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.

Cataluminescence sensor for gaseous acetic acid using a thin film of In2O3

We report on a cataluminescence sensor for the determination of gaseous acetic acid. It is based on a 60-nm thick sol–gel film of In₂O₃ on a ceramic support. SEM, XPS and surface profiling were applied for its characterization. It is found that aluminum ions of the ceramic substrate penetrate into the film and produce a synergetic catalytic effect. The sensor displays high sensitivity and specificity for acetic acid, a low detection limit, a wide linear range and a fast response. No (or only very low) interference was observed by formic acid, ammonia, acrolein, benzene, formaldehyde, ethanol, and acetaldehyde. The sensor was successfully applied to the determination of acetic acid in spiked air samples. We also discuss a conceivable mechanism (based on the reaction products) for the cataluminescence resulting from the oxidation reaction on the surface of the sensor film.

Iodide-induced adsorption of lead(II) ion on a glassy carbon electrode modified with ferroferric oxide nanoparticles

Spherical Fe₃O₄ nanoparticles (NPs) were prepared by hydrothermal synthesis and characterized by scanning electron microscopy and X-ray diffraction. A glassy carbon electrode was modified with such NPs to result in a sensor for Pb(II) that is based on the strong inducing adsorption ability of iodide. The electrode gives a pair of well-defined redox peaks for Pb(II) in pH 5.0 buffer containing 10 mM concentrations of potassium iodide, with anodic and cathodic peak potentials at ?487 mV and ?622 mV (vs. Ag/AgCl), respectively. The amperometric response to Pb(II) is linear in the range from 0.10 to 44 nM, and the detection limit is 40 pM at an SNR of 3. The sensor exhibits high selectivity and reproducibility.

Novel glucose biosensor based on a glassy carbon electrode modified with hollow gold nanoparticles and glucose oxidase

A novel glucose biosensor is presented as that based on a glassy carbon electrode modified with hollow gold nanoparticles (HGNs) and glucose oxidase. The sensor exhibits a better differential pulse voltammetric response towards glucose than the one based on conventional gold nanoparticles of the same size. This is attributed to the good biological conductivity and biocompatibility of HGNs. Under the optimal conditions, the sensor displays a linear range from 2.0?×?10^?6 to 4.6?×?10^?5?M of glucose, with a detection limit of 1.6?×?10^?6?M (S/N?=?3). Good reproducibility, stability and no interference make this biosensor applicable to the determination of glucose in samples such as sports drinks.

Trace determination of zirconium by adsorptive anodic stripping voltammetry of its complex with alizarin violet using a glassy carbon electrode modified with acetylene black-dihexadecyl hydrogen phosphate composite film

We report on a novel electrochemical method for the sensitive determination of trace zirconium (Zr) at a glassy carbon electrode modified with a film of acetylene black containing dihexadecyl hydrogen phosphate and in the presence of alizarin violet (AV). The method is based on the preconcentration of the Zr(IV)-AV complex at a potential of ?200?mV (vs. SCE). The adsorbed complex is then oxidized, producing a response with a peak potential of 526?mV. Compared to the poor electrochemical signal at the unmodified GCE, the electrochemical response of Zr(IV)-AV complex is greatly improved, as confirmed by the significant increase in peak current. The effects of experimental conditions on the oxidation current were studied and a calibration plot established. The oxidation current is linearly related to the Zr(IV) concentration in the 8.0?pM to 10?nM concentration range (c_AV?=?0.2???M) and 10?nM ~0.6???M (c_AV?=?2.0???M), and the detection limit (S/N?=?3) is as low as 4.0?pM for a 3-min accumulation time. The method was successfully employed to the determination of zirconium in standard ore samples.

Non-enzymatic amperometric sensor for hydrogen peroxide based on a biocomposite made from chitosan, hemoglobin, and silver nanoparticles

We report on a novel non-enzymatic sensor for hydrogen peroxide (HP) that is based on a biocomposite made up from chitosan (CS), hemoglobin (Hb), and silver nanoparticles (AgNPs). The AgNPs were prepared in the presence of CS and glucose in an ultrasonic bath, and CS is found to act as a stabilizing agent. They were then combined with Hb and CS to construct a carbon paste biosensor. The resulting electrode gave a well-defined redox couple for Hb, with a formal potential of about ?0.17?V (vs. SCE) at pH?6.86 and exhibited a remarkable electrocatalytic activity for the reduction of HP. The sensor was used to detect HP by flow injection analysis, and a linear response is obtained in the 0.08 to 250?μM concentration range. The detection limit is 0.05?μM (at S/N?=?3). These characteristics, along with its long-term stability make the sensor highly promising for the amperometric determination of HP.

ITO electrode modified by a gold ion implantation technique for direct electrocatalytic sensing of hydrogen peroxide

We report on a non-enzymatic amperometric sensor for hydrogen peroxide (H₂O₂). It was fabricated by electrodeposition of multi-wall carbon nanotubes and polyaniline along with platinum nanoparticles on the surface of a glassy carbon electrode. The modification was probed by scanning electron microscopy and cyclic voltammetry. The resulting sensor exhibits a high sensitivity (748.4?μA·mM^?1·cm^?2), a wide linear range (7.0?μM–2.5?mM), a low detection limit (2.0?μM) (S/N?=?3), a short response time (>5?s), and long-term stability, and is not interfered by common species. It was successfully applied to determine H₂O₂ in disinfectants.

Anodic stripping voltammetry of silver(I) using a carbon paste electrode modified with multi-walled carbon nanotubes

We describe a silver(I)-selective carbon paste electrode modified with multi-walled carbon nanotubes and a silver-chelating Schiff base, and its electrochemical response to Ag(I). Effects of reduction potential and time, accumulation time, pH of the solution and the stripping medium were studied by differential pulse anodic stripping voltammetry and optimized. The findings resulted in a method for the determination of silver over a linear response range (from 0.5 to 235 ng?mL^?1) and with a detection limit as low as 0.08 ng?mL^?1. The sensor displays good repeatability (with the RSD of ±?2.75 % for 7 replicates) and was applied to the determination of Ag(I) in water samples and X-ray photographic films.

Amperometric sensor for detection of bisphenol A using a pencil graphite electrode modified with polyaniline nanorods and multiwalled carbon nanotubes

We report on a simple and highly sensitive amperometric method for the determination of bisphenol A (BPA) using pencil graphite electrodes modified with polyaniline nanorods and multiwalled carbon nanotubes. The modified electrodes display enhanced electroactivity for the oxidation of BPA compared to the unmodified pencil graphite electrode. Under optimized conditions, the sensor has a linear response to BPA in the 1.0 and 400?μM concentration range, with a limit of detection of 10?nM (at S/N?=?3). The modified electrode also has a remarkably stable response, and up to 95 injections are possible with a relative standard deviation of 4.2% at 100?μM of BPA. Recoveries range from 86 to 102% for boiling water spiked with BPA from four brands of baby bottles.

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.

Electrochemical sensor based on a carbon nanotube-modified imprinted sol–gel for selective and sensitive determination of ß2-agonists

We describe a molecularly imprinted electrochemical sensor for selective and sensitive determination of β₂-agonists. It is making use of a combination of single-wall carbon nanotubes (SWNTs) with a molecularly imprinted sol–gel. The SWNTs were introduced in order to enhance electron transport and sensitivity. The imprinted sol–gel film with its specific binding sites acts as a selective recognition element and as a preconcentrator for β₂-agonists. The morphology of the imprinted film was characterized by scanning electron microscopy. The optimized sensor displays high sensitivity and excellent selectivity for the β₂-agonists as shown for their determination in human serum samples.

Double layer enzyme modified carbon nanotubes as label for sandwich-type immunoassay of tumor markers

An immunosensor was prepared for the determination of carcinoembryonic antigen (CEA). It is based on the use of multiwalled carbon nanotubes (MWCNTs) along with horseradish peroxidase-labeled antibody. The enzyme was assembled onto MWCNTs templates using the layer-by-layer technique and then conjugated to carcinoembryonic secondary antibodies (Ab₂) as the enzyme label. The resulting assembly results in a largely amplified sensitivity. The response is linear in the range of 0.05 to 45?ng?mL^-1, with a detection limit of 16.0?pg?mL^-1. The immunosensor possesses good stability and good reproducibility.

Lactate biosensor based on a bionanocomposite composed of titanium oxide nanoparticles, photocatalytically reduced graphene, and lactate oxidase

We have developed a lactate biosensor based on a bionanocomposite (BNC) composed of titanium dioxide nanoparticles (TiO₂-NPs), photocatalytically reduced graphene, and lactate oxidase. Graphene oxide was photochemically reduced (without using any chemical reagents) in the presence of TiO₂-NPs to give graphene nanosheets that were characterized by atomic force microscopy, Raman and X-ray photoelectron spectroscopy. The results show the nanosheets to possess few oxygen functionalities only and to be decorated with TiO₂-NPs. These nanosheets typically are at least 1 μm long and have a thickness of 4.2 nm. A BNC was obtained by mixing lactate oxidase with the nanosheets and immobilized on the surface of a glassy carbon electrode. The resulting biosensor was applied to the determination of lactate. Compared to a sensor without TiO₂-NPs, the sensor exhibits higher sensitivity (6.0 μA mM^?1), a better detection limit (0.6 μM), a wider linear response (2.0 μM to 0.40 mM), and better reproducibility (3.2 %).

Ultrasensitive electrochemiluminescent immunoassay for morphine using a gold electrode modified with CdS quantum dots, polyamidoamine, and gold nanoparticles

We report on a novel electrochemiluminescent (ECL) immunoassay for the ultrasensitive determination of morphine by making use of a gold electrode which was modified with a nanocomposite film containing self-assembled polyamidoamine (PAMAM) CdS quantum dots and electrodeposited gold nanoparticles (Au-NPs). The highly uniform and well-dispersed quantum dots were capped with PAMAM dendrimers. Due to the synergistic effect of the modified quantum dots and the electrodeposited Au-NPs, the ECL response is dramatically enhanced. Under optimal experimental conditions, the immunoreaction between morphine and anti-morphine antibody resulted in a decrease of the ECL signal because of steric hindrance. The calibration plot is linear in the morphine concentration range from 0.2 to 180 ng?mL^?1, with a detection limit as low as 67 pg?mL^?1. The sensor was successfully applied to the determination of morphine in blood plasma. This kind of assay is expected to pave new avenues in label-free drug assays.

Comparison of three different configurations of dual ultramicroelectrodes for the decomposition of S-Nitroso-L-glutathione and the direct detection of nitric oxide

Podoplanin (PDP) is a small transmembrane protein and widely present in various specialized cells throughout the human body. It is a specific marker for identification of lymphatic vessel and a candidate marker for cancer stem cells in squamous cell carcinoma of the lung. We report on method for the highly selective determination of PDP by using a surface plasmon resonance imaging (SPRI) that exploits the highly selective interaction between PDP and anti-human PDP monoclonal antibody (IgG). The sensor has a dynamic range between 0.25 and 1.0?ng?mL^?1, and a detection limit of 15?pg?mL^?1. It was applied to the determination of PDP in blood plasma and tissue homogenates from paired normal and lung tumor tissue.

Nonenzymatic glucose sensor based on glassy carbon electrode modified with a nanocomposite composed of nickel hydroxide and graphene

We report on a nonenzymatic glucose sensor based on a glassy carbon electrode that was electrochemically modified with a nanocomposite prepared from nickel hydroxide and graphene. Scanning electron microscopy revealed that the nickel hydroxide in the nanocomposite was present in the form of a nanostructure of three-dimensional spheres that were assembled by many densely arranged nanosheets. The electrocatalytic activity of the electrode toward the oxidation of glucose was investigated by chronoamperometry. The current response was linearly related to the glucose concentration in the range from 1 to 10?μM, with a sensitivity of 494?μA?mM^–1?cm^–2 and a correlation coefficient of 0.9990, and a second range (from 10 to 1000?μM with a sensitivity of 328?μA?mM^–1?cm^–2 and a correlation coefficient of 0.9990). The detection limit was 0.6?μM at a signal-to-noise ratio of 3, and the response time was as short as 2?s.

A carbon nitride electrode for highly selective and sensitive determination of lead(II)

We have constructed a carbon nitride electrode modified with a bismuth film and show that it can be used for the electroanalysis of lead(II) by differential pulse anodic stripping voltammetry. The combination of such materials is shown to greatly improve the sensing capability of the electrode. Under the optimal conditions, the electrochemical response of the modified electrode is linearly related to the concentration of Pb(II) in the 6 – 1,000 nM concentration range (R = 0.9983). The detection limit is 2.0 pM (at an SNR of 3), and the sensitivity is 8 times better of that of respective graphite electrodes. The sensor enables rapid, highly sensitive, continuous, and environmentally friendly determination of trace levels of Pb(II) at affordable costs.

A solid state Cr(VI) ion-selective electrode based on polypyrrole

We report on a graphite electrode onto which polypyrrole was electrodeposited and then doped with chromate ion. This electrode can serve as a Cr(VI)-selective solid-state electrode. Electropolymerization of pyrrole was performed potentiostatically at 0.80?V (vs. SCE) using battery graphite as the working electrode in a solution containing 0.10?M of pyrrole and 20?mM of chromate. A platinum wire was used as an auxiliary electrode. The new electrode displays high selectivity, a very wide dynamic range, a sufficiently fast response time and a good shelf lifetime. It shows a linear Nernstian response over 1.0?×?10^?6 to 1.0?×?10^?1?M concentration range (with a slope of 26.55?±?0.20?mV per log of concentration). The detection limit is 0.5?μM, and the pH optimum is 7.0.

Electrocatalytic oxidation of hydrazine at a glassy carbon electrode modified with nickel ferrite and multi-walled carbon nanotubes

A hydrothermal technique was used to synthesize nickel ferrite nanoparticles (NF-NPs) deposited on multi-walled carbon nanotubes (MWCNTs). The material was characterized by scanning electron microscopy, energy dispersive spectrometry, and X-ray powder diffraction which showed that the NF-NPs are located on the surface of the carboxylated MWCNTs. The material was used to modify a glassy carbon electrode which then was characterized via cyclic voltammetry, electrochemical impedance spectroscopy, and amperometry. The electrode displays strong electrochemical response to hydrazine. A potential hydrazine sensing scheme is suggested.

Enzyme-linked immunosorbent assay and immunochromatographic strip for rapid detection of atrazine in water samples

We have developed a heterologous direct competitive enzyme-linked immunosorbent assay (ELISA) and a colloidal gold-based immunochromatographic (ICG) strip for the determination of the herbicide atrazine in water samples. The ELISA had a half-maximum inhibition concentration (IC₅₀) of 0.12 ng mL^?1 and a limit of detection (LOD, calculated as the IC₁₅ value) of 0.01 ng mL^?1. The average of recoveries for all spiked water samples was 96.5%. There was a good correlation between the data determined by this ELISA and those obtained by high performance liquid chromatography (HPLC) (r ² ?=?0.996). The visual LOD of the ICG strip assay was 2 ng mL^?1. The assay process only took 10 min, and no sample pretreatment was required. Its high specificity, sensitivity and fast detection made the strip well suited for on-site screening of atrazine in water samples. Both the ELISA and the ICG strip assay are useful for rapid analysis of a large number of water samples at low cost.