Sensor for lead(II) ion based on a glassy carbon electrode modified with double-stranded DNA and ferric oxide nanoparticles

Shuttle-like Fe₂O₃ nanoparticles (NPs) were prepared by microwave-assisted synthesis and characterized by scanning electron microscopy and X-ray diffraction. The NPs were immobilized on a glassy carbon electrode and then covered with dsDNA. The resulting electrode gives a pair of well-defined redox peaks for Pb(II) at pH 6.0, with anodic and cathodic peak potentials occurring at ?0.50?V and ?0.75?V (vs. Ag/AgCl), respectively. The amperometric response to Pb(II) is linear in the range from 0.12 to 40?nM, and the detection limit is 0.1?nM at a signal-to-noise ratio of 3. The sensor exhibits high selectivity and reproducibility.

Simultaneous determination of cadmium (II) and lead (II) with clay nanoparticles and anthraquinone complexly modified glassy carbon electrode

An anthraquinone (AQ) improved Na-montmorillonite nanoparticles (nano-SWy-2) chemically modified electrode (CME) has been developed for the simultaneous determination of trace levels of cadmium (II) and lead (II) by differential pulse anodic stripping voltammetry (DPASV). This method is based on a non-electrolytic preconcentration via ion exchange model, followed by an accumulation period via the complex formation in the reduction stage at −1.2 V, and then by an anodic stripping process. The mechanism of this design was proposed and the analytical performance was evaluated with several variables. Under the optimized working conditions, the detection limit was 3 and 1 nM for Cd²⁺ and Pb²⁺, respectively. The calibration graphs were linear in the concentration ranges of 8×10⁻⁹ to 1×10⁻⁶ mol L⁻¹ (Cd²⁺) and of 2×10⁻⁹ to 1×10⁻⁶ mol L⁻¹ (Pb²⁺). Many inorganic species did not interfere with the assay significantly; the high sensitivity, selectivity, and stability of this nano-SWy-2-AQ CME were demonstrated. The applications for the detection of trace levels of Cd²⁺ and Pb²⁺ in milk powder and lake water samples indicate that it is an economical and potent method.     

A glassy carbon electrode modified with graphene, gold nanoparticles and chitosan for ultrasensitive determination of lead(II)

We have modified a glassy carbon electrode by single-step electrodeposition of graphene (GR), gold nanoparticles (AgNPs), and chitosan (CS) directly from a solution containing graphene oxide, tetrachloroauric acid, and chitosan. The surface and electrochemical properties of the film-modified electrode were investigated by SEM and TEM images. The AuNPs have a diameter of about 20 nm and are uniformly dispersed in the matrix. Combining the advantages of GR (i.e., high surface area and conductivity), of AuNPs (excellent electrical conductivity) and CS (excellent film-forming ability and good water permeability), the hybrid film effectively enhances electron-transfer and promotes the response to lead(II) ion. Under the optimum conditions, a linear relationship exists between electrical current and the concentration of lead (II) ion in the range between 0.5 to 100 μg?L-1, with a detection limit of 1 ng?L-1 (at an SNR of 3). The electrode was successfully applied to the detection of lead(II) in spiked samples of river water.

A lead(II) sensor based on a glassy carbon electrode modified with Fe3O4 nanospheres and carbon nanotubes

We have developed a highly sensitive and selective sensor for lead(II) ions. A glassy carbon electrode was modified with Fe₃O₄ nanospheres and multi-walled carbon nanotubes, and this material was characterized by scanning electron microscopy and X-ray diffraction. The electrode displays good electrochemical activity toward Pb(II) and gives anodic and cathodic peaks with potentials at ?496 mV and ?638 mV (vs. Ag/AgCl) in pH?6.0 solution. The sensor exhibits a sensitive and fairly selective response to Pb(II) ion, with a linear range between 20 pM and 1.6 nM, and a detection limit as low as 6.0 pM (at a signal-to noise ratio of 3). The sensor was successfully applied to monitor Pb(II) in spiked water samples.

Square wave anodic stripping voltammetric determination of lead(II) using a glassy carbon electrode modified with a lead ionophore and multiwalled carbon nanotubes

We report on a glassy carbon electrode (GCE) modified with a lead ionophore and multiwalled carbon nanotubes. It can be applied to square wave anodic stripping voltammetric determination of Pb(II) ion after preconcentration of Pb(II) at ?1.0?V (vs. SCE) for 300?s in pH?4.5 acetate buffer containing 400?μg?L^?1 of Bi(III). The ionophore-MWCNTs film on the GCE possesses strong and highly selective affinity for Pb(II) as confirmed by quartz crystal microbalance experiments. Under the optimum conditions, a linear response was observed for Pb(II) ion in the range from 0.3 to 50?μg?L^?1. The limit of detection (at S/N?=?3) is 0.1?μg?L^?1. The method was applied to the determination of Pb(II) in water samples with acceptable recovery.

Dopamine sensor based on a glassy carbon electrode modified with a reduced graphene oxide and palladium nanoparticles composite

We report on a sensitive electrochemical sensor for dopamine (DA) based on a glassy carbon electrode that was modified with a nanocomposite containing electrochemically reduced graphene oxide (RGO) and palladium nanoparticles (Pd-NPs). The composite was characterized by scanning electron microscopy, energy dispersive spectroscopy, and electrochemical impendence spectroscopy. The electrode can oxidize DA at lower potential (234 mV vs Ag/AgCl) than electrodes modified with RGO or Pd-NPs only. The response of the sensor to DA is linear in the 1–150 μM concentration range, and the detection limit is 0.233 μM. The sensor was applied to the determination of DA in commercial DA injection solutions.

Sensing of picric acid with a glassy carbon electrode modified with CuS nanoparticles deposited on nitrogen-doped reduced graphene oxide

We describe the preparation of a nanohybrid consisting of nitrogen doped reduced graphene oxide and CuS nanoparticles (N-rGO/CuS) by in-situ microwave irradiation at weight ratios of 25/75, 50/50, and 75/25. The resulting nanohybrids were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, FTIR, spectroscopy, scanning electron and transmission electron microscopy, electrochemically by cyclic voltammetry and electrochemical impedance analysis. It is shown that the CuS nanoparticles are evenly decorated onto the N-rGO surface. The nanohybrids was placed on glassy carbon electrode (GCE) where they showed electro-reductive activity towards picric acid, typically at working voltages between ?0.2 and ?0.8 V (vs. SCE). Effects of pH value and scan rate were evaluated, and it is shown that two electrons are involved in electro-reduction. The detection limits of the GCE modified with various N-rGO/CuS hybrids (with 25/75, 50/50, and 75/25 wt%) are 6.2, 3.2, and 0.069 μM respectively. The method demonstrates its applicability in sensing of picric acid with good reproducibility.

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Graphical abstract Nitrogen doped reduced graphene oxide nanohybrids was synthesized for the detection of picric acid. A straightforward and preconcentration free analysis of picric acid was successfully demonstrated at nanomolar levels using the nanohybrids.

     

Amperometric determination of sulfide ion by glassy carbon electrode modified with multiwall carbon nanotubes and copper (II) phenanthroline complex

Electrocatalytic oxidation of sulfide ion on a glassy carbon electrode (GCE) modified with multiwall carbon nanotubes (MWCNTs) and a copper (II) complex was investigated. The Cu(II) complex was used due to the reversibility of the Cu(II)/Cu(III) redox couple. The MWCNTs are evaluated as a transducer, stabilizer and immobilization matrix for the construction of amperometric sensor based on Cu(II) complex adsorbed on MWCNTs immobilized on the surface of GCE. The modified GCE was applied to the selective amperometric detection of sulfide at a potential of 0.47 V (vs. Ag/AgCl) at pH 8.0. The calibration graph was linear in the concentration range of 5 µM–400 µM; while the limit of detection was 1.2 µM, the sensitivity was 34 nA µM^?1. The interference effects of SO₃ ^2?, SO₄ ^2?, S₂O₃ ^2?, S₄O₆ ^2?, Cysteine, and Cystein were negligible at the concentration ratios more than 40 times. The modified electrode is more stable with time and more easily restorable than unmodified electrode surface. Also, modified electrode permits detection of sulfide ion by its oxidation at lower anodic potentials.      

Electromembrane extraction and anodic stripping voltammetric determination of mercury(II) using a glassy carbon electrode modified with gold nanoparticles

This study presents a method for the selective determination of Hg(II) using electromembrane extraction (EME), followed by square wave anodic stripping voltammetry (SWASV), using a gold nanoparticle-modified glassy carbon electrode, (AuNP/GCE). By applying an electrical potential of typically 60 V for 12 min through a thin supported liquid membrane (1-octanol), Hg(II) ions are extracted from a donor phase (i.e., the sample solution) to an acidic acceptor solution (15 μL) placed in the lumen of a hollow fiber. The influences of experimental parameters during EME were optimized using face-centered central composite design. The calibration plot, established at a working voltage of 0.55 V (vs. Ag/AgCl), extends from 0.2 to 10 μg^.L^?1 of Hg(II). The limit of detection, at a signal to noise ratio of 3, is 0.01 μg^.L^?1 and the relative standard deviations (for 5 replicate determinations at 3 concentration levels) are between 7.5 and 8.7 %. The method was successfully applied to the determination of Hg(II) in spiked real water samples to give recoveries ranging from 89 to 97 %. The results were validated by cold vapor atomic absorption spectroscopy.

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Graphical abstract Hg(II) ions were extracted from a donor phase into an acidic acceptor phase (15 μL) placed in the lumen of a hollow fiber using electromembrane extraction. The acceptor phase was then analyzed using anodic stripping voltammetry.

     

Detection of lead(II) using an glassy carbon electrode modified with Nafion, carbon nanotubes and benzo-18-crown-6

A glassy carbon electrode was modified with Nafion, carbon nanotubes and benzo-18-crown-6 to give an electrode for the selective determination of lead(II) via square wave anodic stripping voltammetry. The use of carbon nanotubes with their extraordinary electrical conductivity and strong adsorption ability warrants high sensitivity. Benzo-18-crown-6 is employed as a “molecular scavenger” because of its excellent selectivity for lead(II). The modified electrode shows enhanced sensitivity, reproducibility and selectivity for lead(II) even without applying an electrical potential during the accumulation time. It responds linearly to lead(II) in the 1 to 30 nM concentration range (with a correlation coefficient of 0.9992) after a 10-min accumulation time. The detection limit is 1 nM. The sensor exhibits excellent selectivity over other heavy metal ions such as Cd(II), Cu(II), Zn(II), and Hg(II).

Chronocoulometric DNA biosensor based on a glassy carbon electrode modified with gold nanoparticles, poly(dopamine) and carbon nanotubes

We describe a sensitive chronocoulometric biosensor for the sequence-specific detection of DNA. It is based on a glassy carbon electrode modified with multi-walled carbon nanotubes, polydopamine, and gold nanoparticles. The ruthenium(III)hexammine complex acts as the electrochemical indicator. Electrochemical impedance spectra and scanning electron microscopy are employed to investigate the assembly of the electrode surface. The signals of the ruthenium complex electrostatically bound to the anionic phospho groups of the DNA strands are measured by chronocoulometry before and after hybridization. The difference in signal intensity is linearly related to the logarithm of the concentration of the target DNA in the range of 1.0 nM to 10 fM with a detection limit of 3.5fM (S/N?=?3) under optimal conditions. This biosensor exhibits excellent sensitivity and selectivity and has been used for an assay of complementary target DNA in human serum sample with satisfactory results.

Electrochemical determination of lead using bismuth modified glassy carbon electrode

Electrochemical application of bismuth film modified glassy carbon electrode was studied with the objective of lead detection. Bismuth film on glassy carbon substrate was formed in a plating solution of 2 mmol/L Bi(NO₃)₃, in 1 mol/L HCl at ?1.1 V (vs. Ag/AgCl) for 300 s. Lead was detected by differential pulse anodic voltammetry in acetate buffer of pH 5.0 in the concentration range of 7.5 nmol/L to 12.5 μmol/L. Factors influencing the anodic stripping performance, including deposition time, solution pH, Bi(III) concentration, potential, pulse amplitude, pulse width, have been optimized. Three linear calibration plots in the range 7.5 nmol/L to 0.1 μmol/L, 0.25 to 1 μmol/L, 2.5 to 12.5 μmol/L with regression coefficients of 0.991, 0.986 and 0.978 respectively were obtained. The theoretical detection limit equivalent to three times standard deviation for 7.5 nmol/L lead (n = 5) was calculated to be 5.25 nmol/L utilizing a 5 min deposition time and sensitivity 83.97 A L/mol. The sensitivity and detection limit of the method was compared with reported voltammetric methods for detection of lead and the result obtained was found to be promising for determination of lead.     

Electropolymerized surface ion imprinting films on a gold nanoparticles/single-wall carbon nanotube nanohybrids modified glassy carbon electrode for electrochemical detection of trace mercury(II) in water

Electrochemical detection of Hg(II) using a electropolymerized ion imprinting poly(2-mercaptobenzothiazole) films at the surface of gold nanoparticles/single-walled carbon nanotube nanohybrids modified glassy carbon electrode (PMBT/AuNPs/SWCNTs/GCE) is described for the first time. The Hg(II)-imprinted PMBT/AuNPs/SWCNTs/GCE sensor exhibits larger binding to functionalized capacity, larger affinity, faster binding kinetics and higher selectivity to template Hg(II). The differential pulse anodic stripping voltammetry (DPASV) response of the Hg(II)-imprinted PMBT/AuNPs/SWCNTs/GCE sensor to Hg(II) is ca. 3.7- and 10.5-fold higher than that at the non-imprinted PMBT/AuNPs/SWCNTs/GCE and the imprinted PMBT/AuNPs/GCE, respectively, and the detection limit for Hg(II) is 0.08 nM (S/N = 3, which is well below the guideline value given by the World Health Organization) and a sensitivity of 0.749 μA nM⁻¹ was obtained. Excellent wide linear range (0.4–96.0 nM) and good repeatability (relative standard deviation of 2.6%) were obtained for Hg(II). The interference experiments show that Ag(I), Pb(II), Cd(II), Zn(II) and Cu(II) had little or no influence on the Hg(II) signal. These values, particularly the high sensitivity and excellent selectivity in contrast to the values reported previously in the area of electrochemical Hg(II) detection, demonstrate the analytical performance of the Hg(II)-imprinted PMBT/AuNPs/SWCNTs/GCE toward Hg(II) is superior to the existing electrodes and could be used for efficient determination of Hg(II) in natural water samples.     

High-sensitivity determination of Pb(II) and Cd(II) on a glassy carbon electrode modified with polypyrrole/sepiolite nanofibers

Polypyrrole-sepiolite (PPy/SPL) nanofibers were prepared by in situ chemical oxidation polymerization in the presence of sepiolite. A PPy/SPL composite modified glassy carbon electrode (PPy/SPL/GCE) was prepared and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and electrochemical methods. Differential pulse anodic stripping voltammetry for the simultaneous determination of trace Pb(II) and Cd(II) was carried out at the PPy/SPL/GCE. Operational parameters such as the deposition potential and time, the amount of modified suspension, and the pH values were optimized for the purpose of determination of trace metal ions in 0.10 M acetate buffer solution. Under the optimal conditions, the stripping peak currents showed good linear relationships with Pb(II) and Cd(II) at concentration ranges of 5.0 × 10^–9?1.2 × 10^–6 M and 5.0 × 10^–9?1.2 × 10^–7 M, and the detection limits were 1.2 and 1.5 nM, respectively. The proposed method is applicable to the simultaneous determination of trace Pb(II) and Cd(II) in real water samples with the relative standard deviations of less than 4.4% and the recovery rates of 97.9?102.2%.     

Anodic stripping voltammetric determination of arsenic(III) using a glassy carbon electrode modified with gold-palladium bimetallic nanoparticles

We have developed a method for the determination of the three catecholamines (CAs) epinephrine (EP), norepinephrine (NE), and dopamine (DA) at sub-nanomolar levels. It is found that the luminescence of the complexes formed between the CAs and Tb³⁺ ion is strongly enhanced in the presence of colloidal silver nanoparticles (Ag-NPs). The Ag-NPs cause a transfer of the resonance energy to the fluorophores through the interaction of the excited-state fluorophores and surface plasmon electrons in the Ag-NPs. Under the optimized condition, the luminescence intensity of the system is linearly related to the concentration of the CAs. Linearity is observed in the concentration ranges of 2.5–110?nM for EP, 2.8–240?nM for NE, and 2.4–140?nM for DA, with limits of detection as low as 0.25?nM, 0.64?nM and 0.42?nM, respectively. Relative standard deviations were determined at 10?nM concentrations (for n?=?10) and gave values of 0.98%, 1.05% and 0.96% for EP, NE and DA, respectively. Catecholamines were successfully determined in pharmaceutical preparations, and successful recovery experiments are demonstrated for urine and serum samples.