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Electrochemistry of Atomically Precise Metal Nanoclusters
摘要： Thiolate-protected metal nanoparticles containing a few to few hundred metal atoms are interesting materials exhibiting unique physicochemical properties. They encompass the bulk-to-molecule transition region, where discrete electronic states emerge and electronic band energetics yield to quantum con?nement e?ects. Recent progresses in the synthesis and characterization of ultrasmall gold nanoparticles have opened up new avenues for the isolation of extremely monodispersed nanoparticles with atomically precision. These nanoparticles are also called nanoclusters to distinguish them from other regular metal nanoparticles with core diameter >2 nm. These nanoclusters are typically identi?ed by their actual molecular formulas; prominent among these are Au25(SR)18, Au38(SR)24, and Au102(SR)44, where SR is organothiolate. A number of single crystal structures of these nanoclusters have been disclosed. Researchers have e?ectively utilized density functional theory (DFT) calculations to predict their atomic and electronic structures, as well as their physicochemical properties. The atomically precise metal nanoclusters have been the focus of recent studies owing to their novel size-speci?c electrochemical, optical, and catalytic properties. In this Account, we highlight recent advances in electrochemistry of atomically precise metal nanoclusters and their applications in electrocatalysis and electrochemical sensing. Compared with gold nanoclusters, much less progress has been made in the electrochemical studies of other metal nanoclusters, and thus, we mainly focus on the electrochemistry and electrochemical applications of gold-based nanoclusters. Voltammetry has been extremely powerful in investigating the electronic structure of metal nanoclusters, especially near HOMO and LUMO levels. A sizable opening of HOMO?LUMO gap observed for Au25(SR)18 gradually decreases with increasing nanocluster size, which is in line with the change in the optical gap. Heteroatom-doping has been a powerful strategy to modify the optical and electrochemical properties of metal nanoclusters at the atomic level. While the superatom theory predicts 8-electron con?guration for [Au25(SR)18]? and many doped nanoclusters thereof, Pt- and Pd-doped [PtAu24(SR)18]0 and [PdAu24(SR)18]0 nanoclusters show dramatically di?erent electronic structures, as manifested in their optical spectra and voltammograms, suggesting the occurrence of the Jahn?Teller distortion in these doped nanoclusters. Furthermore, metal-doping may alter their surface binding properties, as well as redox potentials. Metal nanoclusters o?er great potential for attaining high activity and selectivity in their electrocatalytic applications. The well-de?ned core?shell structure of a metal nanocluster is of special advantage because the core and shell can be independently engineered to exhibit suitable binding properties and redox potentials. We discuss recent progress made in electrocatalysis based upon metal nanoclusters tailored for water splitting, CO2 conversion, and electrochemical sensing. A well-de?ned model nanocatalyst is absolutely necessary to reveal the detailed mechanism of electrocatalysis and thereby to lead to the development of a new e?cient electrocatalyst. We envision that atomically controlled metal nanoclusters will enable us to systematically optimize the electrochemical and surface properties suitable for electrocatalysis, thus providing a powerful platform for the discovery of ?nely tuned nanocatalysts.
关键词： quantum con?nement,electrocatalysis,atomically precise metal nanoclusters,electrochemistry,electrochemical sensing
更新于2025-09-23 15:21:21
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Insights into Interfaces, Stability, Electronic Properties, and Catalytic Activities of Atomically Precise Metal Nanoclusters from First Principles
摘要： Atomically precise, ligand-protected metal nanoclusters are of great interest for their well-defined structures, intriguing physicochemical properties, and potential applications in catalysis, biology, and nanotechnology. Their structure precision provides many opportunities to correlate their geometries, stability, electronic properties, and catalytic activities by closely integrating theory and experiment. In this Account, we highlight recent theoretical advances from our efforts to understand the metal?ligand interfaces, the energy landscape, the electronic structure and optical absorption, and the catalytic applications of atomically precise metal nanoclusters. We mainly focus on gold nanoclusters. The bonding motifs and energetics at the gold?ligand interfaces are two main interests from a computational perspective. For the gold?thiolate interface, the ?RS?Au?SR? staple motif is not always preferred; in fact, the bridging motif (?SR?) is preferred at the more open facets such as Au(100) and Au(110). This finding helps understand the diversity of the gold?thiolate motifs for different core geometries and sizes. A great similarity is demonstrated between gold?thiolate and gold?alkynyl interfaces, regarding formation of the staple-type motifs with PhC≡C? as an example. In addition, N-heterocyclic carbenes (NHCs) without bulky groups also form the staple-type motif. Alkynyls and bulky NHCs have the strongest binding with the gold surface from comparing 27 ligands of six types, suggesting a potential to synthesize NHC-protected gold clusters. The energy landscape of nanosystems is usually complex, but experimental progress in synthesizing clusters of the same Au?S composition with different R groups and isomers of the same Aun(SR)m formula have made detailed theoretical analyses of energetic contributions possible. Ligand?ligand interactions turn out to play an important role in the cluster stability, while metastable isomers can be obtained via kinetic control. Although the superatom-complex theory is the starting point to understand the electronic structure of atomically precise gold clusters, other factors also greatly affect the orbital levels that manifest themselves in the experimental optical absorption spectra. For example, spin?orbit coupling needs to be included to reproduce the splitting of the HOMO?LUMO transition observed experimentally for Au25(SR)18?, the poster child of the family. In addition, doping can lead to structural changes and charge states that do not follow the superatomic electron count. Atomically precise metal nanoclusters are an ideal system for understanding nanocatalysis due to their well-defined structures. Active sites and catalytic mechanisms are explored for selective hydrogenation and hydrogen evolution on thiolate-protected gold nanoclusters with and without dopants. The behavior of H in nanogold is analyzed in detail, and the most promising site to attract H is found to be coordinately unsaturated Au atoms. Many insights have been gained from first-principles studies of atomically precise, ligand-protected gold nanoclusters. Interesting and important questions remaining to be addressed are pointed out in the end.
关键词： atomically precise metal nanoclusters,gold nanoclusters,catalytic activities,first principles,metal?ligand interfaces,electronic properties
更新于2025-09-23 15:21:01
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Alkali Metal Ions: A Secret Ingredient for Metal Nanocluster-Sensitized Solar Cells
摘要： The presence of alkali metal ions (AMIs) during the adsorption of thiolated Au nanoclusters (NCs) onto TiO2 plays a critical role in achieving high power conversion efficiency and suppressing anomalous current?voltage hysteresis in metal nanocluster-sensitized solar cells. This hidden role of the AMIs is intimately related to the adsorption strength between the NCs and TiO2, indicating the importance of seeking a comprehensive understanding of NC?TiO2 interfaces and devising interfacial engineering techniques to support the next advance in light energy conversion applications of NCs.
关键词： alkali metal ions,metal nanoclusters,current?voltage hysteresis,power conversion efficiency,solar cells
更新于2025-09-23 15:21:01
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Metal Nanoclusters: Engineering Functional Metal Materials at the Atomic Level (Adv. Mater. 47/2018)
摘要： Customizing functional metal materials at an atom-by-atom basis is one of the most ambitious dreams of materials scientists. In article number 1802751, Jianping Xie and co-workers summarize recent progress in introducing such fine capability of structural modulation into functional metal nanoclusters, based on a protein-like hierarchical structure scheme.
关键词： structural modulation,metal nanoclusters,protein-like hierarchical structure
更新于2025-09-23 15:21:01
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Probing the Advantageous Photosensitization Effect of Metal Nanoclusters over Plasmonic Metal Nanocrystals in Photoelectrochemical Water Splitting
摘要： Atomically precise metal nanoclusters (NCs)-based photocatalytic systems have garnered enormous attention owing to the fascinating merits including unique physicochemical properties, quantum confinement effect and photosensitization effect, which are distinct from conventional metal nanocrystals (NYs). Nevertheless, systematic comparison between electrons photoexcited from metal NCs and hot electrons from surface plasmonic resonance (SPR) effect of metal NYs in boosting photoelectrochemical water splitting reaction remains blank. Here, we report the strict and comprehensive comparison on the capability of electrons photoexcited from glutathione-capped gold nanoclusters (Aux@GSH) and hot electrons from plasmonic excitation of gold nanoparticles (Au NYs) self-transformed from Aux@GSH to trigger the PEC water splitting reaction under visible light irradiation. The results indicate photoelectrons of Aux NCs trigger more efficient charge transport rate than hot electrons of plasmonic Au NYs in terms of light harvesting and conversion efficiency under the identical conditions. Moreover, charge transfer characteristics in Aux NCs and Au NYs-based PEC systems were established. This work would reinforce our deep understanding on these two pivotal sectors of metal nanomaterials for solar energy conversion.
关键词： photosensitization effect,plasmonic metal nanocrystals,charge transfer,photoelectrochemical water splitting,metal nanoclusters
更新于2025-09-23 15:19:57
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Role of Regeneration of Nanoclusters in Dictating the Power Conversion Efficiency of Metal-Nanocluster-Sensitized Solar Cells
摘要： Metal nanoclusters (NCs) have emerged as feasible alternatives to dyes and quantum dots in light energy conversion applications. Despite the remarkable enhancement in power conversion efficiency (PCE) in recent years and the increase in the number of NCs available as sensitizers, a comprehensive understanding of the various interfacial charge-transfer, transport, and recombination events in NCs is still lacking. This understanding is vital to the establishment of design principles for an efficient photoelectrode that uses NCs. In this work, we carefully design a comparison study of two representative NCs, Au and Ag, based on transient absorption spectroscopy and electrochemical impedance spectroscopy, methods that shed light on the true benefits and limitations of NC sensitizers. Low NC regeneration efficiency is the most critical factor that limits the performance of metal-nanocluster-sensitized solar cells (MCSSCs). The slow regeneration that results from sluggish hole transfer kinetics not only limits photocurrent generation efficiency but also has a profound effect on the stability of MCSSCs. This finding calls for urgent attention to the development of an efficient redox couple that has a great hole extraction ability and no corrosive nature. This work also reveals different interfacial behaviors of Au and Ag NCs in photoelectrodes, suggesting that utilizing the benefits of both types of NCs simultaneously by co-sensitization or using AuAg alloy NCs may be one avenue to further PCE improvement in MCSSCs.
关键词： metal nanoclusters,regeneration,light energy conversion,solar cells,hole transfer
更新于2025-09-23 15:19:57
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Stimuli‐Responsive Luminescent Copper Nanoclusters in Alginate and Their Sensing Ability for Glucose
摘要： Visually observable pH-responsive luminescent materials are developed through integrating the properties of aggregation-induced emission enhancement of Cu nanocluster (NCs) and the Ca2+ triggered gelatin of alginate. Sodium alginate, CaCO3 nanoparticles and Cu NCs are dispersed in aqueous solution, which is in a transparent fluid state, showing a weak photoluminescence (PL). The introduced H+ can react with the CaCO3 nanoparticles to produce free Ca2+, which can cross-link the alginate chains into gel networks. Meanwhile, a dramatically increase on the PL intensity of Cu NCs and a blue shift on the PL peak appeared, assigned to the Ca2+ induced enhancement and gelatin induced enhancement, respectively. Their potential application as a sensor for glucose is also demonstrated based on the principle that glucose oxidase can recognize glucose and produce H+, which further triggers the above mentioned two-stage enhancement. A linear relationship between the PL intensity and concentration of glucose in the range of 0.1 to 2.0 mM is obtained, with a limit of detection calculated as 3.2×10-5 M.
关键词： alginate,stimuli‐responsive materials,aggregation-induced emission,photoluminescence,metal nanoclusters,glucose
更新于2025-09-19 17:15:36
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Thermal Shock Synthesis of Metal Nanoclusters within On-the-fly Graphene Particles
摘要： Metal nanoclusters (1-10 nm) have drawn great attention due to their potential applications including energy storage, catalysis, nanomedicine and electronic devices. However, manufacturing ultra-small metal nanoparticles at high concentrations in an unaggregated state is not a solved problem. Here we report an aerosol-based thermal shock technique for in situ synthesis of well-dispersed metal nanoclusters in on-the-fly graphene aerosols. A rapid thermal shock to the graphene aerosol has been used to nucleate and grow the metal nanoclusters with subsequent quenching to freeze the newly formed nanoclusters in the graphene aerosol matrix. A characteristic time analysis comparison with experiment shows that the nanocluster formation is governed by nucleation and subsequent surface growth, and that the graphene retards coagulation, enabling unaggregrated metal nanoclusters. The method is generic, and we show the formation of sub-10 nm Ni, Co and Sn nanoclusters. This continuous aerosol-based thermal shock technique offers considerable potential for the scalable synthesis of well-dispersed and uniform metal nanoclusters stabilized within a host matrix. As an example of potential application, we demonstrate very favorable catalytic properties.
关键词： thermodynamics,in situ growth,growth mechanism,thermal shock synthesis,kinetics,metal nanoclusters
更新于2025-09-19 17:15:36
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Optical absorption in complexes of abasic DNA with noble-metal nanoclusters by first principles calculations
摘要： Optical absorption in complexes of abasic DNA with noble-metal nanoclusters by first principles calculations. Abasic sites (AP site) in a DNA duplex have been experimentally used to produce fluorescent Ag nanoclusters (NC) with a small number of atoms (n ≤ 6). These AP-DNA:NC complexes act as biological markers that help to locate genes associated with diseases related to single nucleotide polymorphisms (SNP), for example. Abasic sites are the most common SNP genetic variation, and their detection may help predict a host of genetically determined diseases. In this work, we report a theoretical study of the optical absorption spectra of AP-DNA:Ag4 and AP-DNA:Au4 complexes using a fully ab initio methodology. We consider several different base environments for the noble-metal nanocluster occupying the AP site, and compute the absorption spectra of sixteen AP-DNA:Ag4 and sixteen AP-DNA:Au4 complexes. We find that optical absorption in the AP-DNA:Ag4 complexes tends to concentrate in the green-to-violet range of frequencies (2.50 eV ≤ ?ω ≤ 3.2 eV) and that AP-DNA:Au4 complexes display absorption peaks in the violet-to-ultraviolet interval (?ω ≥ 3.0 eV). An analysis of the optical absorption mechanisms in these AP-DNA:NC complexes shows that they can be of local, charge-transfer, or hybrid nature, i.e., AP-DNA:NC complexes display the full variety of optical absorption processes in molecular systems. In particular, we identify both charge-transfer and hybrid processes involving several DNA bases surrounding the NC. Importantly, we find that even sequences where the Ag4 cluster is not in a guanine rich neighborhood display absorption peaks in the visible-light spectrum. Moreover, we obtain that the maximum intensities of the absorption peaks in complexes with pyrimidine vacancies are generally higher than those in complexes with purine vacancies. Regarding the selectivity of single-vacancy AP-DNA to specific noble-metal nanocluster sizes, our calculations show that the four-atom Ag4 (Au4) species fits naturally and binds into the AP-site in a single-vacancy AP-DNA.
关键词： noble-metal nanoclusters,optical absorption,first principles calculations,abasic DNA,Au4,charge-transfer,hybrid processes,Ag4
更新于2025-09-19 17:15:36
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Electronic and Geometric Structure, Optical Properties, and Excited State Behavior in Atomically Precise Thiolate-Stabilized Noble Metal Nanoclusters
摘要： Ligand-protected noble metal nanoclusters are of interest for their potential applications in areas such as bioimaging, catalysis, photocatalysis, and solar energy harvesting. These nanoclusters can be prepared with atomic precision, which means that the properties of these nanoclusters can vary significantly depending on the exact stoichiometry and geometric structure of the system. This leads to important questions such as: What are the general principles that underlie the physical properties of these nanoclusters? Do these principles hold for all systems? What properties can be “tuned” by varying the size and composition of the system? In this Account, we describe research that has been performed to analyze the electronic structure, linear optical absorption, and excited state dynamics of thiolate-stabilized noble metal nanoclusters. We focus primarily on two systems, Au25(SR)18? and Au38(SR)24, as models for understanding the principles underlying the electronic structure, optical properties, luminescence, and transient absorption in these systems. In these nanoclusters, the orbitals near the HOMO?LUMO gap primarily arise from atomic 6sp orbitals located on Au atoms in the gold core. The resulting nanocluster orbitals are delocalized throughout the core of these systems. Below the core-based orbitals lies a set of orbitals that are primarily composed of Au 5d and S 3p atomic orbitals from atoms located around the exterior gold?thiolate oligomer motifs. This set of orbitals has a higher density of states than the set arising from the core 6sp orbitals. Optical absorption peaks in the near-infrared and visible regions of the absorption spectrum arise from excitations between core orbitals (lowest energy peaks) and excitations from oligomer-based orbitals to core-based orbitals (higher energy peaks). Nanoclusters with different stoichiometries have varying gaps between the core orbitals themselves as well as between the band of oligomer-based orbitals and the band of core orbitals. These gaps can slow down nonradiative electron transfer between excited states that have different character; the excited state electron and hole dynamics depend on these gaps. Nanoclusters with different stoichiometries also exhibit different luminescence properties. Depending on factors that may include the symmetry of the system and the rigidity of the core, the nanocluster can undergo large or small nuclear changes upon photoexcitation, which affects the observed Stokes shift in these systems. This dependence on stoichiometry and composition suggests that the size and the corresponding geometry of the nanocluster is an important variable that can be used to tune the properties of interest. How does doping affect these principles? Replacement of gold atoms with silver atoms changes the energetics of the sp and d atomic orbitals that make up the nanocluster orbitals. Silver atoms have higher energy sp orbitals, and the resulting nanocluster orbitals are shifted in energy as well. This affects the HOMO?LUMO gap, the oscillator strength for transitions, the spacings between the different bands of orbitals, and, as a consequence, the Stokes shift and excited state dynamics of these systems. This suggests that nanocluster doping is one way to control and tune properties for use in potential applications.
关键词： ligand-protected noble metal nanoclusters,doping,electronic structure,optical properties,transient absorption,luminescence,atomic precision
更新于2025-09-10 09:29:36