Selective Detection Of Copper Ions Research Articles

Smartphone-assisted sensing platform based on dual-responsive nitrogen-doped carbon dots for enzyme-free and visual quantitative detection of Cu2+ and glyphosate

Rapid and selective detection of copper ion (Cu2+) and glyphosate (GLY) is crucial to environmental pollution control, especially when using a simple and portable device. In this study, an enzyme-free and visual fluorescence sensor based on nitrogen-doped carbon dots (N-CDs) is successfully designed, featuring strong blue fluorescence and excellent stability. The sensor shows a linear response to Cu2+ over a wide detection range of 0.048 to 40 μM with a low limit of detection (LOD, 48 nM), resulting in fluorescence quenching at 435 nm. Meanwhile, the rapid enhancement in fluorescence intensity of the quenched N-CDs/Cu2+ system can be triggered by GLY owing to the strong complexation between Cu2+ and GLY, with a LOD of GLY as low as 0.24 μM. Furthermore, we develop a smartphone-assisted sensing platform using N-CDs/polyvinyl alcohol films, which captures and analyzes fluorescence images to detect Cu2+ and GLY with sensitive LODs of 73 nM and 0.32 μM, respectively. Satisfactory recoveries, ranging from 94.0 % to 104.6 %, are achieved in real sample detection, implying the potential application in the field of enzyme-free and on-site pesticides detection.

Nanocomposite-modified nanopores: A promising platform for selective detection of copper ions

This research introduces an innovative platform designed for the selective detection of copper (II) (Cu2+) ions, employing a singular nanopore embedded within a 12 μ m-thick polyethylene terephthalate (PET) membrane. The track-etched nanopore was subsequently modified with nanomaterials in an allylamine hydrochloride (PAH)-modified asymmetric nanopore through electrostatic interactions. The nanomaterials included copper oxide (CuO), graphene oxide (GO), and their composite (GO/CuO), were synthesized using wet chemistry, and their structures and optical properties were thoroughly investigated using x-ray diffraction and diffuse reflectance spectroscopy. In the distinctive feature of the platform, Cu2+ ions gain access to coordination sites across a broad surface covered by the immobilized nanomaterials, facilitating effective binding. The selective response of GO/CuO modified pores towards Cu2+ ions was notably observed through ion transportation (I –V) studies, surpassing the response of unmodified nanopores and those modified with CuO alone. This selective behavior was demonstrated in the presence of various monovalent and divalent competing ions. Quantitative assessment of I –V studies was conducted by evaluating the intrinsic rectification ratio of asymmetric nanopores, providing a robust measure of platform's efficacy. Furthermore, we identified the optimal pH for detecting Cu2+ ions as 7, enhancing the specificity and accuracy of our method.

An eco-friendly colorimetric strategy based on gold nanoparticles modified with 3-pyridinylboronic acid for detecting copper ions

Copper is an essential element in the human body. Excess accumulations of copper, however, would become a potential threat. Therefore, it is of great significance to detect copper ions. Owing to their controllable morphology, dispersal characteristics, high extinction coefficient, and easily functionalized surfaces, gold nanoparticles (AuNPs) have been highly employed as attractive sensing probes for environmental and biological analyses. We herein propose an eco-friendly colorimetric strategy based on AuNPs modified with 3-pyridinylboronic acid (PA) for sensitive and selective detection of copper ions (Cu2+) in water at trace level. The color changes of the system from wine-red to gray-blue with increasing amounts of copper ions is due to the binding of AuNPs modified with 3-pyridinylboronic acid to copper ions, which in turn leads to the aggregation of AuNPs with fine anti-interference. Strengths of the work: 1) rapid response time without complex pre-treatment; 2) high sensitivity with low limit of detection (LOD) and the good linear relationship (R2 = 0.98, LOD = 3.0 μM by the naked eye and 72 nM by ultraviolet-visible spectroscopy); 3) high selectivity under other interfering ions. In addition, the detection mechanism of this work has been successfully confirmed by density functional theory (DFT), transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), Zeta potential analysis and ultraviolet-visible spectroscopy (UV–vis).

Solid-state real-time colorimetric sensing of ultra-trace copper ions using aqueous compatible chromatic probe imbued porous polymer monolithic sensor

In this work, we design an aqua-compatible and sustainable chromatic sensor for the selective detection of copper ions in aqueous solutions for application in industrial quality control and environmental analysis. The solid-state chromatic sensor is fabricated through the uniform decoration of an indigenously synthesized unique chromoionophoric probe (TMAP), i.e., (2,2′-(((1E,1′E)-thiophene-2,5-diylbis(methaneylylidene)) bis(azaneylylidene))diphenol) onto a bimodal macro-/meso‑porous polymer monolith, poly(2VP-co-DVB), i.e., poly(2vinylpyridine-co-divinylbenzene), to exploit the possibility of solid-state colorimetric ion sensing. The polymer monolith and sensor materials' topography and morphology are characterized through p-XRD, FE-SEM, XPS, EDX, TEM, SAED, TGA, FT-IR and BET/BJH analysis. The ion-sensing is accompanied by a discernible color transition from vivid yellow to subdued red, with a detection and quantification limit value of 0.20 and 0.51 μg/L for Cu2+, respectively. The sensor affirms a fast detection (≤60 s) for Cu2+, with a linear signal/colorimetric response in the concentration range of 3–100 μg/L. The parameters such as sensor dosage, chromatic receptor dose, pH, temperature, sensing kinetics and reusability are optimized for reliable and reproducible ion-sensing. The solid-state sensor reveals excellent selectivity and sensitivity for Cu2+, and its practical utility with environmental/industrial samples proves its utility as a portable sensor kit for real-time on-site analysis for ultra-trace Cu2+.

Indole-based Fluorometric and Colorimetric Chemosensors for the Selective Detection of Cu2+: A Brief Review From the Year 2011-2021

The development of chemosensors has been driven by concurrently advanced research in fluorescence and colorimetric chemosensing. Over the last few decades, the development of copper ion-selective fluorogenic and chromogenic chemosensors has been extensively studied due to their high sensitivity, low cost, and simplicity. They can interact with the metal ion in a unique manner and create measurable color, fluorescence, or redox potential changes. Copper (Cu2+) ion is deemed the third most prevalent transition metal in human beings owing to its various biological and physiological processes. It has drawn a great deal of attention from many researchers in various disciplines such as biology, medicine, and environmental studies. However, an excessive buildup of copper in the body has been linked to several diseases. Thus, more recent research is being focused on developing fluorometric and colorimetric chemosensors for the selective detection of copper ions. Recently, there have been a lot of studies reported in this field of study that describe highly sensitive and sophisticated indole-based chemosensors for various metal ions of interest. In addition, indole derivatives possess inherent fluorescence properties due to their electron-rich nature caused by the π-excessive system of indole, and therefore they can be employed in chemosensors for metal ion detection. Both cations and anions employ it as a molecular recognition system. This review summarizes selective and sensitive Cu2+ ion detection accomplished byvarious indole-based chemosensors between the years 2011 to 2021. Furthermore, sensor design, sensing methods, ligand-metal binding stoichiometry, association constant, and the detection limit by the chemosensors are all summarized and explored.
 Keywords: Indole, Fluorescent chemosensors, Colorimetric chemosensors, Cu2+, Turn-on, Turn-off

A porphyrin-based metal-organic framework Al-TCPP for highly selective sensing of copper ions with exceptional low limit of detection

Sensitive and selective detection of copper ions (Cu2+) using fluorometric methods is of growing significance due to their widespread industrial use, which poses severe environmental and health risks. Here, we reported a porphyrin-based luminescent metal-organic framework (labelling LMOF), Al-TCPP, which exhibits dual emission peaks at 467 and 646 nm upon excitation by a single wavelength. When exposed to Cu2+ ions, the fluorescence peak at 646 nm reduces while the intensity of the 467 nm remains steady. This intriguing property enables the construction of a ratio-metric fluorescence sensor that utilizes an internal standard, significantly enhancing Cu2+ sensing accuracy. Our study establishes a linear relationship (y = 0.0454x + 0.3081) between the fluorescence intensity ratio I467/I646 and the Cu2+ concentration, with a high correlation coefficient R2 = 0.9943. Impressively, the present Al-TCPP achieves a low limit of detection (LOD) of 5.28 nM, one of the lowest reported values for Cu2+ detection. The mechanism underlying this phenomenon involves charge transfer from TCPP ligands in Al-TCPP to Cu2+ ions, as revealed by solid-state NMR and X-ray photoelectron spectroscopy analysis. Utilizing Al-TCPP, we successfully developed test strips for the practical Cu2+ detection. Furthermore, the present Al-TCPP has also effectively applied to determine low Cu2+ content in various samples, including water, tea and serum. This study demonstrates the versatility and practical applicability of present Al-TCPP LMOF for selective detection of Cu2+ ions in diverse environments.

Silica nanoparticle-modified paper strip-based new rhodamine B chemosensor for highly selective detection of copper ions in drinking water.

A new rhodamine B derivative (RDB) was synthesized and utilized for the colorimetric detection of copper ions (Cu2+). This chemosensor utilized a paper strip as a support and a smartphone as a detector for on-site quantitative detection of Cu2+ in water samples. Silica nanoparticles (SiNPs) were investigated as the modifier nanoparticles to achieve uniform color on the paper strip and showed a color response 1.9-fold higher than the one without SiNPs. The RDB chemosensor-based paper strip provided high selectivity toward Cu2+ with a detection limit of 0.7mg/L, and the working concentrations for Cu2+ ranged from 1 to 17mg/L. Parallel analyses of eight drinking water samples were conducted by inductively coupled plasma optical emission spectroscopy. The results were in good agreement, indicating the practical reliability of the established method with a short assay time and high selectivity. These indicate its great potential for on-site detection of Cu2+.

An ESIPT solvatochromic fluorescent and colorimetric probe for sensitive and selective detection of copper ions in environmental samples and cell lines.

Copper is one of the most important transition metals in our body for various physiological functions. An imbalance in the homeostasis of copper in our body can lead to various neurological disorders such as Alzheimer's disease, Parkinson's, and Menkes disease. As a result, there is a need for the detection of excess copper present in the environment and the human system. In this work, we have designed a quinoline-based fluorescent/colorimetric probe (QHS) for rapid and selective detection of copper ions via quenching of fluorescence/color change from yellow to peach which is visible to the naked eye. The probe displayed high selectivity towards copper(II), i.e., Cu(II) in the presence of different metal analytes in water samples. The sensing mechanism of the probe was confirmed by NMR, HRMS, IR spectroscopy, and SEM. The detection limit of Cu(II) ions was found to be 0.493 μM which is lower than the tolerable limit of copper (20 μM) in drinking water as per the EPA. The probe was also utilized for the visualization of Cu(II) in cell lines. The probe was also demonstrated for its application in real-time detection of aqueous samples using portable paper strips.

Lanthanide ternary complex as a fluorescent probe for highly sensitive and selective detection of copper ions based on selective recognition and photoinduced electron transfer

Copper ions have a very important role in human health, industrial and agricultural production. Herein, lanthanide ternary complex of 2,6-pyridinedicarboxylic acid (DPA)-Eu3+-polyethyleneimine (PEI) as a fluorescent probe was thus fabricated for highly sensitive and selective detection of copper ions. PEI itself is non-fluorescent, the PEI-Eu3+complex is also non-fluorescent, and PEI has specific recognition to copper ions due to its higher affinity ability to copper ion than other metal ions. It was found that Cu2+ ions cannot quench the characteristic fluorescence of Eu3+ in the DPA-Eu3+ system, while in the DPA-Eu3+-PEI system, Cu2+ ions can greatly quench the characteristic fluorescence of Eu3+ due to photoinduced electron transfer (PET). The luminescent and quenching mechanism was also discussed in detail. The DPA-Eu3+-PEI probe not only has high sensitivity and selectivity, but also has very rapid fluorescence response and the response time is only 1 min. A good linear relationship between the fluorescence ratios of F0/F and the concentrations of Cu2+ was obtained in the range of 0.02 ∼ 10.0 μM (R2 = 0.998), and the limit of detection (LOD) is 8.0 nM. The probe was successfully applied for the detection of Cu2+ ions in the lake and river water samples, wastewater and urine samples. This work may provide a new strategy for fabricating simple and effective fluorescence probe and a promising application for the rapid and on-site detection in environmental monitoring and biological fluids.

Fabrication of hydrophilic luminescent zinc oxide quantum dots for selective detection of copper ions and efficient inhibition of harmful fungi

In this study, we have successfully prepared surface modified zinc oxide quantum dots (M-ZnO QDs) with ultra-stable fluorescence and excellent hydrophilicity through introducing (3-aminopropyl)triethoxysilane (APTES). The as-prepared M-ZnO QDs under the optimum condition presented strong yellow fluorescence emission under 355 nm excitation and showed satisfied reproducibility. Physical and chemical properties of the synthesized ZnO QDs were further studied by various characterization techniques. Transmission electron microscopy showed homogeneous distribution of spherical M-ZnO QDs with the average particle size of 4.03 nm. According to the characteristic that metal ions can quench fluorescence, M-ZnO QDs-based fluorescence sensor for the detection of Cu 2+ in aqueous solution is developed in this work, which has the advantages of excellent selectivity, good sensitivity and a wide linear range. The limit of detection was 0.51 μM and the linear detection range was 1–200 μM for Cu 2+ determination. The practicability of the fluorescent probe is further validated in the lake water and the satisfactory spiked recoveries of Cu 2+ ranges from 99.1 % to 108.8 %. Besides, M-ZnO QDs displayed concentration inhibition effect and strain effect on the growth of fungi. Thus, the as-prepared M-ZnO QDs are demonstrated to be promising for Cu 2+ determination and anti-fungal applications.

Photoelectrochemical sensor based on Au/ZnS/ZnO nanomaterials for selective detection of copper ions

Composite electrodes of Au/ZnS/ZnO sensor were prepared by hydrothermal method and electrodeposition for photoelectrochemical (PEC) detection of copper(Cu2+) ions. Firstly, ZnO nanorods are made of nickel (Ni) foam, and then ZnS microspheres are grown on this basis, and then gold (Au) nanoparticles (NPs) are fixed on the surface to form an Au/ZnS/ZnO overall system. The electrochemical properties of Au/ZnS/ZnO materials were measured by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in an aqueous solution of 1 M KOH. When the sensor detects Cu2+ ions, its photocurrent response can be improved. The detection response of Au/ZnS/ZnO electrode for Cu2+ ions is in the linear range of 0.1–10 μM, and its detection limit is 0.01 μM. The results show that the material has better stability and electrochemical performance for the detection of Cu2+ ions.

Highly selective and sensitive colorimetric probes for Cu2+ ions based on ethoxyaniline croconaine dyes

Two highly sensitive and selective colorimetric ethoxyaniline croconaine dye probes, (E)-2-((2-ethoxyphenyl)amino)-5-((2-ethoxyphenyl)iminio)-3,4-dioxocyclopent-1-en-1-olate (ONKT) and (E)-2-((4-ethoxyphenyl)amino)-5-((4-ethoxyphenyl)iminio)-3,4-dioxocyclopent-1-en-1-olate) (PNKT) for sensing of Cu2+ ion have been synthesized and characterized. Compared with other metal cations tested, the colorimetric behavior of the probes is significantly different in the presence of Cu2+ ions. When Cu2+ ions were added, the colors of ONKT and PNKT changed from orange to colorless, and the absorbance at the maximum absorption wavelength decreased obviously. The probes have been proved to be sensitive, selective, linear and low in detection limit for Cu2+ ions. In addition, with Cu2+ and EDTA as input signals and the absorption intensity of ONKT at 500 nm as output signal, ONKT is designed as a molecular logic gate with storage and deletion functions. Therefore, these probes provide a new colorimetric method for qualitative and quantitative selective detection of copper ions.

A simple pyridine based fluorescent chemosensor for selective detection of copper ion

A feasibly constructed novel pyridine based receptor (S) has been reported for the selective detection of copper ion over other metal ions. The metal sensing ability of receptor with diverse metal ions were studied by colorimetry, absorption and emission spectroscopic systems in CH3CN/H2O (7:3, v/v). This receptor reveals a drastic color converts from vapid to yellow and cyan under normal light and UV light with copper ion. Further, S-Cu2+ complex exhibits new UV–Visible band at 419 nm and intense fluorescence band at 494 nm upon the excitation at 388 nm. The stoichiometric binding ratio of receptor with metal ion was confirmed with Job’s method and ESI-Mass also further supported the complexation. Besides, limits of detection of Cu2+ were calculated to be 0.25 μM. The limiting capacity of receptor with Cu2+ ion was additionally explored by quantum chemical calculation. Moreover, this receptor was effectively utilized for the measurement of Cu2+ ion in various water tests.

A Bright Nitrogen-doped-Carbon-Dots based Fluorescent Biosensor for Selective Detection of Copper Ions

A Bright Nitrogen-doped-Carbon-Dots based Fluorescent Biosensor for Selective Detection of Copper Ions

Dual sensing of methionine and aspartic acid in aqueous medium by a quinoline-based fluorescent probe.

A quinoline-based Schiff base sensor, 6-methyl-2-oxo-1,2-dihydro-quinoline-3-carboxaldehyde-4(N)-phenylsemicarbazone (6MPS), has been developed for selective sensing of methionine and aspartic acid in aqueous medium through "on-off-on" type selective detection of copper ion. Fluorescence imaging of 6MPS, 6MPSC, 6MPSCN, 6MPSC-met, 6MPSCN-met, 6MPSC-asp and 6MPSCN-asp has been successfully demonstrated, in which the sensing probes 6MPSC-met, 6MPSCN-met, 6MPSC-asp and 6MPSCN-asp displayed bright green fluorescence in both in vitro and in vivo live cells.

A Novel High Selective Colorimetric Chemosensor for Determination of Copper in Food Samples: Visual Detection

AbstractRhodamine B hydrazide and 2‐chloroquinoline‐3‐carbaldehyde derivatives were used to synthesize novel colorimetric sensors for highly selective detection of copper ion. The measurement was based on the interaction between the synthesized ligands and Cu2+ and the sharp color change of the ligand from yellow to pink in the presence of Cu2+. Increase in absorbance intensity at the new appeared absorbance peak was used as an analytical signal. The effect of parameters, such as time and sensor concentration were also investigated and discussed. The calibration curve was considered too under the optimum experimental conditions and was linear in the range 0.05–5.00 μg mL−1 with a limit of detection 0.016 μg mL−1. The interferences of some common ions were studied and the synthetic ligand was found to be a high selective sensor. Selectivity of the proposed method makes it as an applicable technique for the determination of copper in foodstuff samples.

A turn-on red-emitting fluorescent probe for determination of copper(II) ions in food samples and living zebrafish

Herein, we developed a turn-on red-emitting fluorescent probe for the sensitive and selective detection of copper ions (Cu2+) in food samples and living zebrafish. The probe employs a hemicyanine scaffold as the fluorophore and a 2-pyridinecarbonyl group as the recognition receptor and quenching moiety. The 2-pyridinecarbonyl moiety can be specifically cleaved by Cu2+ and results in an approximately 18-fold fluorescence enhancement of the probe, thereby providing a fluorescence turn-on assay for Cu2+. Additionally, the probe exhibited excellent selectivity, high sensitivity, a broad linear relationship (0.020 to 8.0 μM), and a low limit of detection (4.0 nM, S/N = 3) for Cu2+. Concomitantly, the probe exhibited satisfactory analytical performance when used with actual food samples. Moreover, the probe could be used for in situ determination of Cu2+ in both living plant tissues and in living zebrafish.

Highly fluorescent hematoporphyrin modified graphene oxide for selective detection of copper ions in aqueous solutions

Here, a highly sensitive and selective copper ion (Cu2+) fluorescence sensor is reported. The Hematoporphyrin functionalized Graphene Oxide (HP-GO) fluorescence sensor were synthesized via esterification reaction between Graphene Oxide and Hematoporphyrin (HP). The HP-GO sensor was fully characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electrom Microscopy (SEM), UV–Vis spectroscopy, Transmission Electron Microscopy (TEM), Fluor meter spectroscopy, X-Ray photoelectron spectroscopy(XPS), and Raman spectroscopy measurements. The HP-GO sensor advertised two linear regions over the range of 0–1.18 × 103 nM and 3.93 × 103 to 47.27 nM of copper (II) with detection limit of 54 nM in the aqueous solution. The selectivity of HP-GO for Cu2+ is much higher than that of other metal ions due to the presence of aza macrocyclic ring on the surface of HP-GO which has a high binding affinity with Cu2+. Additionally, the HP-GO shows wide pH viable range (pH 6–10). The effect of other metal ions on the fluorescence intensity of the HP-GO was also studied and other metal ions show a low interference response in the detection of Cu2+. HP-GO sensor manifests advantages of high reproducibility (The quenched fluorescence of HP/GO-Cu can be recovered by EDTA), attractive long term fluorescence stability (>21 days) in water, also remarkable selectivity regarding number of metal ions (Na+, K+, Ca2+, Fe3+, Fe2+, Al3+, Pb2+, Mn2+, Mg2+, Co2+, Ni2+, Cr6+, Cd2+, Hg2+, and Zn2+), low toxicity and can detect Cu2+ in real water samples which acquire well for its promising in environmental applications.

A colorimetric chemosensor for selective detection of copper ions

AbstractA water‐applicable hexamethylbenzene (HMB) chemosensor, (E)‐2‐((2‐hydroxy‐3‐methoxybenzylidene)amino)benzamide, displayed a selective colour change from colourless to yellow in the existence of copper ions. The detection limit was computed as 1.57 μmol/L, which is substantially lower than the World Health Organisation guideline (31.5 μmol/L) for copper ions. Probe HMB could also sense and quantify copper ions in real water samples. The coordination mode of HMB to copper ions was demonstrated through Job plot, electrospray ionisation mass spectroscopy and proton nuclear magnetic resonance titration, and was also supported by theoretical studies.

Facile and highly effective synthesis of nitrogen-doped graphene quantum dots as a fluorescent sensing probe for Cu2+ detection

Nitrogen-doped graphene quantum dots (N-GQDs) with high blue fluorescence efficiency were synthesized by the hydrothermal method from p-Phenylenediamine and p-Coumaric acid. The N-GQDs possess several superiorities, most significantly in excellent solubility and superior photostability. Besides, the as-prepared N-GQDs exhibit a uniform size distribution with a diameter of about 3.8 ± 0.5 nm. After dispersing the N-GQDs in water, the formed aqueous solution still presents a stable and homogeneous phase even after 2 months at room temperature. The N-GQD dispersion was further utilized as sensing probes for the selective detection of copper ions (Cu2+), which is realized by the photoluminescence (PL) quenching of N-GQDs after adding Cu2+. The detection limit for Cu2+ was found to be 57 nM L−1, with superior selectivity in the presence of other commonly interfering metal ions. The presented results in this study provide a facile and high-efficiency method for synthesizing N-GQDs, with ultra-high detectivity and selectivity for Cu2+ detection, offering numerous opportunities for the development of biosensing, bioimaging, environment monitoring, and others.