Simultaneous determination of hydrazine and hydroxylamine on a magnetic bar carbon paste electrode modified with reduced graphene oxide/Fe3O4 nanoparticles and a heterogeneous mediator

Voltammetric determination of hydrogen peroxide at decorated palladium nanoparticles/poly 1,5-diaminonaphthalene modified carbon-paste electrode

In this work, palladium nanoparticles (PdNPs)/p1,5-DAN/ carbon paste electrode (CPE) and p1,5-DAN/CPE sensors have been developed for determination of hydrogen peroxide. Both sensors showed a highly sensitive and selective electrochemical behaviour, which were derived from a large specific area of poly 1,5 DAN and super excellent electroconductibility of PdNPs. PdNPs/p1,5-DAN/CPE exhibited excellent performance over p1,5-DAN/CPE. Thus, it was used for detecting hydrogen peroxide (H2O2) with linear ranges of 0.1 to 250 µM and 0.2 to 300 µM as well as detection limits (S/N = 3) of 1.0 and 5.0 nM for square wave voltammetry (SWV) and cyclic voltammetry (C.V) techniques, respectively. The modified CPE has good reproducibility, adequate catalytic activity, simple synthesis and stability of peak response during H2O2 oxidation on long run that exceeds many probes. Both reproducibility and stability for H2O2 detection are attributable to the PdNPs immobilized on the surface of p1,5-DAN/CPE. The modified CPE was used for determining H2O2 in real specimens with good stability, sensitivity, and reproducibility.

Determination of lead ions in fish and oyster samples using a nano-adsorbent of functionalized magnetic graphene oxide nanosheets-humic acid and the flame atomic absorption technique

This study aims at the functionalization of magnetic graphene oxide nanosheets and the binding of humic acid as a lead complex ligand. Graphene oxide nanosheets possess a large surface area and various carboxylic acid groups which can be activated easily by activating agents. Therefore, they are suitable to be used for the extraction of heavy metals. To have a better process of extracting lead ions, magnetic graphene oxide was used in this research. Humic acid, as a lead metal complex agent, has an amine functional group which can be bound to modified graphene oxide from one side. The process of constructing the nano-adsorbent proposed for the preconcentration of lead ions as well as its characterization was studied by infrared spectroscopy (IR), ultraviolet-visible spectroscopy (UV-visible), field emission scanning electron microscopy (FESEM), and vibrating sample magnetometry (VSM). The designed nano-adsorbent was tested to measure lead ions in simulated and real samples of sea water, fish, and oysters. The detection limit obtained in the simulated samples was 0.07 μg/L, and the linear range was 0.2-12 μg/L. The apparatus used to measure the ions was a flame atomic absorption device. In the analysis of the real samples, the values obtained through flame atomic absorption were compared with those obtained through furnace atomic absorption. The proposed technique is advantageous due to being cheap, precise, and sensitive for the trace measurement of lead ions.

Integrating brucine with carbon nanotubes toward electrochemical sensing of hydroxylamine

Based on the intrinsic electrochemical features of brucine integrated with carbon nanotubes (brucine/SWNTs), dimeric quinoid brucine was electrochemically generated by electroactivation of a brucine/SWNTs-modified GC electrode and used as a novel electrocatalyst for efficient electro-oxidation of hydroxylamine (HA). The electrocatalytic activity was investigated with cyclic voltammetry in the range pH 2.0 to pH 11.0, and the best electrocatalytic performance of the electrocatalyst was obtained at pH 10.0. By taking advantage of the electrocatalytic activity of the dimeric quinoid brucine toward HA, we have developed an electrochemical sensor for HA measurements based on a brucine/SWNTS-modified GC electrode using amperometry with the applied potential of + 0.1 V (vs. Ag/AgCl). Under the optimized conditions, the current response toward HA concentration shows a linear relationship in the dynamic ranges of 0.1-10 μM and 10-1000 μM with a detection limit of 0.021 μM based on the 3σ criterion. The sensor was used to assay HA in pharmaceuticals including hydroxyurea tablets and pralidoxime iodide injections with satisfactory results. The spike-and-recovery for samples of tap water (n = 9) and lake water (n = 9) was within 97.17-100.16%. Graphical abstract Schematic illustration of electrochemical sensing of hydroxylamine (HA) enabled by integrating brucine with single-walled carbon nanotube (brucine/SWNTs) based on electro-activation of brucine/SWNTs-modified GC electrode.

Electrosynthesis of carbon aerogel-modified AuNPs@quercetin via an environmentally benign method for hydrazine (HZ) and hydroxylamine (HA) detection

An ultrasensitive electrochemical sensor fabricated using a hydrothermal and environmentally benign methods for the detection of environmental pollutions, namely, hydrazine (HZ) and hydroxylamine (HA) has been described.

Screen-Printed Electrode Modified by Bismuth /Fe₃O₄ Nanoparticle/Ionic Liquid Composite Using Internal Standard Normalization for Accurate Determination of Cd(II) in Soil

The quality and safety of agricultural products are threatened by heavy metal ions in soil, which can be absorbed by the crops, and then accumulated in the human body through the food chain. In this paper, we report a low-cost and easy-to-use screen-printed electrode (SPE) for cadmium ion (Cd(II)) detection based on differential pulse voltammetry (DPV), which decorated with ionic liquid (IL), magnetite nanoparticle (Fe₃O₄), and deposited a bismuth film (Bi). The characteristics of Bi/Fe₃O₄/ILSPE were investigated using scanning electron microscopy, cyclic voltammetry, impedance spectroscopy, and linear sweep voltammetry. We found that the sensitivity of SPE was improved dramatically after functionalized with Bi/Fe₃O₄/IL. Under optimized conditions, the concentrations of Cd(II) are linear with current responses in a range from 0.5 to 40 µg/L with the lowest detection limit of 0.05 µg/L (S/N = 3). Additionally, the internal standard normalization (ISN) was used to process the response signals of Bi/Fe₃O₄/ILSPE and established a new linear equation. For detecting three different Cd(II) concentrations, the root-mean-square error using ISN (0.25) is lower than linear method (0.36). Finally, the proposed electrode was applied to trace Cd(II) in soil samples with the recovery in the range from 91.77 to 107.83%.

Iron-Based Nanomaterials/Graphene Composites for Advanced Electrochemical Sensors

Iron oxide nanostructures (IONs) in combination with graphene or its derivatives-e.g., graphene oxide and reduced graphene oxide-hold great promise toward engineering of efficient nanocomposites for enhancing the performance of advanced devices in many applicative fields. Due to the peculiar electrical and electrocatalytic properties displayed by composite structures in nanoscale dimensions, increasing efforts have been directed in recent years toward tailoring the properties of IONs-graphene based nanocomposites for developing more efficient electrochemical sensors. In the present feature paper, we first reviewed the various routes for synthesizing IONs-graphene nanostructures, highlighting advantages, disadvantages and the key synthesis parameters for each method. Then, a comprehensive discussion is presented in the case of application of IONs-graphene based composites in electrochemical sensors for the determination of various kinds of (bio)chemical substances.

Developing an electrochemical sensor based on a carbon paste electrode modified with nano-composite of reduced graphene oxide and CuFe2O4 nanoparticles for determination of hydrogen peroxide

In this paper, a highly sensitive voltammetric sensor based on a carbon paste electrode with CuFe₂O₄ nanoparticle (RGO/CuFe₂O₄/CPE) was designed for determination of hydrogen peroxide (H₂O₂). The electrocatalytic reduction of H₂O₂ was examined using various techniques such as cyclic voltammetry (CV), chronoamperometry, amperometry and differential pulse voltammetry (DPV). CuFe₂O₄ nanoparticles were synthesized by co-precipitation method and characterized with scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) techniques. Then, a high conductive platform based on a carbon paste electrode modified with RGO and CuFe₂O₄ nanoparticles was prepared as a suitable platform for determination of hydrogen peroxide. Under the optimum conditions (pH5), the modified electrode indicated a fast amperometric response of <2s, good linear range of 2 to 200μM, low detection limit of 0.52μM for determination of hydrogen peroxide. Also, the peak current of differential pulse voltammetry (DPV) of hydrogen peroxide is increased linearly with its concentration in the ranges of 2 to 10μM and 10 to 1000μM. The obtained detection limit for hydrogen peroxide was evaluated to be 0.064μM by DPV. The designed sensor was successfully applied for the assay of hydrogen peroxide in biological and pharmaceutical samples such as milk, green tea, and hair dye cream and mouthwash solution.

Simultaneous electrochemical determination of hydrazine and hydroxylamine by CuO doped in ZSM-5 nanoparticles as a new amperometric sensor

In this work, a novel electrochemical sensor using a carbon paste modified electrode with CuO doped in ZSM-5 nanoparticles (CuO/ZSM-5 NPs/CPE) is successfully fabricated for simultaneous determination of hydrazine (HY) and hydroxylamine (HA).

Fabrication of Highly Sensitive and Stable Hydroxylamine Electrochemical Sensor Based on Gold Nanoparticles and Metal-Metalloporphyrin Framework Modified Electrode

This paper describes the immobilization of gold nanoparticles on metal-metalloporphyrin frameworks (AuNPs/MMPF-6(Fe)) through electrostatic adsorption. The composites were characterized by powder X-ray diffraction, zeta potential, transmission electron microscopy, electrochemical impedance spectroscopy, and voltammetric methods. MMPF-6(Fe) exhibited a pair of redox peaks of the Fe(III)TCPP/Fe(II)TCPP redox couple. The AuNPs/MMPF-6(Fe)-based electrochemical sensor demonstrates a distinctly higher electrocatalytic response to the oxidation of hydroxylamine due to the synergic effect of the gold metal nanoparticles and metal-metalloporphyrin matrix. The voltammetric current response exhibits two linear dynamic ranges, 0.01-1.0 and 1.0-20.0 μmol L(-1), and the detection limit was as low as 0.004 μmol L(-1) (S/N = 3). Moreover, the biosensor exhibits high reproducibility and stability in acid solution. Our work not only offers a simple way to achieve the direct electrochemical behavior of metalloporphyrin but also expands the potential applications of MOFs-based composites in bioanalysis.

Highly sensitive biosensor based on the synergistic effect of Fe3O4–Co3O4 bimetallic oxides and graphene

Synergistic effect of Fe₃O₄–Co₃O₄ nanoparticles and reduced graphene oxide allows the sensitive electrochemical detection of dopamine and uric acid.

Ultrasensitive and selective hydrazine sensor development based on Sn/ZnO nanoparticles

Fabrication of highly sensitive (∼5.0108 μA cm⁻² μM⁻¹) and selective hydrazine chemical sensor based on wet-chemically prepared Sn/ZnO nanoparticles deposited glassy carbon electrodes with a detection limit as low as 18.95 ± 0.02 pM (at an S/N of 3).