Metal Nanoclusters Research Articles

Structural Changes in Atomically Precise Ag29 Nanoclusters upon Sequential Attachment and Detachment of Secondary Ligands.

Elucidating the structural dynamics of ligand-stabilized noble metal nanoclusters (NCs) is critical for understanding their properties and for developing applications. Ligand rearrangement at NC surfaces is an important contributor to structural change. In this study, we investigate the dynamic behavior of ligand-protected [Ag29(L)12]3- NC's (L = 1,3-benzenedithiol) interacting with secondary ligand 2,2'-[1,4-phenylenebis (methylidynenitrilo)] bis[benzenethiol] (referred to as L'). We specifically focus on the structural characteristics of NC-based adducts [Ag29(L)12]L'n3- where n ranges from 1 to 4. This is probed experimentally by using a combination of ultraviolet-visible (UV-vis) spectroscopy, high-resolution electrospray ionization mass spectrometry (ESI MS), and ion mobility mass spectrometry (IM MS) coupled with collision-induced dissociation (MS2 IMS). Density functional theory (DFT) calculations infer comparatively weak noncovalent interactions between the NCs and attached secondary ligands consistent with the fragmentation behavior and experimentally determined collision cross-sections (CCSs), which show a monotonic CCS increase of [Ag29(L)12]L'n3- with an increasing number of L' (n = 1-4). From a detailed analysis of the predicted structures, we infer progressive expansion of the Ag-S staple framework of the precursor NC as secondary ligands are added. Interestingly, detachment of L' from gas-phase [Ag29(L)12]L'n3- by collisional heating yields structures which retain "footprints" of the detached secondary ligands on a millisecond time scale.

Precision Metal Nanoclusters Meet Proteins: Crafting Next-Gen Hybrid Materials.

Metal nanoclusters (NCs), owing to their atomic precision and unique molecule-like properties, have gained widespread attention for applications ranging from catalysis to bioimaging. In recent years, proteins, with their hierarchical structures and diverse functionalities, have emerged as good candidates for functionalizing metal NCs, rendering metal NC-protein conjugates with combined and even synergistically enhanced properties featured by both components. In this Perspective, we explore key questions regarding why proteins serve as complementary partners for metal NCs, the methodologies available for conjugating proteins with metal NCs, and the characterization techniques necessary to elucidate the structures and interactions within this emerging bionano system. We also highlight the emerging applications of metal NC-protein conjugates in biomedicine, catalysis, and biosensing in which the hybrid conjugates demonstrate remarkable performance. Furthermore, key challenges hampering further development of metal NC-protein conjugates, which include understanding binding mechanisms, expanding the diversity of proteins used for conjugation, and exploiting the individual roles of metal NCs and proteins within the hybrid systems, are discussed. This Perspective aims to systemize current synthetic methodologies and design principles for metal NC-protein conjugates, adding to their acceptance in precision nanotechnology.

Protein-templated metal nanoclusters for chemical sensing

Metal nanoclusters (MNCs) possess unique optical properties, discrete energy levels, biocompatibility and photostability, making them pivotal photoluminescent probes in chemical sensing. While substantial work has addressed the synthesis, theoretical studies and applications of gold-, copper-, and silver-based MNCs, this review introduces fresh perspectives on how the nature and concentration of templates—particularly protein molecules—affect the optical properties, stability and sensing capabilities of MNCs. We delve into the merits of using protein templates for creating highly stable MNCs with tunable photoluminescence (PL), providing a detailed comparison with non-protein based systems. This review also unveils recent advancements in the photophysical characteristics and chemical sensing applications of protein-templated MNCs, setting it apart from previous reviews by focusing on cutting-edge innovations in template influence. Challenges and future prospects for protein-templated MNCs in chemical sensing are highlighted, marking critical pathways for upcoming research. This work not only integrates current knowledge but also identifies gaps and opportunities not covered extensively in earlier reviews, such as the nuanced effects of template variation on MNCs’ functional properties.

Structural Changes in Metal Chalcogenide Nanoclusters Associated with Single Heteroatom Incorporation.

Atomically precise nanoclusters (NCs) are promising building blocks for designing materials and interfaces with unique properties. By incorporating heteroatoms into the core, the electronic and magnetic properties of NCs can be precisely tuned. To accurately predict these properties, density functional theory (DFT) is often employed, making the rigorous benchmarking of DFT results particularly important. In this study, we present a benchmarking approach based on metal chalcogenide NCs as a model system. We synthesized a series of bimetallic, iron-cobalt chalcogenide NCs [Co6-xFexS8(PEt3)6]+ (x = 0-6) (PEt = triethyl phosphine) and investigated the effect of heteroatoms in the octahedral metal chalcogenide core on their size and electronic properties. Using ion mobility-mass spectrometry (IM-MS), we observed a gradual increase in the collision cross section (CCS) with an increase in the number of Fe atoms in the core. DFT calculations combined with trajectory method CCS simulations successfully reproduced this trend, revealing that the increase in cluster size is primarily due to changes in metal-ligand bond lengths, while the electronic properties of the core remain largely unchanged. Moreover, this method allowed us to exclude certain multiplicity states of the NCs, as their CCS values were significantly different from those predicted for the lowest-energy structures. This study demonstrates that gas-phase IM-MS is a powerful technique for detecting subtle size differences in atomically precise NCs, which are often challenging to observe using conventional NC characterization methods. Accurate CCS measurements are established as a benchmark for comparison with theoretical calculations. The excellent correspondence between experimental data and theoretical predictions establishes a robust foundation for investigating structural changes of transition metal NCs of interest to a broad range of applications.

Understanding the Ag-S interface stability and electrocatalytic activity of CO2 electroreduction in atomically precise Ag25 nanoclusters.

Elucidating the catalytic properties of metal nanoclusters (NCs) with essentially the same structure but different core metals is of fundamental interest. Our current studies have demonstrated that the thiolated Ag25(SR)18 NC exhibits SR ligand leaching dynamics and electrocatalytic activity in CO2 reduction distinct from those of its Au25(SR)18 NC structural analogue.

Atomically Precise Cu12 Nanoclusters with Thermally Activated Delayed Fluorescence Properties.

Ligand-stabilized metal nanoclusters with atomic precision are considered to be promising materials in the field of light-emitting and harvesting. Among these, nanoclusters with thermally activated delayed fluorescence (TADF) properties are highly sought after. While several gold and silver nanoclusters with TADF properties have been reported in recent years, research on copper counterparts has significantly lagged behind. In this study, we present the synthesis, total structure determination, and photoluminescent properties of a copper cluster with TADF properties. The cluster, with the molecular formula (PPh4)[Cu12(NO3)6(AdmS)6] (PPh4 is tetraphenylphosphine tetraphenylboron, and AdmSH is adamantanethiol), was obtained in a single reaction in the presence of air and fully characterized using electrospray ionization mass spectroscopy (ESI-MS), X-ray photoelectron spectroscopy, nuclear magnetic resonance, and ultraviolet-visible spectroscopy (UV-vis). The molecular structure of the cluster, as determined by X-ray crystallographic analysis, reveals the stabilization of a Cu12 core (layer-by-layer growth mode of Cu3@Cu6@Cu3) with 6 NO3- and 6 AdmS- ligands acting as stabilizing ligands. Interestingly, the cluster exhibits photoluminescence in both crystalline and solution states and displays typical TADF characteristics within the temperature range of 163-243 K. This study not only presents a pioneering example of copper nanoclusters with TADF properties but also highlights the promising future of copper clusters in material science.

Plasmon-Enhanced Luminescence of Gold Nanoclusters by Using Silver and Gold Metal Nanostructures.

Plasmonic materials can be utilized as effective platforms to enhance luminescent signals of luminescent metal nanoclusters (LMNCs). Both surface enhanced fluorescence (SEF) and shell-isolated nanoparticle-enhanced fluorescence (SHINEF) strategies take advantage of the localized and increased external electric field created around the plasmonic metal surface when excited at or near their characteristic plasmonic resonance. In this context,we present an experimental and computational study of different plasmonic composites, (Ag) Ag@SiO2 and (Au) Au@SiO2 nanoparticles, which were used to enhance the luminescent signal of Au nanoclusters coated with glutathione (GSH) molecule (Au25GSH NCs). This specific LMNC has recently attracted particular interest due to its luminescent response and characteristic photostability. Our study presents a wide characterization of the optical and morphologic features of the synthetized particles: plasmonic metal nanostructures and Au25GSH NCs through different experimental techniques including UV-Visible, IR, luminescentspectroscopies, along with TEM and AFM microscopies. Additionally, we have carried out computational simulations based on time-dependent density functional theory (TD-DFT) and classical electrodynamics simulation based on Mie Theory to support our experimental findings. In this study, we report up to 3-fold luminescence enhancement of Au25GSH NCs which is mainly attributed to slow dynamics SEF.

Sequential addition of cations increases photoluminescence quantum yield of metal nanoclusters near unity

Photoluminescence is one of the most intriguing properties of metal nanoclusters derived from their molecular-like electronic structure, however, achieving high photoluminescence quantum yield (PLQY) of metal core-dictated fluorescence remains a formidable challenge. Here, we report efficient suppression of the total structural vibrations and rotations, and management of the pathways and rates of the electron transfer dynamics to boost a near-unity absolute PLQY, by decorating progressive addition of cations. Specifically, with the sequential addition of Zn2+, Ag+, and Tb3+ into the 3-mercaptopropionic acids capped Au nanoclusters (NCs), the low-frequency vibration of the metal core progressively decreases from 144.0, 55.2 to 40.0 cm−1, and the coupling strength of electrons-high-frequency vibration related to surface motifs gradually diminishes from 40.2, 30.5 to 14.4 meV. Moreover, introducing cation additives significantly reduces electron transfer time from 40, 27 to 12 ps in the pathway from staple motifs to the metal core. This benefits from the shrinkage of the total structure that speeds up the shell-core electron transition, and in particular, the Tb3+ provides a hopping platform for the excited electrons as their intrinsic ladder-like energy level structure. As a result, it allows a remarkable enhancement in PLQY, from 51.2%, 83.4%, up to 99.5%.

Eight-electron Pt/Cu superatom encapsulating three "electron-donating" hydrides.

Hydrides in metal complexes or nanoclusters are typically viewed as electron-withdrawing. Several recent reports have demonstrated the emergence of "electron-donating" hydrides in tailoring the structure, electronic structure, and reactivity of metal nanoclusters. However, the number of such hydrides included in each cluster kernel is limited to one or two. There is even no structure model, neither theoretical nor experimental, for encapsulating a third electron-donating hydride into one cluster entity. Here, we present a structurally precise superatomic nanocluster, PtH3Cu23(iso-propyl-PhS)18(PPh3)4 (PtH3Cu23), which contains three interstitial electron-donating hydrides. The molecular structure of PtH3Cu23 describes the encapsulation of a PtCu12 core that contains three interstitial hydrides in a distorted anticuboctahedral architecture, in an outer sphere consisting of copper atoms and thiolate and phosphine ligands. Density functional theory calculations reveal that the three hydrides in PtH3Cu23 contribute their valence electrons to the cluster superatomic electron count of eight. In this regard, the cluster represents a rare Pt-included copper-hydride superatom with eight free electrons.

Engineering Metal Nanoclusters at the Atomic Level for Effective Electrocatalysis

Engineering Metal Nanoclusters at the Atomic Level for Effective Electrocatalysis

Cluster Engineering in Water Catalytic Reactions: Synthesis, Structure-Activity Relationship and Mechanism.

Four fundamental reactions are essential to harnessing energy from water sustainably: oxidation reduction reaction (ORR), oxygen reduction reaction (OER), hydrogen oxidation reaction (HOR), and hydrogen evolution reaction (HER). This review summarizes the research advancements in the electrocatalytic reaction of metal nanoclusters for water splitting. It covers various types of nanoclusters, particularly those at the size level, that enhance these catalytic reactions. The synthesis of cluster-based catalysts and the elucidation of the structure-activity relationships and reaction mechanisms are discussed. Emphasis is placed on utilizing atomically precise cluster materials and the interplay between the carrier and cluster in water catalysis, especially for applying catalytic engineering principles (such as synergy, coordination, heterointerface, and lattice strain engineering) to understand structure-activity relationships and catalytic mechanisms for cluster-based catalysts. Finally, the field of cluster water catalysis is summarized and prospected. We believe that developing cluster-based catalysts with high activity, excellent stability, and high selectivity will significantly promote the development of renewable energy conversion reactions.

Understanding the Role of Potential and Cation Effect on Electrocatalytic CO2 Reduction in All-Alkynyl-Protected Ag15 Nanoclusters.

Atomically precise metal nanoclusters (NCs) have emerged as an intriguing class of model catalysts for electrochemical CO2 reduction reactions (CO2RR). However, the interplay between the interface environment (e.g., potential, cation concentration) and electron-proton transfer (ET/PT) kinetics─particularly in alkynyl-protected metal NCs─remains poorly understood. Here, we combined first-principles simulations and electrochemical experiments to investigate the role of potential and cation effect on CO2RR performance in a prototype all-alkynyl-protected Ag15(C≡C-CH3)+ cluster. Our simulations revealed that the applied reduction potential triggers the elimination of the alkynyl ligand via sequentially breaking two π-type Ag-C bonds and one σ-type Ag-C bond to expose the catalytically active Ag sites, and the barrier of the Ag-C breakage monotonically decreases with the lowering in potential. Furthermore, we show that introducing the inner-sphere Na+ ions greatly enhances *CO2 activation and promotes proton transfer to generate *COOH and *CO by forming the Na+-CO2(*COOH) complexes, while the competitive hydrogen evolution reaction (HER) from water dissociation is greatly suppressed, thus dramatically improving the selectivity of CO2 electroreduction. The electrochemical measurements further validated our predictions, where the CO Faradaic efficiency (FECO) and current density (jCO) show a pronounced dependence on the Na+ concentration. At an optimal concentration of 0.1 M NaCl, FECO can reach up to ∼96%, demonstrating the crucial role of cations in promoting the CO2RR. Our findings provide vital insights into the atomic-level reaction mechanism of the CO2RR on alkynyl-protected Ag15 NCs and highlight the important role of potential and electrolyte cation in governing the electron/proton transfer kinetics.

Advances in precise synthesis of metal nanoclusters and their applications in electrochemical biosensing of disease biomarkers.

Metal nanoclusters (NCs), comprising tens to hundreds of metal atoms, are condensed matter with concrete molecular structures and discrete energy levels. Compared to metal atoms and nanoparticles, metal NCs exhibit unique physicochemical properties, especially fascinating electrocatalytic activities. This review focuses on recent progress in the precise synthesis of metal NCs and their applications in electrochemical analysis of various disease biomarkers. First, we provide a brief overview of current nanotechnology-enabled electrochemical biosensors. Subsequently, we highlight the precise synthesis of metal NCs protected by various ligands such as peptides, proteins and nucleic acids. Next, we summarize the design and construction of electrochemical biosensors that utilize metal NCs as electrode materials to detect electrochemically active and inactive disease-associated biomarkers, including small biomolecules (glucose, reactive oxygen species, cholesterol, neurotransmitters and amino acids) and biomacromolecules (proteins, enzymes, and nucleic acids). Due to unique electrocatalytic properties, high specific surface areas, and atomically modulated structures, metal NCs promote electron exchange or act as a redox medium in these electrochemical sensing platforms. Finally, we conclude with present challenges and propose future research directions, with the aim to enhance the specificity, sensitivity, and durability of customized metal NC-based electrochemical biosensors for precise disease diagnostics.

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

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

Tailoring the photoluminescence of AIE-type gold nanoclusters via biomineralization-inspired polymorphism.

Tailoring the aggregation-induced emission (AIE) characteristics of well-defined metal nanoclusters (MNCs) is highly sought after for numerous practical applications. Studies have primarily focused on assembling AIE-type MNCs using monomorphic molecules. Achieving polymorphic assemblies, with different molecular arrangements could provide valuable insights into the role of external molecular matrices on the photoluminescence (PL) behaviour of these NCs. In this study, by mimicking biomineralization, we successfully embedded AIE-type Au22SG18 NCs within different polymorphic environments of CaCO3. Upon incorporation into CaCO3 matrices such as, calcite, vaterite and a mixture of both, the PL was enhanced in all the inorganic composites accompanied by a significant blue shift. In the metastable vaterite matrix, Au22SG18 NCs exhibited the highest blue shift in the PL spectrum while in the stable crystalline matrix of calcite, the NCs showed the highest PL intensity as well as excited state lifetime. Time-resolved spectroscopic and single-molecule Raman studies revealed that variations in the PL of NCs are linked to the stability of their polymorphic structures, progressing from vaterite to a vaterite/calcite mixture, and finally to calcite. These findings shed light on the crucial role of external molecular arrangement in the AIE behaviour of MNCs.

Recent advances and future prospects in oxidative-reduction low-triggering-potential electrochemiluminescence strategies based on nanoparticle luminophores.

The oxidative-reduction electrochemiluminescence (ECL) potential of a luminophore is one of the most significant parameters during light generation processes when considering the growing demand for anti-interference analysis techniques, electrode compatibility and the reduction of damage to biological molecules due to excessive excitation potential. Nanoparticle luminophores, including quantum dots (QDs) and metal nanoclusters (NCs), possess tremendous potential for forming various ECL sensors due to their adjustable surface states. However, few reviews focused on nanoparticle luminophore-based ECL systems for low-triggering-potential (LTP) oxidative-reduction ECL to avoid the possible interference and oxidative damage of biological molecules. This review summarizes the recent advances in the LTP oxidative-reduction ECL potential strategy with nanoparticle luminophores as ECL emitters, including matching efficient coreactants and nanoparticle luminophores, doping nanoparticle luminophores, constructing donor-acceptor systems, choosing suitable working electrodes, combining multiplex nanoparticle luminophores, and employing surface-engineering strategies. In the context of the different LTP ECL systems, potential-lowering strategies and bio-related applications are discussed in detail. Additionally, the future trends and challenges of low ECL-triggering-potential strategies are discussed.

Inclusion of gold ions in tiara-like nickel hexanuclear nanoclusters.

Tiara-like metal nanoclusters (TNCs) composed of group 10 transition metals and thiolates can easily change their number of polymerization and include various molecules or metal ions as guests within their ring structures. Therefore, they are expected to be applied in sensing, storage, and catalyst materials based on their selective inclusion characteristics. However, there are very few reports regarding the principles of selective inclusion for guest molecules/ions in TNCs. In this study, we focused on the nickel (Ni) hexanuclear TNC, Ni6(PET)12 (PET = 2-phenylethanethiolate), to clarify the kinds of metal ions that can be included in TNCs. As a result, we found that the gold (Au) ion can be selectively included in Ni6(PET)12 among various metal ions to form a stable structure. From various experiments and density functional theory calculations, we concluded that the main reasons for this are that [Ni6(PET)12]0 has (1) a pore large enough to include Au ions and (2) Ni and Au favour the formation of bonding orbitals based on charge transfer interactions. These insights are expected to lead to a better understanding of host-guest interactions in TNCs and provide clear design guidelines for forming various inclusion structures in the future.

Rational design and synthesis of atomically precise nanocluster-based nanocomposites: a step towards environmental catalysis.

Atomically precise metal nanoclusters (NCs) and metal-organic frameworks (MOFs) possess distinct properties that can present challenges in certain applications. However, integrating these materials to create new composite functional materials has gained significant interest due to their unique characteristics through a range of applications, particularly in catalysis. Considering MOFs as hosts and NCs as guests, several synergistic effects have been observed in composites, particularly in environmental catalytic reactions. However, the precise role of encapsulated NCs within the MOF pore structure is still in its infancy. Besides, stabilizing NCs, whether through intact ligands or without ligands via the MOF host, presents challenges that are currently being investigated. This feature article reviews recent advancements in the synthesis of NC@MOF composites, focusing on cutting-edge strategies for selecting MOFs and the roles of NC ligands, as well as characterization and catalytic applications.

Ultrasmall metal nanoclusters as efficient luminescent probes for bioimaging.

Ultrasmall metal nanoclusters (NCs, <2 nm) have emerged as a novel class of luminescent probes due to their atomically precise size and tailored physicochemical properties. The rapid advancements in the design and utilization of metal NC-based luminescent probes are facilitated by the atomic-level manipulation of metal NCs. This review article explores (i) the engineering of metal NCs' functions for bioimaging applications, and (ii) the diverse uses of metal NCs in bioimaging. We begin by presenting an overview of the engineering functions of metal NCs as luminescent probes for bioimaging applications, highlighting key strategies for enhancing NCs' luminescence, biocompatibility and targeting capabilities towards biological specimens. Our discussion then centers on the bioimaging applications of metal NCs in subcellular organelles, individual cells, tissues, and entire organs. Finally, we offer a perspective on the challenges and potential developments in the future use of metal NCs for bioimaging applications.

Symmetrical and asymmetrical surface structure expansions of silver nanoclusters with atomic precision.

Controlling symmetrical or asymmetrical growth has allowed a series of novel nanomaterials with prominent physicochemical properties to be produced. However, precise and continuous size growth based on a preserved template has long been a challenging pursuit, yet little has been achieved in terms of manipulation at the atomic level. Here, a correlated silver cluster series has been established, enabling atomically precise manipulation of symmetrical and asymmetrical surface structure expansions of metal nanoclusters. Specifically, the C 3-axisymmetric Ag29(BDTA)12(PPh3)4 nanocluster underwent symmetrical and asymmetrical surface structure expansions via an acid-mediated synthetic procedure, giving rise to C 3-axisymmetric Ag32(BDTA)12(PPh3)10 and C 1-axisymmetric Ag33(BDTA)12(PPh3)11, respectively. In addition, structural transformations, including structural degradation from Ag32 to Ag29 and asymmetrical structural expansion from Ag32 to Ag33, were rationalized theoretically. More importantly, the asymmetrically structured Ag33 nanoclusters followed a chiral crystallization mode, and their crystals displayed high optical activity, derived from CD and CPL characterization. This work not only provides an important model for unlocking the symmetrical/asymmetrical size growth mechanism at the atomic level but also pioneers a promising approach to activate the optical activity of cluster-based nanomaterials.