Copper Nanoclusters Research Articles

Novel Cu nanocluster superlattice/MBene-induced ECL enhancement strategy for miRNA-221 detection

In this paper, copper nanoclusters with superlative structure (Cu NCSL) were developed as luminescence probe for miRNA-221 detection. The tightly aligned superlattice structure of Cu NCSL effectively reduced the disordered and chaotic accumulation of nanoparticles, which further limited the intramolecular vibration and internal rotation of Cu NCs. Meanwhile, the compact particle stacking in the superlattice structure greatly improved the electron transport efficiency. As a result, the luminescence of Cu NCSL was enhanced greatly with the increase of radiation energy transfer rate. Furthermore, the two-dimensional MBene with good electrical conductivity and high electrochemical performance has been prepared as electrode modification material. In the constructed electrochemiluminescence (ECL) sensor for miRNA-221 detection, the ECL signal of Cu NCSL was amplified by the MBene nanosheets effectively. Finally, the results in the actual tumor tissues showed that the Cu NCSL/MBene-based biosensor has high selectivity, stability and low detection limit in the clinical cancer detection.

A Highly NIR Emissive Cu16Pd1 Nanocluster.

The construction of stable copper nanoclusters (Cu-NCs) with near-infrared (NIR) emission that can be used for catalysis is highly desired, yet remains a challenge. Herein, an atomically precise bimetallic Cu/Pd NC with a molecular formula of Cu16Pd1L10(PPh3)2(Pz)6 (Pz=3,5-(CF3)2Pyrazolate, L=4-CH3OPhC≡C-), abbreviated as Cu16Pd1, is synthesized. Single-crystal X-ray crystallographic analysis of Cu16Pd1 reveals a Cu10Pd1 kernel with pseudo-gyroelongated square bipyramid confirmation surrounded by other 6 Cu(I) ions and protected ligands. Interestingly, it exhibits strong NIR emission with the highest photoluminescence quantum yield (PLQY) among all the Cu NCs/Cu alloys (λem>800nm) in the solid-state, and also displays NIR emission in solution. Experimental results and theoretical calculations suggest that the impressive NIR emission is attributed to abundant supramolecular interactions in the solid-state, including intramolecular metal-metal and intermolecular interactions. Of note, the bimetallic Cu16Pd1 can catalyze the reduction of 4-nitrophenol. This work provides a novel method for synthesizing Cu/Pd NCs and reminds that the less studied Cu/Pd NC can serve as outstanding luminescent material, which is seldom noticed in atomically precise nanoclusters.

A ratiometric fluorescent “off-on” sensor for acrylamide detection in toast based on red-emitting copper nanoclusters stabilized by bovine serum albumin

Acrylamide, as a Class 2A carcinogen, poses serious threats to human health. To achieve rapid and accurate determination of acrylamide in food, a ratiometric fluorescent “off–on” sensor was designed by incorporating red-emitting copper nanoclusters and glutathione. Copper nanoclusters with bimodal emission at 395 nm and 650 nm (excited at 310 nm) were synthesized by using bovine serum albumin as the ligand and ascorbic acid as the reductant. With glutathione addition, the fluorescence intensity at 650 nm gradually decreased, while the case at 395 nm slightly increased. The quenched fluorescence at 650 nm was subsequently restored by acrylamide through thiol-ene Michael addition reaction between acrylamide and glutathione. The constructed sensor showed excellent performance towards acrylamide detection in the range of 5–300 μM with a detection limit of 1.48 μM, and was further applied to real-sample detection of acrylamide in toast and exhibited good recoveries (90.29–101.30 %), indicating potential applications of this sensor.

Sensitive Detections of Sodium Dichloroisocyanurate and Rosmarinic Acid by Polyvinylpyrrolidone Coated Copper Nanoclusters.

In this article, the water-soluble blue-light-emitting copper nanoclusters (CuNCs) were prepared by polyvinylpyrrolidone (PVP) and ascorbic acid as templating and reducing agents, respectively. The optimization of synthesis conditions of PVP-CuNCs were studied and analyzed. And the quantum yield of the PVP-CuNCs was calculated to be 14.97%. It had good specificity and exceptionally sensitive detection for sodium dichloroisocyanurate (DCCNa)/rosmarinic acid (RA), with a linear response range of 0.030-2.400/0.030-0.900 μM and corresponding LOD value of 10.766/8.985 nM. Moreover, the fluorescent reaction mechanisms of the PVP-CuNCs-DCCNa and PVP-CuNCs-DCCNa-RA systems were discussed, and the sensing probe could be effectively used for the assays of DCCNa and RA in genuine samples, whose results were acceptable.

In situ formation of copper nanoclusters for efficient analysis of β-glucosidase activity

An efficient and convenient fluorescent method has been developed to detect β-glucosidase via utilizing the in situ synthesis of double-stranded DNA templated copper nanoclusters (dsDNA-Cu NCs). The dsDNA-Cu NCs can be formed by using random dsDNA with (AT-TA) rich sequence as the template. However, with the addition of amygdalin and β-glucosidase, amygdalin was catalyzed by β-glucosidase to generate cyanide ion (CN−). The CN− had the high affinity to bind with Cu2+ to inhibit the production of fluorescent dsDNA-Cu NCs, resulting in low fluorescence intensity. This method exhibits both sensitivity and specificity in detecting β-glucosidase under the optimal conditions. In addition, the technique's detection limit is 0.00084 U mL−1. The serum samples were also used to verify this fluorescent strategy with satisfactory results. In addition, this method does not require complex preparation process of probes and fluorescent dye labelling, greatly simplifying the experimental processes. Thus, it can provide a sensitive method for the β-glucosidase related biomedical research.

Highly Stable Fluorescent-Traffic-Light Sensor for Point-of-Care Detection of Tetracycline.

Fluorescent point-of-care (POC) sensors have found great utility in fields like clinical diagnosis, food testing, and environmental monitoring. Herein, we developed a highly stable POC sensor that enabled the visual detection of tetracycline (TC) in a distinct fluorescent-traffic-light manner. In the sensor, a composite material of copper nanoclusters and metal-organic framework (CuNCs@MOF-5) prepared with a facile one-pot synthetic strategy was employed as the core element for target recognition and signal transduction. As evidenced by experiments, the as-prepared CuNCs@MOF-5 exhibited significantly improved fluorescence properties in terms of emission enhancement (about 28-fold) and stability improvement (over 110 days) compared to the CuNCs without confining and protection by MOF-5. More importantly, it was found that TC could uniquely interact with Zn(II) to trigger the disassembly of CuNCs@MOF-5, resulting in green fluorescence emission from the TC-Zn(II) complex and red fluorescence weakening of CuNCs. On the basis of this finding, a simple and stable sensor was proposed for POC detection of TC, which demonstrated high sensitivity, selectivity, and reproducibility. In addition to homogeneous visual detection in a 96-well plate, a CuNCs@MOF-5-contained agarose gel array was easily fabricated to achieve direct detection of TC in milk without any pretreatment, thanks to the size-sieving effect of the gel. Moreover, a test paper array was also put forward for low-cost TC detection, which indicates the extensibility and practicability of this sensing strategy.

Ascorbic Acid‐Capped Copper Nanoclusters: A Turn‐On Fluorescence Sensor for Biliverdin

AbstractA simple and facile turn‐on fluorescence sensor has been developed for the effective determination of an important bile pigment‐ Biliverdin (BVD), using ascorbic acid capped copper nanoclusters (AA CuNCs). This yellow colored, biocompatible material exhibits emission maximum at 445 nm on an excitation wavelength of 365 nm. The fluorescence intensity of AA CuNCs was enhanced efficiently in presence of BVD within the linear range 1.00×10−5 M to 2.00×10−6 M with a limit of detection 2.88×10−7 M. An aggregation induced emission enhancement (AIEE) mechanism was suggested for the sensor. Practical utility of the proposed sensor has been validated in artificial urine and blood serum.

Synthesis of Greenish-Yellow Fluorescent Copper Nanocluster for the Selective and Sensitive Detection of Fipronil Pesticide in Vegetables and Grain Samples.

In this paper, a new synthetic route is introduced for the synthesis of high-luminescent greenish-yellow fluorescent copper nanoclusters (PVP@A. senna-Cu NCs) using Avaram senna (A. senna) and polyvinylpyrrolidone (PVP) as templates. A. senna plant extract mainly contains variety of phytochemicals including glycosides, sugars, saponins, phenols, and terpenoids that show good pharmacological activities such as anti-inflammatory, antioxidant, and antidiabetic. PVP is a stable and biocompatible polymer that is used as a stabilizing agent for the synthesis of PVP@A. senna-Cu NCs. The size, surface functionality, and element composition of the fabricated Cu NCs were confirmed by various analytical techniques. The as-prepared greenish-yellow fluorescent Cu NCs exhibit significant selectivity towards fipronil, thereby favoring to assay fipronil pesticide with good linearity in the range of 3.0-30μM with a detection limit of 65.19nM. More importantly, PVP@A. senna-Cu NCs are successfully applied to assay fipronil in vegetable and grain samples.

Simultaneous Detection of Citric Acid and Oxalic Acid Based on Dual Spectrum and Biomimetic Peroxidase for Urolithiasis Screening with a Fully Automatic Urine Analyzer.

Urolithiasis stands as a prevalent ailment within the urinary system, with hyperoxaluria and hypocitraturia being the most frequent manifestations characterized by excessive oxalic acid (OA) and deficient citric acid (CA) levels in urine. Detecting these compounds in urine quantitatively holds paramount importance for early urolithiasis screening. Existing methodologies fall short in achieving simultaneous and on-site identification of OA and CA, posing challenges for accurate urolithiasis screening. Addressing this concern, the study successfully accomplishes the concurrent identification of OA and CA in urine through a combination of dual-spectral analysis and biomimetic peroxidase utilization. Bovine serum albumin and dithiothreitol-modified copper nanoclusters (BSA-DTT-CuNCs) are employed as biomimetic peroxidases, effectively mitigating interference and enabling the simultaneous determination of OA and CA. The quantification range spans from 0 to 12mm for OA and 0.5 to 2.5mm for CA, with detection limits of 0.18 and 0.11mm, respectively. To facilitate swift and on-location urine analysis, a fully automated urine analyzer (FAUA) is introduced that streamlines the process of biomarker pretreatment and identification within urine samples. Validation with real urine samples from urolithiasis patients demonstrates the method's diagnostic precision, highlighting the dual-spectral technique and analyzer's promising role in urolithiasis screening.

Construction of nanohybrid Tb@CDs/GSH-CuNCs as a ratiometric probe to detect phosphate anion based on aggregation-induced emission and FRET mechanism.

The simple preparation of a nanohybrid of terbium-doped carbon dots/glutathione-capped copper nanoclusters (Tb@CDs/GSH-CuNCs) was for the first time developed for ratiometric detection of phosphate anion (Pi). Blue-emission of Tb@CDs can trigger non-luminescence of GSH-CuNCs for aggregation-induced emission (AIE) performance due to the strong reserved coordination capacity of Tb3+. Thus, Tb@CDs/GSH-CuNCs rapidly generated dual-emission signals at 630 nm and 545 nm by directly mixing the two individual materials via the AIE effect, alongside fluorescence resonance energy transfer (FRET) process. However, by the introduction of Pi, both AIE and FRET processes were blocked because of the stronger binding affinity of Tb3+ and Pi than that of Tb3+ and -COOH on Tb@CDs, thus realizing successful ratiometric detection of Pi. The linear concentration range was 0-16 μM, with the limit of detection (LOD) of 0.32 μM. The proposed method provided new ideas for designing nanohybrid of CDs and nanoclusters (MNCs) as ratiometric fluorescent probes for analytical applications.

Droplet-based luminescent sensor supported onto hydrophobic cellulose substrate for assessing fish freshness following smartphone readout.

In this work, two sensitive droplet-based luminescent assays with smartphone readout for the determination of trimethylamine nitrogen (TMA-N) and total volatile basic nitrogen (TVB-N) are reported. Both assays exploit the luminescence quenching of copper nanoclusters (CuNCs) produced when exposed to volatile nitrogen bases. In addition, hydrophobic-based cellulose substrates demonstrated their suitability as holders for both in-drop volatile enrichment and subsequent smartphone-based digitization of the enriched colloidal solution of CuNCs. Under optimal conditions, enrichment factors of 181 and 153 were obtained with the reported assays for TMA-N and TVB-N, respectively, leading to methodological LODs of 0.11mg/100g and 0.27mg/100g for TMA-N and TVB-N, respectively. The repeatability, expressed as RSD, was 5.2% and 5.6% for TMA-N and TVB-N, respectively (N=8). The reported luminescent assays were successfully applied to the analysis of fish samples, showing statistically comparable results to those obtained with the reference methods of analysis.

Unveiling the Long-Lived Emission of Copper Nanoclusters Embedded in a Protein Scaffold.

Protein-conjugated coinage metal nanoclusters have become promising materials for optoelectronics and biomedical applications. However, the origin of the photoluminescence, especially the long-lived excited state emission in these metal nanoclusters, is still elusive. Here, we unveiled the underlying mechanism of long-lived emission in albumin protein-conjugated copper nanoclusters (Cu NCs) using steady state and time-resolved spectroscopic techniques. Our findings reveal room-temperature phosphorescence (RTP) in protein-conjugated Cu NCs. Time-resolved area-normalized spectra distinguished short- and long-lived components, where the former arises from the singlet state and the latter from the triplet state, thus resulting in RTP. The similarity of the emission spectra at room (298 K) and cryogenic (77 K) temperature ascertains the RTP phenomenon by harvesting the higher-lying triplet states. Time-gated bioimaging of A549 cells using the long-lived emission not only supports RTP emission in the cellular environment but also provides exciting avenues in long-term bioimaging using bovine serum albumin-conjugated Cu NCs.

Preparation method of copper nanoclusters with PVP as ligand

Preparation method of copper nanoclusters with PVP as ligand

Ligand-induced Assembly of Copper Nanoclusters with Enhanced Electrochemcial Excitation and Radiative Transition for Electrochemiluminescence.

Copper nanoclusters (CuNCs) are emerging electrochemiluminescence (ECL) emitters with unique molecule-like electronic structures, high abundance, and low cost. However, the synthesis of CuNCs with high ECL efficiency and stability in a scalable manner remains challenging. Here, we report a facile gram-scale approach for preparing self-assembled CuNCs (CuNCsAssy ) induced by ligands with exceptionally boosted anodic ECL and stability. Compared to the disordered aggregates that are inactive in ECL, the CuNCsAssy shows a record anodic ECL efficiency for CuNCs (10 %, wavelength-corrected, relative to Ru(bpy)3 Cl2 /tripropylamine). Mechanism studies revealed the unusual dual functions of ligands in simultaneously facilitating electrochemical excitation and radiative transition. Moreover, the assembly addressed the limitation of poor stability of conventional CuNCs. As a proof of concept, an ECL biosensor for alkaline phosphatase detection was successfully constructed with an ultralow limit of detection of 8.1×10-6 U/L.

Ligand‐induced Assembly of Copper Nanoclusters with Enhanced Electrochemical Excitation and Radiative Transition for Electrochemiluminescence**

AbstractCopper nanoclusters (CuNCs) are emerging electrochemiluminescence (ECL) emitters with unique molecule‐like electronic structures, high abundance, and low cost. However, the synthesis of CuNCs with high ECL efficiency and stability in a scalable manner remains challenging. Here, we report a facile gram‐scale approach for preparing self‐assembled CuNCs (CuNCsAssy) induced by ligands with exceptionally boosted anodic ECL and stability. Compared to the disordered aggregates that are inactive in ECL, the CuNCsAssy shows a record anodic ECL efficiency for CuNCs (10 %, wavelength‐corrected, relative to Ru(bpy)3Cl2/tripropylamine). Mechanism studies revealed the unusual dual functions of ligands in simultaneously facilitating electrochemical excitation and radiative transition. Moreover, the assembly addressed the limitation of poor stability of conventional CuNCs. As a proof of concept, an ECL biosensor for alkaline phosphatase detection was successfully constructed with an ultralow limit of detection of 8.1×10−6 U/L.

Toxic Effects of Copper Fungicides on the Development and Behavior of Zebrafish in Early-Life Stages.

Copper-based fungicides have been used to control various plant diseases for more than one hundred years and play very important roles in agriculture. Accumulation of copper in freshwater and environment pose severe threats to human health and the environment. The current study evaluated the developmental and behavioral toxicity of PEG@Cu NCs (copper nanoclusters), Kocide® 3000 (copper hydroxide), and Cu(CH3COO)2 (copper acetate) to zebrafish in early-life stages. The developmental toxicity was evaluated according to the parameters of mortality, hatching rate, autonomous movement and heartbeat of embryos, and body length of larvae. The 9 dpf (days postfertilization)-LC50 (50% lethal concentration) of embryonic mortality was 0.077, 0.174 or 0.088 mg/L, and the 9 dpf-EC50 (effective concentration of 50% embryos hatching) of hatching rate was 0.079 mg/L, 0.21 mg/L and 0.092 mg/L when the embryos were exposed to PEG@Cu NCs, Kocide® 3000 or Cu(CH3COO)2, respectively. Kocide® 3000 and Cu(CH3COO)2 obviously decreased the spontaneous movements, while PEG@Cu NCs had no adverse effects on that of embryos. The reduced heartbeat can return to normal after exposure to PEG@Cu NCs for 96 h, while it cannot recover from Kocide® 3000. In addition, Kocide® 3000 (≥0.2 mg/L), PEG@Cu NCs and Cu(CH3COO)2 with 0.05 mg/L or higher concentration exhibited obvious behavioral toxicity to zebrafish larvae according to the parameters of movement distance, average velocity, absolute sinuosity, absolute turn angle and absolute angular velocity.

Electrostatically-driven self-assembly of copper nanoclusters and carbon dots for quantitative protamine and heparin determination

A novel nanosystem composed of red-emissive thiolate-capped copper nanoclusters (GSH-CuNCs) and blue-emissive polyethyleneimine-tailored carbon dots (B-CDs+) was utilized for the quantitative determination of protamine and heparin. Addition of B-CDs+ to a solution containing GSH-CuNCs resulted in a significant increase in the fluorescence emission of GSH-CuNCs due to their self-assembly through an electrostatic interaction. However, in the presence of protamine, a polycationic protein, the fluorescence emission of GSH-CuNCs at 590 nm was decreased as a result of adsorbing protamine on GSH-CuNCs surface instead of B-CDs+. This led to disassembling of GSH-CuNCs, while the fluorescence emission of B-CDs+ at 470 nm remained unchanged during the determination. In the presence of heparin, a negatively charged molecule, the fluorescence emission of GSH-CuNCs nanosystem was recovered due to strong electrostatic interaction between protamine and heparin. The displaced B-CDs+ aggregated the GSH-CuNCs, restoring its fluorescence emission. Under optimized conditions, the fluorescence responses were increased with the protamine and heparin concentrations in the range of 0.004–40 µg/mL and 0.01–28 µg/mL, with LODs (S/N = 3) of 0.001 µg/mL and 0.004 µg/mL, respectively. The nanosystem offers several merits, including an ultra-low LODs, wide dynamic linear range, good anti-interference, satisfactory detection reliability, and short response time. Importantly, this strategy was successfully devoted to estimate protamine and heparin in urine and serum samples, and the results were found to be acceptable.

Polyethylenimine-protected green-emission copper nanoclusters as highly effective fluorescent and colorimetric nanoprobe for selective cobalt ions and temperature sensing

Excessive uptake of Co2+ is harmful to one's physical health and should not be ignored. Herein, a polyethylenimine (PEI) protected hydrophilic copper nanoclusters (PEI-CuNCs) with strong green fluorescence emission around 510 nm was apace synthesized employing a one-pot method without hyperthermia. Interestingly, the as-prepared water-soluble PEI-CuNCs can be specifically quenched by Co2+ at pH 6.0, with a wide detection range (0–500 μM) and a sensitive detection limit of 14.9 nM, which was lower than the maximum level in the body. Besides, the colorimetric detection of Co2+ could be additionally realized based upon the typical yellow color of PEI-CuNCs changed to baby-pink color of the PEI-Co2+ complex. Furthermore, the PEI-CuNCs was employed in fabrication portable test strip for visual detection of Co2+ by capturing the change in fluorescence color, which can be ascribed to the coordination interaction between Co2+ and amine groups in PEI, and also the aggregated quenching of large PEI-CuNCs-Co2+ particles formation. Moreover, the PEI-CuNCs displayed excellent reversible thermo-responsive within a temperature range of 20–65 °C. It is worth mentioning that the PEI-CuNCs exhibited low bio-toxicity and excellent cell permeability when selectively detecting Co2+ in living cells by fluorescence microscopy imaging. Armed with these engaging properties, the sensing system paved a new avenue for the effective development of a convenient fluorescence colorimetry sensor for general assessment of potential risks and specific assessment of human security.

Ratiometric and sensitivity detection of AChE: Silicon nanomaterial-triggered aggregation-induced emission of copper nanoclusters

As an important kind of hydrolase, acetylcholinesterase (AChE) is closely related to many neurological diseases. Therefore, the development of reliable and sensitive methods for the determination of its activity is of great research significance. In this work, silicon nanomaterials (SiNPs) with positive charge and glutathione-modified copper nanoclusters (CuNCs) with negative charge were designed to establish a ratiometric fluorescence system (SiNPs@CuNCs) based aggregation-induced emission (AIE) strategy. The SiNPs@CuNCs could directly detect the AChE activity without any intermediate quencher. Acetylthiocholine iodide could be catalyzed and hydrolyzed into thiocholine (TCh) by AChE. TCh could effectively quench the fluorescence intensity (FI) of CuNCs in SiNPs@CuNCS, yet the FI of SiNPs was unchanged. The activity of AChE was measured by FI ratio (FCuNCs/FSiNPs). The linear range of SiNPs@CuNCs for the quantitative detection of AChE was 0–0.05 U/mL, and the limit of detection was 0.003 U/mL. SiNPs@CuNCs successfully realized the trace detection of AChE activity in a real serum sample, and satisfactory results were obtained. This research will provide unique insights into the development of new ratiometric fluorescent nanomaterials for the determination of other hydrolase.

PH-dependent Synthesis and Interactions of Fluorescent L-Histidine Capped Copper Nanoclusters with Metal Ions.

In this work, L-Histidine-protected copper nanoclusters synthesized by changing the pH levels of precursor solution have been shown to display different emission wavelengths and intensities. As determined by mass spectrometry, nanoclusters Cu3L2 synthesized at acidic pH have 3 atoms in their core and emit in the greenish-yellow region, and nanoclusters Cu2L2, synthesized in the basic conditions have 2 atoms in their core and emit in the blue-green region. They are expected to have coordination through the carboxylate group and nitrogen of the imidazole ring of histidine ligand, respectively. Metal ions Mg2+, Mn2+, Zn2+, and Pb2+ selectively enhance the interaction between carboxylate - copper metal core and increase the emission intensity of Cu3L2. These metal ions weaken the interaction between imidazole nitrogen and copper metal core and quench the emission intensity of Cu2L2. As synthesized, nanoclusters exhibit good water solubility and photostability, they can act as fluorescent probes to sense the metal ions, therefore, they were utilized for the optical sensing of the mentioned metal ions. Fluorescent nanoclusters were found to sense even a very low concentration of metal ions with a limit of detection (3 σ/slope) in nanomolar range.