Nitrogen Donor Protection for Atomically Precise Metal Nanoclusters

Surface organic ligands are critical in dictating the structures and properties of atomically precise metal nanoclusters. In contrast to the conventionally used thiolate, phosphine and alkynyl ligands, nitrogen donor ligands have not been used in the protection for well-defined metal nanoclusters until recently. This review focuses on recent developments in atomically precise metal nanoclusters stabilized by different types of nitrogen donor ligands, in which the synthesis, total structure determination and various properties are covered. We hope that this review will provide insights into the rational design of N donor-protected metal nanoclusters in terms of structural and functional modulation.     

Capped Bimetallic and Trimetallic Nanoparticles for Catalysis and Information Technology

Summary: Polymer-capped metal nanoparticles can be recognized as a kind of macromolecule-metal nanoparticle complexes. Here the preparations of the capped bimetallic and trimetallic nanoparticles, in which each particle contains two and three elements of metal, respectively, are presented. They may have a random alloy, a core/shell, or other kinds of structure depending on the preparation method and the combination of elements. The core/shell structure is advantageous to electronically control the activity of metal catalysts. The triple core/shell structured trimetallic nanoparticles were found to have higher catalytic activity than the corresponding monometallic and bimetallic nanoparticles in three cases. Capped metal nanoparticles were also used as a dopant to liquid crystals. Liquid crystal displays, fabricated by metal nanoparticle-doped liquid crystals, showed faster response than those without dopants. Bimetalization could increase the long-term stability in the doped liquid crystal displays. Thus, metal nanoparticles can improve the electronic display system, which occupies an important position in information technology. In addition, SmCo₅ nanomagnets were successfully prepared by a chemical method, possibly providing a new building block for information technology. The prepared SmCo₅ nanoparticles have a coercivity of 1500 Oe at room temperature. The bimetallic nanoparticles may open a new field in super-high-density magnetic memories.     

Cu2+‐Induced Structural Isomers: Effect of Foreign Metal Ions on the Structure and Properties of Silver Nanoclusters

Metal ions have an important impact on the precise control of the synthesis and atomic structural arrangement of noble metal nanoclusters. In this work, the effect of metal ions on the isomer generation of metal nanoclusters is revealed for the first time. Compared with the previous Ag₂₃ nanoclusters with two face‐centered cubic (fcc) unit cells twisting 27°, the Ag₂₃ isomer had a higher symmetry structure with two fcc unit cells almost overlapping. In addition, the UV/Vis absorption spectrum of the isomer showed a slight redshift of approximately 14 nm. The redshift might be because of the modulation of electronic structure, which is derived from fine‐tuned crystal structure. Based on the experimental results, we provide mechanisms to explain the Cu²⁺ effect on the structural isomer. This work reports a significant finding to tune precisely the crystal structure and understand the mechanism of shape‐controlled synthesis of metal nanoclusters.     

液相合成金纳米团簇

作为过渡金属团簇的一种,金纳米团簇由于具有不同于其它纳米材料的特殊物化性能,在催化、光学、电学及生物技术等领域具有潜在的应用前景。本文综述了液相合成金纳米团簇的研究进展,主要包括有机膦化物和硫醇保护的金纳米团簇的合成方法与晶体结构,这将为金纳米团簇的研究者提供一定的参考。     

Spectral,Thermal and Structural Studies of Two 3D Coordination Polymers Based on Tetracarboxylic Ligand

Two new coordination polymers,[M_6L_3(DMA)_3(H_2O)](M=Zn for 1,Cu for 2,L=tetrakis[3-(carboxyphenyl)oxamethyl]methane acid,DMA = N,N-dimethylacetamide) have been solvothermally synthesized. Single-crystal X-ray diffraction analysis reveals that compounds 1 and 2 are isostructural and crystallize in the trigonal space group R. The asymmetrical unit contains two metal ions,one L~(4-) ligand and two coordinated DMA molecules. The metal ions are connected through six aromatic rings into a linear trimetallic zinc building unit. The whole structure is connected through tetrehedral ligand and the trimetallic building units to form a 4,6-connected framework of the toc topology. Compounds 1 and 2 are further studied by IR spectroscopy,thermogravimetric analyses and PXRD. The solid-state UV-Vis and photoluminescent properties of compounds 1 are also investigated.     

Rational Design of Pt−Pd−Ni Trimetallic Nanocatalysts for Room-Temperature Benzaldehyde and Styrene Hydrogenation

Nanostructures of the multimetallic catalysts offer great scope for fine tuning of heterogeneous catalysis, but clear understanding of the surface chemistry and structures is important to enhance their selectivity and efficiency. Focussing on a typical Pt−Pd−Ni trimetallic system, we comparatively examined the Ni/C, Pt/Ni/C, Pd/Ni/C and Pt−Pd/Ni/C catalysts synthesized by impregnation and galvanic replacement reaction. To clarify surface chemical/structural effect, the Pt−Pd/Ni/C catalyst was thermally treated at X=200, 400 or 600 °C in a H₂ reducing atmosphere, respectively termed as Pt−Pd/Ni/C−X. The as-prepared catalysts were characterized complementarily by XRD, XPS, TEM, HRTEM, HS-LEIS and STEM-EDS elemental mapping and line-scanning. All the catalysts were comparatively evaluated for benzaldehyde and styrene hydrogenation. It is shown that the “PtPd alloy nanoclusters on Ni nanoparticles” (PtPd/Ni) and the synergistic effect of the trimetallic Pt−Pd−Ni, lead to much improved catalytic performance, compared with the mono- or bi- metallic counterparts. However, with the increase of the treatment temperature of the Pt−Pd/Ni/C, the catalytic performance was gradually degraded, which was likely due to that the favourable nanostructure of fine “PtPd/Ni” was gradually transformed to relatively large “PtPdNi alloy on Ni” (PtPdNi/Ni) particles, thus decreasing the number of noble metal (Pt and Pd) active sites on the surface of the catalyst. The optimum trimetallic structure is thus the as synthesised Pt−Pd/Ni/C. This work provides a novel strategy for the design and development of highly efficient and low-cost multimetallic catalysts, e. g. for hydrogenation reactions.     

Biomolecules as promising ligands in the synthesis of metal nanoclusters: Sensing,bioimaging and catalytic applications

The use of metal nanoclusters as sensing probes has recently attracted considerable interest from researchers. In particular, metallic nanoclusters (e.g., Au, Ag, Cu, Pt) have been noticed a wide range of applications in the field of fluorescence sensing and bioimaging. The stabilization of metal nanoclusters with organic molecules, proteins, and amino acids enhances their optical properties and analytical applications. In this review, synthetic routes for the fabrication of metal nanoclusters are summarized. This review also describes the metal nanoclusters properties including aggregation-induced emission, optical absorption, non-linear optical, and chiral properties. We discussed the analytical applications of metal nanoclusters for sensing of wide variety of analytes including drugs, biomolecules, biomarkers. Further, the catalytic applications of metal nanoclusters are also briefly summarized. Finally, we summarize the challenges and future perspectives of metal nanoclusters in analytical chemistry.     

Theoretical Study on the Structures and Thermal Properties of Ag–Pt–Ni Trimetallic Clusters

The structures and thermal properties of Ag–Pt–Ni ternary nanoclusters varying with different compositions and sizes are studied by Monte Carlo and molecular dynamics simulations. It can be found that silver atoms tend to occupy the surface and platinum atoms favor the subsurface occupation, whereas the inner is occupied by nickel atoms due to the different surface energies and lattice parameters. In addition, there is a non-monotonous relationship between the melting points and compositions of Ag–Pt–Ni ternary nanoclusters according to molecular dynamics simulations. In addition, a linear decrease in melting point with \(N^{ - 1/3}\) is found for both monometallic and trimetallic clusters. This behavior is consistent with Pawlow’s law.     

Ligand Engineering in Metal Nanoclusters: from Structural Control to Functional Modulation

Ligand-protected metal nanoclusters have drawn increasing research interest because of their unique physicochemical properties and practical applications. Great efforts have been made in pursuing rational synthesis of metal nanoclusters and establishing the structure-property relationships. As an indispensable part of ligand-protected metal nanoclusters, ligands play multiple roles in determining their structures and properties. In this perspective, we demonstrate the importance of ligand engineering in terms of the control of structures, optical and catalytic properties of metal nanoclusters. Furthermore, we will show that ligand engineering is prospective in structural design and preorganization of surface metal sites.     

金原子簇催化碳——碳偶联反应的研究进展

Well-defined gold nanoclusters have been documented as new and promising materials in the field of nanoscience. They have been well explored for the nanocatalysis of reactions like selective oxidation and hydrogenation, carbon-carbon coupling, etc. These Au nanoclusters possess unique electronic properties and crystal structure, which provide an excellent opportunity to correlate atomic structure with intrinsic catalytic property and to investigate the mechanisms of reactions over Au nanoclusters. In this review, we generalize the catalytic application of gold nanoclusters in carbon-carbon coupling reactions, including Ullmann, Sonogashira, Suzuki, and A³-coupling reactions. Herein, we have discussed ligand engineering (e.g., aromatic and aliphatic thiolate) as well as the effect of metal dopants (e.g., Cu, Ag, Pt, and Pd). Finally, the tentative catalytic mechanisms and the structure-performance relationships were discussed at the atomic level, which will give some clue for the design of efficient gold cluster catalysts.     

Giant multiporphyrin arrays as artificial light-harvesting antennas

Synthetic giant multiporphyrin arrays with well-defined architectures are reviewed in terms of artificial light-harvesting materials. Meso,meso-linked porphyrin arrays and multiporphyrin dendrimers have successfully mimicked the light-harvesting function of bacterial photosynthetic systems. We have also developed novel multiporphyrin-modified metal nanoclusters where porphyrins employed as a light-harvesting unit are well organized onto metal nanoclusters by self-assembly processes. Multiporphyrin-modified metal nanoclusters have been applied to photocatalyses and photovoltaic cells. In particular, they have been assembled with fullerenes step-by-step to make large, uniform clusters on nanostructured semiconductor electrodes, which exhibit a high power-conversion efficiency close to 1%. These systems provide valuable information on the design of porphyrin molecular assemblies that can be tailored to construct molecular photonic devices as well as artificial photosynthetic systems.     

原子级精确的币金属纳米团簇在光催化应用方面的研究进展

光催化技术可以直接将太阳能转化为化学能,制造化学燃料或环境友好的产品。然而,常用的光催化剂大多为具有宽能隙的半导体材料,所需光源大多在紫外区,对太阳光的利用率不高;并且电子-空穴复合率高,导致光催化反应效率低。币金属纳米团簇具有超小尺寸（<2 nm）和分立能级,能够实现电子和空穴的分离,电子结构可调,可以通过调节其电子结构进而提高其光催化性能。同时,精确的原子级组成和结构使其成为一种在原子水平上探索光催化机制的理想模型。本文报道了基于币金属纳米团簇的光催化反应的现状,包括水分解产氢、有机污染物降解和光催化氧化胺等。通过探讨调节币金属纳米团簇的光催化性能的策略,对币金属纳米团簇光催化剂的发展前景予以展望。     

Superatom-in-Superatom Nanoclusters: Synthesis,Structure, and Photoluminescence

We report a new strategy in which a thiolate-protected Ag₂₅ nanocluster can be doped with open d-shell group 8 (Ru, Os) and 9 (Ir) metals by forming metal hydride (RuH₂, OsH₂, IrH) superatoms with a closed d-shell. Structural analyses using various experimental and theoretical methods revealed that the Ag₂₅ nanoclusters were co-doped with the open d-shell metal and hydride species to produce superatom-in-superatom nanoclusters, establishing a novel superatom doping phenomenon for open d-shell metals. The synthesized superatom-in-superatom nanoclusters exhibited dopant-dependent photoluminescence (PL) properties. Comparative PL lifetime studies of the Ag₂₅ nanoclusters doped with 8–10 group metals revealed that both radiative and nonradiative processes were significantly dependent on the dopant. The former is strongly correlated with the electron affinity of the metal dopant, whereas the latter is governed predominantly by the kernel structure changed upon the doping of the metal hydride(s).     

“非保护型”金属胶体纳米簇形成机理研究

碱-乙二醇法制备的"非保护型"金属及合金纳米簇由表面吸附的溶剂分子和简单离子实现稳定化,它们被广泛用于制备高性能复相催化剂和研究复相催化剂中的尺寸、组成、载体表面基团以及修饰剂对催化性能的影响。关于此类非保护金属纳米簇的形成过程及机理的认识尚有待进一步深化。本文采用原位快速扫描X射线吸收精细结构谱(QXAFS)、原位紫外-可见(UV-Vis)吸收光谱、透射电子显微镜和动态光散射技术研究了碱-乙二醇法合成中非保护型金属胶体纳米簇的形成过程与机理。结果表明,在碱-乙二醇法合成非保护型Pt金属纳米簇的过程中,室温下即有部分Pt(IV)被还原至Pt(II)。随着反应温度的升高,OH-逐渐取代与Pt离子配位的Cl-,在Pt―Pt键形成之前,反应体系的UV-Vis吸收光谱中可观察到明显的纳米粒子的散射信号,原位QXAFS分析表明Pt纳米簇是由Pt氧化物纳米粒子还原所形成的;在Ru金属纳米簇的形成过程中,OH-首先取代了Ru Cl_3中的Cl~-,形成羟基配合物Ru(OH) _6~(3-),后者进一步缩合形成氧化钌纳米粒子,最终Ru金属纳米簇由乙二醇还原氧化钌纳米粒子形成。由于先形成了氧化物纳米粒子,后续的还原反应被限制在氧化物纳米粒子内,使最终得到的非保护型金属纳米簇具有尺寸小、分布窄的特点。本工作所获得的知识对发展高性能能源转化催化剂、精细化学合成催化剂、传感器等功能体系具有重要意义。     

Synthesis of metal nanoclusters within microphase-separated diblock copolymers: a ‘universal’ approach

A general methodology has been established for the synthesis of transition metal nanoclusters within the carboxylic acid functionalized domains of microphase-separated block copolymer films. In this technique the films are soaked in aqueous metal salt solutions prior to reduction of the sequestered metal ions with hydrogen or aqueous NaBH₄. Transmission electron microscopy observation, scanning transmission electron microscopy observation, electron scattering analysis and wide-angle X-ray scattering analysis were used to characterize the size, composition and crystal structure of the resulting metal nanoclusters.     

金属纳米簇在CO2光催化还原中的研究进展

化石燃料的大量燃烧不仅造成能源危机，而且排放的二氧化碳（CO2）会使气候变暖。以清洁、储量丰富的太阳光作为能量来源，将CO2光催化还原为高附加值的化学产品是缓解当前环境问题和能源问题的主要方法之一。然而，CO2在常温常压下非常的稳定，因此需要设计并构筑高效光催化剂来捕捉和转化CO2，以达到高效光催化CO2还原的目的。在众多研究的光催化剂中，金属纳米簇因其具有独特的结构特点、优异的物理和化学性质，所以在光催化CO2还原领域得到了广泛的应用。基于此，我们首先对金属纳米簇进行了分类，将其分为贵金属纳米簇和非贵金属纳米簇；然后分别对贵金属和非贵金属纳米簇在光催化CO2还原中的研究进展进行了归纳与总结。本文通过及时全面概述近几年该领域的研究进展，从而为未来研究方向提供新思路。     

Functionalization of nanofibrillated cellulose with silver nanoclusters: fluorescence and antibacterial activity

Native cellulose nanofibers are functionalized using luminescent metal nanoclusters to form a novel type of functional nanocellulose/nanocluster composite. Previously, various types of cellulose fibers have been functionalized with large, non-luminescent metal nanoparticles. Here, mechanically strong native cellulose nanofibers, also called nanofibrillatedcellulose (NFC), microfibrillatedcellulose (MFC) ornanocellulose, disintegrated from macroscopic cellulose pulp fibers are used as support for small and fluorescent silver nanoclusters. The functionalization occurs in a supramolecular manner, mediated by poly(methacrylic acid) that protects nanoclusters while it allows hydrogen bonding with cellulose, leading to composites with fluorescence and antibacterial activity.     

铜纳米簇的制备、聚集诱导荧光增强性能及应用研究进展

铜纳米簇不仅具有金属纳米簇的特异性,还有前驱体价格便宜等优点,因此有广泛的应用前景。从配体辅助法、模板法、微波法、电化学法和刻蚀法等综述了铜纳米簇的制备方法。从离子诱导聚集、pH诱导聚集、组装诱导聚集和溶剂诱导聚集增强发射等方面综述了铜纳米簇聚集诱导荧光发射增强性能。从离子检测、小分子检测、酶活性检测、生物大分子检测和生物成像等方面综述了铜纳米簇的应用,并对铜纳米簇的制备、性能优化和应用等方面作了展望。     

Effect of the organic solvent on the formation and stabilization of CdS and PbS nanoclusters

Nanoclusters of CdS and PbS were prepared using two different organic solvents as stabilizers in order to understand the factors affecting their formation and stabilization. Growth of the nanoclusters was monitored by optical absorption spectroscopy at regular intervals of time. Mean cluster size was characterized by X-ray diffraction (XRD). The surface structure of nanoclusters was analyzed using infrared (IR) spectroscopy. Spectroscopic studies under identical experimental conditions reveal interesting correlations between the stability of the nanoclusters formed, the nature of the solvent and the size of metal ion involved, leading to a better understanding of nanocluster formation.     

Chemiluminescence and electrochemiluminescence applications of metal nanoclusters

Due to strong photoluminescence, extraordinary photostability, excellent biocompatibility, and good water-solubility, metal nanoclusters have attracted enormous attention since discovered. They are found to be novel fluorescence labels for biological applications and environmental monitoring. Recently the chemiluminescence (CL) or electrochemiluminescence (ECL) of metal nanoclusters has received increasing attention. This review covers recent vibrant developments in this field of the past 5 years, and highlights different functions of metal nanoclusters in various CL and ECL systems, such as luminophores, catalysts, and quenchers. Latest synthetic methods of metal nanoclusters used in CL or ECL are also summarized. Furthermore, we discuss some perspectives and critical challenges of this field in the near future.