Synthesis Of Nanoclusters Research Articles

Fast and high-yield synthesis of thiolate Ag44 and Au12Ag32 nanoclusters via the CTAB reverse micelle method

To advance the development of atomically precise Ag and Ag-alloyed nanoclusters, it is critical to develop effective synthetic methods. Herein, we successfully extend the CTAB (cetyl trimethyl ammonium bromide) reverse micelle method to synthesize a high-purity Ag44(p-MBA)30 (p-MBA = para-mercaptobenzoic acid) nanocluster and its corresponding alloy cluster Au12Ag32(p-MBA)30 in a short time (15 min and 5 min), with a high yield of ∼83% and ∼85%, respectively. Furthermore, the mechanism regarding the reverse micelle method has been clearly elucidated. Through characterizing the reaction system by Raman spectroscopy and NMR spectroscopy techniques, it can be revealed that employing CTAB to form reverse micelles to construct a sealed chemical environment is critical for realizing the fast and high-yield synthesis.

Studies on the interactions of Ag(i) with DNA and their implication on the DNA-templated synthesis of silver nanoclusters and on the interaction with complementary DNA and RNA sequences.

Silver nanoclusters (AgNCs) prepared by the reduction of silver ions in the presence of DNA oligonucleotides have attracted great interest as potential diagnostic tools for their tunable and high fluorescent properties. In this work, three DNA sequences that consist of a 12-nucleotide long probe sequence at the 5′-end linked to the complementary sequence to three miRNAs are studied. First, the interaction of these sequences with Ag(i) was characterized by means of circular dichroism spectroscopy. By applying multivariate methods to the analysis of spectroscopic data, two complexes with different Ag(i) : DNA ratios were resolved. Secondly, the impact of several experimental variables, such as temperature, borohydride concentration and reaction time, on the formation of AgNCs templated by these three sequences was studied. Finally, the fluorescence properties of the duplexes formed by DNA probes with complementary DNA or miRNA sequences were studied. The results presented here highlight the role of the secondary structure adopted by the DNA probe on the fluorescence properties of DNA-stabilized AgNCs which, in turn, affect the development of methods for miRNA detection.

Synthesis of Proline-Stabilized Cu Nanoclusters for Detection of Picric Acid

Synthesis of Proline-Stabilized Cu Nanoclusters for Detection of Picric Acid

The synthesis of novel fluorescent bimetal nanoclusters for aqueous mercury detection based on aggregation-induced quenching.

In this research, new bimetal nanoclusters (DAMP-AuAg BNCs) with 4,6-diamino-2-mercaptopyrimidine (DAMP) as a reducing agent and stabilizer ligand were exploited. The nanoclusters displayed excellent fluorescent properties, very small size, good stability, and water solubility. It was found that the as-prepared DAMP-AuAg BNCs exhibited strong fluorescent emission at 640 nm under an excitation wavelength of 473 nm with a large Stokes shift of 167 nm, and the red fluorescence could be readily quenched with aqueous Hg2+. The DAMP-AuAg BNCs showed good specificity and sensitivity toward Hg2+ in aqueous solution, and the fluorescence analysis of Hg2+ showed a wide linear range from 0.85 μM to 246 μM and a detection limit of 20 nM. It is demonstrated that strong Hg2+-Au+ interactions led to the aggregation of nanoclusters, which caused the quenching of the fluorescence, and the affinity of Hg2+ for nitrogen should also be considered. Due to the relevant good performance of DAMP-AuAg BNCs, they were applied to the fluorescence analysis of Hg2+ in real water samples and were found to be a potential fluorescent sensor for aqueous mercury ions.

Synthesis and enantioseparation of chiral Au13 nanoclusters protected by bis-N-heterocyclic carbene ligands.

A series of chiral Au13 nanoclusters were synthesized via the direct reduction of achiral dinuclear Au(i) halide complexes ligated by ortho-xylyl-linked bis-N-heterocyclic carbene (NHC) ligands. A broad range of functional groups are tolerated as wingtip substituents, allowing for the synthesis of a variety of functionalized chiral Au13 nanoclusters. Single crystal X-ray crystallography confirmed the molecular formula to be [Au13(bisNHC)5Cl2]Cl3, with a chiral helical arrangement of the five bidentate NHC ligands around the icosahedral Au13 core. This Au13 nanocluster is highly luminescent, with a quantum yield of 23%. The two enantiomers of the Au13 clusters can be separated by chiral HPLC, and the isolated enantiomers were characterized by circular dichroism spectroscopy. The clusters show remarkable stability, including configurational stability, opening the door to further investigation of the effect of chirality on these clusters.

Intercluster exchanges leading to hydride-centered bimetallic clusters: a multi-NMR, X-ray crystallographic, and DFT study.

Encouraged by the successful syntheses of alloy nanoclusters (or nanoparticles) via intercluster (or interparticle) reactions, herein we apply this methodology to prepare a series of bimetallic hydride clusters. Mixing of two clusters, [Ag7(H){E2P(OiPr)2}6] (E = S, 1; Se, 3) and [Cu7(H){E2P(OiPr)2}6] (E = S, 2; Se, 4), yields two series of hydride-centered bimetallic clusters, [CuxAg7-x(H){E2P(OiPr)2}6] (x = 0-7; E = S, 5; Se, 6). Their compositions are fully characterized by positive-mode ESI-MS spectrometry, multi-NMR spectroscopy, and the structures of [Cu6Ag(H){S2P(OiPr)2}6] (5a) and [CuAg6(H){Se2P(OiPr)2}6] (6a) by single crystal X-ray diffraction. The presence of individual compounds in solution is the result of a (dynamic) chemical equilibrium primarily driven by metal exchanges. In fact, the process of inter-cluster exchange of 1 and 2 leading to hydride-centered bimetallic clusters 5 can be monitored by concentration-dependent 31P NMR spectroscopy of which the higher concentration of 1 in the reaction, the closer to its resonance will be the distribution, in accord with Le Chatelier's principle. The dynamic equilibrium is further confirmed by 2D exchange spectroscopy that reveals a stepwise process involving one metal exchange at a time. DFT calculations on a model series of clusters 6 show that silver prefers occupying the inner tetrahedral positions, while copper favors capping positions, in full agreement with the crystal structure of 5a and 6a.

Controllable synthesis and formation mechanism study of homoleptic alkynyl-protected Au nanoclusters: recent advances, grand challenges, and great opportunities.

In the past decade, atomically precise coinage metal nanoclusters have been a subject of major interest in nanoscience and nanotechnology because of their determined compositions and well-defined molecular structures, which are beneficial for establishing structure-property relationships. Recently ligand engineering has been extended to alkynyl molecules. Homoleptic alkynyl-protected Au nanoclusters (Au NCs) have emerged as a hotspot of research interest, mainly due to their unique optical properties, molecular configuration, and catalytic functionalities, and more importantly, they are used as a counterpart object for fundamental study to compare with the well-established thiolate Au NCs. In this review, we first summarize the recently reported various controllable synthetic strategies for atomically precise homoleptic-alkynyl-protected Au NCs, with particular emphasis on the ligand exchange method, direct reduction of the precursor, one-pot synthesis, and the synchronous nucleation and passivation strategy. After that, we switch our focus to the formation mechanism and structure evolution process of homoleptic alkynyl-protected Au NCs, where Au144(PA)60 and Au36(PA)24 (PA = phenylacetylide) are given as examples, along with the prediction of the possible formation mechanism of some other cluster molecules. In the end of this review, the outlook and perspective of this rapidly developing field including grand challenges and great opportunities are discussed. This review can stimulate more research efforts towards developing new synthetic strategies to enrich the limited examples and unravel the formation/growth mechanism of homoleptic alkynyl-protected Au NCs.

Rapid template‐guided ligand‐free synthesis of ultrasmall Pt nanoclusters with efficient hydrogen evolution reaction activity and their versatile release

AbstractThe design of ligand‐free platinum nanoclusters (PtNCs) for the field of renewable energy is still challenging. Herein, we reported a fast synthesis of ligand‐free Pt nanoclusters (NCs) by utilizing the outer defect of a representative type of zeolitic imidazolate framework (ZIF). Structural investigation suggests a homogenous distribution of the PtNCs on the outer layer of the ZIF‐8 structure. The as‐prepared PtNCs@ZIF‐8 exhibits high catalytic activity for the hydrogen evolution reaction (HER). The extremely low overpotential with 1.4 mV, high kinetic current (specific and mass activity at 50 mV), and larger exchange current density were achieved in acidic solution, better than those of the commercial 20% Pt/C catalysts under the same condition. Furthermore, the PtNCs can be extracted from the ZIF‐8 structure to both aqueous and non‐aqueous solvent, which could be further used for other systems. These findings allow for a simple route of template‐guided NC synthesis and their release.

Ligand-Protected Ultrasmall Pd Nanoclusters Supported on Metal Oxide Surfaces for CO Oxidation: Does the Ligand Activate or Passivate the Pd Nanocatalyst?

Herein, we report on the synthesis of ultrasmall Pd nanoclusters (∼2 nm) protected by L-cysteine [HOCOCH(NH2 )CH2 SH] ligands (Pdn (L-Cys)m ) and supported on the surfaces of CeO2 , TiO2 , Fe3 O4 , and ZnO nanoparticles for CO catalytic oxidation. The Pdn (L-Cys)m nanoclusters supported on the reducible metal oxides CeO2 , TiO2 and Fe3 O4 exhibit a remarkable catalytic activity towards CO oxidation, significantly higher than the reported Pd nanoparticle catalysts. The high catalytic activity of the ligand-protected clusters Pdn (L-Cys)m is observed on the three reducible oxides where 100 % CO conversion occurs at 93-110 °C. The high activity is attributed to the ligand-protected Pd nanoclusters where the L-cysteine ligands aid in achieving monodispersity of the Pd clusters by limiting the cluster size to the active sub-2-nm region and decreasing the tendency of the clusters for agglomeration. In the case of the ceria support, a complete removal of the L-cysteine ligands results in connected agglomerated Pd clusters which are less reactive than the ligand-protected clusters. However, for the TiO2 and Fe3 O4 supports, complete removal of the ligands from the Pdn (L-Cys)m clusters leads to a slight decrease in activity where the T100% CO conversion occurs at 99 °C and 107 °C, respectively. The high porosity of the TiO2 and Fe3 O4 supports appears to aid in efficient encapsulation of the bare Pdn nanoclusters within the mesoporous pores of the support.

Engineering Fluorescent Gold Nanoclusters Using Xanthate-Functionalized Hydrophilic Polymers: Toward Enhanced Monodispersity and Stability.

We introduce xanthate-functionalized poly(cyclic imino ethers)s (PCIEs), specifically poly(2-ethyl-2-oxazoline) and poly(2-ethyl-2-oxazine) given their stealth characteristics, as an attractive alternative to conventional thiol-based ligands for the synthesis of highly monodisperse and fluorescent gold nanoclusters (AuNCs). The xanthate in the PCIEs interacts with Au ions, acting as a well-controlled template for the direct formation of PCIE-AuNCs. This method yields red-emitting AuNCs with a narrow emission peak (λem = 645 nm), good quantum yield (4.3-4.8%), long fluorescence decay time (∼722-844 ns), and unprecedented product yield (>98%). The PCIE-AuNCs exhibit long-term colloidal stability, biocompatibility, and antifouling properties, enabling a prolonged blood circulation, lower nonspecific accumulation in major organs, and better renal clearance when compared with AuNCs without polymer coating. The advances made here in the synthesis of metal nanoclusters using xanthate-functionalized PCIEs could propel the production of highly monodisperse, biocompatible, and renally clearable nanoprobes in large-scale for different theranostic applications.

New Routes for Multicomponent Atomically Precise Metal Nanoclusters.

Atomically precise metal nanoclusters (NCs), protected by a monolayer of ligands, are regarded as potential building blocks for advanced technologies. They are considered as intermediates between the atomic/molecular regime and the bulk. Incorporation of foreign metals in NCs enhances several of their properties such as catalytic activity, luminescence, and so on; hence, it is of high importance for tuning their properties and broadening the scope of applications. In most of the cases, enhancement in specific properties was observed upon alloying due to the synergistic effect. In the past several years, many alloy clusters have been synthesized, which show a tremendous change in the properties than their monometallic analogs. However, controlling the synthesis and tuning the structures of alloy NCs with atomic precision are major challenges. Various synthetic methodologies have been developed so far for the controlled synthesis of alloy NCs. In this perspective, we have highlighted those diverse synthetic routes to prepare alloys, which include co-reduction, galvanic reduction, antigalvanic reduction, metal deposition, ligand exchange, intercluster reaction, and reaction of NCs with bulk metals. Advancement in synthetic procedures will help in the preparation of alloy NCs with the desired structure and composition. Future perceptions concerning the progress of alloy nanocluster science are also provided.

Fluorescent bovine serum albumin-silver nanoclusters loaded with paclitaxel can traverse the blood-brain barrier to inhibit the migration of glioma

Abstract Objective: Glioma is the most common and aggressive primary brain tumor. Here, we aimed to establish a nano-drug carrier system to traverse the blood-brain barrier for the treatment and inhibition of glioma migration. Methods: The synthesis of bovine serum albumin protected-silver nanoclusters (BSA-AgNCs) was performed using chemical reduction. The drug paclitaxel (PTX) can be loaded into BSA-AgNCs through electrostatic and hydrophobic interactions to formulate spherical BSA-AgNC-PTX nanoparticles (BSA-AgNC-PTX NPs). A glioma mouse model was established by injecting U251-GFP-Luc cells into the mouse striatum, and all surgical procedures were approved by the Animal Ethics Committee of Nanchang University (SYXK2019-0003) on December 29, 2019. Results: The BSA-AgNC-PTX NPs were able to efficiently pass through the blood-brain barrier, both in vitro and in vivo, to deliver the drug to the tumor site. The in vivo assessment of BSA-AgNC-PTX NPs in glioblastoma multiforme-bearing mice revealed the significant inhibition of tumor growth and migration, prolonging the survival of the mice. Conclusion: These results indicated that BSA-AgNCs might represent an ideal nanocarrier for the treatment of glioma and has the potential to be used in the treatment of a variety of central nervous system diseases.

Ligand-free Few Atoms Ag Nanoclusters Synthesis and Their Potential Application as Photocatalytic Agents

Reducing the size of a metal from macroscopic to the nanoscale generates a scaling behavior in physical and chemical properties due to the large surface-to-volume fraction. While a further size reduction to small clusters under 2 nm (<~100 atoms) yield geometric and electronic structures which are still different from their nanoparticle (NP) counterpart. These small clusters adopt special atomic arrangements to reduce their surface energy, and their electronic structures are no longer continuous, as in bulk metals, but rather discretized.

Enhanced and stabilized hydrogen production from methanol by ultrasmall Ni nanoclusters immobilized on defect-rich h-BN nanosheets

Employing liquid organic hydrogen carriers (LOHCs) to transport hydrogen to where it can be utilized relies on methods of efficient chemical dehydrogenation to access this fuel. Therefore, developing effective strategies to optimize the catalytic performance of cheap transition metal-based catalysts in terms of activity and stability for dehydrogenation of LOHCs is a critical challenge. Here, we report the design and synthesis of ultrasmall nickel nanoclusters (∼1.5 nm) deposited on defect-rich boron nitride (BN) nanosheet (Ni/BN) catalysts with higher methanol dehydrogenation activity and selectivity, and greater stability than that of some other transition-metal based catalysts. The interface of the two-dimensional (2D) BN with the metal nanoparticles plays a strong role both in guiding the nucleation and growth of the catalytically active ultrasmall Ni nanoclusters, and further in stabilizing these nanoscale Ni catalysts against poisoning by interactions with the BN substrate. We provide detailed spectroscopy characterizations and density functional theory (DFT) calculations to reveal the origin of the high productivity, high selectivity, and high durability exhibited with the Ni/BN nanocatalyst and elucidate its correlation with nanocluster size and support-nanocluster interactions. This study provides insight into the role that the support material can have both regarding the size control of nanoclusters through immobilization during the nanocluster formation and also during the active catalytic process; this twofold set of insights is significant in advancing the understanding the bottom-up design of high-performance, durable catalytic systems for various catalysis needs.

Synthesis and characterization of nanoclusters: Inorganic-organic hybrid copper and cobalt containing arsenotungstates(III) with lone pair on heteroatom incorporating bidentate N-donating ligands

Three inorganic-organic hybrid nanoclusters of copper and cobalt containing arsenotungstates with lone pair on heteroatom have been synthesized under mild reactions conditions. All the compounds have been characterized by single crystal X-ray diffraction, Fourier transform infrared, UV/visible spectroscopy, thermogravimetric and field emission scanning electron microscopic (FE-SEM) analysis. The compound [NaRb{Cu(phen) (H 2 O) 2 Cl} 2 ][{Cu(phen)(H 2 O)} 2 {Cu(phen) (H 2 O)Cl} 2 {Cu 2 As 2 W 19 O 67 (H 2 O)] (1a) is a sandwiched type arsenotungstate with two copper atoms in square planar environment in the belt region. The polyanion- 1 is decorated by four copper phenanthroline complexes through a terminal oxygen atom of the polyanion. In addition, two other cobalt containing inorganic-organic hybrid lone pair containing arsenotungstates(III) with 1,10-phenanthroline [NaRbCo(phen) 3 ][{Co(phen)(H 2 O) 3 }CoAs 2 W 20 O 67 (H 2 O) 3 ] (2a) and 2,2’-bipyridine[Na 3 RbCo(2,2-bipy) 3 ][CoAs 2 W 20 O 67 (H 2 O) 3 ] (3a) has also been synthesized under mild conditions. The polyanion ( 2 ) is a mono cobalt substituted sandwiched type structure that is decorated by a cobalt phenanthroline complex attached to the polyanion through a terminal oxygen atom. Meanwhile the other complex ( 3 ) is also a monocobalt substituted sandwiched type structure which contains a cobalt 2,2’-bipyridine complex in the cationic part. Polyanion- 1 shows intermolecular π-π stacking interaction between the phenanthroline ligand in the cationic part and one that is attached directly to the polyanion. The compounds are also characterized by FE-SEM analysis and the compound 3a shows ultra- smooth cuboids with grain size in the range of 1 to several micrometer though some very small irregular particles with the size of a few micrometer were also observed.

Atomically Precise Alloy Nanoclusters.

Metal nanoclusters (NCs) have a particle size of about one nanometer, which makes them the smallest unit that can give a function to a substance. In addition, metal NCs possess physical and chemical properties that are different from those of the corresponding bulk metals. Metal NCs with such characteristics are expected to be important for use in nanotechnology. Research on the precise synthesis of metal NCs and elucidation of their physical/chemical properties and functions is being actively conducted. When metal NCs are alloyed, it is possible to obtain further various electronic and geometrical structures and functions. Thus, research on alloy NCs has become a hot topic in the study of metal NCs and the number of publications on alloy NCs has increased explosively in recent years. Such publications have provided much insight into the effects of alloying on the electronic structure and function of metal NCs. However, the rapid increase in knowledge has made it difficult for researchers (especially those new to the field) to grasp all of it. Therefore, in this review, we summarize the reported chemical composition, geometrical structure, electronic structure, and physical and chemical properties of Aun-x Mx (SR)m , Agn-x Mx (SR)m , Aun-x Mx (PR3 )l (SR)m , and Agn-x Mx (PR3 )l (SR)m (Au=gold, Ag=silver, M=heteroatom, PR3 =phosphine, and SR=thiolate) NCs. This review is expected to help researchers understand the characteristics of alloy NCs and lead to clear design guidelines to develop new alloy NCs with intended functions.

Eco-Friendly Synthesis of Carboxymethyl Cellulose-Stabilized Ru0.57Co0.43 Nanoclusters as Extremely Efficient and Durable Catalysts for Hydrolytic Dehydrogenation of Methylamine Borane

Herein, we report the first ever eco-friendly and easy synthesis of carboxymethyl cellulose-stabilized RuCo nanoclusters (Ru0.57Co0.43@CMC) and their use as highly efficient and durable catalysts t...

The synthesis of high bright silver nanoclusters with aggregation-induced emission for detection of tetracycline

In this study, the silver nanoclusters (Ag NCs) with aggregation-induced emission property were synthesized successfully by reflux method using silver nitrate (AgNO3) as raw material and N-acetyl-L-cysteine (NAC) as the reductant and capped ligand. The synthesis process was simple, environmentally friendly and the process did not require the addition of other surfactants or common reductant such as sodium borohydride, ascorbic acid. The obtained Ag NCs possessed the special Ag(0)@Ag(I)–SR core-shell structure with aggregation-induced emission characteristic. The Ag NCs exhibited strong green luminescence with an optimal emission wavelength of 494 nm, high quantum yield of 0.44, microsecond long life of 11.07 μs and high content of Ag(I) component. In addition, the obtained Ag NCs were used to detect the tetracycline (TC) with the range of linearity from 1.12 μM to 230 μM and a detection limit of 0.47 μM on account of the quenching mechanism of the internal filtration effect (IFE) and the static quenching effect between tetracycline and Ag NCs. The proposed sensing method based on NAC@Ag NCs showed good sensitivity and selectivity for tetracycline, wide range of linearity, low detection limit and strong anti-interference ability. This method had been applied to detect tetracycline concentration reliably and accurately in actual sample milk.

Peptide-inspired green synthesis of hedgehog-like CuO nanoclusters on reduced graphene oxide for non-enzymatic hydrogen peroxide sensor

Bioinspired synthesis provides a potential green method for creating functional nanomaterials on graphene supports. In this study, we demonstrate the preparation of hedgehog-like cupric oxide nanoclusters (CuONCs) on peptide-modified reduced graphene oxide (RGO-Pep) nanohybrids through a solution-phase synthesis in which the bound peptide molecules (GNNQQNYEE) mediate the non-covalent modification of GO and provide the adsorption of Cu[Formula: see text] ions and the nucleation sites for the growth of CuONCs. The synthesized RGO-Pep-CuONCs hybrids were further utilized for the modification of a glass carbon electrode to fabricate a non-enzymatic electrochemical sensor for hydrogen peroxide (H2O2). It was found that the fabricated H2O2 sensor exhibited good performances for sensing H2O2 with a detection limit of [Formula: see text]M and two wide linear detection ranges. In addition, this sensor revealed good selectivity and stability. It is expected that the strategies used in this study will be valuable to inspire the creation of various functional biomolecule- and graphene-based hybrid bionanomaterials for the applications in materials science, sensors, biomedical engineering, tissue engineering, nanotechnology, and other fields.

Simple and Selective Synthesis of Copper-Containing Metal Nanoclusters Using (PPh3 )2 CuBH4 as Reducing Agent.

A simple and selective synthetic protocol, using (PPh3 )2 CuBH4 as reducing agent, for Cu-containing mixed metal nanoclusters (NCs) is reported. Representative NCs include alkynyl-protected [Ag25 Cu4 (PhCC)12 (PPh3 )12 Cl6 H8 ]3+ (1), thiolate-capped [AuCu14 (SR)12 (PPh3 )6 ]+ (R = 4-flurothiophenol) (2), and phosphine-stabilized [Au9 Cu2 (PPh3 )8 Cl2 ]+ (3), which are fully characterized by single-crystal X-ray diffraction analysis, electrospray ionization mass, nuclear magnetic resonance (1 H, 2 H, 13 C, and 31 P NMR), and optical measurements, respectively. This work demonstrates the advantages of using (PPh3 )2 CuBH4 as a reducing agent in the synthesis of Cu-containing heterometallic NCs in terms of versatility as well as high yield and high purity of the products. This work may open the door to utilizing functional metal borohydride, as a new generation of reducing agent for the simple and selective synthesis of metal NCs.