Precise Nanoclusters Research Articles

Ligand effects on geometric structures and catalytic activities of atomically precise copper nanoclusters

The ligand effects have been extensively investigated in Au and Ag nanoclusters, while corresponding research efforts focusing on Cu nanoclusters remain relatively insufficient. Such a scarcity could primarily be attributed to the inherent instability of Cu nanoclusters relative to their Au/Ag analogues. In this work, we report the controllable preparation and structural determination of a hydride-containing Cu28 nanocluster with a chemical formula of Cu28H10(SPhpOMe)18(DPPOE)3. The combination of Cu28H10(SPhpOMe)18(DPPOE)3 and previously reported Cu28H10(SPhoMe)18(TPP)3 constructs a structure-correlated cluster pair with comparable structures and properties. Accordingly, the ligand effects in directing the geometric structures and physicochemical properties (including optical absorptions and catalytic activities towards the selected hydrogenation) of copper nanoclusters were analyzed. Overall, this work presents a structure-correlated Cu28 pair that enables the atomic-level understanding of ligand effects on the structures and properties of metal nanoclusters.

Differential Activation of Alkynes between Capped and Naked Ag Nanoclusters Anchored by Highly-Open Mesoporous CeO2 for Two Coupling Reactions with CO2.

The cyclization of 3-hydroxy alkynes and the carboxylation of terminal alkynes both with CO2 are two attractive strategies to simultaneously reduce CO2 emission and produce value-added chemicals. Herein, the differential activation of alkynes over atomically precise Ag nanoclusters (NCs) supported on Metal-organic framework-derivedhighly-open mesoporous CeO2 (HM-CeO2) by reserving or removing their surface captopril ligands is reported. The ligand-capped Ag NCs possess electron-rich Ag atoms as efficient π-activation catalytic sites in cyclization reactions, while the naked Ag NCs possess partial positive-charged Ag atoms as perfect σ-activation catalytic sites in carboxylation reactions. Impressively, via coupling with HM-CeO2 featuring abundant basic sites and quick mass transfer, the ligand-capped Ag NCs afford 97.9% yield of 4,4-dimethyl-5-methylidene-1,3-dioxolan-2-one for the cyclization of 2-methyl-3-butyn-2-ol with CO2, which is 4.5 times that of the naked Ag NCs (21.7%), while the naked Ag NCs achieve 98.5% yield of n-butyl 2-alkynoate for the carboxylation of phenylacetylene with CO2, which is 15.6 times that of ligand-capped Ag NCs (6.3%). Density functional theory calculations reveal the ligand-capped Ag NCs can effectively activate alkynyl carbonate ions for the intramolecular ring closing in cyclization reaction, while the naked Ag NCs are highly affiliative in stabilizing terminal alkynyl anions for the insertion of CO2 in carboxylation reaction.

Unraveling the Photocatalytic Mechanism of N2 Fixation on Single Ruthenium Sites.

Photocatalytic N2 fixation offers promise for ammonia synthesis, yet traditional photocatalysts encounter challenges such as low efficiency and short carrier lifetimes. Atomically precise ligand-metal nanoclusters emerge as a solution to address these issues, but the photophysical mechanism remains elusive. Inspired by the synthesis of Au4Ru2 NCs, we investigate the mechanism behind N2 activation on Au4Ru2, focusing on photoactivity and carrier dynamics. Our results reveal that vibration of the Ru-N bond in the low-frequency domain suppresses the deactivation process leading to a long lifetime of the excited N2. By the strategy of isoelectronic substitution, we identify the single Ru sites as the active sites for N2 activation. Furthermore, these ligand-protected M4Ru2 (M = Au, Ag, Cu) NCs show robust thermal stability in explicit solvation and decent photochemical activity for N2 activation and NH3 production. These findings have significant implications for the optimization of catalysts for sustainable ammonia synthesis.

Strategic Fabrication of Au4Cu2 NC/ZIF‐8 Composite Via In Situ Integration Technique for Enhanced Energy Storage Applications

AbstractMetal–organic frameworks (MOFs), known for their extensive porosity and versatile crystallinity, play a crucial role in the development of advanced energy storage materials. However, their application is limited by stability and conductivity issues. This study addresses these challenges by integrating ultrasmall metal nanoclusters, specifically Au4Cu2 NC, synthesized using a mixed ligand strategy combining 2, 4‐Dimethyl benzene thiol (2,4‐DMBTH) and 1,2‐bis(diphenylphosphino)ethane (dppe). The bimetallic Au4Cu2 NC, characterized by Single Crystal X‐Ray Diffraction (SCXRD), is applied to zeolitic imidazolate framework‐8 (ZIF‐8) using both in situ and ex situ methods to explore their electrochemical and physicochemical properties in energy storage. The in situ Au4Cu2 NC/ZIF‐8 composite demonstrated a specific capacitance that is almost two times higher than its ex situ counterpart, attributed to homogeneous dispersion and hence enhanced conductivity. This in situ integration of atomically precise bimetallic nanoclusters on MOFs significantly boosts supercapacitor performance, offering a more effective and reliable solution for energy storage. Further, in practical applications, this device demonstrated an energy density of 87.2 Wh kg−1 at a power density of 1474 W kg−1, highlighting its robustness and potential for high‐performance energy storage applications. This approach effectively combats the issue of nanocluster aggregation on substrates, marking a significant progression in supercapacitor technology.

Anchoring Atomically Precise Chiral Bismuth Oxido Nanoclusters on Gold: The Role of Amino Acid Linkers.

The adsorption of chiral molecules onto metallic surfaces triggers electron spin polarization at the interface, paving the way for applications in chiral opto-spintronics. However, the spin effects sensitively depend on the binding and ordering of the chiral species on surfaces. This study explores the adsorption of chiral thioether-functionalized atomically precise bismuth oxido nanoclusters (BiO-NCs) on gold (Au) surfaces, extending the conventional approach of using thiol-containing molecules and complexes to nanoclusters. Starting from the precursor [Bi38O45(NO3)20(dmso)28](NO3)4·4dmso (A), chiral BiO-NCs were synthesized by substituting the nitrates with N-(tert-butoxycarbonyl)-l-methionine (Boc-l-Met-O-) ligands to obtain [Bi38O45(Boc-l-Met-O)24] (2). The full exchange of nitrate by the Boc-l-methionine ligand was demonstrated by powder X-ray diffractograms, dynamic light scattering, electrospray ionization mass spectrometry, nuclear magnetic resonance, infrared, circular dichroism, and X-ray photoelectron spectroscopy. Compared to previously reported [Bi38O45(Boc-l-Phe-O)24(dmso)9] (1), BiO-NC 2 shows differences in the growth mode on a Au surface as revealed by scanning electron microscopy, wherefore a stronger binding of BiO-NC 2 is assumed. Anchoring of BiO-NC 2 to the Au surface through thioether groups induced a discernible change in the optical response of the Au surface analyzed by spectroscopic ellipsometry (SE). From the numerical modeling of the SE parameters, a layer thickness of ∼2 nm, corresponding to a monolayer of BiO-NC 2, was estimated for the samples prepared by dip coating. Thus, strong adsorption of BiO-NC 2 to the Au surface is concluded, which is an essential prerequisite for chiral-induced interface spin polarization.

Luminescent Hydride-Free [Cu7(SC5H9)7(PPh3)3] Nanocluster: Facilitating Highly Selective C-C Bond Formation.

Amidst burgeoning interest, atomically precise copper nanoclusters (Cu NCs) have emerged as a remarkable class of nanomaterials distinguished by their unparalleled reactivity. Nonetheless, the synthesis of hydride-free Cu NCs and their role as stable catalysts remain infrequently explored. Here, we introduce a facile synthetic approach to fabricate a hydride-free [Cu7(SC5H9)7(PPh3)3] (Cu7) NC and delineate its photophysical properties intertwined with their structural configuration. Moreover, the utilization of its photophysical properties in a photoinduced C-C coupling reaction demonstrates remarkable specificity toward cross-coupling products with high yields. The combined experimental and theoretical investigation reveals a nonradical mechanistic pathway distinct from its counterparts, offering promising prospects for designing hydride-free Cu NC catalysts in the future and unveiling the selectivity of the hydride-free [Cu7(SC5H9)7(PPh3)3] NC in photoinduced Sonogashira C-C coupling through a polar reaction pathway.

Dithiophosphonate-Protected Eight-Electron Superatomic Ag21 Nanocluster: Synthesis, Isomerism, Luminescence, and Catalytic Activity.

The structure-property relationship considering isomerism-tuned photoluminescence and efficient catalytic activity of silver nanoclusters (NCs) is exclusive. Asymmetrical dithiophosphonate NH4[S2P(OR)(p-C6H4OCH3)] ligated first atomically precise silver NCs [Ag21{S2P(OR)(p-C6H4OCH3)}12]PF6 {where, R = nPr (1), Et (2)} were established by single-crystal X-ray diffraction and characterized by electrospray ionization mass spectrometry, NMR (31P, 1H, 2H), X-ray photoelectron spectroscopy, UV-visible, energy-dispersive X-ray spectroscopy, Fourier transforms infrared, thermogravimetric analysis, etc. NCs 1 and 2 consist of eight silver atoms in a cubic framework and enclose an Ag@Ag12-centered icosahedron to constitute an Ag21 core of Th symmetry, which is concentrically inscribed within the S24 snub-cube, P12 cuboctahedron, and the O12 truncated tetrahedron formed by 12 dithiophosphonate ligands. These NCs facilitate to be an eight-electron superatom (1S21P6), in which eight capping Ag atoms exhibit structural isomerism with documented isoelectronic [Ag21{S2P(OiPr)2}12]PF6, 3. In contrast to 3, the stapling of dithiophosphonates in 1 and 2 triggered bluish emission within the 400 to 500 nm region at room temperature. The density functional theory study rationalized isomerization and optical properties of 1, 2, and 3. Both (1, and 2) clusters catalyzed a decarboxylative acylarylation reaction for rapid oxindole synthesis in 99% yield under ambient conditions and proposed a multistep reaction pathway. Ultimately, this study links nanostructures to their physical and catalytic properties.

Unraveling the Solvent Regulation in the Heteroatom-Doped Endohedral Gold Clusters: A Theoretical Study on the Electronic Properties and O2 Activation.

Liquid-phase synthesis of atomically precise nanoclusters has experienced rapid development recently, where polar solvents are indispensable in such a process. However, the regulation effect of solvents on the structural and electronic properties of different metal clusters and cluster assembly materials is still not well understood. Herein, a comprehensive density functional theory calculation has been performed to explore the solvation effect on heteroatom-doped endohedral gold clusters that always have remarkable stabilities and tunable electronic structures. The solvation free energy of the M@Au12 clusters (M = Cr, Mo, W, Co, Rh, Ir, Cu, Ag, and Au) was found to be related to the charge distribution of the central doped-atom M and the outer Au12 cage. Moreover, the aqueous solvent was observed to be able to increase the adsorption capacity of M@Au12 to O2 following the activation of O2 through the charge transfer from M@Au12 to O2, in which the transferred electrons occupy the π antibonding orbital of O2. In addition, the water solvent can also improve the hydrogenation reaction of O2 to form OOH over M@Au12, where the activation energy barrier for this process is very low with the participation of the solvent. Considering the importance of solvents in the liquid-phase synthesis of atomically precise clusters, these findings highlighted here could provide valuable theoretical guidance in potential applications of functional gold nanoclusters, especially in the liquid-phase cluster catalysis.

Atomically precise gold nanoclusters as ROS-scavenging clusterzymes to treat high-fat diet-induced obesity

Obesity is widely considered a chronic inflammatory disease and is recognized as one of the major challenges to global public health, but there is no successful anti-inflammatory therapy for obesity so far. In this study, atomically precise Au22 nanoclusters are introduced as reactive oxygen species (ROS)-scavenging clusterzymes, with the aim of achieving anti-inflammation in high-fat diet (HFD)-induced obesity. Au22 clusterzymes display high catalase (CAT)-like and superoxide dismutase (SOD)-like activities, excellent antioxidant capacity. We demonstrate that Au22 clusterzymes treatment can effectively scavenge ROS, relieve the antioxidant system disorder, and restrain the inflammation in HFD-induced obese mice, with good biocompatibility. After 30 days of Au22 clusterzymes treatment, high therapeutic efficacy in anti-obesity is observed in HFD-induced obese mice, including decreased body weight by 13%, reduced serum levels of key inflammatory factors (IL-1β, IL-6, and TNF-α) in the obese mice by 23 – 48%, improved glucose tolerance and lipid metabolism, and increased browning of white adipose tissue (WAT). Overall, Au22 clusterzymes have good performance on ROS-scavenging and anti-inflammation in vivo, offering a promising approach to combat obesity and related metabolic diseases.

Boosted solar water oxidation steered by atomically precise alloy nanocluster

Boosted solar water oxidation steered by atomically precise alloy nanocluster

Effect of Hybridization on the Photoluminescence Properties of Atomically Precise Silver Nanoclusters

AbstractThe Förster Resonance Energy Transfer (FRET) is a widely used mechanism harnessed for sensing applications. For temporal stability of the energy transfer between donor and acceptor molecules their photostability and maintenance of the coupling geometry are important. A donor‐acceptor system was created from silicon nanoclusters (Si NCs) and silver nanoclusters (dihydrolopic acid (DHLA)‐protected Ag29 NCs). Optical spectroscopy and lifetime measurements helped to understand the energy transfer process between the Si NCs and Ag29 NCs. Compared with donor‐acceptor pairs based on gold nanocluster and organic dyes, the FRET pair formed between Si NCs and Ag29 (DHLA)12 NCs reaches a coequal efficiency of 60 %. A fine‐tuning of the system‘s parameters opens the door to investigating the sensitivity of the two nanocluster FRET system to various species and incorporating highly photostable moieties in a process relying on photoluminescence.

Fluorescence resonance energy transfer in atomically precise metal nanoclusters by cocrystallization-induced spatial confinement

Understanding the fluorescence resonance energy transfer (FRET) of metal nanoparticles at the atomic level has long been a challenge due to the lack of accurate systems with definite distance and orientation of molecules. Here we present the realization of achieving FRET between two atomically precise copper nanoclusters through cocrystallization-induced spatial confinement. In this study, we demonstrate the establishment of FRET in a cocrystallized Cu8(p-MBT)8(PPh3)4@Cu10(p-MBT)10(PPh3)4 system by exploiting the overlapping spectra between the excitation of the Cu10(p-MBT)10(PPh3)4 cluster and the emission of the Cu8(p-MBT)8(PPh3)4 cluster, combined with accurate control over the confined space between the two nanoclusters. Density functional theory is employed to provide deeper insights into the role of the distance and dipole orientations of molecules to illustrate the FRET procedure between two cluster molecules at the electronic structure level.

Luminescence properties of endohedrally doped group-IV clusters.

Endohedrally doped clusters form a large category of cage clusters, with unique structures, diverse elemental compositions, and highly tunable electronic structures and physisochemical properties. They have been widely achieved in laboratory and may serve as functional building blocks for assembling new supermolecular structures and devices. In this paper, for the first time, we disclosed the luminescence properties of endohedrally doped group-IV clusters by time-dependent density functional theory calculations. A total of 64 cage clusters have been explored in terms of stability, emission wavelength, and the energy difference between the first excited singlet and triplet states. The key geometric and electronic factors governing the photophysical properties of these cage clusters were unveiled, to provide crucial insights for crafting atomically precise nanoclusters for optical and optoelectronic applications.

Hierarchical Self-assembly of Atomically Precise Au Nanoclusters with Molecular Rotor-based Ligands

Hierarchical Self-assembly of Atomically Precise Au Nanoclusters with Molecular Rotor-based Ligands

Vibration‐Dependent Dual‐Phosphorescent Cu4 Nanocluster with Remarkable Piezochromic Behavior

AbstractThe dual emission (DE) characteristics of atomically precise copper nanoclusters (Cu NCs) are of significant theoretical and practical interest. Despite this, the underlying mechanism driving DE in Cu NCs remains elusive, primarily due to the complexities of excited state processes. Herein, a novel [Cu4(PPh3)4(C≡C−p−NH2C6H4)3]PF6 (Cu4) NC, shielded by alkynyl and exhibiting DE, was synthesized. Hydrostatic pressure was applied to Cu4, for the first time, to investigate the mechanism of DE. With increasing pressure, the higher‐energy emission peak of Cu4 gradually disappeared, leaving the lower‐energy emission peak as the dominant emission. Additionally, the Cu4 crystal exhibited notable piezochromism transitioning from cyan to orange. Angle‐dispersive synchrotron X‐ray diffraction results revealed that the reduced inter‐cluster distances under pressure brought the peripheral ligands closer, leading to the formation of new C−H⋅⋅⋅N and N−H⋅⋅⋅N hydrogen bonds in Cu4. It is proposed that these strengthened hydrogen bond interactions limit the ligands′ vibration, resulting in the vanishing of the higher‐energy peak. In situ high‐pressure Raman and vibrationally resolved emission spectra demonstrated that the benzene ring C=C stretching vibration is the structural source of the DE in Cu4.

Vibration-Dependent Dual-Phosphorescent Cu4 Nanocluster with Remarkable Piezochromic Behavior.

The dual emission (DE) characteristics of atomically precise copper nanoclusters (Cu NCs) are of significant theoretical and practical interest. Despite this, the underlying mechanism driving DE in Cu NCs remains elusive, primarily due to the complexities of excited state processes. Herein, a novel [Cu4(PPh3)4(C≡C-p-NH2C6H4)3]PF6 (Cu4) NC, shielded by alkynyl and exhibiting DE, was synthesized. Hydrostatic pressure was applied to Cu4, for the first time, to investigate the mechanism of DE. With increasing pressure, the higher-energy emission peak of Cu4 gradually disappeared, leaving the lower-energy emission peak as the dominant emission. Additionally, the Cu4 crystal exhibited notable piezochromism transitioning from cyan to orange. Angle-dispersive synchrotron X-ray diffraction results revealed that the reduced inter-cluster distances under pressure brought the peripheral ligands closer, leading to the formation of new C-H⋅⋅⋅N and N-H⋅⋅⋅N hydrogen bonds in Cu4. It is proposed that these strengthened hydrogen bond interactions limit the ligands' vibration, resulting in the vanishing of the higher-energy peak. In situ high-pressure Raman and vibrationally resolved emission spectra demonstrated that the benzene ring C=C stretching vibration is the structural source of the DE in Cu4.

Planar Core and Macrocyclic Shell Stabilized Atomically Precise Copper Nanocluster Catalyst for Efficient Hydroboration of C-C Multiple Bond.

Atomically precise metal nanoclusters (NCs) have become an important class of catalysts due to their catalytic activity, high surface area, and tailored active sites. However, the design and development of bond-forming reaction catalysts based on copper NCs are still in their early stages. Herein, we report the synthesis of an atomically precise copper nanocluster with a planar core and unique shell, [Cu45(TBBT)29(TPP)4(C4H11N)2H14]2+ (Cu45) (TBBT: 4-tert-butylbenzenethiol; TPP: triphenylphosphine), in high yield via a one-pot reduction method. The resulting structurally well-defined Cu45 is a highly efficient catalyst for the hydroboration reaction of alkynes and alkenes. Mechanistic studies show that a single-electron oxidation of the in situ-formed ate complex enables the hydroboration via the formation of boryl-centered radicals under mild conditions. This work demonstrates the promise of tailored copper nanoclusters as catalysts for C-B heteroatom bond-forming reactions. The catalysts are compatible with a wide range of alkynes and alkenes and functional groups for producing hydroborated products.

Interparticle Antigalvanic Reactions of Atomically Precise Silver Nanoclusters with Plasmonic Gold Nanoparticles: Interfacial Control of Atomic Exchange

Interparticle Antigalvanic Reactions of Atomically Precise Silver Nanoclusters with Plasmonic Gold Nanoparticles: Interfacial Control of Atomic Exchange

A Theoretical Benchmark of the Geometric and Optical Properties for 3d Transition Metal Nanoclusters via Density Functional Theory.

Understanding structure-property relationships in atomically precise metal nanoclusters is vital in finding selective and tunable catalysts. In this study, density functional theory (DFT) was used to benchmark seven exchange correlation functionals at different basis sets for 17 atomically precise nanoclusters against experimentally determined geometries, band gaps, and optical gaps. The set contains both monometallic and bimetallic clusters that possess at least two types of 3d transition metals (specifically, Cu, Ni, Fe, or Co). The benchmark highlights that PBE0 is a good functional to use regardless of the basis set, and Minnesota functionals do well with respect to specific metals. Further, while long-range corrected functionals overestimate band and optical gaps, they model absorption features better than the other considered functionals. The study additionally looks at the photoinduced hydrogen evolution reaction (HER) and the CO2 reduction mechanism on nanoclusters reported from the literature.

Temperature‐Controlled Selective Formation of Silver Nanoclusters and Their Transformation to the Same Product

AbstractHerein, two atomically precise silver nanoclusters, Ag54 and Ag33, directed by inner anion templates (CrO42− and/or Cl−), are initially isolated as a mixed phase from identical reactants across a wide temperature range (20–80 °C). Interestingly, fine‐tuning the reaction temperature can realize pure phase synthesis of the two nanoclusters; that is, a metastable Ag54 is kinetically formed at a low temperature (20 °C), whereas such a system is steered towards a thermodynamically stable Ag33 at a relatively high temperature (80 °C). Electrospray ionization mass spectrometry illustrates that the stability of Ag33 is superior to that of Ag54, which is further supported by density functional theory calculations. Importantly, the difference in structural stability can influence the pathway of 1,4‐bis(pyrid‐4‐yl)benzene induced transformation reaction starting from Ag54 and Ag33. The former undergoes a dramatic breakage‐reorganization process to form an Ag31 dimer (Ag31), while the same product can be also achieved from the latter following a noninvasive ligand exchange process. Both the Ag54 and Ag33 have the potential for further remote laser ignition applications. This work not only demonstrates how temperature controls the isolation of a specific phase, but also sheds light on the structural transformation pathway of nanoclusters with different stability.