Ligand effect on switching the rate-determining step of water oxidation in atomically precise metal nanoclusters

A chloride-doped Cu18 nanocluster: synthesis, bonding and nonlinear optical properties

Atomically precise copper nanoclusters have emerged as an essential class of materials that have found applications in a wide range of fields. However, the design and development of copper cluster nanomaterials are still in their embryonic stages, with most of the focus being on those containing hydride atoms. In this report, we present the discovery of a copper nanocluster doped with other non-metallic atoms, which represents a new and promising type of material. A novel chloride-doped Cu18 cluster, with the chemical composition of [ClCu18(PET)16(PPh3)4]+ (PET is 2-phenylethanethiol), was synthesized using a one-pot process. The molecular structure of the cluster, as determined by single-crystal X-ray diffraction analysis, reveals the stabilization of the ClCu6 kernel by a Cu12 cage, which is further passivated by thiolate and phosphine ligands. The cluster exhibits typical optical limiting effects, suggesting that copper nanoclusters doped with non-metallic atoms are a new family of advanced materials in the field of nonlinear optics.

Cyclodextrin-Assisted l-Cysteine-Capped Copper Nanoclusters: Rapid Synthesis, Enhanced Photoluminescence, and Small Molecule Interactions in Complex Biological Matrices

The rapid synthesis of stable copper nanoclusters has long been challenging. To address this, here we report the synthesis of cysteine-capped copper nanoclusters (Cys-Cu NCs) in just 30 min under ambient aqueous conditions. The incorporation of γ-cyclodextrin (γ-CD) enhanced the stability and immediately amplified the photoluminescence of the nanoclusters by triggering aggregation-induced emission (AIE), increasing their quantum yield from 0.15 to 0.24. The remarkable photoluminescence of γ-CD-assisted Cys-Cu NCs (γ-CD-Cys-Cu NCs) was selectively quenched by protoporphyrin IX (PPIX), enabling ultrasensitive detection with an exceptionally low limit of 70 pM. Stern-Volmer analysis revealed the underlying interaction mechanisms between γ-CD-Cys-Cu NCs and PPIX. This precise detection of PPIX is critical for diagnosing and monitoring porphyrias and other heme-related disorders. The method demonstrated excellent PPIX recovery in complex biological matrices, such as human serum and artificial urine, across a broad PPIX concentration range (0.5-10 µM), highlighting its applicability in real-world systems. Additionally, the nanoclusters exhibited strong sensitivity to reactive oxygen species (ROS), underscoring their potential for oxidative stress monitoring. These findings position γ-CD-Cys-Cu NCs as a versatile, cost-effective, diagnostic tool for clinical and biomedical applications.

Recent progress in the electrocatalytic applications of thiolate-protected metal nanoclusters

Ultrasmall metal nanoclusters (NCs) with atomic precision possess a size range between individual atoms and plasmonic nanomaterials. These atomically precise materials represent an emerging class of nanocatalysts, offering unique opportunities to explore electrocatalytic properties and establish precise structure-property correlations at the atomic scale. Among the large number of metal NCs that are stabilized by various ligands, thiolate-protected metal NCs are a particularly prominent class for electrocatalytic investigations. Recent experimental and theoretical studies have demonstrated the significant potential of these materials in enhancing various electrocatalytic reactions, including hydrogen evolution, oxygen reduction and CO2 reduction reactions. However, comprehensive and in-depth discussions regarding their catalytic properties, particularly from a theoretical standpoint, are limited and require further explorations. In this review, we focus on the recent progress in thiolate-protected metal NCs in the field of electrocatalysis. The influences of structure, ligand, doping and interface control on their electrocatalytic activity/selectivity and the reaction mechanisms are discussed. Importantly, the perspectives we propose regarding future research endeavors are expected to offer valuable references for subsequent investigations in this area.

Efficient Electrocatalytic Semi-Hydrogenation of Alkynes by Interfacial Engineering of Atomically Precise Silver Nanoclusters

Owing to its green energy and hydrogen sources, electrocatalytic semi-hydrogenation of alkynes is an attractive alternative for industrial alkene production. However, its broad application is hindered by low selectivity and low Faradaic efficiency (FE) due to side reactions like over-hydrogenation to alkanes. Here, we demonstrate that atomically precise Ag25(MHA)18 nanoclusters (NCs) can electrocatalyze alkyne semi-hydrogenation with 98 % conversion, 99 % selectivity, and 85 % FE, in a broad substrate pool. This is achieved by engineering the local environment at the catalytically active sites. We leverage amphiphilic MHA (6-mercaptohexanoic acid) ligands to pre-concentrate water molecules and alkynes near the ligand-layer/Ag25 interface. Long-chain ligands can disrupt the hydrogen-bond network at the interface, the high negative charge of Ag25 can attract weakly hydrogen-bonded water through counterions and promote the generation of active hydrogen (H*), while the enzyme-like catalytic pockets on the surface of Ag25 NCs facilitate adsorption of terminal alkynes via σ-bonding to the surface Ag atoms. Density functional theory calculations confirmed the preference of the σ-bonding model of alkyne and further revealed the facile release of product alkene. This work not only exemplifies an atomically precise interface engineering strategy to control the local environment of active sites for optimized activity and selectivity.

Arylation of gold nanoclusters and insights into structure-related CO2 reduction reaction performances

Research on arylgold complexes and ligand-protected gold nanoclusters has proceeded independently thus far due to the difficulty in controllably introducing aryl groups to synthesize arylgold nanoclusters. Herein we synthesized an arylgold Au15 nanocluster, Au15(DPPOE)3(S-Ph p Me)4(Ph)2, thereby bridging the two independent research fields. Tetraarylborates were exploited as arylating agents to transfer aryl groups onto the nanocluster kernel, triggering the arylation of the Au15 cluster while maintaining the molecular framework. Furthermore, two other arylgold Au15 nanoclusters with halogenated surfaces were controllably synthesized by substituting the arylating agent NaBPh4 with its benzene ring-halide derivatives. In addition, the change in the electronic structure from Au-SR to Au-aryl and the energetics of the arylation process from Au15-SR to Au15-Ph were elucidated computationally. Furthermore, the catalytic capability of the two Au15 nanoclusters with nuanced ligand differences was investigated in the electrochemical reduction of CO2, and the comparable reactivity of the two cluster-based nanocatalysts was theoretically rationalized. Our findings have cross-fertilized the fields of arylgold complexes and gold nanoclusters, pointing toward a new avenue of exploration for novel arylgold nanoclusters.

Computational and Experimental Elucidation of the Charge-Dependent Acid-Etching Dynamics and Electrocatalytic Performance of Au25(SR)18 q(q = -1, 0, +1) Nanoclusters

Using thiolate-protected Au25(SR)18 nanocluster (NC) with different charge states as the test candidate, how the charge effect affects the etching dynamics of thiolate ligands in acid and the electrocatalytic performance is explored. The ab initio molecular dynamics (AIMD) simulations revealed the charge-dependent reaction kinetics in acid, where the anionic and neutral Au25(SCH3)18 q (q = -1, 0) favorably react with the acid and partially remove the thiolate ligands via two-step proton attack, while the cationic Au25(SCH3)18 + NC is acid-resistant with no tendency for -SR removal. Density functional theory (DFT) calculations further predict that the dethiolated Au sites exhibit enhanced catalytic activity for CO2 electroreduction to CO, with the anionic Au25 - showing significantly superior activity. Acid etching and electrocatalytic experiments further confirmed partial removal of thiolate ligands in Au25(SCH3)18 q (q = -1, 0), with dethiolated Au25 NCs showing enhanced catalytic performance in CO2 electroreduction, particularly Au25 - exhibiting better activity than Au25 0. This work revealed an interesting charge state-mediated interface dynamics and electrocatalytic behaviors in Au25 NCs, which can be applied to modulate the interface and catalytic properties of other atomically precise metal nanoclusters.

The Influence of Flexibility of Alkynyl Ligands on the Formation of an Fcc Au110 Nanocluster

Isomerization of nanoclusters is helpful for understanding the relationships between structures and properties. Surface-protecting ligands play a crucial role in controlling the atomic packing mode of the inner core. The synthesis and total structural determination of the all alkynyl-protected gold nanocluster (NEt3CH2Cl)2[Au110(C≡CC3H6Ph)48] (Au110-1) are reported. Au110-1 and the previously reported [Au110(C≡CC6H4-4-CF3)]2- (Au110-2) constitute the largest alkynyl-protected nanocluster quasi-isomers (> 100 metal atoms). Both Au110 consist of an fcc Au86 kernel and a shell of 24 RC≡C─Au─C≡CR staples, but the specific arrangements are different. The application of the flexible alkynyl ligands creates a significant difference in the face-centered cubic (fcc) kernel structure in Au110-1, showing a different electronic structure, thermal- and photo-stability. Transient absorption spectra reveal that Au110-1 still does not show any metallic characteristics, even though it has a smaller energy gap (Eg) than Au110-2.

Linker driven site-specific catalysis in atomically precise silver cluster assemblies

Metal nanoclusters (NCs) exhibit potential as catalysts for electrochemical studies, providing atomic-level insights into mechanisms. However, it remains elusive to construct an integrated catalyst with a molecular-level understanding of its mechanism, especially in silver cluster assemblies. In this study, we have shown that atomically precise Ag12 cluster assemblies Ag12-py, Ag12-pyz, Ag12-bpy, Ag12-bpa, Ag12-azopy, (where Ag12 = secondary building unit, Py = pyridine, pyz = pyrazine, bpy = 4,4'-bipyridine, bpa = 1,2-bis(4-pyridyl)ethane, and azopy = 4,4'-azopyridine) serve as paradigms for demonstrating the hydrogen evolution reaction (HER), where the catalytic activity is fine-tuned using two functional units: the cluster core and the linkers. The atomic resolution of such catalysts allows tracing the reaction process via experiments coupled with theory and structural analysis. Site-specific catalysis for Ag12-pyz induced by metal cluster assembly and linker synergy can be accurately elucidated to dominate in the series. Taking advantage of the pyrazine linker due to its lower basicity and the isotropic nature of inter-cluster interactions in Ag12-pyz, it shows enhanced catalytic activity and selective hydrogen adsorption at the sulfur site, different from others in the series with nearly five times higher efficiency. This work on a series of silver cluster assemblies provides a substantial structural model to understand the catalyst's active site and activity, further driving advancements in functional cluster-based assemblies.

Bimetallic Ni-Co-MOF Nanostructures for Seawater Electrolysis: Unveiling the Mechanism of the Oxygen Evolution Reaction Using Impedance Spectroscopy

Designing anode electrodes with long-term stability and efficiency for seawater electrolysis is crucial for addressing key challenges in sustainable hydrogen production and clean energy systems. Here, we developed self-supporting bimetallic Ni-Co-MOF electrodes, demonstrating exceptional performance and durability in alkaline seawater electrolysis due to their high voltammetric charge density and increased electrochemically accessible active sites. The reaction kinetics of the water oxidation reaction in the presence of Cl- ions (at concentrations ranging from 0.5 M to 3.5 M) were investigated through electrochemical impedance spectroscopy (EIS) analysis, focusing on the kinetic parameters, suggesting that the rate-determining step (RDS) is the chemical process following the initial electron transfer. Notably, Cl- ions in the electrolyte medium do not alter the OER rate-limiting step, as indicated by negligible variations in the anodic transfer coefficient values. However, blocking active sites is evident from the decrease in interfacial chemical capacitance (Cchem) values with increasing Cl- concentration. These findings offer a deeper understanding of OER reaction kinetics in chloride-containing environments by correlating electrochemical kinetic parameters with active site availability. This work highlights critical considerations for designing efficient and durable anodes for seawater electrolysis.

Ligand-induced changes in the electrocatalytic activity of atomically precise Au25 nanoclusters

Atomically precise gold nanoclusters have shown great promise as model electrocatalysts in pivotal electrocatalytic processes such as the hydrogen evolution reaction (HER) and carbon dioxide reduction reaction (CO2RR). Although the influence of ligands on the electronic properties of these nanoclusters is well acknowledged, the ligand effects on their electrocatalytic performances have been rarely explored. Herein, using [Au25(SR)18]- nanoclusters as a prototype model, we demonstrated the importance of ligand hydrophilicity versus hydrophobicity in modulating the interface dynamics and electrocatalytic performance. Our first-principles calculations revealed that Au25 protected by hydrophilic -SCH2COOH ligands exhibits faster kinetics in stripping the thiolate ligand and better HER activity due to enhanced proton transfer facilitated by boosted interface hydrogen bonding. Conversely, Au25 protected by hydrophobic -SCH2CH3 ligands demonstrates enhanced CO2RR performance by minimizing water interference to stabilize the key *COOH intermediate and lower the barrier for CO formation. Experimental validation using synthesized hydrophilic and hydrophobic ligand-protected Au25 nanoclusters (NCs), such as [Au25(MPA)18]- (MPA = mercaptopropionic acid), [Au25(MHA)18]- (MHA = 6-mercaptohexanoic acid), and [Au25(SC6H13)18]-, confirms these findings, where the hydrophilic ligand-protected Au25 NCs exhibit better activity and stability in the HER, while the hydrophobic ligand-protected Au25 NCs achieve higher faradaic efficiency and current density in the CO2RR. The mechanistic insights in this study provide valuable guidance for the rational design of surface microenvironments in efficient nanocatalysts for sustainable energy applications.

A comprehensive review of atomically precise metal nanoclusters with emergent photophysical properties towards diverse applications

Atomically precise metal nanoclusters (MNCs) composed of a few to hundreds of metal atoms represent an emerging class of nanomaterials with a precise composition. With the size approaching the Fermi wavelength of electrons, their energy levels are well-separated, leading to molecule-like properties, like discrete single electronic transitions, tunable photoluminescence (PL), inherent structural anisotropy, and distinct redox behavior. Extensive synthetic efforts and electronic structure revelation have expanded applicability of MNCs in catalysis, optoelectronics, and biology. This review highlights the intriguing photophysical and electrochemical behaviors of MNCs and their regulatory parameters and applications. Initially, we present a brief discussion on the evolution of MNCs from gas-phase naked metal clusters to monolayer ligand-protected MNCs along with representative studies on their electronic structure. Due to their quantized molecular orbitals, they often exhibit PL, which can be regulated based on their capping ligands, number of atoms, crystal packing, presence of heterometal, and surrounding environment. Apart from PL, the relaxation pathways of MNCs on an ultrafast time scale have been extensively studied, which significantly differ from that of plasmonic metal nanoparticles. Moreover, their interaction with high-intensity light results in unique non-linear optical properties. The synergy between MNCs in a hierarchical self-assembled structure has been exploited to enhance their PL by precisely tuning their non-covalent interactions. Moreover, several NC-based hybrids have been designed to exhibit efficient electron or energy transfer in the photoexcited state. In the next section, we briefly focus on the redox behavior of NCs and facile electron transfer to suitable substrates, which result in enzyme-like catalytic activity. Utilizing these photophysical and electrochemical behaviors, NCs are widely employed in catalysis, optical sensing, and light-harvesting applications, which are also discussed in this review. In the final section, conclusions and open questions for the NC research community are included. This review will provide a comprehensive view of the emerging physicochemical properties of MNCs, thereby enabling an understanding for their precise modulation in future.

Theory-Directed Ligand-Shell Engineering of Ultrasmall Gold Clusters: Remarkable Effects of Ligand Arrangement on Optical Properties

Ligand-shell engineering of ultrasmall metal clusters is a burgeoning research field aiming to develop cluster-specific properties. However, predicting these properties prior to synthesis is challenging due to their high sensitivity to geometric and/or electronic variations in ultrasmall metal cores, hindering further exploration. In this study, we present a theory-directed ligand-shell design and significant red-shift in absorption of a prolate-shaped [Au8(diphosphine)4Cl2]2+ cluster by synthesizing and characterizing enantiopure octagold clusters bearing chiral BINAP-type ligands [BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl]. Crystallographic analysis reveals the predesigned ligand arrangement and twisted gold-core framework. The enantiomeric clusters show significant changes in both absorption and photoluminescence compared with a previous Au8 analogue and exhibit chiroptical signals. Furthermore, theoretical calculations visually unveil the atomic level origins of their optical and chiroptical absorption characteristics. This work not only highlights the effectiveness of ligand-shell engineering in creating unique photophysical properties but also offers a viable, theory-guided strategy for designing and functionalizing ligated metal clusters.

Synergistic Intramolecular Charge Transfer Promotes Au Nanoclusters with Enhanced NIR-II Photoluminescence

Gold nanoclusters (Au NCs) protected by molecular ligands represent a new class of second-generation near-infrared (NIR-II) luminescent materials that have been widely studied. However, the photoluminescence efficiencies of most NIR-II emitting Au NCs in aqueous solution are generally lower than 0.2%, and to fully exploit the advantages of AuNCs in the NIR-II region, improving their photoluminescence efficiency has become an urgent need. Considering the holistic nature of the core-shell structure of Au NCs, herein, we propose a synergistic intramolecular charge transfer (ICT) strategy to enhance the luminescence. The NIR-II fluorescence quantum yield of Au NCs was increased 6-fold to 5.59% by the synergistic effect of heteroatomic copper doping and ligand p-MBA deprotonation. Experimental characterization results show that the strong p-π conjugation between d10 metal and the deprotonated p-MBA enhances the charge transfer between the metal core and ligand. The synergistic ICT process strongly suppressed the nonradiative process, thereby enhancing the emission intensity. Our findings provide a facile method for understanding the integrity of the core-shell structure of Au NCs and regulating their photoluminescence properties.

Catalytic N-Formylation of CO2 by Atomically Precise Au8Pd1(DPPF)4 2+ Clusters into a Two-Dimensional Metal-Organic Framework

By highly efficient ligand-exchange strategy, atomically precise Au8Pd1(PPh3)8 2+ (PPh3=triphenylphosphine) cluster can be transformed into a Au8Pd1(DPPF)4 2+ (DPPF=1,1'-bis(diphenylphosphino)ferrocene) cluster that can maintain the atomic-packing structure but overcome the lability of Au8Pd1(PPh3)8 2+. Catalytic evaluation for the CO2 hydrogenation coupled with o-phenylenediamine demonstrates that the Au8Pd1(DPPF)4 2+ catalyst can remarkably enhance both activity and stability compared to the Au8Pd1(PPh3)8 2+ catalyst. More notably, the direct construction of a two-dimensional metal-organic framework (2D MOF) can be elaborately accomplished in the formylation process of o-phenylenediamine, CO2 and H2 with zinc nitrate enabled by the Au8Pd1(DPPF)4 2+ catalyst. The 2D MOF further enables the capture and transformation of CO2 to combine in the organic synthesis with epoxides under mild conditions. This work provides opportunities for creating highly active cluster sites for the chemical recycling of CO2.

Synthesis, Structural Characterization, and Electronic Structure Analysis of F2-type Superatomic Molecules

The investigation of bonding interactions between superatoms continues to be a largely unexplored area of study. In this study, we present the synthesis and characterization of two F2-type superatomic molecules [Au2Ag25(C7H4NOS)13(DPPB)3] and [Au9Ag18(C5H4NS)11(DPPM)5]2+ (Au2Ag25 and Au9Ag18 for short, respectively). The overall structures were confirmed via X-ray crystallography, revealing the horizontal expansion of the biicosahedral Au2Ag21 yielding [Au2Ag25(C7H4NOS)13(DPPB)3] and vertical expansion of the biicosahedral Au8Ag15 yielding [Au9Ag18(C5H4NS)11(DPPM)5]2+. Furthermore, their electronic structures were elucidated through density functional theory (DFT) calculations. Spectroscopic analysis of electronic absorption characteristics, in conjunction with Tamm-Dancoff approximation DFT (TDA-DFT) calculations, revealed that the Au2Ag21(+9) and Au8Ag15(+9) cores were analogues of the F2 molecule in electronic configuration.

Atomically Precise Cu Nanoclusters: Recent Advances, Challenges, and Perspectives in Synthesis and Catalytic Applications

Atomically precise metal nanoclusters are an emerging type of nanomaterial which has diverse interfacial metal-ligand coordination motifs that can significantly affect their physicochemical properties and functionalities. Among that, Cu nanoclusters have been gaining continuous increasing research attentions, thanks to the low cost, diversified structures, and superior catalytic performance for various reactions. In this review, we first summarize the recent progress regarding the synthetic methods of atomically precise Cu nanoclusters and the coordination modes between Cu and several typical ligands and then discuss the catalytic applications of these Cu nanoclusters with some explicit examples to explain the atomical-level structure-performance relationship. Finally, the current challenges and future research perspectives with some critical thoughts are elaborated. We hope this review can not only provide a whole picture of the current advances regarding the synthesis and catalytic applications of atomically precise Cu nanoclusters, but also points out some future research visions in this rapidly booming field.

Electronic state modulation of Ag30 nanoclusters within a ring-shaped polyoxometalate

Atomically precise Ag nanoclusters display distinctive properties that are dictated by their structures and electronic states. However, manipulating the electronic states of Ag nanoclusters is challenging owing to their inherent instability and susceptibility to undesired structural changes, decomposition, and aggregation. Recently, we reported the synthesis of a body-centered cubic {Ag30}22+ nanocluster encapsulated within a ring-shaped polyoxometalate (POM) [P8W48O184]40- by reacting 16 Ag+-containing [P8W48O184]40- with Ag+ using N,N-dimethylformamide (DMF) as a mild reducing agent. This led to a redox-induced structural transformation into a face-centered cubic {Ag30}16+ nanocluster. In this study, we demonstrated the modulation of the electronic states of Ag30 nanoclusters within the ring-shaped POM through two different approaches. A face-centered cubic {Ag30}18+ nanocluster, featuring distinct oxidation states compared to previously reported {Ag30}22+ and {Ag30}16+ nanoclusters, was synthesized using tetra-n-butylammonium borohydride, a stronger reducing agent than DMF, in the reaction of 16 Ag+-containing [P8W48O184]40- and Ag+. Additionally, by leveraging the acid-base properties of POMs, we demonstrated the reversible, stepwise modulation of the charge distribution in the Ag30 nanocluster through controlling protonation states of the ring-shaped POM ligand. These results highlight the potential of engineering POM-stabilized Ag nanoclusters with diverse structures and electronic states, thereby facilitating the exploration of novel properties and applications utilizing the unique characteristics of the POM ligands.

When Metal Nanoclusters Meet Smart Synthesis

Atomically precise metal nanoclusters (MNCs) represent a fascinating class of ultrasmall nanoparticles with molecule-like properties, bridging conventional metal-ligand complexes and nanocrystals. Despite their potential for various applications, synthesis challenges such as a precise understanding of varied synthetic parameters and property-driven synthesis persist, hindering their full exploitation and wider application. Incorporating smart synthesis methodologies, including a closed-loop framework of automation, data interpretation, and feedback from AI, offers promising solutions to address these challenges. In this perspective, we summarize the closed-loop smart synthesis that has been demonstrated in various nanomaterials and explore the research frontiers of smart synthesis for MNCs. Moreover, the perspectives on the inherent challenges and opportunities of smart synthesis for MNCs are discussed, aiming to provide insights and directions for future advancements in this emerging field of AI for Science, while the integration of deep learning algorithms stands to substantially enrich research in smart synthesis by offering enhanced predictive capabilities, optimization strategies, and control mechanisms, thereby extending the potential of MNC synthesis.

Regulating interaction with surface ligands on Au25 nanoclusters by multivariate metal-organic framework hosts for boosting catalysis

While atomically precise metal nanoclusters (NCs) with unique structures and reactivity are very promising in catalysis, the spatial resistance caused by the surface ligands and structural instability poses significant challenges. In this work, Au25(Cys)18 NCs are encapsulated in multivariate metal-organic frameworks (MOFs) to afford Au25@M-MOF-74 (M = Zn, Ni, Co, Mg). By the MOF confinement, the Au25 NCs showcase highly enhanced activity and stability in the intramolecular cascade reaction of 2-nitrobenzonitrile. Notably, the interaction between the metal nodes in M-MOF-74 and Au25(Cys)18 is able to suppress the free vibration of the surface ligands on the Au25 NCs and thereby improve the accessibility of Au sites; meanwhile, the stronger interactions lead to higher electron density and core expansion within Au25(Cys)18. As a result, the activity exhibits the trend of Au25@Ni-MOF-74 > Au25@Co-MOF-74 > Au25@Zn-MOF-74 > Au25@Mg-MOF-74, highlighting the crucial roles of microenvironment modulation around the Au25 NCs by interaction between the surface ligands and MOF hosts.

Atomically precise alkynyl-protected Ag19Cu2 nanoclusters: synthesis, structure analysis, and electrocatalytic CO2 reduction application

We report the synthesis, structure analysis, and electrocatalytic CO2 reduction application of Ag19Cu2(CCArF)12(PPh3)6Cl6 (abbreviated as Ag19Cu2, CCArF: 3,5-bis(trifluoromethyl)phenylacetylene) nanoclusters. Ag19Cu2 has characteristic absorbance features and is a superatomic cluster with 2 free valence electrons. Single-crystal X-ray diffraction (SC-XRD) revealed that the metal core of Ag19Cu2 is composed of an Ag11Cu2 icosahedron connected by two Ag4 tetrahedra at the two terminals of the Cu-Ag-Cu axis. Notably, Ag19Cu2 exhibited excellent catalytic performance in the electrochemical CO2 reduction reaction (eCO2RR), manifested by a high CO faradaic efficiency of 95.26% and a large CO current density of 257.2 mA cm-2 at -1.3 V. In addition. Ag19Cu2 showed robust long-term stability, with no significant drop in current density and FECO after 14 h of continuous operation. Density functional theory (DFT) calculations disclosed that the high selectivity of Ag19Cu2 for CO in the eCO2RR process is due to the shedding of the -CCArF ligand from the Ag atom at the very center of the Ag4 unit, exposing the active site. This study enriches the potpourri of alkynyl-protected bimetallic nanoclusters and also highlights the great advantages of using atomically precise metal nanoclusters to probe the atomic-level structure-performance relationship in the catalytic field.

Improving the reliability of machine learned potentials for modeling inhomogeneous liquids

The atomic-scale response of inhomogeneous fluids at interfaces and surrounding solute particles plays a critical role in governing chemical, electrochemical, and biological processes. Classical molecular dynamics simulations have been applied extensively to simulate the response of fluids to inhomogeneities directly, but are limited by the accuracy of the underlying interatomic potentials. Here, we use neural network potentials (NNPs) trained to ab initio simulations to accurately predict the inhomogeneous responses of two distinct fluids: liquid water and molten NaCl. Although NNPs can be readily trained to model complex bulk systems across a range of state points, we show that to appropriately model a fluid's response at an interface, relevant inhomogeneous configurations must be included in the training data. In order to sufficiently sample appropriate configurations of such inhomogeneous fluids, we develop protocols based on molecular dynamics simulations in the presence of external potentials. We demonstrate that NNPs trained on inhomogeneous fluid configurations can more accurately predict several key properties of fluids-including the density response, surface tension and size-dependent cavitation free energies-for liquid water and molten NaCl, compared to both empirical interatomic potentials and NNPs that are not trained on such inhomogeneous configurations. This work therefore provides a first demonstration and framework to extract the response of inhomogeneous fluids from first principles for classical density-functional treatment of fluids free from empirical potentials.

Tuning Electrocatalytic Water Oxidation Activity: Insights from the Active-Site Distance in LnCu6 Clusters

Atomically precise metal clusters serve as a unique model for unraveling the intricate mechanism of the catalytic reaction and exploring the complex relationship between structure and activity. Herein, three series of water-soluble heterometallic clusters LnCu6, abbreviated as LnCu6-AC (Ln = La, Nd, Gd, Er, Yb; HAC = acetic acid), LnCu6-IM (Ln = La and Nd; IM = Imidazole), and LnCu6-IDA (Ln = Nd; H2IDA = Iminodiacetic acid) are presented, each featuring a uniform metallic core stabilized by distinct protected ligands. Crystal structure analysis reveals a triangular prism topology formed by six Cu2+ ions around one Ln3+ ion in LnCu6, with variations in Cu···Cu distances attributed to different ligands. Electrocatalytic oxygen evolution reaction (OER) shows that these different LnCu6 clusters exhibit different OER activities with remarkable turnover frequency of 135 s-1 for NdCu6-AC, 79 s-1 for NdCu6-IM and 32 s-1 for NdCu6-IDA. Structural analysis and Density Functional Theory (DFT) calculations underscore the correlation between shorter Cu···Cu distances and improves OER catalytic activity, emphasizing the pivotal role of active-site distance in regulating electrocatalytic OER activities. These results provide valuable insights into the OER mechanism and contribute to the design of efficient homogeneous OER electrocatalysts.

Dynamic Evolution and Reversibility of a Single Au25 Nanocluster for the Oxygen Reduction Reaction

Ultrasmall metallic nanoclusters (NCs) protected by surface ligands represent the most promising catalytic materials; yet understanding the structure and catalytic activity of these NCs remains a challenge due to dynamic evolution of their active sites under reaction conditions. Herein, we employed a single-nanoparticle collision electrochemistry method for real-time monitoring of the dynamic electrocatalytic activity of a single fully ligand-protected Au25(PPh3)10(SC2H4Ph)5Cl22+ nanocluster (Au252+ NC) at a cavity carbon nanoelectrode toward the oxygen reduction reaction (ORR). Our experimental results and computational simulations indicated that the reversible depassivation and passivation of ligands on the surface of the Au252+ NC, combined with the dynamic conformation evolution of the Au259+ core, led to a characteristic current signal that involves "ON-OFF" switches and "ON" fluctuations during the ORR process of a single Au252+ NC. Our findings reinvent the new perception and comprehension of the structure-activity correlation of NCs at the atomic level.

A Cages-on-Cluster Structure Constructed by Post-Clustering Covalent Modifications and Guest-Enabled Stimuli-Responsive Luminescence

A gold(I)-cluster-based twin-cage has been constructed by post-clustering covalent modification of a hexa-aldehyde cluster precursor with triaminotriethylamines. The cages-on-cluster structure has double cavities and four binding sites, which show site-discriminative binding for silver(I) and copper(I) guests. The guests in the tripodal hats affect the luminescence of the cluster: the tetra-silver(I) host-guest complex is weakly red-emissive, while the bis-copper(I)-bis-silver(I) one is non-emissive but is a stimuli-responsive supramolecule. The copper(I) ion inside the tri-imine cavity is oxidation sensitive, which enables the release of the bright emissive precursor cluster triggered by H2O2 solution. The hybridization of a cluster with cavities to construct a cluster-based cage presents an innovative concept for functional cluster design, and the post-clustering covalent modification opens up new avenues for finely tuning the properties of clusters.

Bioinspired Surface Ligand Engineering Regulates Electron Transfers in Gold Clusterzymes to Enhance the Catalytic Activity for Improving Sensing Performance

Metal nanoclusters feature a hierarchical structure, facilitating their ability to mimic enzyme-catalyzed reactions. However, the lack of true catalytic centers, compounded by tightly bound surface ligands hindering electron transfers to substrates, underscores the need for universal rational design methodologies to emulate the structure and mechanisms of natural enzymes. Motivated by the electron transfer in active centers with specific chemical structures, by integrating the peroxidase cofactor Fe-TCPP onto the surface of glutathione-stabilized gold nanoclusters (AuSG), we engineered AuSG-Fe-TCPP clusterzymes with a remarkable 39.6-fold enhancement in peroxidase-like activity compared to AuSG. Fe-TCPP not only mimics the active center structure, enhancing affinity to H2O2, but also facilitates the electron transfer process, enabling efficient H2O2 activation. By exemplifying the establishment of a detecting platform for trace H2O2 produced by ultrasonic cleaners, we substantiate that the bioinspired surface-ligand-engineered electron transfer can improve sensing performance with a wider linear range and lower detection limit.

Dithiocarbonate-Protected Au25 Nanorods of a Chiral D5 Configuration and NIR-II Phosphorescence

Innovative surface-protecting ligands are in constant demand due to their crucial role in shaping the configuration, property, and application of gold nanoclusters. Here, the unprecedented O-ethyl dithiocarbonate (DTX)-stabilized atomically precise gold nanoclusters, [Au25(PPh3)10(DTX)5Cl2]2+ (Au25DTX-Cl) and [Au25(PPh3)10(DTX)5Br2]2+ (Au25DTX-Br), were synthesized and structurally characterized. The introduction of bidentate DTX ligands not only endowed the gold nanocluster with unique staggered Au25 nanorod configurations but also generated the symmetry breaking from the D5d geometry of the Au25 kernels to the chiral D5 configuration of the Au25 molecules. The chirality of Au25 nanorods was notably revealed through single-crystal X-ray diffraction, and chiral separation was induced by employing chiral DTX ligands. The staggered configurations of Au25 nanorods, as opposed to eclipsed ones, were responsible for the large red shift in the emission wavelengths, giving rise to a promising near-infrared II (NIR-II, >1000 nm) phosphorescence. Furthermore, their performances in photocatalytic sulfide oxidation and electrocatalytic hydrogen evolution reactions have been examined, and it has been demonstrated that the outstanding catalytic activity of gold nanoclusters is highly related to their stability.

RuSe2 and CoSe2 Nanoparticles Incorporated Nitrogen-Doped Carbon as Efficient Trifunctional Electrocatalyst for Zinc-Air Batteries and Water Splitting

The development of affordable, highly active, and stable trifunctional electrocatalysts is imperative for sustainable energy applications such as overall water splitting and rechargeable Zn-air battery. Herein, we report a composite electrocatalyst with RuSe2 and CoSe2 hybrid nanoparticles embedded in nitrogen-doped carbon (RuSe2CoSe2/NC) synthesized through a carbonization-adsorption-selenylation strategy. This electrocatalyst is a trifunctional electrocatalyst with excellent hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) activities. An in-depth study of the effect of Se on the electrocatalytic process was conducted. Notably, the incorporation of Se moderately adjusted electronic structure of Ru and Co, enhancing all three types of catalytic performance (HER, η10 = 31 mV; OER, η10 = 248 mV; ORR, E1/2 = 0.834 V) under alkaline condition with accelerated kinetics and improved stability. Density functional theory (DFT) calculation reveals that the (210) crystal facet of RuSe2 is the dominant HER active site as it exhibited the lowest ΔGH* value. The in situ Raman spectra unravel the evolution process of the local electronic environment of Co-Se and Ru-Se bonds, which synergistically promotes the formation of CoOOH as the active intermediate during the OER. The superior catalytic efficiency and remarkable durability of RuSe2CoSe2/NC as an electrode for water splitting and zinc-air battery devices demonstrate its great potential for energy storage and conversion devices.

Enzyme-Inspired Ligand Engineering of Gold Nanoclusters for Electrocatalytic Microenvironment Manipulation

Natural enzymes intricately regulate substrate accessibility through specific amino acid sequences and folded structures at their active sites. Achieving such precise control over the microenvironment has proven to be challenging in nanocatalysis, especially in the realm of ligand-stabilized metal nanoparticles. Here, we use atomically precise metal nanoclusters (NCs) as model catalysts to demonstrate an effective ligand engineering strategy to control the local concentration of CO2 on the surface of gold (Au) NCs during electrocatalytic CO2 reduction reactions (CO2RR). The precise incorporation of two 2-thiouracil-5-carboxylic acid (TCA) ligands within the pocket-like cavity of [Au25(pMBA)18]- NCs (pMBA = para-mercaptobenzoic acid) leads to a substantial acceleration in the reaction kinetics of CO2RR. This enhancement is attributed to a more favorable microenvironment in proximity to the active site for CO2, facilitated by supramolecular interactions between the nucleophilic Nδ- of the pyrimidine ring of the TCA ligand and the electrophilic Cδ+ of CO2. A comprehensive investigation employing absorption spectroscopy, mass spectrometry, isotopic labeling measurements, electrochemical analyses, and quantum chemical computation highlights the pivotal role of local CO2 enrichment in enhancing the activity and selectivity of TCA-modified Au25 NCs for CO2RR. Notably, a high Faradaic efficiency of 98.6% toward CO has been achieved. The surface engineering approach and catalytic fundamentals elucidated in this study provide a systematic foundation for the molecular-level design of metal-based electrocatalysts.

Photoluminescence Quenching of Hydrophobic Ag29 Nanoclusters Caused by Molecular Decoupling during Aqueous Phase Transfer and EmissionRecovery through Supramolecular Recoupling

Exploiting emissive hydrophobic nanoclusters for hydrophilic applications remains a challenge because of photoluminescence (PL) quenching during phase transfer. In addition, the mechanism underlying PL quenching remains unclear. In this study, the PL-quenching mechanism was examined by analyzing the atomically precise structures and optical properties of a surface-engineered Ag29 nanocluster with an all-around-carboxyl-functionalized surface. Specifically, phase-transfer-triggered PL quenching was justified as molecular decoupling, which directed an unfixed cluster surface and weakened the radiative transition. Furthermore, emission recovery of the quenched nanoclusters was accomplished by using a supramolecular recoupling approach through the glutathione-addition-induced aggregation of cluster molecules, wherein the restriction of intracluster motion and intercluster rotation strengthened the radiative transition of the clusters. The results of this work offer a new perspective on structure-emission correlations for atomically precise nanoclusters and hopefully provide insight into the fabrication of highly emissive cluster-based nanomaterials for downstream hydrophilic applications.

Dynamic surface reconstruction of individual gold nanoclusters by using a co-reactant enables color-tunable electrochemiluminescence

Here we report for the first time the phenomenon of continuously color-tunable electrochemiluminescence (ECL) from individual gold nanoclusters (Au NCs) confined in a porous hydrogel matrix by adjusting the concentration of the co-reactant. Specifically, the hydrogel-confined Au NCs exhibit strong dual-color ECL in an aqueous solution with triethylamine (TEA) as a co-reactant, with a record-breaking quantum yield of 95%. Unlike previously reported Au NCs, the ECL origin of the hydrogel-confined Au NCs is related to both the Au(0) kernel and the Au(i)-S surface. Surprisingly, the surface-related ECL of Au NCs exhibits a wide color-tunable range of 625-829 nm, but the core-related ECL remains constant at 489 nm. Theoretical and experimental studies demonstrate that the color-tunable ECL is caused by the dynamic surface reconstruction of Au NCs and TEA radicals. This work opens up new avenues for dynamically manipulating the ECL spectra of core-shell emitters in biosensing and imaging research.

A bowl-shaped phosphangulene-protected cubic Cu58 nanocluster

A bowl-shaped phosphangulene-protected cubic Cu58 nanocluster has been synthesized. The structure was determined by X-ray crystallography and further analyzed by multiple techniques. The phosphangulenes not only enable ligand substitutions with triphenylphosphines in a cluster-to-cluster transformation way, but also facilitate inter-cluster interactions with fullerenes. These interactions further influence the entirety's photocurrent response and ability to liberate hydrogen when stimulated by light.

Structure-Performance Correlation Inspired Platinum-Assisted Anode with a Homogeneous Ionomer Layer for Proton Exchange Membrane Water Electrolysis

PEMWE is becoming one of the most promising technologies for efficient and green hydrogen production, while the anode OER process is deeply restricted by the now commercially used iridium oxide with sluggish reaction kinetics and super high cost. Deeply exploring the essential relationship between the underlying substrate materials and the performance of PEMWE cells while simultaneously excavating new practical and convenient methods to reduce costs and increase efficiency is full of challenges. Herein, two representative kinds of iridium oxide were studied, and their performance difference in PEMWE was precisely analyzed with electrochemical techniques and physical characterization and further linked to the ionomer/catalyst compound features. A novel anode with a uniform thin ionomer coating was successfully constructed, which simultaneously optimized the ionomer/catalyst aggregates as well as electrical conductivity, resulting in significantly enhanced PEMWE performance. This rigorous qualitative analysis of the structure-performance relationship as well as effective ionomer-affinitive optimization strategies are of great significance to the development of next-generation high-performance PEM water electrolyzers.

Self-Assembly of Atomically Precise Silver Nanoclusters in Crowded Colloids into Ultra-Long Ribbons with Tunable Supramolecular Chirality

Atomically precise metal nanoclusters (NCs) emerge as fascinating synthons in self-assembled materials. The self-assembly of metal NCs are highly sensitive to the environment because they have an inorganic-organic hybridized structure and a relatively complicated conformation. Here, it is shown that when confined in crowded colloids, a water-soluble Ag9 -cored nanocluster (Ag9 -NC) can self- assemble into ultra-long (up to millimeters) and photoluminescent ribbons with high flexibility. The ribbon contains rectangularly organized columns of Ag9 -NCs and can undergo secondary self-assembly to form bundled and branched structures. Formation of ribbons is observed in all the tested colloids, including lyotropic liquid crystals and disordered, three-dimensional network. The high viscosity/elasticity of the crowded colloids weakens gravity-induced sedimentation of the ribbons, leading to the formation of an interesting class of inorganic-organic composite materials where the hard Ag-containing skeleton strengthens the soft matter. The simultaneously occurring symmetry breaking during the self-assembly of Ag9 -NCs gives uncontrolled supramolecular chirality, which can be tuned through the majority rule and soldier-and-sergeant rule by the introduction of chiral seeds. The regulated chirality and the intrinsic photoluminescence of the Ag9 -NCs ribbons impart the composite material circularly polarized luminescence, opening the door for a variety of potential applications.

Nanocluster Surface Microenvironment Modulates Electrocatalytic CO2 Reduction

The catalytic activity and product selectivity of the electrochemical CO2 reduction reaction (eCO2 RR) depend strongly on the local microenvironment of mass diffusion at the nanostructured catalyst and electrolyte interface. Achieving a molecular-level understanding of the electrocatalytic reaction requires the development of tunable metal-ligand interfacial structures with atomic precision, which is highly challenging. Here, the synthesis and molecular structure of a 25-atom silver nanocluster interfaced with an organic shell comprising 18 thiolate ligands are presented. The locally induced hydrophobicity by bulky alkyl functionality near the surface of the Ag25 cluster dramatically enhances the eCO2 RR activity (CO Faradaic efficiency, FECO : 90.3%) with higher CO partial current density (jCO ) in an H-cell compared to Ag25 cluster (FECO : 66.6%) with confined hydrophilicity, which modulates surface interactions with water and CO2 . Remarkably, the hydrophobic Ag25 cluster exhibits jCO as high as -240 mA cm-2 with FECO >90% at -3.4 V cell potential in a gas-fed membrane electrode assembly device. Furthermore, this cluster demonstrates stable eCO2 RR over 120 h. Operando surface-enhanced infrared absorption spectroscopy and theoretical simulations reveal how the ligands alter the neighboring water structure and *CO intermediates, impacting the intrinsic eCO2 RR activity, which provides atomistic mechanistic insights into the crucial role of confined hydrophobicity.