edge strategy to discern the contributions of different single-atom gold species and nanoparticles in 1,3-butadiene hydrogenation, through coupling of advanced spectroscopic techniques, electron microscopy-based automated image analyses, and steady-state and kinetic studies. While all the carbon-hosted single gold atoms display negligible initial activity, the in situ-evolved gold nanoparticles are highly active. Full metal-species quantification is realized by combining electron-microscopy-based atom recognition statistics and deep-learning-driven nanoparticle segmentation algorithm, allowing the structure-activity correlations for the hybrid catalysts containing different Au architectures to be established. Surface exposure density of Au nanoparticles, as revealed by electron-microscopy-based statistics, is revealed as a new and reliable activity descriptor.

Discerning the Contributions of Gold Species in Butadiene Hydrogenation: From Single Atoms to Nanoparticles

AbstractIdentification of the roles of different active sites is vital for the rational design of catalysts. We present a cutting‐edge strategy to discern the contributions of different single‐atom gold species and nanoparticles in 1,3‐butadiene hydrogenation, through coupling of advanced spectroscopic techniques, electron microscopy‐based automated image analyses, and steady‐state and kinetic studies. While all the carbon‐hosted single gold atoms display negligible initial activity, the in situ‐evolved gold nanoparticles are highly active. Full metal‐species quantification is realized by combining electron‐microscopy‐based atom recognition statistics and deep‐learning‐driven nanoparticle segmentation algorithm, allowing the structure–activity correlations for the hybrid catalysts containing different Au architectures to be established. Surface exposure density of Au nanoparticles, as revealed by electron‐microscopy‐based statistics, is revealed as a new and reliable activity descriptor.

Single-atom gold species within zeolite for efficient hydroformylation

Various transition metals including Rh, Co, Ir, Ru, Os, Pt, Pd, Fe, and Ni have been proven to be efficient active centers for hydroformylation. Although Au is conventionally considered inactive for hydroformylation due to its intrinsic inertness, we design an atomically dispersed Au catalyst confined in zeolite with excellent activity and selectivity toward propene hydroformylation. The Au catalyst achieves 3,794 μmol of butyraldehyde and shows superior durability after 5 cycles, which is even comparable to Rh-based catalysts. Impregnating Au on the zeolite or increasing the mass loading of an encapsulated one will increase the size of active metal Au, which is unfavorable to hydroformylation. Detailed characterizations and theoretical calculations indicate that the isolated Au atoms within the zeolite matrix are stabilized via oxygen-bridge bonds. The formed Au1-O-SiOX motifs render maximum active site density and high structural stability, which are identified as the real active sites for efficient hydroformylation.

Elucidating Active CO–Au Species on Au/CeO2(111): A Combined Modulation Excitation DRIFTS and Density Functional Theory Study

In this work we elucidate the main steps of the CO oxidation mechanism over Au/CeO2(111), clarifying the course of CO adsorption at a broad variety of surface sites as well as of transmutations of one CO species into another. By combining transient spectroscopy with DFT calculations we provide new evidence that the active centers for CO conversion are single gold atoms. To gain insight into the reaction mechanism, we employ Modulation Excitation (ME) DRIFT spectroscopy in combination with the mathematical tool of Phase Sensitive Detection to identify the active species and perform DFT calculations to facilitate the assignments of the observed bands. The transient nature of the ME-DRIFTS method allows us to sort the observed species temporally, providing further mechanistic insight. Our study highlights the potential of combined transient spectroscopy and theoretical calculations (DFT) to clarify the role of adsorbates observed and to elucidate the reaction mechanism of CO oxidation over supported gold and other noble-metal catalysts.