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Elucidation of the electronic structures of thiolate-protected gold nanoclusters by electrochemical measurements. Dalton Trans 2023; 52:15152-15167. [PMID: 37712891 DOI: 10.1039/d3dt02005c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/16/2023]
Abstract
Metal nanoclusters (NCs) with sizes of approximately 2 nm or less have different physical/chemical properties from those of the bulk metals owing to quantum size effects. Metal NCs, which can be size-controlled and heterometal doped at atomic accuracy, are expected to be the next generation of important materials, and new metal NCs are reported regularly. However, compared with conventional materials such as metal complexes and relatively large metal nanoparticles (>2 nm), these metal NCs are still underdeveloped in terms of evaluation and establishment of application methods. Electrochemical measurements are one of the most widely used methods for synthesis, application, and characterisation of metal NCs. This review summarizes the basic knowledge of the electrochemistry and experimental techniques, and provides examples of the reported electronic states of thiolate-protected gold NCs elucidated by electrochemical approaches. It is expected that this review will provide useful information for researchers starting to study metal NCs.
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Coherent Vibrational Dynamics of Au 144(SC 8H 9) 60 Nanoclusters. J Phys Chem Lett 2023:6679-6685. [PMID: 37463467 DOI: 10.1021/acs.jpclett.3c01477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2023]
Abstract
The coherent vibrational dynamics of Au144(SC8H9)60, obtained from femtosecond time-resolved transient absorption spectroscopy, are described. Two acoustic modes were identified and assigned, including 2.0 THz breathing and 0.7 THz quadrupolar vibrations. These assignments are consistent with predictions using classical mechanics models, indicating that bulk models accurately describe the vibrational properties of Au144(SC8H9)60. Coherent phonon signals were persistent for up to 3 ps, indicating energy dissipation by the nanocluster was the primary dephasing channel. The initial excitation phases of the breathing and quadrupolar modes were π-phase-shifted, reflecting differences in the displacive nuclear motion of the vibrations. The combined agreement of the vibrational frequencies, relative phases, and decoherence times supported predictions based on classical models. The vibrational frequencies were insensitive to silver substitution for gold but did show increased inhomogeneous damping of the coherent phonons. The ability to predict the vibrational properties of metal nanoclusters can have an impact on nanoresonator and mass sensing technologies.
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3
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Intrinsic Optical Properties and Emerging Applications of Gold Nanostructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2206700. [PMID: 36620937 DOI: 10.1002/adma.202206700] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Revised: 12/21/2022] [Indexed: 06/09/2023]
Abstract
The collective oscillation of free electrons at the nanoscale surface of gold nanostructures is closely modulated by tuning the size, shape/morphology, phase, composition, hybridization, assembly, and nanopatterning, along with the surroundings of the plasmonic surface located at a dielectric interface with air, liquid, and solid. This review first introduces the physical origin of the intrinsic optical properties of gold nanostructures and further summarizes stimuli-responsive changes in optical properties, metal-field-enhanced optical signals, luminescence spectral shaping, chiroptical response, and photogenerated hot carriers. The current success in the landscape of nanoscience and nanotechnology mainly originates from the abundant optical properties of gold nanostructures in the thermodynamically stable face-centered cubic (fcc) phase. It has been further extended by crystal phase engineering to prepare thermodynamically unfavorable phases (e.g., kinetically stable) and heterophases to modulate their intriguing phase-dependent optical properties. A broad range of promising applications, including but not limited to full-color displays, solar energy harvesting, photochemical reactions, optical sensing, and microscopic/biomedical imaging, have fostered parallel research on the multitude of physical effects occurring in gold nanostructures.
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4
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Eight-Electron Superatomic Cu 31 Nanocluster with Chiral Kernel and NIR-II Emission. J Am Chem Soc 2023; 145:10355-10363. [PMID: 37104621 DOI: 10.1021/jacs.3c02215] [Citation(s) in RCA: 21] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Abstract
Owing to the inherent instability caused by the low Cu(I)/Cu(0) half-cell reduction potential, Cu(0)-containing copper nanoclusters are quite uncommon in comparison to their Ag and Au congeners. Here, a novel eight-electron superatomic copper nanocluster [Cu31(4-MeO-PhC≡C)21(dppe)3](ClO4)2 (Cu31, dppe = 1,2-bis(diphenylphosphino)ethane) is presented with total structural characterization. The structural determination reveals that Cu31 features an inherent chiral metal core arising from the helical arrangement of two sets of three Cu2 units encircling the icosahedral Cu13 core, which is further shielded by 4-MeO-PhC≡C- and dppe ligands. Cu31 is the first copper nanocluster carrying eight free electrons, which is further corroborated by electrospray ionization mass spectrometry, X-ray photoelectron spectroscopy and density functional theory calculations. Interestingly, Cu31 demonstrates the first near-infrared (750-950 nm, NIR-I) window absorption and the second near-infrared (1000-1700 nm, NIR-II) window emission, which is exceptional in the copper nanocluster family and endows it with great potential in biological applications. Of note, the 4-methoxy groups providing close contacts with neighboring clusters are crucial for the cluster formation and crystallization, while 2-methoxyphenylacetylene leads only to copper hydride clusters, Cu6H or Cu32H14. This research not only showcases a new member of copper superatoms but also exemplifies that copper nanoclusters, which are nonluminous in the visible range may emit luminescence in the deep NIR region.
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Suppression of kernel vibrations by layer-by-layer ligand engineering boosts photoluminescence efficiency of gold nanoclusters. Nat Commun 2023; 14:658. [PMID: 36746958 PMCID: PMC9902523 DOI: 10.1038/s41467-023-36387-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Accepted: 01/24/2023] [Indexed: 02/08/2023] Open
Abstract
The restriction of structural vibration has assumed great importance in attaining bright emission of luminescent metal nanoclusters (NCs), where tremendous efforts are devoted to manipulating the surface landscape yet remain challenges for modulation of the structural vibration of the metal kernel. Here, we report efficient suppression of kernel vibration achieving enhancement in emission intensity, by rigidifying the surface of metal NCs and propagating as-developed strains into the metal core. Specifically, a layer-by-layer triple-ligands surface engineering is deployed to allow the solution-phase Au NCs with strong metal core-dictated fluorescence, up to the high absolute quantum yields of 90.3 ± 3.5%. The as-rigidified surface imposed by synergistic supramolecular interactions greatly influences the low-frequency acoustic vibration of the metal kernel, resulting in a subtle change in vibration frequency but a reduction in amplitude of oscillation. This scenario therewith impedes the non-radiative relaxation of electron dynamics, rendering the Au NCs with strong emission. The presented study exemplifies the linkage between surface chemistry and core-state emission of metal NCs, and proposes a strategy for brighter emitting metal NCs by regulating their interior metal core-involved motion.
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Insight into the Role of Copper in the Transformation of a [Ag 25(2,5-DMBT) 16(DPPF) 3] + Nanocluster: Doping or Oxidation. Inorg Chem 2022; 61:18450-18457. [DOI: 10.1021/acs.inorgchem.2c02655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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7
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Coherent vibrational dynamics of Au 144(SR) 60 nanoclusters. Chem Sci 2022; 13:8124-8130. [PMID: 35919416 PMCID: PMC9278113 DOI: 10.1039/d2sc02246j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Accepted: 06/16/2022] [Indexed: 11/26/2022] Open
Abstract
The coherent vibrational dynamics of gold nanoclusters (NCs) provides important information on the coupling between vibrations and electrons as well as their mechanical properties, which is critical for understanding the evolution from a metallic state to a molecular state with diminishing size. Coherent vibrations have been widely explored in small-sized atomically precise gold NCs, while it remains a challenge to observe them in large-sized gold NCs. In this work, we report the coherent vibrational dynamics of atomically precise Au144(SR)60 NCs via temperature-dependent femtosecond transient absorption (TA) spectroscopy. The population dynamics of Au144(SR)60 consists of three relaxation processes: internal conversion, core-shell charge transfer and relaxation to the ground state. After removing the population dynamics from the TA kinetics, fast Fourier transform analysis on the residual oscillation reveals distinct vibrational modes at 1.5 THz (50 cm-1) and 2 THz (67 cm-1), which arise from the wavepacket motions along the ground-state and excited-state potential energy surfaces (PES), respectively. These results are helpful for understanding the physical properties of gold nanostructures with a threshold size that lies in between those of molecular-like NCs and metallic-state nanoparticles.
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A Review of State of the Art in Phosphine Ligated Gold Clusters and Application in Catalysis. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2105692. [PMID: 35332703 PMCID: PMC9130904 DOI: 10.1002/advs.202105692] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 02/23/2022] [Indexed: 05/28/2023]
Abstract
Atomically precise gold clusters are highly desirable due to their well-defined structure which allows the study of structure-property relationships. In addition, they have potential in technological applications such as nanoscale catalysis. The structural, chemical, electronic, and optical properties of ligated gold clusters are strongly defined by the metal-ligand interaction and type of ligands. This critical feature renders gold-phosphine clusters unique and distinct from other ligand-protected gold clusters. The use of multidentate phosphines enables preparation of varying core sizes and exotic structures beyond regular polyhedrons. Weak gold-phosphorous (Au-P) bonding is advantageous for ligand exchange and removal for specific applications, such as catalysis, without agglomeration. The aim of this review is to provide a unified view of gold-phosphine clusters and to present an in-depth discussion on recent advances and key developments for these clusters. This review features the unique chemistry, structural, electronic, and optical properties of gold-phosphine clusters. Advanced characterization techniques, including synchrotron-based spectroscopy, have unraveled substantial effects of Au-P interaction on the composition-, structure-, and size-dependent properties. State-of-the-art theoretical calculations that reveal insights into experimental findings are also discussed. Finally, a discussion of the application of gold-phosphine clusters in catalysis is presented.
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9
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Directional Doping and Cocrystallizing an Open-Shell Ag 39 Superatom via Precursor Engineering. ACS NANO 2022; 16:5507-5514. [PMID: 35353504 DOI: 10.1021/acsnano.1c09911] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Metal precursors employed in the bottom-up synthesis of metal nanoclusters (NCs) are of great importance in directing their composition and geometrical structure. In this work, a silver nanocluster co-protected by phosphine and thiolate, namely, [Ag39(PFBT)24(TPP)8]2- (Ag39, PFBT = pentafluorobenzenethiol, TPP = triphenylphosphine), was isolated and structurally characterized. It adopts a three-layered Ag13@Ag18@Ag8S24P8 core-shell structure. The Ag13@Ag18 kernel is unusual in multilayer noble metal NCs. By introducing a copper precursor in the synthesis, a bimetallic nanocluster [Ag37Cu2(PFBT)24(TPP)8]2- (Ag37Cu2) with an identical structure to Ag39 apart from two outer Ag atoms being substituted by Cu atoms was obtained. Astoundingly, the Cu precursor used in the synthesis was found to be critical in determining the final structure. The alteration of the Cu precursor led to the cocrystallization of the above alloy nanocluster with a Ag14 nanocluster, namely, [Ag37Cu2(PFBT)24(TPP)8]2-·[Ag14(PFBT)6(TPP)8] (Ag37Cu2·Ag14). The electronic structure analyzed by theoretical calculation reveals that Ag39 is a 17-electron open-shell superatom. The optical absorption of Ag39, Ag37Cu2, and Ag37Cu2·Ag14 was compared and studied in detail. This work not only enriches the family of alloy metallic nanoclusters but also provides a metal NC-based cocrystal platform for in-depth study of its crystal growth and photophysical property.
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10
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Metal-nanocluster Science and Technology: My Personal History and Outlook. Phys Chem Chem Phys 2022; 24:7569-7594. [DOI: 10.1039/d1cp05689a] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Metal nanoclusters (NCs) are among the leading targets in research of nanoscale materials, and elucidation of their properties (science) and development of control techniques (technology) have been continuously studied for...
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11
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On the Roles of Electron Transfer in Catalysis by Nanoclusters and Nanoparticles. Chemistry 2021; 27:16291-16308. [PMID: 34427365 DOI: 10.1002/chem.202102477] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Indexed: 01/09/2023]
Abstract
Electron transfer plays a major role in chemical reactions and processes, and this is particularly true of catalysis by nanomaterials. The advent of metal nanoparticle (NP) catalysts, recently including atomically precise nanoclusters (NCs) as parts of nanocatalyst devices has brought increased control of the relationship between NP and NC structures and their catalytic functions. Consequently, the molecular definition of these new nanocatalysts has allowed a better understanding and management of various kinds of electron transfer involved in the catalytic processes. This Minireview brings a chemist's view of several major aspects of electron-transfer functions concerning NPs and NCs in catalytic processes. Particular focus concerns the role of NPs and NCs as electron reservoirs and light-induced antenna in catalytic processes from H2 generation to more complex reactions and sustainable energy production.
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Programmable Metal Nanoclusters with Atomic Precision. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2006591. [PMID: 33984169 DOI: 10.1002/adma.202006591] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 10/26/2020] [Indexed: 06/12/2023]
Abstract
With the recent establishment of atomically precise nanochemistry, capabilities toward programmable control over the nanoparticle size and structure are being developed. Advances in the synthesis of atomically precise nanoclusters (NCs, 1-3 nm) have been made in recent years, and more importantly, their total structures (core plus ligands) have been mapped out by X-ray crystallography. These ultrasmall Au nanoparticles exhibit strong quantum-confinement effect, manifested in their optical absorption properties. With the advantage of atomic precision, gold-thiolate nanoclusters (Aun (SR)m ) are revealed to contain an inner kernel, Au-S interface (motifs), and surface ligand (-R) shell. Programming the atomic packing into various crystallographic structures of the metal kernel can be achieved, which plays a significant role in determining the optical properties and the energy gap (Eg ) of NCs. When the size increases, a general trend is observed for NCs with fcc or decahedral kernels, whereas those NCs with icosahedral kernels deviate from the general trend by showing comparably smaller Eg . Comparisons are also made to further demonstrate the more decisive role of the kernel structure over surface motifs based on isomeric Au NCs and NC series with evolving kernel or motif structures. Finally, future perspectives are discussed.
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Abstract
The boundary between molecular and metallic gold nanoclusters is of special interest. The difficulty in obtaining atomically precise nanoclusters larger than 2 nm limits the determination of such a boundary. The synthesis and total structural determination of the largest all-alkynyl-protected gold nanocluster (Ph4P)6[Au156(C≡CR)60] (R = 4-CF3C6H4-) (Au156) are reported. It presents an ideal platform for studying the relationship between the structure and the metallic nature. Au156 has a rod shape with the length and width of the kernel being 2.38 and 2.04 nm, respectively. The cluster contains a concentric Au126 core structure (Au46@Au50@Au30) protected by 30 linear RC≡C-Au-C≡CR staple motifs. It is interesting that Au156 displays multiple excitonic peaks in the steady-state absorption spectrum (molecular) and pump-power-dependent excited-state dynamics as revealed in the transient absorption spectrum (metallic), which indicates that Au156 is a critical crossover cluster for the transition from molecular to metallic state. Au156 is the smallest-sized gold nanocluster showing metal-like electron dynamics, and it is recognized that the cluster shape is one of the important factors determining the molecular or metallic nature of a gold nanocluster.
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The Critical Number of Gold Atoms for a Metallic State Nanocluster: Resolving a Decades-Long Question. ACS NANO 2021; 15:13980-13992. [PMID: 34490772 DOI: 10.1021/acsnano.1c04705] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Probing the transition from a metallic state to a molecular state in gold nanoparticles is fundamentally important for understanding the origin of surface plasmon resonance and the nature of the metallic bond. Atomically precise gold nanoclusters are desired for probing such a transition based upon a series of precise sizes with X-ray structures. While the definition of the metallic state in nanoclusters is simple, that is, when the HOMO-LUMO gap (Eg) becomes negligibly small (Eg < kBT, where kB is the Boltzmann constant and T the temperature), the experimental determination of ultrasmall Eg (e.g., of kBT level) is difficult, and the thermal excitation of valence electrons apparently comes into play in ultrasmall Eg nanoclusters. Although a sharp transition from nonmetallic Au246(SR)80 to metallic Au279(SR)84 (SR: thiolate) has been observed, there is still uncertainty about the transition region. Here, we summarize several criteria on determining the metallic state versus the molecular (or nonmetallic) state in gold nanoclusters, including (1) Eg determined by optical and electrochemical methods, (2) steady-state absorption spectra, (3) cryogenic optical spectra, (4) transient absorption spectra, (5) excited-state lifetime and power dependence, and (6) coherent oscillations in ultrafast electron dynamics. We emphasize that multiple analyses should be performed and cross-checked in practice because no single criterion is definitive. We also review the photophysics of several gold nanoclusters with nascent surface plasmon resonance. These criteria are expected to deepen the understanding of the metallic to molecular state transition of gold and other metal nanoclusters and also promote the design of functional nanomaterials and their applications.
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Unraveling the Nucleation Process from a Au(I)-SR Complex to Transition-Size Nanoclusters. J Am Chem Soc 2021; 143:15224-15232. [PMID: 34498861 DOI: 10.1021/jacs.1c06354] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Atomically precise noble metal nanoclusters provide a critical benchmark for the fundamental research of the origin of condensed matter because they retain the original state of the metal bonds. Also, knowledge about the transition from organometallic complexes to a nanoclusters is important for understanding the structural evolution of the nanoclusters, particularly their nucleation mechanism. Herein, three transition-size gold nanoclusters are prepared via a controlled diphosphine-mediated top-down routine. Starting from small-size nanoclusters, three new nanoclusters including Au13(SAdm)8(L4)2(BPh4) (Au13), Au14(S-c-C6H11)10L4 (Au14), and Au16(S-c-C6H11)11LPh* (Au16) are obtained by controlled clipping on the surface and kernel of initial nanoclusters. Combining their atomically precise structures with DFT theoretical calculations, the overall atom-by-atom structural evolution process from Au12(SR)12 (0 e-) to Au18(SR)14 (4 e-) is mapped out. In addition, studies on their electronic structures show that the evolution from an organometallic complex to nanoclusters is accompanied by a dramatic decrease in the HOMO-LUMO gaps. Most importantly, the formation of the first Au-Au bond is captured in the "Au4S4 to Au5" nucleation process from Au12(SR)12 complex to the Au13 nanocluster. This work provides a deep insight into the origin of inner core in Au NCs and their structural transition relationship with metal complexes.
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Contributions of Internal Atoms of Atomically Precise Metal Nanoclusters to Catalytic Performances. Chemistry 2021; 27:11539-11547. [PMID: 34096132 DOI: 10.1002/chem.202101310] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Indexed: 12/28/2022]
Abstract
Every atom of a heterogeneous catalyst can play a direct or indirect role in its overall catalytic properties. However, it is extremely challenging to determine explicitly which atom(s) of a catalyst can contribute most to its catalytic performance because the observed performance usually reflects an average of all the atoms in the catalyst. The emergence of atomically precise metal nanoclusters brings unprecedented opportunities to address these central issues, as the crystal structures of such nanoclusters have been solved, and hence very fundamental understanding of nanocatalysis can be attained at an atomic level. This minireview focuses on recent efforts to reveal the contributions of the internal atoms or vacancies of nanocluster catalysts to the catalytic processes, including how the catalytic activity can be dramatically changed by the central doping of a foreign atom, how catalytic activation and inactivation can be reversibly switched by shuttling the central atom into and out of nanoclusters, and how evolution in catalytic activity can be driven by structural periodicity in the inner kernels of the nanoclusters. We anticipate that progress in this research area could represent a novel conceptual framework for understanding the crucial roles of internal atoms of the catalysts in tuning the catalytic properties.
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Elucidating the stabilities and properties of the thiolate-protected Au nanoclusters with detaching the staple motifs. J Chem Phys 2021; 155:044302. [PMID: 34340381 DOI: 10.1063/5.0056933] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Thiolate-protected Au nanoclusters (AuNCs) have been widely studied in areas of catalysis, biosensors, and bioengineering. In real applications, e.g., catalytic reactions, the thiolate groups are normally partially detached. However, which of the thiolate groups are easily detached and how the detachment of the ligands affects the geometries and electronic structures of the Au nanoclusters have been rarely studied. In this work, we employed the density functional theory calculations as well as the molecular orbital analysis to explore the detachment effect of the ligands using nine thiolate-protected AuNCs as examples. Our results showed that there existed a nearly linear relationship between the averaged detachment energies and the numbers of Au atoms in the motifs. Detaching longer motifs normally required more energies owing to the stronger aurophilic effects. For detaching a full motif, based on the structure decomposition via the grand unified model, analysis on the inner Au core indicated that the change in Au-Au bond length was more sensitive for the inter-block compared to the intra-block. The detachment of the -SH fragment generally needs less energy and brings less structural deformations when compared to the removal of a full motif. Molecular orbital analysis showed that the relative energies of the HOMO orbitals were elevated, which led to the narrow down of the HOMO-LUMO gap. This work provides a primary description of the correlation of the ligands' detachment with the relative stabilities and structures of the AuNCs, which would be beneficial for establishing the structure-property relationship of AuNCs in real applications.
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Thiolate-Protected Metal Nanoclusters: Recent Development in Synthesis, Understanding of Reaction, and Application in Energy and Environmental Field. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 17:e2005328. [PMID: 33522090 DOI: 10.1002/smll.202005328] [Citation(s) in RCA: 58] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Revised: 11/30/2020] [Indexed: 06/12/2023]
Abstract
Metal nanoclusters (NCs), which are composed of about 250 or fewer metal atoms, possess great potential as novel functional materials. Fundamental research on metal NCs gradually started in the 1960s, and since 2000, thiolate (SR)-protected metal NCs have been the main metal NCs actively studied. The precise and systematic isolation of SR-protected metal NCs has been achieved in 2005. Since then, research on SR-protected metal NCs for both basic science and practical application has rapidly expanded. This review describes this recent progress in the field of SR-protected metal NCs in three areas: synthesis, understanding, and application. Specifically, the recent study of alloy NCs and connected structures composed of NCs is highlighted in the "synthesis" section, recent knowledge on the reactivity of NCs in solution is highlighted in the "understanding" section, and the applications of NCs in the energy and environmental field are highlighted in the "application" section. This review provides insight on the current state of research on SR-protected metal NCs and discusses the challenges to be overcome for further development in this field as well as the possibilities that these materials can contribute to solving the problems facing modern society.
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Abstract
Understanding the excited-state dynamics of nanomaterials is essential to their applications in photoenergy storage and conversion. This review summarizes recent progress in the excited-state dynamics of atomically precise gold (Au) nanoclusters (NCs). We first discuss the electronic structure and typical relaxation pathways of Au NCs from subpicoseconds to microseconds. Unlike plasmonic Au nanoparticles, in which collective electron excitation dominates, Au NCs show single-electron transitions and molecule-like exciton dynamics. The size-, shape-, structure-, and composition-dependent dynamics in Au NCs are further discussed in detail. For small-sized Au NCs, strong quantum confinement effects give rise to relaxation dynamics that is significantly dependent on atomic packing, shape, and heteroatom doping. For relatively larger-sized Au NCs, strong size dependence can be observed in exciton and electron dynamics. We also discuss the origin of coherent oscillations and their roles in excited-state relaxation. Finally, we provide our perspective on future directions in this area.
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Open questions on the transition between nanoscale and bulk properties of metals. Commun Chem 2021; 4:28. [PMID: 36697528 PMCID: PMC9814084 DOI: 10.1038/s42004-021-00466-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Accepted: 02/01/2021] [Indexed: 01/28/2023] Open
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A 34‐Electron Superatom Ag
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Cluster with Regioselective Ternary Ligands Shells and Its 2D Rhombic Superlattice Assembly. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202013681] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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23
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A 34‐Electron Superatom Ag
78
Cluster with Regioselective Ternary Ligands Shells and Its 2D Rhombic Superlattice Assembly. Angew Chem Int Ed Engl 2020; 60:4231-4237. [DOI: 10.1002/anie.202013681] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Indexed: 12/27/2022]
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Inhomogeneous Quantized Single-Electron Charging and Electrochemical-Optical Insights on Transition-Sized Atomically Precise Gold Nanoclusters. ACS NANO 2020; 14:16781-16790. [PMID: 33196176 DOI: 10.1021/acsnano.0c04914] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Small differences in electronic structures, such as an emerging energy band gaps or the splitting of degenerated orbitals, are very challenging to resolve but important for nanomaterials properties. A signature electrochemical property called quantized double layer charging, i.e., "continuous" one-electron transfers (1e, ETs), in atomically precise Au133(TBBT)52, Au144(BM)60, and Au279(TBBT)84 is analyzed to reveal the nonmetallic to metallic transitions (whereas TBBT is 4-tert-butylbenzenethiol and BM is benzyl mercaptan; abbreviated as Au133, Au144, and Au279). Subhundred milli-eV energy differences are resolved among the "often-approximated uniform" peak spacings from multipairs of reversible redox peaks in voltammetric analysis, with single ETs as internal standards for calibration and under temperature variations. Cyclic and differential pulse voltammetry experiments reveal a 0.15 eV energy gap for Au133 and a 0.17 eV gap for Au144 at 298 K. Au279 is confirmed metallic, displaying a "bulk-continuum" charging response without an energy gap. The energy gaps and double layer capacitances of Au133 and Au144 increase as the temperature decreases. The temperature dependences of charging energies and HOMO-LUMO gaps of Au133 and Au144 are attributed to the counterion permeation and the steric hindrance of ligand, as well as their molecular compositions. With the subtle energy differences resolved, spectroelectrochemistry features of Au133 and Au144 are compared with ultrafast spectroscopy to demonstrate a generalizable analysis approach to correlate steady-state and transient energy diagram for the energy-in processes. Electrochemiluminescence (ECL), one of the energy-out processes after the charge transfer reactions, is reported for the three samples. The ECL intensity of Au279 is negligible, whereas the ECLs of Au133 and Au144 are relatively stronger and observable (but orders of magnitudes weaker than our recently reported bimetallic Au12Ag13). Results from these atomically precise nanoclusters also demonstrate that the combined voltammetric and spectroscopic analyses, together with temperature variations, are powerful tools to reveal subtle differences and gain insights otherwise inaccessible in other nanomaterials.
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Toward Active-Site Tailoring in Heterogeneous Catalysis by Atomically Precise Metal Nanoclusters with Crystallographic Structures. Chem Rev 2020; 121:567-648. [DOI: 10.1021/acs.chemrev.0c00495] [Citation(s) in RCA: 189] [Impact Index Per Article: 47.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Abstract
Metal nanoclusters fill the gap between discrete atoms and plasmonic nanoparticles, providing unique opportunities for investigating the quantum effects and precise structure-property correlations at the atomic level. As a versatile strategy, alloying can largely improve the physicochemical performances compared to the corresponding homo-metal nanoclusters, and thus benefit the applications of such nanomaterials. In this review, we highlight the achievements of atomically precise alloy nanoclusters, and summarize the alloying principles and fundamentals, including the synthetic methods, site-preferences for different heteroatoms in the templates, and alloying-induced structure and property changes. First, based on various Au or Ag nanocluster templates, heteroatom doping modes are presented. The templates with electronic shell-closing configurations tend to maintain their structures during doping, while the others may undergo transformation and give rise to alloy nanoclusters with new structures. Second, alloy nanoclusters of specific magic sizes are reviewed. The arrangement of different atoms is related to the symmetry of the structures; that is, different atoms are symmetrically located in the nanoclusters of smaller sizes, and evolve into shell-by-shell structures at larger sizes. Then, we elaborate on the alloying effects in terms of optical, electrochemical, electroluminescent, magnetic and chiral properties, as well as the stability and reactivity via comparisons between the doped nanoclusters and their homo-metal counterparts. For example, central heteroatom-induced photoluminescence enhancement is emphasized. The applications of alloy nanoclusters in catalysis, chemical sensing, bio-labeling, and other fields are further discussed. Finally, we provide perspectives on existing issues and future efforts. Overall, this review provides a comprehensive synthetic toolbox and controllable doping modes so as to achieve more alloy nanoclusters with customized compositions, structures, and properties for applications. This review is based on publications available up to February 2020.
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Abstract
Many important chemical transformations enabled by plasmonic hot carrier photocatalysis have been reported, although their efficiencies are often too low for practical applications. We examine how the efficiency of plasmon-induced hot electron transfer depends on the Au particle size in Au-tipped CdS nanorods. We show that with decreasing Au size, the plasmon width increases due to enhanced surface damping contributions. The excitation of Au nanoparticles leads to an instrument response time-limited ultrafast hot electron transfer process to CdS (≪140 fs). The quantum efficiency of this process increases from ∼1% to ∼18% as the particle size decreases from 5.5 ± 1.1 to 1.6 ± 0.5 nm due to both enhanced hot electron generation and transfer efficiencies in small Au particles. Our finding suggests that decreasing plasmonic particle size is an effective approach for improving plasmon-induced hot carrier transfer efficiency and provides important insight for the rational improvement of plasmonic hot carrier-based devices.
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Abstract
Fine metal clusters have attracted much attention from the viewpoints of both basic and applied science for many years because of their unique physical/chemical properties and functions, which differ from those of bulk metals. Among these materials, thiolate (SR)-protected gold clusters (Aun(SR)m clusters) have been the most studied metal clusters since 2000 because of their ease of synthesis and handling. However, in the early 2000s, it was not easy to isolate these metal clusters. Therefore, high-resolution separation methods were explored, and several atomic-level separation methods, including polyacrylamide gel electrophoresis (PAGE), high-performance liquid chromatography (HPLC), and thin-layer chromatography (TLC), were successively established. These techniques have made it possible to isolate a series of Aun(SR)m clusters, and much knowledge has been obtained on the correlation between the chemical composition and fundamental properties such as the stability, electronic structure, and physical properties of Aun(SR)m clusters. In addition, these high-resolution separation techniques are now also frequently used to evaluate the distribution of the product and to track the reaction process. In this way, high-resolution separation techniques have played an essential role in the study of Aun(SR)m clusters. However, only a few reviews have focused on this work. This review focuses on PAGE, HPLC, and TLC separation techniques, which offer high resolution and repeatability, and summarizes previous studies on the high-resolution separation of Aun(SR)m and related clusters with the purpose of promoting a better understanding of the features and the utility of these techniques.
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Three-Stage Evolution from Nonscalable to Scalable Optical Properties of Thiolate-Protected Gold Nanoclusters. J Am Chem Soc 2019; 141:19754-19764. [DOI: 10.1021/jacs.9b09066] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Au
130−
x
Ag
x
Nanoclusters with Non‐Metallicity: A Drum of Silver‐Rich Sites Enclosed in a Marks‐Decahedral Cage of Gold‐Rich Sites. Angew Chem Int Ed Engl 2019; 58:18798-18802. [DOI: 10.1002/anie.201908694] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Indexed: 12/14/2022]
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Au
130−
x
Ag
x
Nanoclusters with Non‐Metallicity: A Drum of Silver‐Rich Sites Enclosed in a Marks‐Decahedral Cage of Gold‐Rich Sites. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201908694] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Controlling magnetism of Au 133(TBBT) 52 nanoclusters at single electron level and implication for nonmetal to metal transition. Chem Sci 2019; 10:9684-9691. [PMID: 32015802 PMCID: PMC6977549 DOI: 10.1039/c9sc02736j] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 09/04/2019] [Indexed: 12/14/2022] Open
Abstract
The [Au133(SR)52]q nanocluster is discovered to possess one spin per particle when q = 0, but no unpaired electron when q = +1.
The transition from the discrete, excitonic state to the continuous, metallic state in thiolate-protected gold nanoclusters is of fundamental interest and has attracted significant efforts in recent research. Compared with optical and electronic transition behavior, the transition in magnetism from the atomic gold paramagnetism (Au 6s1) to the band behavior is less studied. In this work, the magnetic properties of 1.7 nm [Au133(TBBT)52]0 nanoclusters (where TBBT = 4-tert-butylbenzenethiolate) with 81 nominal “valence electrons” are investigated by electron paramagnetic resonance (EPR) spectroscopy. Quantitative EPR analysis shows that each cluster possesses one unpaired electron (spin), indicating that the electrons fill into discrete orbitals instead of a continuous band, for that one electron in the band would give a much smaller magnetic moment. Therefore, [Au133(TBBT)52]0 possesses a nonmetallic electronic structure. Furthermore, we demonstrate that the unpaired spin can be removed by oxidizing [Au133(TBBT)52]0 to [Au133(TBBT)52]+ and the nanocluster transforms from paramagnetism to diamagnetism accordingly. The UV-vis absorption spectra remain the same in the process of single-electron loss or addition. Nuclear magnetic resonance (NMR) is applied to probe the charge and magnetic states of Au133(TBBT)52, and the chemical shifts of 52 surface TBBT ligands are found to be affected by the spin in the gold core. The NMR spectrum of Au133(TBBT)52 shows a 13-fold splitting with 4-fold degeneracy of 52 TBBT ligands, which are correlated to the quasi-D2 symmetry of the ligand shell. Overall, this work provides important insights into the electronic structure of Au133(TBBT)52 by combining EPR, optical and NMR studies, which will pave the way for further understanding of the transition behavior in metal nanoclusters.
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Anomalous phonon relaxation in Au 333(SR) 79 nanoparticles with nascent plasmons. Proc Natl Acad Sci U S A 2019; 116:13215-13220. [PMID: 31209027 DOI: 10.1073/pnas.1904337116] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Research on plasmons of gold nanoparticles has gained broad interest in nanoscience. However, ultrasmall sizes near the metal-to-nonmetal transition regime have not been explored until recently due to major synthetic difficulties. Herein, intriguing electron dynamics in this size regime is observed in atomically precise Au333(SR)79 nanoparticles. Femtosecond transient-absorption spectroscopy reveals an unprecedented relaxation process of 4-5 ps-a fast phonon-phonon relaxation process, together with electron-phonon coupling (∼1 ps) and normal phonon-phonon coupling (>100 ps) processes. Three types of -R capped Au333(SR)79 all exhibit two plasmon-bleaching signals independent of the -R group as well as solvent, indicating plasmon splitting and quantum effect in the ultrasmall core of Au333(SR)79 This work is expected to stimulate future work on the transition-size regime of nanometals and discovery of behavior of nascent plasmons.
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Gold Nanoclusters: Bridging Gold Complexes and Plasmonic Nanoparticles in Photophysical Properties. NANOMATERIALS 2019; 9:nano9070933. [PMID: 31261666 PMCID: PMC6669669 DOI: 10.3390/nano9070933] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 06/21/2019] [Accepted: 06/25/2019] [Indexed: 01/10/2023]
Abstract
Recent advances in the determination of crystal structures and studies of optical properties of gold nanoclusters in the size range from tens to hundreds of gold atoms have started to reveal the grand evolution from gold complexes to nanoclusters and further to plasmonic nanoparticles. However, a detailed comparison of their photophysical properties is still lacking. Here, we compared the excited state behaviors of gold complexes, nanolcusters, and plasmonic nanoparticles, as well as small organic molecules by choosing four typical examples including the Au10 complex, Au25 nanocluster (1 nm metal core), 13 diameter Au nanoparticles, and Rhodamine B. To compare their photophysical behaviors, we performed steady-state absorption, photoluminescence, and femtosecond transient absorption spectroscopic measurements. It was found that gold nanoclusters behave somewhat like small molecules, showing both rapid internal conversion (<1 ps) and long-lived excited state lifetime (about 100 ns). Unlike the nanocluster form in which metal–metal transitions dominate, gold complexes showed significant charge transfer between metal atoms and surface ligands. Plasmonic gold nanoparticles, on the other hand, had electrons being heated and cooled (~100 ps time scale) after photo-excitation, and the relaxation was dominated by electron–electron scattering, electron–phonon coupling, and energy dissipation. In both nanoclusters and plasmonic nanoparticles, one can observe coherent oscillations of the metal core, but with different fundamental origins. Overall, this work provides some benchmarking features for organic dye molecules, organometallic complexes, metal nanoclusters, and plasmonic nanoparticles.
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Three-orders-of-magnitude variation of carrier lifetimes with crystal phase of gold nanoclusters. SCIENCE (NEW YORK, N.Y.) 2019; 364:279-282. [PMID: 31000661 DOI: 10.1126/science.aaw8007] [Citation(s) in RCA: 84] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 03/22/2019] [Indexed: 11/02/2022]
Abstract
We report a three-orders-of-magnitude variation of carrier lifetimes in exotic crystalline phases of gold nanoclusters (NCs) in addition to the well-known face-centered cubic structure, including hexagonal close-packed (hcp) Au30 and body-centered cubic (bcc) Au38 NCs protected by the same type of capping ligand. The bcc Au38 NC had an exceptionally long carrier lifetime (4.7 microseconds) comparable to that of bulk silicon, whereas the hcp Au30 NC had a very short lifetime (1 nanosecond). Although the presence of ligands may, in general, affect carrier lifetimes, experimental and theoretical results showed that the drastically different recombination lifetimes originate in the different overlaps of wave functions between the tetrahedral Au4 building blocks in the hierarchical structures of these NCs.
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Atomically Tailored Gold Nanoclusters for Catalytic Application. Angew Chem Int Ed Engl 2019; 58:8291-8302. [PMID: 30633857 DOI: 10.1002/anie.201814156] [Citation(s) in RCA: 161] [Impact Index Per Article: 32.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Indexed: 11/07/2022]
Abstract
Recent advances in the synthetic chemistry of atomically precise metal nanoclusters (NCs) have significantly broadened the accessible sizes and structures. Such particles are well defined and have intriguing properties, thus, they are attractive for catalysis. Especially, those NCs with identical size but different core (or surface) structure provide unique opportunities that allow the specific role of the core and the surface to be mapped out without complication by the size effect. Herein, we summarize recent work with isomeric Aun NCs protected by ligands and isostructural NCs but with different surface ligands. The highlighted work includes catalysis by spherical and rod-shaped Au25 (with different ligands), quasi-isomeric Au28 (SR)20 with different R groups, structural isomers of Au38 (SR)24 (with identical R) and Au38 S2 (SR)20 with body-centred cubic (bcc) structure, and isostructural [Au38 L20 (PPh3 )4 ]2+ (different L). These isomeric and/or isostructural NCs have provided valuable insights into the respective roles of the kernel, surface staples, and the type of ligands on catalysis. Future studies will lead to fundamental advances and development of tailor-made catalysts.
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Deepening the Understanding of Thiolate-Protected Metal Clusters Using High-Performance Liquid Chromatography. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2019. [DOI: 10.1246/bcsj.20180357] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Linker Flexibility-Dependent Cluster Transformations and Cluster-Controlled Luminescence in Isostructural Silver Cluster-Assembled Materials (SCAMs). Chemistry 2019; 25:3376-3381. [DOI: 10.1002/chem.201805808] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 01/05/2019] [Indexed: 11/07/2022]
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Abstract
Due to their atomically precise structures and intriguing chemical/physical properties, metal nanoclusters are an emerging class of modular nanomaterials. Photo-luminescence (PL) is one of their most fascinating properties, due to the plethora of promising PL-based applications, such as chemical sensing, bio-imaging, cell labeling, phototherapy, drug delivery, and so on. However, the PL of most current nanoclusters is still unsatisfactory-the PL quantum yield (QY) is relatively low (generally lower than 20%), the emission lifetimes are generally in the nanosecond range, and the emitted color is always red (emission wavelengths of above 630 nm). To address these shortcomings, several strategies have been adopted, and are reviewed herein: capped-ligand engineering, metallic kernel alloying, aggregation-induced emission, self-assembly of nanocluster building blocks into cluster-based networks, and adjustments on external environment factors. We further review promising applications of these fluorescent nanoclusters, with particular focus on their potential to impact the fields of chemical sensing, bio-imaging, and bio-labeling. Finally, scope for improvements and future perspectives of these novel nanomaterials are highlighted as well. Our intended audience is the broader scientific community interested in the fluorescence of metal nanoclusters, and our review hopefully opens up new horizons for these scientists to manipulate PL properties of nanoclusters. This review is based on publications available up to December 2018.
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A Correlated Series of Au/Ag Nanoclusters Revealing the Evolutionary Patterns of Asymmetric Ag Doping. J Am Chem Soc 2018; 140:14235-14243. [DOI: 10.1021/jacs.8b08335] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Large-Scale Synthesis, Crystal Structure, and Optical Properties of the Ag 146Br 2(SR) 80 Nanocluster. ACS NANO 2018; 12:9318-9325. [PMID: 30114922 DOI: 10.1021/acsnano.8b04233] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Solving the atomic structure of large-sized metal nanoclusters is a highly challenging task yet critically important for understanding the properties and developing applications. Herein, we report a stable silver nanocluster-Ag146Br2(SR)80 (where SR = 4-isopropylbenzenethiolate)-with its structure solved by X-ray crystallography. Gram-scale synthesis with high yield has been achieved by a one-pot reaction, which offers opportunities for functionalization and applications. This silver nanocluster possesses a core-shell structure with a Ag51 core surrounded by a shell of Ag95Br2S80. The Ag51 core can be viewed as a distorted decahedron, endowing this nanocluster with quantized electronic transitions. In the surface-protecting layer, five different types of S-Ag coordination modes are observed, ranging from the linear Ag-S-Ag to S-Ag3 (triangle) and S-Ag4 (square). Furthermore, temperature-dependent optical absorption and ultrafast electron dynamics are conducted to explore the relationship between the properties and structure, demonstrating that the distorted metal core and "flying saucer"-like shape of this nanocluster have significant effects on the electronic behavior. A comparison with multiple sizes of Ag nanoclusters also provides some insights into the evolution from molecular to metallic behavior.
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Total Structure Determination of Au16(S-Adm)12 and Cd1Au14(StBu)12 and Implications for the Structure of Au15(SR)13. J Am Chem Soc 2018; 140:10988-10994. [DOI: 10.1021/jacs.8b04257] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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Sharp Transition from Nonmetallic Au246 to Metallic Au279 with Nascent Surface Plasmon Resonance. J Am Chem Soc 2018; 140:5691-5695. [DOI: 10.1021/jacs.8b02487] [Citation(s) in RCA: 129] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Sputter Deposition toward Short Cationic Thiolated Fluorescent Gold Nanoclusters: Investigation of Their Unique Structural and Photophysical Characteristics Using High-Performance Liquid Chromatography. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:4024-4030. [PMID: 29526107 DOI: 10.1021/acs.langmuir.8b00067] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We herein present the preparation of short, bulky cationic thiolate (thiocholine)-protected fluorescent Au nanoclusters via sputter deposition over a liquid polymer matrix. The obtained Au nanoclusters showed near-infrared fluorescence and had an average core diameter of 1.7 ± 0.6 nm, which is too large compared to that of the reported fluorescent Au nanoclusters prepared via chemical means. We revealed the mechanism of formation of this unique material using single-particle electron microscopy, optical measurements, X-ray photoelectron spectroscopy (XPS), and high-performance liquid chromatography fractionations. The noncrystallized image was observed via single-particle high-angle annular dark-field scanning transmission electron microscopy observations and compared with chemically synthesized crystalline Au nanoparticle with the same diameter, which demonstrated the unique structural characteristic speculated via XPS. The size fractionation and size-dependent fluorescence measurement, together with other observations, indicated that the nanoclusters most probably contained a mixture of very small fluorescent species in their aggregated form and were derived from the sputtering process itself and not from the interaction between thiol ligands.
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Au 279(SR) 84: The Smallest Gold Thiolate Nanocrystal That Is Metallic and the Birth of Plasmon. J Phys Chem Lett 2018; 9:1295-1300. [PMID: 29493241 DOI: 10.1021/acs.jpclett.8b00308] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We report a detailed study on the optical properties of Au279(SR)84 using steady-state and transient absorption measurements to probe its metallic nature, time-dependent density functional theory (TDDFT) studies to correlate the optical spectra, and density of states (DOS) to reveal the factors governing the origin of the collective surface plasmon resonance (SPR) oscillation. Au279 is the smallest identified gold nanocrystal to exhibit SPR. Its optical absorption exhibits SPR at 510 nm. Power-dependent bleach recovery kinetics of Au279 suggests that electron dynamics dominates its relaxation and it can support plasmon oscillations. Interestingly, TDDFT and DOS studies with different tail group residues (-CH3 and -Ph) revealed the important role played by the tail groups of ligands in collective oscillation. Also, steady-state and time-resolved absorption for Au36, Au44, and Au133 were studied to reveal the molecule-to-metal evolution of aromatic AuNMs. The optical gap and transient decay lifetimes decrease as the size increases.
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