Structure and Optical Properties of an Ag135Cu60 Nanocluster Incorporating an Ag135 Buckminsterfullerene-like Topology

Nanoscience Chemistry Materials Science Inorganic Chemistry Metallic Materials Materials Chemistry
nanocluster silver-copper alloy optical properties fullerene structure materials science

Metal nanoclusters are nanoscale materials that bridge the gap between molecules and metals, exhibiting unique physicochemical properties, especially in the study of the relationship between atomic structure and physical properties. In recent years, researchers have shown great interest in organic ligand-protected metal nanoclusters due to their precisely defined atomic structures, fascinating geometric features, and potential applications. Particularly, multi-shell metal nanoclusters with fullerene-like topologies have become a research hotspot due to their high symmetry and stability. However, the synthesis of fullerene structures composed of non-carbon elements has been challenging due to stability issues, which has slowed progress in related studies.

This study aims to address this challenge by synthesizing a novel silver-copper nanocluster, Ag135Cu60, exploring its structure and optical properties, and revealing its potential applications in nanoscience and materials science. This cluster features a Buckminsterfullerene-like topology, providing new experimental support for studying the relationship between the structure of metal nanoclusters and their metallic states.

Source of the Paper

This paper was co-authored by Li Tang, Weinan Dong, Qikai Han, Bin Wang, Zhennan Wu, and Shuxin Wang. The research team is affiliated with the College of Chemistry and Molecular Engineering, College of Materials Science and Engineering at Qingdao University of Science and Technology, and the College of Electronic Science and Engineering at Jilin University, China. The paper was published in Nature Synthesis in April 2025, titled “Structure and optical properties of an Ag135Cu60 nanocluster incorporating an Ag135 Buckminsterfullerene-like topology.”

Research Process

1. Synthesis and Characterization

The Ag135Cu60 nanocluster was synthesized using a one-pot method. The specific steps are as follows:
1. Preparation of Materials: 4-CH3C6H4SO3Ag, CuCl2·2H2O, and 2-phenylethanethiol were dissolved in a mixture of dichloromethane and methanol.
2. Reduction Reaction: NaBH4 was added as a reducing agent, and the reaction was stirred at room temperature for 12 hours. The solution gradually changed from a white suspension to a reddish-brown color, indicating the formation of nanoclusters.
3. Purification and Crystallization: Free ions and by-products were removed through centrifugation and washing, and the final product was crystallized in a dichloromethane/n-hexane solvent mixture to yield black crystals.

The synthesized product was characterized using thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and nuclear magnetic resonance (NMR), confirming its chemical formula as Ag135Cu60(S(CH2)2Ph)60Cl42.

2. Structural Analysis

The structure of Ag135Cu60 was detailed through single-crystal X-ray diffraction (XRD) analysis. The cluster consists of five shells:
1. Core Layer: Ag13 icosahedron.
2. Second Layer: Ag42 icosahedron.
3. Third Layer: Ag60 fullerene-like topology, consisting of 12 pentagons and 20 hexagons.
4. Fourth Layer: Cl12 icosahedron.
5. Outermost Layer: Cu60 truncated dodecahedron.

This layer-by-layer nested structure endows Ag135Cu60 with high symmetry and stability, laying the foundation for its unique optical properties.

3. Optical Properties Study

The optical properties of Ag135Cu60 were revealed through ultraviolet-visible (UV-Vis) absorption spectroscopy and femtosecond transient absorption spectroscopy (fs-TA).
1. UV-Vis Absorption Spectroscopy: Multiple absorption peaks were observed at 407 nm, 500 nm, 643 nm, 731 nm, and 884 nm, indicating the dual characteristics of molecular and metallic states.
2. Femtosecond Transient Absorption Spectroscopy: The study found that the excited-state dynamics of Ag135Cu60 exhibit significant power dependence, suggesting that its electron relaxation pathways are closely related to phonon coupling.

4. Electrochemical Properties

The electrochemical properties of Ag135Cu60 were further investigated using differential pulse voltammetry (DPV) and cyclic voltammetry (CV). The results showed that the cluster has a tiny HOMO-LUMO gap (0.01 eV), exhibiting metallic-like behavior.

Main Results

  1. Structural Confirmation: Through XRD and various characterization methods, the five-shell structure of Ag135Cu60 was confirmed. The core layer Ag13 and the second layer Ag42 form stable icosahedrons, while the third layer Ag60 exhibits a fullerene-like topology.
  2. Optical Properties: UV-Vis absorption spectroscopy and fs-TA revealed the dual characteristics of molecular and metallic states in Ag135Cu60, particularly the absorption peak at 500 nm, which resembles plasmonic absorption.
  3. Electrochemical Properties: DPV indicated that Ag135Cu60 has a tiny HOMO-LUMO gap, exhibiting metallic-like behavior.

Conclusion and Significance

This study successfully synthesized a novel silver-copper nanocluster, Ag135Cu60, and detailed its structure and optical properties. The cluster features a fullerene-like topology and exhibits dual characteristics of molecular and metallic states, providing new experimental support for studying the relationship between the structure and physical properties of metal nanoclusters. Additionally, the synthesis method of Ag135Cu60 offers important references for designing more complex nanoclusters in the future, with broad application prospects, particularly in nanotechnology and materials science.

Research Highlights

  1. Novel Structure: Ag135Cu60 is the largest silver-copper core-shell nanocluster reported to date, with a five-shell structure exhibiting high symmetry and stability.
  2. Dual Characteristics: The cluster exhibits dual characteristics of molecular and metallic states, providing new insights into the electronic behavior of metal nanoclusters.
  3. Innovative Method: The study employed a one-pot method to synthesize Ag135Cu60 and detailed its structure and properties through various characterization techniques, offering important references for future research.

Additional Valuable Information

The crystallographic data of this study have been submitted to the Cambridge Crystallographic Data Centre (CCDC), and readers can access it for free through their website. Additionally, the research team provided detailed supplementary information, including experimental methods, data analysis, and related discussions, facilitating a deeper understanding of the study.

This research not only advances the field of metal nanoclusters but also provides important theoretical foundations and experimental support for designing novel nanomaterials in the future. By revealing the structure and optical properties of Ag135Cu60, the researchers have opened up new directions in nanoscience and technology.