Sensitive Detection Of Copper Ions Research Articles

An electrochemical sensor for highly sensitive detection of copper ions based on a new molecular probe Pi-A decorated on graphene

In this paper, a new electrochemical sensor based on a new fluorescent probe N-(2-(1-(p-tolyl)-1H-phenanthro[9,10-d]imidazol-2-yl)phenyl)picolinamide (Pi-A) decorated reduced graphene oxide (RGO) modified glassy carbon electrode (GCE) was developed for highly selective detection of copper ions using the electrochemical method.

Sensitive detection of copper ions via ion-responsive fluorescence quenching of engineered porous silicon nanoparticles.

Heavy metal pollution has been a problem since the advent of modern transportation, which despite efforts to curb emissions, continues to play a critical role in environmental pollution. Copper ions (Cu2+), in particular, are one of the more prevalent metals that have widespread detrimental ramifications. From this perspective, a simple and inexpensive method of detecting Cu2+ at the micromolar level would be highly desirable. In this study, we use porous silicon nanoparticles (NPs), obtained via anodic etching of Si wafers, as a basis for undecylenic acid (UDA)- or acrylic acid (AA)-mediated hydrosilylation. The resulting alkyl-terminated porous silicon nanoparticles (APS NPs) have enhanced fluorescence stability and intensity, and importantly, exhibit [Cu2+]-dependent quenching of fluorescence. After determining various aqueous sensing conditions for Cu2+, we demonstrate the use of APS NPs in two separate applications – a standard well-based paper kit and a portable layer-by-layer stick kit. Collectively, we demonstrate the potential of APS NPs in sensors for the effective detection of Cu2+.

Post-oxidation treated graphene quantum dots as a fluorescent probe for sensitive detection of copper ions

Graphene quantum dots (GQDs) have been an ideal probe for copper ions detection due to its excellent optical properties, low toxicity and biocompatibility. However, most of GQDs prepared by present methods have low oxidation degree, which could hinder the complexation between copper ions and oxygen functional groups on the surface of GQDs. Therefore, we proposed a universal, mild and in situ post-treated approach for modifying GQDs obtained by any methods, which will increase the oxidation degree of GQDs without any other affect and its influence on the responsivity of copper ions.

Green synthesis of carbon dots from prawn shells for highly selective and sensitive detection of copper ions

A facile, economical and effective green method was developed for synthesis of fluorescent carbon dots (C-dots) from prawn shells. The results showed that these C-dots (with an average diameter of 4nm) possess many excellent features such as to eliminate blue fluorescence under UV light (λ=365nm), with high monodispersity, good stability, excellent water solubility and high quantum yield (9%). We further explored these C-dots as effective sensing probes for Cu2+ detection and found that they exhibit excellent selectivity and sensitivity toward Cu2+ with a low detection limit of 5nM. We further demonstrated this novel sensing platform on Cu2+ ions analysis from seawater samples. This method is extremely rapid, low cost, ecofriendly, highly selective and sensitive for Cu2+ ions sensing from various sources of environment such as drinking water, river water and sea water.

Selective extraction and release using (EDTA-Ni)-layered double hydroxide coupled with catalytic oxidation of 3,3′,5,5′-tetramethylbenzidine for sensitive detection of copper ion

Copper is an important heavy metal in various biological processes. Many methods have been developed for detecting of copper ions (Cu2+) in aqueous samples. However, an easy, cheap, selective and sensitive method is still desired. In this study, a selective extraction-release-catalysis approach has been developed for sensitive detection of copper ion. Ethylenediaminetetraacetic acid (EDTA) chelated with nickel ion (Ni2+) were intercalated in a layered double hydroxide via a co-precipitation reaction. The product was subsequently applied as sorbent in dispersive solid-phase extraction for the enrichment of Cu2+ at pH 6. Since Cu2+ has a stronger complex formation constant with EDTA, Ni2+ exchanged with Cu2+ selectively. The resulting sorbent containing Cu2+ was transferred to catalyze the 3,3′,5,5′-tetramethylbenzidine oxidation reaction, since Cu2+ could be released by the sorbent effectively and has high catalytic ability for the reaction. Blue light emitted from the oxidation product was measured by ultraviolet–visible spectrophotometry for the determination of Cu2+. The extraction temperature, extraction time, and catalysis time were optimized. The results showed that this method provided a low limit of detection of 10nM, a wide linear range (0.05–100μM) and good linearity (r2=0.9977). The optimized conditions were applied to environmental water samples. Using Cu2+ as an example, this work provided a new and interesting approach for the convenient and efficient detection of metal cations in aqueous samples.

C2-Symmetric Benzene-based Low Molecular Weight Hydrogel Modified Electrode for Highly Sensitive Detection of Copper Ions

In this paper, a new type of low molecular weight gelators (LMWGs), C2-symmetric benzene-based hydrogel (C2-BHG) with a 1,4-dimine benzene was self-assembled on glassy carbon electrode (GCE) and mica surface based on the hydrogen bond or hydrophobic interaction. Atomic force microscopy (AFM) characterization demonstrated the formation process of the C2-BHG hydrogel layer from particles to clusters, and finally to interconnected fiber network gel. The C2-BHG hydrogel layer resulted in the increase of the hydrophilicity of GCE surface. The C2-BHG modified GCEs (C2-BHG/GCE) with different assembly time were studied by cyclic voltammetry and electrochemical impedance spectroscopy in the presence of Fe(CN)64−/3− redox probe. The rich amide and hydroxyl groups in the gel film make the C2-BHG/GCE suitable as ultrasensitive sensor for the detection of Cu(II) ions by stripping voltammetry with the limit of detection of 5×10−10g/L (S/N>3). Under the optimal conditions, the two linear ranges of Cu(II) ions were found to be 1×10−9∼1×10−7g/L and 1×10−7∼1×10−4g/L. The strong coordination interaction of C2-BHG with Cu(II) ions was confirmed by UV-Visible characterization. This new type of C2-BHG modified electrode was promising for highly sensitive Cu(II) ions sensor application due to high stability and excellent selectivity of the analytical signal.

Highly sensitive fluorescence detection of copper ion based on its catalytic oxidation to cysteine indicated by fluorescein isothiocyanate functionalized gold nanoparticles

An innovative fluorescence method for sensitive detection of copper ion (Cu2+) was developed based on fluorescein isothiocyanate functionalized gold nanoparticles (FITC-AuNPs). Due to the stronger binding affinity of isothiocyanate functional group to gold, FITC molecules could adsorb on the surface of AuNPs, forming a simple fluorescence resonance energy transfer (FRET) system, and the fluorescence intensity of FITC was remarkably quenched. Upon adding cysteine, FITC could be displaced from the surface of AuNPs because the formation constant (K-f) of Au-S linkage (K-f(AuS-) = 4 x 10(35)) was much higher than AuSCN linkage (K-f(Au(SCN)(2-)) = 10(23)), leading to the recovery of fluorescence intensity. However, Cu2+ could catalyze O-2 oxidation of cysteine, and the generated disulfide cystine could not remove FITC from AuNPs' surface. Therefore, the recovery of fluorescence intensity was much weaker when compared with that of in the absence of Cu2+. And on the basis of this principle the concentration of Cu2+ could be detected quantitatively. Under optimal conditions, our method exhibited high selectivity toward Cu2+ and provided a good linear relationship in the range of 1.0-17.0 nM with the detection limit of 0.37 nM calculated by 3 sigma/S. Furthermore, complicated synthetic procedures and poor water solubility could be ignored in this proposed fluorescent sensor. (C) 2015 Elsevier B. V. All rights reserved.

Highly sensitive detection of copper ions by densely grafting fluorescein inside polyethyleneimine core-silica shell nanoparticles.

In this work, polyethyleneimine (PEI) core-silica shell nanoparticles were synthesized and used for densely grafting fluorescent receptor units inside the core of these particles to result in multi-receptor units collectively sensing a target. Herein, copper ion quenching of the fluorescence intensity of a fluorescein isothiocyanate (FITC) system was selected as a model to confirm our proof-of-concept strategy. Our results showed that, compared to free FITC in solution, a 10-fold enhancement of the Stern-Volmer constant value for Cu(2+) quenching of the fluorescence intensity of the grafted state of FITC in PEI core-silica shell nanoparticles was achieved. Furthermore, compared to a previous collective sensing scheme by densely grafting fluorescent receptor units on a silica nanoparticle surface, the proposed scheme, which grafted fluorescent receptor units inside a polymer nano-core, was simple, highly efficient and presented higher sensitivity.

A visual volumetric hydrogel sensor enables quantitative and sensitive detection of copper ions.

We propose a visual volumetric sensor with 5,6-dicarboxylic fluorescein cross-linked amine-functionalized polyacrylamide hydrogel. The sensor undergoes volume response to Cu(2+) ions at the μM level, which enables naked-eye quantitative detection by reading the graduation on a pipette.

Label-free silicon quantum dots as fluorescent probe for selective and sensitive detection of copper ions

In this work, label-free silicon quantum dots (SiQDs) were used as a novel fluorescence probe for the sensitive and selective detection of Cu2+. The fluorescence of the SiQDs was effectively quenched by H2O2 from the reaction of ascorbic acid with O2, and hydroxyl radicals from Fenton reaction between H2O2 and Cu+. The fluorescence intensity of SiQDs was quenched about 25% in 15min after the addition of H2O2 (1mM). While the SiQDs was incubated with AA (1mM) and Cu2+ (1µM) under the same conditions, the fluorescence intensity of SiQDs decreased about 55%. Obviously, the recycling of Cu2+ in the test system may lead to a dramatical decrease in the fluorescence of SiQDs. Under the optimized experimental conditions, the rate of fluorescence quenching of SiQDs was linearly dependent on the Cu2+ concentration ranging from 25 to 600nM with the limit of detection as low as 8nM, which was much lower than that of existing methods. Moreover, the probe was successfully applied to the determination of Cu2+ in different environmental water samples and human hair.

Two-Photon Ratiometric Fluorescent Sensor Based on Specific Biomolecular Recognition for Selective and Sensitive Detection of Copper Ions in Live Cells

In this work, we develop a ratiometric two-photon fluorescent probe, ATD@QD-E2Zn2SOD (ATD = amino triphenylamine dendron, QD = CdSe/ZnSe quantum dot, E2Zn2SOD = Cu-free derivative of bovine liver copper-zinc superoxide dismutase), for imaging and sensing the changes of intracellular Cu(2+) level with clear red-to-yellow color change based on specific biomolecular recognition of E2Zn2SOD for Cu(2+) ion. The inorganic-organic nanohybrided fluorescent probe features two independent emission peaks located at 515 nm for ATD and 650 nm for QDs, respectively, under two-photon excitation at 800 nm. Upon addition of Cu(2+) ions, the red fluorescence of QDs drastically quenches, while the green emission from ATD stays constant and serves as a reference signal, thus resulting in the ratiometric detection of Cu(2+) with high accuracy by two-photon microscopy (TPM). The present probe shows high sensivity, broad linear range (10(-7)-10(-3) M), low detection limit down to ∼10 nM, and excellent selectivity over other metal ions, amino acids, and other biological species. Meanwhile, a QD-based inorganic-organic probe demonstrates long-term photostability, good cell-permeability, and low cytotoxicity. As a result, the present probe can visualize Cu(2+) changes in live cells by TPM. To the best of our knowledge, this is the first report for the development of a QD-based two-photon ratiometric fluorescence probe suitable for detection of Cu(2+) in live cells.

A commercially available fluorescence chemosensor for copper ion and its application in bioimaging

The commercially available fluorescent probe, 1,8-diamino naphthalene with a naphthalene ring as a chromophore and two amino groups as binding sites has been developed for sensitive detection of copper ions by fluorescence spectrometer in aqueous solution. It displayed an excellent selectivity and sensitivity for Cu2+ over other metal ions. The mechanism is that the fluorescence of probe was quenched by the paramagnetic effect from spin–orbit coupling of the Cu2+ after probe coordinated with Cu2+, and mechanism was proved by ESI-MS. The probe can be used to react to Cu2+ in live cells, providing a potentially powerful approach for probing Cu2+ chemistry in biological system.

Label-free colorimetric sensing of copper(ii) ions based on accelerating decomposition of H2O2 using gold nanorods as an indicator

A novel label-free colorimetric strategy was reported for sensitive detection of copper ions (Cu(2+)) by using the decelerating etching of gold nanorods (GNRs). H2O2 was employed as the oxidant for corrosion of GNRs, leading to the decrease of the aspect ratio of GNRs. In the absence of Cu(2+), the redox corrosion of GNRs by H2O2 occurred rapidly, causing the distinct color change of GNRs from bluish green to purplish red. By virtue of the strong and specific catalysis by Cu(2+) of the decomposition of H2O2, the rate of redox corrosion can be decelerated. Relevant experimental parameters, including pH value, concentrations of NaSCN and H2O2, incubation temperature and time were evaluated. Under optimal conditions, our method gave a good linear range of 10-300 nM (R = 0.9985) for Cu(2+) and the detection limit with the naked eye is as low as 10 nM. Thus, the proposed colorimetric sensor is simple, sensitive (4.96 nM) and selective, and it has been successfully applied to detect Cu(2+) in shellfish samples. Moreover, the potential mechanism was also discussed.

Gold nanoparticle-sensitized quartz crystal microbalance sensor for rapid and highly selective determination of Cu(ii) ions

A novel quartz crystal microbalance (QCM) sensor for rapid, highly selective and sensitive detection of copper ions was developed. As a signal amplifier, gold nanoparticles (Au NPs) were self-assembled onto the surface of the sensor. A simple dip-and-dry method enabled the whole detection procedure to be accomplished within 20 min. High selectivity of the sensor towards copper ions is demonstrated by both individual and coexisting assays with interference ions. This gold nanoparticle mediated amplification allowed a detection limit down to 3.1 μM. Together with good repeatability and regeneration, the QCM sensor was also applied to the analysis of copper contamination in drinking water. This work provides a flexible method for fabricating QCM sensors for the analysis of important small molecules in environmental and biological samples.

Fluorescence enhancement of CdTe/CdS quantum dots by coupling of glyphosate and its application for sensitive detection of copper ion

A novel fluorescent probe for Cu2+ determination based on the fluorescence quenching of glyphosate (Glyp)-functionalized quantum dots (QDs) was firstly reported. Glyp had been used to modify the surface of QDs to form Glyp-functionalized QDs following the capping of thioglycolic acid on the core–shell CdTe/CdS QDs. Under the optimal conditions, the response was linearly proportional to the concentration of Cu2+ between 2.4×10−2μgmL−1 and 28μgmL−1, with a detection limit of 1.3×10−3μgmL−1 (3δ). The Glyp-functionalized QDs fluorescent probe offers good sensitivity and selectivity for detecting Cu2+. The fluorescent probe was successfully used for the determination of Cu2+ in environmental samples. The mechanism of reaction was also discussed.

Polyamine-Functionalized Carbon Quantum Dots as Fluorescent Probes for Selective and Sensitive Detection of Copper Ions

A novel sensing system has been designed for Cu(2+) ion detection based on the quenched fluorescence (FL) signal of branched poly(ethylenimine) (BPEI)-functionalized carbon quantum dots (CQDs). Cu(2+) ions can be captured by the amino groups of the BPEI-CQDs to form an absorbent complex at the surface of CQDs, resulting in a strong quenching of the CQDs' FL via an inner filter effect. Herein, we have demonstrated that this facile methodology can offer a rapid, reliable, and selective detection of Cu(2+) with a detection limit as low as 6 nM and a dynamic range from 10 to 1100 nM. Furthermore, the detection results for Cu(2+) ions in a river water sample obtained by this sensing system agreed well with that by inductively couple plasma mass spectrometry, suggesting the potential application of this sensing system.

Silver nanoclusters as fluorescent probes for selective and sensitive detection of copper ions

Fluorescent DNA-Ag NCs are demonstrated as novel, label-free, and turn-on fluorescence probes for Cu(2+) ions sensors. We also used this novel fluorescent probe to determine Cu(2+) ions in Montana soil (SRM 2710) and pond water.