Copper Nanoclusters Research Articles

Using Electrodeposition of Carboxylated Chitosan for Green Preparation of Copper Nanoclusters and Nanocomposite Films

Using Electrodeposition of Carboxylated Chitosan for Green Preparation of Copper Nanoclusters and Nanocomposite Films

Fluorescent “On‐Off‐On” Probe for Cascade Detection of Ag(I) and Ascorbic Acid Using Folic Acid Protected Copper Nanoclusters

AbstractFolic acid (FA) protected copper nanoclusters (FA‐CuNCs, λex=350 nm, λem=445 nm) were synthesized and used as a fluorescent “on‐off‐on” probe for the cascade detection of Ag+ and ascorbic acid (AA). The fluorescence emission of FA‐CuNCs at 445 nm was quenched significantly by Ag+ due to the analyte‐induced aggregation followed by the formation of larger nanoparticles. However, when AA was added to the in‐situ generated Ag@FA‐CuNCs, the fluorescence emission of FA‐CuNCs was recovered at 445 nm because of the AA‐directed reduction of Ag+ to Ag0. The experimental conditions, such as pH, incubation time, and quencher Ag+ concentrations, were optimized to achieve improved sensitivity. The detection limit for Ag+ and AA was estimated as 37.1 nM and 0.27 μM with a linearity range of 2.49–22 μM and 4.71–81.53 μM, respectively. In real sample analysis, the recoveries of Ag+ ions in river water and AA in orange juice samples were found between 99–93 % and 97–94 % using the probes FA‐CuNCs and Ag@FA‐CuNCs, respectively. Overall, this work offers a viable method for the sequential detection of Ag+ and AA using FA‐CuNCs via a fluorescence “on‐off‐on” switch mechanism.

Thiolated RAFT-PISA nano-templates power on luminescent copper nanoclusters (CuNCs) for selective mercury (II) detection

In this study, we expand the scope of polymerization-induced self-assembly (PISA) by modifying one of the most prototypical copolymers derived from RAFT-mediated PISA, poly(glycerol methacrylate)-b-poly(hydroxypropyl methacrylate) (pGMA-b-pHPMA), by incorporating a comonomer with a protected thiol group-2-(acetylthio)ethyl methacrylate (AcSEMA) into the hydrophobic block. The photoinitiated synthesis of pGMA-b-p(HPMA-co-AcSEMA) was conducted in a water/ethanol mixture (60/40 v/v) to increase the solubility of AcSEMA. Thus, this modification enabled the formation of diverse polymeric nano-morphologies such as spheres, worms, and vesicles, dictated by the balance between hydrophilic and hydrophobic block ratios and the AcSEMA content. Besides, the strong metal affinity of thiol groups makes the incorporation of AcSEMA into self-assembled nanostructures a versatile platform for generating advanced hybrid materials with potential applications in biomedicine, sensing, catalysis, or water purification. As evidenced in this work, the post-hydrolysis of the thioacetate group into thiol allowed the use of polymeric nano-objects as templates to power on the luminescenece of functionalized copper nanoclusters (CuNCs). These polymeric CuNCs, composed of several to hundreds of copper atoms, exhibit remarkable red emission, positioning the synthesized hybrids as promising luminescent probes for the development of highly selective “switch-off” luminescent sensors for Hg2+ detection. This work paves the way for the design of multifunctional hybrid nanomaterials with advanced applications.

Fluorometric detection of quinolones via AIE and FRET with terbium-doped carbon dots and copper nanoclusters

Fluorometric detection of quinolones via AIE and FRET with terbium-doped carbon dots and copper nanoclusters

Construction of an efficient microRNA sensing platform based on terminal deoxynucleotidyl transferase-mediated synthesis of copper nanoclusters

A conceptual innovative electrochemical sensing platform was constructed for microRNA (miRNA) detection based on terminal deoxynucleotidyl transferase (TdT)-mediated synthesis of copper nanoclusters. In principle, the substrate strand immobilized on working electrode acted as the template for the TdT-mediated DNA extension reaction, while the DNAzyme probe would be activated in the absence of miRNA 21, which led to the cleavage of the substrate strand to produce the 5’ phosphate terminus and inhibited the TdT-mediated DNA extension reaction. On the other hand, the presence of miRNA 21 initiated the toehold-mediated strand displacement reaction, causing the disassembly of the DNAzyme structure and preventing the substrate strand from being cleaved. This enabled the recycle amplification of target miRNA 21, and TdT catalyzed the DNA extension reaction on the 3’ hydroxyl terminus of the substrate strand, producing a large number of poly thymine (polyT) sequences. These sequences bound with copper ions for in-situ synthesis of copper nanoclusters on the sensing electrode, and the increased electrochemical signal of copper was recorded by differential pulse stripping voltammetry (DPSV), which paved the way for sensitive determination of miRNA 21 extracted from cancer cells with a detection limit of 36 aM. Due to its high sensitivity, user-friendly operation, and cost-effectiveness, this method is helpful for the fundamental research of sensing mechanism as well as the diagnosis of related diseases.

Copper Nanoclusters Imparted Metalloporphyrin based Metal-Organic Frameworks for Enhanced CO2 Electroreduction.

Strategies that can introduce catalytic auxiliary into electrocatalysts to boost the performance of electrocatalytic CO2 reduction reaction (CO2RR) are meaningful in exploring hybrid electrocatalytic systems. Here, a series of hybrid elelctrocatalysts (Cu NCs@MOF-545-M, M = Fe, Co and Ni) have been prepared by assembly Cu NCs with MOF-545-M (M = Fe, Co and Ni) and successfully applied in electrocatalytic CO2RR. In the obtained MOF-545-M (M = Fe, Co and Ni), the integration of Cu NCs with MOF-545-M (M = Fe, Co and Ni) can create a hybrid electrocatalytic system that enhances the charge transfer efficiency and electrocatalytic CO2RR activity. Specifically, the optimal Cu NCs@MOF-545-Co achieves high FECO (100%), CO generation rate (10.9 mol m-2 h-1) and energy efficiency (69%), which is superior to Cu NCs and MOF-545-Co, and represented to be one of the best performances to date. This work demonstrates a facile approach to significantly improve the FECO by loading metal nanoclusters into MOFs, providing a valuable reference for future studies on hybridization strategies to enhance the performance of electrocatalysts.

Short-Peptide-Modified Copper Nanoclusters as a Fluorescent Probe for the Specific Detection of Ascorbic Acid.

Metal nanoclusters assembled using short peptides as templates exhibit significant potential for development and application in the fields of catalysis and biomedicine, owing to their distinctive electronic structure, favorable optical properties, and biocompatibility. Among them, tripeptides exhibit a simpler structure and greater flexibility, enabling them to readily co-assemble with other functional components to create novel materials with significant application value. They can be assembled with copper ions to synthesize highly efficient luminescent nanoclusters, which can serve as an effective fluorescent probe. Here, we report a method for the synthesis of copper nanoclusters (Cu NCs) using tripeptides as templates, which also act as stabilizers and reducing agents. The synthesis conditions and properties were explored and optimized. Under optimal conditions, the Cu NCs exhibit excellent stability and are strongly fluorescent. The Cu NCs can detect 0.1-1.0 μmol/L of ascorbic acid with a low detection limit of 0.075 μmol/L, demonstrating high sensitivity and offering significant application potential for the trace of ascorbic acid in various substances. It also provides new ideas for the assembly of metal nanoclusters and the construction of fluorescent probe sensing platforms.

Exploring Selective Fluorescence Turn-On Sensing of Caspase-3 with Molybdenum Disulfide Quenched Copper Nanoclusters: FRET Biosensor.

Sensing caspase-3 activity is essential for understanding the role of apoptosis in cancer dynamics, controlling therapeutic strategies, and improving patient care in cancer treatment. In this study, we demonstrate a highly sensitive recombinant human caspase-3 (rhC3) detection technique in biological fluids. This technique uses a copper nanocluster stabilized with bovine serum albumin (BSA-CuNCs) as a metal-based fluorescent biosensor, conjugated with anti-human caspase-3 (ahC3). To turn its fluorescence off, molybdenum disulfide nanosheets (MoS2 NSs) are added; this partnership is termed ahC3@BSA-CuNCs/MoS2 nanocouple. In the presence of rhC3, the energy transfer process is affected by strong ahC3/rhC3 interactions. When in close proximity, the rhC3 molecules cause detachment of the nanocluster from the MoS2 NS surface by attracting the ahC3 component of the nanocluster. This increases the distance between the nanocluster and quencher with a consequent restoration of intensity. As the concentration of rhC3 increases, the fluorescence intensity of the system also increases. A proportional response is seen in the concentration between 0.1 and 1.3 ng/mL with a very low limit of detection of 2.75 pg/mL and a quantification limit of 8.60 pg/mL. A simple filter paper strip was made to visually identify the presence of rhC3 under UV light.

Aggregation-induced emissive copper nanoclusters with peroxidase-like activity for colorimetric detection of cholesterol

Accurate and point-of-care cholesterol detection is of paramount significance for the prevention of cardiovascular diseases. The colorimetric assay based on peroxidase is a commonly used approach for cholesterol detection, without requiring any complicated biomolecular labeling or sophisticated instrumentation. Copper nanoclusters (CuNCs), exhibiting luminescent properties and peroxidase activity, have garnered significant attention in biomedical application recently. Herein, the glutathione-stabilized copper nanoclusters (GSH-CuNCs) were prepared with an easy one-pot method, employing glutathione as both a reducing agent and stabilizer. An optimization of the GSH-CuNCs preparation was carried out to obtain the highest peroxidase-like activity. UV-Vis absorption was measured to explore the steady-state kinetics of the GSH-CuNCs-catalyzed oxidation of 3,3',5,5' - tetramethylbenzidine (TMB) by H2O2. A colorimetric method for cholesterol detection was developed by combining the catalytic reaction of CuNCs and the enzymatic oxidation of cholesterol with cholesterol oxidase (ChOx). Under the optimized conditions, the UV-Vis absorbance of oxidized TMB (oxTMB) is proportional to the concentration of cholesterol within the range of 6.2-187.5 μM, and the limit of detection (LOD) is determined to be 3.0 μM. More importantly, cholesterol levels can be directly distinguished with the naked eye. Furthermore, the practicality of the method for detecting cholesterol in human serum has been verified with promising results. As expected, this simple, cost-effective, and easy-to-operate colorimetric method for cholesterol detection has potential applications in clinical diagnosis and provides valuable insights into the colorimetric sensing based on CuNCs.

Sensitive Determination of Diosmetin Using Orange‐Red Fluorescent Copper Nanoclusters

AbstractDiosmetin (Dio) has attracted much attention because of its good pharmacological effects, thus it is necessary to determine its content in scientific research and production. In the study, stable orange‐red copper nanoclusters with 4‐hydroxy‐2‐mercapto‐6‐propylpyrimidine (PTU) as reducing agent and ligand (PTU‐CuNCs) was prepared by a simple approach with superior quantum yield (18.03 %), and the PTU‐CuNCs with red fluorescence could improve the anti‐interference ability of detection. Meanwhile, the synthesis conditions of PTU‐CuNCs were optimized and analyzed in detail. Through a series of experiments, it was found that inner filter effect (IFE) and dynamic quenching might become the main reasons for the fluorescence quenching of PTU‐CuNCs by Dio. Based on the mechanism, a fluorescence probe for the determination of Dio was established. In the range of 0.33–31.67 μmol L−1, the fluorescence quenching efficiency of PTU‐CuNCs was linearly related to the contents of Dio, and corresponding limit of determination (LOD) was estimated to be 101.3 nmol L−1, and limit of quantitation (LOQ) was calculated to be 337.4 nmol L−1. Furthermore, the method could be used effectively for the assay of Dio in practical samples.

Ultralow Potential Cathodic Electrochemiluminescence Aptasensor for Detection of Kanamycin Using Copper Nanoribbons as Coreaction Accelerator.

An ultralow cathodic potential electrochemiluminescence (ECL) aptasensor was designed, employing DNA nanoribbon template self-assembly copper nanoclusters (DNR-CuNCs) as a novel coreaction accelerator within the luminol-H2O2 system for the sensitive detection of kanamycin (KANA). Mechanistic investigations revealed that the DNR-CuNCs preferred to generate highly active hydroxyl radicals by facilitating the reduction of the coreactant H2O2 under neutral pH conditions, consequently enhancing cathodic luminescence. By the strong π-π stacking effect of KANA aptamer and graphene as a signal modulation switch, DNR-CuNCs were displaced from the electrode surface due to the affinity of KANA and its aptamer, resulting in the inhibition of the luminol-H2O2 system and a decrease in the ECL signal. Under optimal experiments, the aptasensor demonstrated exceptional sensitivity in detecting KANA within the concentration range from 1 × 10-2 to 5 × 105 pg/mL, with the detection limit as low as 0.18 fg/mL. This innovative strategy provided a novel approach to designing effective ECL emitters for monitoring food safety.

Stable and Recyclable Copper Nanoclusters with Exposed Active Sites for Broad‐Scope Protosilylation in Open Air

Despite recent advances in cluster‐based catalysis for organic synthesis, the substrate scope of reactions catalyzed by metal nanoclusters is typically not superior to previously established catalytic systems. Herein, we develop new atomically precise copper nanoclusters for protosilylation, with scope expanding to alkenes and simple enynes that were not suitable for prior synthetic methodologies with traditional copper complexes. The involvement of a second copper center in the metal kernel during the migratory insertion step is thought to be responsible for the expanded scope. In addition, the reaction is highly compatible with water and can be carried out in open air rather than under inert gas protection. Mechanistic studies suggest that the cluster‐catalyzed protosilylation proceeds in the absence of silyl radicals. The current findings demonstrate the potential of using metal nanoclusters for practical and sustainable chemical synthesis.

Stable and Recyclable Copper Nanoclusters with Exposed Active Sites for Broad-Scope Protosilylation in Open Air.

Despite recent advances in cluster-based catalysis for organic synthesis, the substrate scope of reactions catalyzed by metal nanoclusters is typically not superior to previously established catalytic systems. Herein, we develop new atomically precise copper nanoclusters for protosilylation, with scope expanding to alkenes and simple enynes that were not suitable for prior synthetic methodologies with traditional copper complexes. The involvement of a second copper center in the metal kernel during the migratory insertion step is thought to be responsible for the expanded scope. In addition, the reaction is highly compatible with water and can be carried out in open air rather than under inert gas protection. Mechanistic studies suggest that the cluster-catalyzed protosilylation proceeds in the absence of silyl radicals. The current findings demonstrate the potential of using metal nanoclusters for practical and sustainable chemical synthesis.

Self-assembly of S,N-codoped Ce/Cu bimetallic nanoparticles for fluorescence and visual detection of hexavalent chromium.

Ce2(SO4)3 was doped into 4,6-diamino-2-mercaptopyrimidine (DAMP)-encapsulated copper nanoclusters (CuNCs) via a facile, rapid, low-temperature, and green self-assembly synthesis method to obtain fluorescent S,N-codoped Cu/Ce-DAMP nanoparticles (S,N-codoped Cu/CeNPs) for the detection of Cr(VI). The prepared Cu/CeNPs exhibit double emission peaks at 470nm and 610nm. Thefluorescence emission at 610nm is significantly enhanced due to the aggregation-induced emission (AIE) effect, and the quantum yield is as high as 20.19%. The fluorescence emission at 610nm can be selectively quenched by Cr(VI) due to the internal filter effect (IFE) and dynamic quenching, whereas the weak fluorescence at 470nm remains almost stable. On this basis, a fluorescence assay method for Cr(VI) was established, with good linearity in the concentration range 0.5-120µM and a detection limit (LOD) of 134nM. Using a smartphone to take photos of the fluorescence signals changes caused by Cr(VI) rapid visual detectionis achieved with a linear range of 10-130 μM and a LOD of 2.35 μM. The proposed method was successfully applied to the detection of Cr(VI) in actual water samples.

Supramolecular Luminescent Copper-Nanocluster-Based Dough with Excellent Electrical Conductivity Sensing Properties.

In recent years, the rapid advancement of flexible conductive materials has significantly increased the demand for dough materials that offer high flexibility and conductivity for diverse applications. Here, we developed a flexible, stretchable, and self-healing dough utilizing hydrogen-bonding interactions between glutathione-stabilized copper nanoclusters (GSH-Cu NCs) and poly(acrylic acid) (PAA). The dough materials can be kneaded, readily reshaped, and further processed to create bulk materials of arbitrary form factors. The incorporation of PAA not only preserved the vibrant blue emission of GSH-Cu NCs but also enhanced their electrical conductivity and stretchability. The dough can be stretched up to 25 times its initial length and achieves complete self-healing in a short time. Moreover, the dough can automatically repair physical damage and return to its initial conductivity levels after healing. Surprisingly, the electrical conductivity of the dough can reach as high as 2.97 S/m, which is relatively superior compared to that of conventional conductive materials. This study presents a dough that serves as a highly sensitive strain sensor, capable of effectively monitoring human movement across a broad range of strains.

Long Stability of Atomically Precise Red Emissive Copper Nanoclusters within the Gel and Their Use As a Potential Catalyst and Fluorescent Ink.

Herein, an amphiphile-based hydrogel (with 5% DMF) containing natural amino acid residue has been used to prepare and stabilize red-emitting CuNCs for several months. Though different methods have been attempted, amphiphile and 4-mercaptobenzoic acid (4-MBA)-containing hydrogels are pinpointed to be the base medium to stabilize this new Cu-cluster. From a MALDI-TOF MS analysis it was found that it is a Cu8-atom cluster stabilized by three 4-MBA ligands. Copper acetate monohydrate (Cu(CH3COO)2·H2O) has been used as a copper precursor, and l-ascorbic acid has been used as a reducing agent. FEG-TEM analysis shows that the Cu cluster has an average size of 2.83 nm. Interestingly, these clusters can be used as a fluorescent ink with a visibility of the solid state under a UV-lamp with an excitation of 365 nm. This envisaged applying these CuNCs for anticounterfeiting. These Cu-clusters show an excitation of 420 nm with an emission of 620 nm, as is evident from the fluorescence spectroscopic analysis. Based on our knowledge, this is the first example of making and consequently stabilizing Cu-clusters using hydrogel as a template for a few months. Moreover, these CuNCs can also be used as a catalyst for the reduction of nitro derivatives to their amine derivatives in aqueous medium.

Tailoring the Heterointerfaces of Earth-Abundant Transition-Metal Nanoclusters on Nickel Oxide Nanosheets for Enhanced Overall Water Splitting through Electronic Structure Optimization.

Evolving highly competent and economical electrocatalysts for alkaline water electrolysis is crucial in renewable hydrogen energy technologies. The slow hydrogen evolution reaction (HER)/oxygen evolution reaction (OER) kinetics under alkaline electrolytes, still, has troubled developments in high-performance green hydrogen production systems. Herein, we demonstrate the tailoring of the interface of earth-abundant transition-metal nanoclusters (MNCs), including iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) nanoclusters on nickel oxide nanosheets (M NCs|NiO NS) through metal-support interaction for enriched overall water splitting under an alkaline electrolyte. The strong metal-metal oxide interaction allows alteration of the binding capabilities of hydrogen ions (*H) and hydroxyl ions (*OH) on Ni electrodes. Specifically, the robust interaction between Fe and NiO reveals optimized binding of H* and OH* energies, facilitating the water-splitting reaction under an alkaline electrolyte. In addition, the improved HER/OER catalytic activity is attained with the Fe NCs|NiO NS with small overpotentials of ∼62.0 and ∼380.0 mV for the HER and OER, respectively, a high mass activity of ∼90.0 A g-1, a turnover frequency of ∼5.94 s-1, and long-lasting stability via offering abundant electrochemical active sites, three-dimensional (3D) morphologies, and high dispersion of nanoclusters that provide effective charge and mass transport processes. This study provides a promising strategy for the effective design of efficient bifunctional electrocatalysts based on earth-abundant materials for alkaline water electrolyzers.

Atomically precise Cu32 nanoclusters with selenide doping: Synthesis, bonding, and catalysis

AbstractCopper nanoclusters with stable compositions and precise structures have long been sought after, as they possess properties that are absent in gold and silver counterparts. However, the creation of copper nanoclusters with novel compositions, structures, and functionalities remains largely unexplored in the literature. In this study, we demonstrate that selenide doping is an effective method for fabricating stable copper nanostructures through controlled synthesis and structure determination of a copper–selenide nanocluster. The nanocluster of [Cu32Se7(BnSe)18(PPh3)6]+ (denoted as Cu32Se7, Bn is benzyl) has been prepared by reducing copper salts in the presence of organic diselenides. The atomic structure of the Cu32Se7 cluster, accurately determined through single‐crystal X‐ray diffraction, reveals a core–shell arrangement of Cu20Se7@Cu12(BnSe)18(PPh3)6, where Se2− anions are well dispersed in the Cu20 framework. Notably, this cluster represents a rare example of copper–selenide semiconductor nanoclusters. Experimental and theoretical analysis shows strong interactions between Se ligands and metal atoms, resulting in high stability of the Cu32Se7 cluster. Furthermore, the cluster exhibits excellent catalytic performance in the hydroboration reaction of alkynes, producing a range of vinylboron compounds with adjustable structures and functions. Importantly, the cluster undergoes no structural or nuclearity changes during the reaction, as confirmed by extended X‐ray absorption fine structure and X‐ray photoelectron spectroscopy studies. This study not only presents a molecular cluster model highlighting the effectiveness of selenide dopants in fabricating new copper nanostructures but also paves the way for utilizing stable copper nanoclusters in diverse and exciting areas beyond catalysis.

Atomically precise copper nanoclusters mediated Fenton-like reaction for cancer chemodynamic therapy.

We developed stable luminescent morpholine-appended copper nanoclusters CuNCs@MorMB with an ultra-small size (<3 nm) and a long emission lifetime (577 ns). They mediate a Fenton-like reaction to produce reactive hydroxyl radicals (˙OH), subsequently depleting antioxidant glutathione levels for cancer chemodynamic therapy (CDT).

A highly sensitive dual-mode detection platform based on the novel copper/molybdenum bimetallic nanoclusters and Co–Fe layered doubled hydroxide nanozyme for butyrylcholinesterase activity sensing

Herein, a novel copper/molybdenum bimetallic nanoclusters (Cu/Mo NCs) with intense blue emission were synthesized by using polyvinylpyrrolidone (PVP) as template and ascorbic acid as reducing agent. Owing to the synergistic effect between Cu and Mo, the fluorescence intensity of Cu/Mo NCs was significantly improved about 6-time than monometallic copper nanoclusters. A novel and sensitive ratiometric fluorescence and colorimetric dual-mode sensing platform for monitoring butyrylcholinesterase (BChE) was strategically constructed by the integration of Cu/Mo NCs with excellent optical properties and Co–Fe layered doubled hydroxide (CoFe-LDH) with superior peroxidase-like activity for the first time. In the presence of H2O2, nonfluorescent and colorless o-phenylenediamine (OPD) was oxidized to fluorescent and yellow 2,3-diaminophenazine (DAP) with maximum fluorescence emission peak at 564 nm and ultraviolet absorption peak at 418 nm by CoFe-LDH with peroxidase-like activity. Simultaneously, the generation of DAP could effectively quench Cu/Mo NCs fluorescence at 444 nm through the inner-filter effect (IFE). The hydrolysis of S-butyrylthiocholine iodide (BTCh) can be catalyzed by butyrylcholinesterase (BChE) to generate thiocholine (TCh) that could hinder the oxidation of OPD, leading to the fluorescence and ultraviolet absorption of DAP decreased, meanwhile, the fluorescence of Cu/Mo NCs recovered. The ratiometric fluorescence signal F564/F444 and colorimetric system both performed a satisfactory response to the concentration of BChE in the range 0.5 to 90 U L−1 and 1 to 100 U L−1 with the LOD of 0.18 U L−1 and 0.36 U L−1, respectively. The dual-mode sensing for BChE exhibited outstanding application potential in biosensing.