Electrochemical Sensor Based on ZnFe2O4/RGO Nanocomposite for Ultrasensitive Detection of Hydrazine in Real Samples

Fabrication of Curcumin-Based Electrochemical Nanosensors for the Detection of Environmental Pollutants: 1,4-Dioxane and Hydrazine

This work reports the development of novel curcuminoid-based electrochemical sensors for the detection of environmental pollutants from water. In this study, the first set of electrochemical experiments was carried out using curcumin-conjugated multi-walled carbon nanotubes (MWCNT-CM) for 1,4-dioxane detection. The MWCNT-CM/GCE showed good sensitivity (103.25 nA nM-1 cm-2 in the linear range 1 nM to 1 µM), with LOD of 35.71 pM and LOQ of 108.21 pM. The second set of electrochemical experiments was carried out with bisdemethoxy curcumin analog quantum dots (BDMCAQD) for hydrazine detection. The BDMCAQD/GCE exhibited good sensitivity (74.96 nA nM-1 cm-2 in the linear range 100 nM to 1 µM), with LOD of 10 nM and LOQ of 44.93 nM. Thus, this work will serve as a reference for the fabrication of metal-free electrochemical sensors using curcuminoids as the redox mediator for the enhanced detection of environmental pollutants.

Platforms of graphene/MXene heterostructure for electrochemical monitoring of rutin in drug and Tartary buckwheat tea

The use of two-dimensional heterostructure composite as electrode modification material has become a new strategy to improve the electrocatalytic activity and electroactive sites of electrochemical sensor. Herein, a soluble heterostructure, namely rGO-PSS@MXene, was designed and synthesized by integrating poly (sodium p-styrenesulfonate)-functionalized reduced graphene oxide into MXene nanosheets via ultrasonic method. The interactive heterostructure can effectively alleviate the self-stacking of MXene and rGO, endowing them with superior electron transfer capacity and large specific surface area, thereby producing prominent synergistic electrocatalytic effect towards rutin. In addition, the excellent enrichment effect of rGO-PSS@MXene for rutin also plays an important role through the electrostatic and π-π stacking interactions. The electrochemical characteristics of rutin on the sensor were examined in detail and a sensitive sensing method was proposed. Under optimized conditions, the method showed satisfactory linear relationship for rutin in the concentration range of 0.005-10.0 μM, with limit of detection of 1.8 nM (S/N = 3). The quantitative validation results in herbal medicine and commercial Tartary buckwheat tea were highly consistent with the labeled quantity and the results of HPLC determination, respectively, suggesting the sensor possessed excellent selectivity and accuracy. This proposed strategy for rutin determination is expected to expand the application of MXene heterostructure in electrochemical sensors, and is envisioned as a promising candidate for quality monitoring of drugs and foods.

Laccase-Conjugated Nanostructured ZnFe2O4/rGO-Modified Electrode-Based Interfaces for Electrochemical Impedance Monitoring of Adrenaline: A Promising Biosensor for Management of Neurodegenerative Disorders

A propitious biosensor for adrenaline (AD) detection in bovine serum albumin (BSA) real samples, which can be used for diagnosis and treatment of neurodegenerative disorders, is reported here. The biosensor consists of a La/ZF/rGO/ITO bioelectrode, which is fabricated by electrophoretic deposition of zinc ferrite/reduced graphene oxide (ZF/rGO) nanohybrid followed by drop casting of laccase (La) enzymes. The material characterization and electrochemical studies revealed that the ZF/rGO nanohybrid enhanced the electroactive surface and facilitated direct electron transfer between the electrode and electrolyte interface, resulting in enhanced electrocatalytic performance. The cyclic voltammetry and electrochemical impedance spectroscopy results asserted that the ZF/rGO nanohybrid decreased the charge-transfer resistance (Rct) and increased the surface adsorption, leading to a high diffusion coefficient (D) of 0.192 cm2/s. The biosensor exhibited a high sensitivity of 0.71 Ω/μM cm2, a good linear range (0.1 to 140 μM with R2 = 0.98), and a low limit of detection (LOD) is 12.5 μM, demonstrating the synergic effect of ZF and rGO in the La/ZF/rGO/ITO bioelectrode with AD. The biosensor also exhibited high selectivity and stability (55 days) in the presence of interfering substances and in BSA samples, with a recovery percentage close to 100 ± 5% RSD, indicating its potential biosensing applications for real-world applications in disease diagnostics, monitoring, and treatment.

Carbon Nanomaterials-Based Screen-Printed Electrodes for Sensing Applications

Electrochemical sensors consisting of screen-printed electrodes (SPEs) are recurrent devices in the recent literature for applications in different fields of interest and contribute to the expanding electroanalytical chemistry field. This is due to inherent characteristics that can be better (or only) achieved with the use of SPEs, including miniaturization, cost reduction, lower sample consumption, compatibility with portable equipment, and disposability. SPEs are also quite versatile; they can be manufactured using different formulations of conductive inks and substrates, and are of varied designs. Naturally, the analytical performance of SPEs is directly affected by the quality of the material used for printing and modifying the electrodes. In this sense, the most varied carbon nanomaterials have been explored for the preparation and modification of SPEs, providing devices with an enhanced electrochemical response and greater sensitivity, in addition to functionalized surfaces that can immobilize biological agents for the manufacture of biosensors. Considering the relevance and timeliness of the topic, this review aimed to provide an overview of the current scenario of the use of carbonaceous nanomaterials in the context of making electrochemical SPE sensors, from which different approaches will be presented, exploring materials traditionally investigated in electrochemistry, such as graphene, carbon nanotubes, carbon black, and those more recently investigated for this (carbon quantum dots, graphitic carbon nitride, and biochar). Perspectives on the use and expansion of these devices are also considered.

Clinically Deployable Bioelectronic Sensing Platform for Ultrasensitive Detection of Transferrin in Serum Sample

Varying levels of transferrin (Tf) have been associated with different disease conditions and are known to play a crucial role in various malignancies. Regular monitoring of the variations in Tf levels can be useful for managing related diseases, especially for the prognosis of certain cancers. We fabricated an immunosensor based on graphene oxide (GO) nanosheets to indirectly detect Tf levels in cancer patients. The GO nanosheets were deposited onto an indium tin oxide (ITO)-coated glass substrate and annealed at 120 °C to obtain reduced GO (rGO) films, followed by the immobilization of an antibody, anti-Tf. The materials and sensor probe used were systematically characterized by UV-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), atomic force microscopy (AFM), and Fourier transform infrared spectroscopy (FTIR). Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) were also used for the stepwise sensor probe characterizations and Tf detection in serum samples, respectively. The anti-Tf/rGO/ITO immunosensor DPV output demonstrated an excellent Tf detection capability in the linear range of 0.1 mg mL^-1 to 12 mg mL^-1 compared to the enzyme-linked immunosorbent assay (ELISA) detection range, with a limit of detection (LOD) of 0.010 ± 0.007 mg mL^-1. Furthermore, the results of the fabricated immunosensor were compared with those of the ELISA and autobioanalyzer techniques, showing an outstanding match with < 5% error and demonstrating the immunosensor's clinical potential.

In Situ Fabrication of Mn-Doped NiMoO4 Rod-like Arrays as High Performance OER Electrocatalyst

The slow kinetics of the oxygen evolution reaction (OER) is one of the significant reasons limiting the development of electrochemical hydrolysis. Doping metallic elements and building layered structures have been considered effective strategies for improving the electrocatalytic performance of the materials. Herein, we report flower-like nanosheet arrays of Mn-doped-NiMoO₄/NF (where NF is nickel foam) on nickel foam by a two-step hydrothermal method and a one-step calcination method. The doping manganese metal ion not only modulated the morphologies of the nickel nanosheet but also altered the electronic structure of the nickel center, which could be the result of superior electrocatalytic performance. The Mn-doped-NiMoO₄/NF electrocatalysts obtained at the optimum reaction time and the optimum Mn doping showed excellent OER activity, requiring overpotentials of 236 mV and 309 mV to drive 10 mA cm^-2 (62 mV lower than the pure NiMoO₄/NF) and 50 mA cm^-2 current densities, respectively. Furthermore, the high catalytic activity was maintained after continuous operation at a current density of 10 mA cm^-2 of 76 h in 1 M KOH. This work provides a new method to construct a high-efficiency, low-cost, stable transition metal electrocatalyst for OER electrocatalysts by using a heteroatom doping strategy.

Electrochemical Sensors Based on a Composite of Electrochemically Reduced Graphene Oxide and PEDOT:PSS for Hydrazine Detection

In this study, hydrazine sensors were developed from a composite of electrochemically reduced graphene oxide (ErGO) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), deposited onto a glassy carbon electrode (GCE). The structural properties, electrochemical characterization, and surface morphologies of this hydrazine sensor were characterized by Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). In addition, the proposed hydrazine sensor also demonstrates good electrochemical and analytical performance when investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometry techniques under optimal parameters. Using these investigated parameters, DPV and amperometry were chosen as techniques for hydrazine measurements and showed a linear range of concentration in the range of 0.2-100 μM. The obtained limits of detection and limits of quantitation for hydrazine measurements were 0.01 and 0.03 μM, respectively. In addition, the proposed sensor demonstrated good reproducibility and stability in hydrazine measurements in eight consecutive days. This fabricated hydrazine sensor also exhibited good selectivity against interference from Mg²⁺, K⁺, Zn²⁺, Fe²⁺, Na⁺, NO₂ ^-, CH₃COO^-, SO₄ ^2-, Cl^-, ascorbic acid, chlorophenol, and triclosan and combined interferences, as well as it depicted %RSD values of less than 5%. In conclusion, this proposed sensor based on GCE modified with ErGO/PEDOT:PSS displays exceptional electrochemical performance for use in hydrazine measurements and have the potential to be employed in practical applications.

The development of disposable electrochemical sensor based on MoSe2-rGO nanocomposite modified screen printed carbon electrode for amitriptyline determination in the presence of carbamazepine, application in biological and water samples

The present attempt developed a simple sensing system based on the modification of screen-printed carbon electrode (SPCE) with MoSe₂/reduced graphene oxide (rGO) nanocomposite (MoSe₂-rGO/SPCE) to voltammetrically co-detect amitriptyline and carbamazepine. Different techniques such as field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were employed to characterize MoSe₂-rGO nanocomposite morphology and structure. Moreover, chronoamperometry, differential pulse voltammetry (DPV) and linear sweep voltammetry (LSV) were utilized to explore the electrochemical oxidation of amitriptyline. Data revealed a great current sensitivity for the MoSe₂-rGO/SPCE towards amitriptyline. The peak currents of amitriptyline oxidation on the MoSe₂-rGO/SPCE had linear dynamic range (0.02-380.0 μM) and a narrow limit of detection (0.007 μM). The MoSe₂-rGO/SPCE was successful in sensing carbamazepine and amitriptyline in real specimens, with appreciable recovery rates.

A novel voltammetric amaranth sensor based on screen printed electrode modified with polypyrrole nanotubes

Azo dyes are the most used type of dye in the textile industry. Some of these dyes have the potential to be extremely toxic to both human health and the environment. The purpose of this study was to develope an electrochemical sensor for detection of amaranth. The electrochemical sensor based on the modification of a screen-printed electrode via polypyrrole nanotubes (PPy NTs/SPE) for detection of amaranth was developed. The preparation of PPy NTs was performed through the pyrrole monomer oxidation with iron (III) chloride in exposure to methyl orange as structure-guiding agent. Findings exhibited an excellent electrocatalytic activity of as-fabricated sensor for amaranth detection. Our sensor under the optimized circumstances also had a broad linear dynamic range (between 0.03 μM and 290.0 μM) and a narrow limit of detection (0.01 μM) towards the amaranth detection. Moreover, the proposed sensor could practically and successfully determine the amaranth content present in the real food specimens, with acceptable recovery rates.

Simple Preparation and Characterization of Hierarchical Flower-like NiCo2O4 Nanoplates: Applications for Sunset Yellow Electrochemical Analysis

The current work was performed to construct a novel electrochemical sensing system for determination of sunset yellow via the modification of screen-printed graphite electrode modified with hierarchical flower-like NiCo₂O₄ nanoplates (NiCo₂O₄/SPGE). The prepared material (hierarchical flower-like NiCo₂O₄ nanoplates) was analyzed by diverse microscopic and spectroscopic approaches for the crystallinity, composition, and morphology. Chronoamperometry, differential pulse voltammetry, linear sweep voltammetry, and cyclic voltammetry were used for determination of the electrochemical behavior of sunset yellow. The as-fabricated sensor had appreciable electro-catalytic performance and current sensitivity in detecting the sunset yellow. There were some advantages for NiCo₂O₄/SPGE under the optimized circumstances of sunset yellow determination, including a broad dynamic linear between 0.02 and 145.0 µM, high sensitivity of 0.67 μA/(μM.cm²), and a narrow limit of detection of 0.008 μM. The practical applicability of the proposed sensor was verified by determining the sunset yellow in real matrices, with satisfactory recoveries.

Electrochemical Sensor Based on Ni-Co Layered Double Hydroxide Hollow Nanostructures for Ultrasensitive Detection of Sumatriptan and Naproxen

In this work, Ni-Co layered double hydroxide (Ni-Co LDH) hollow nanostructures were synthesized and characterized by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and Fourier-transform infrared spectroscopy (FT-IR) techniques. A screen-printed electrode (SPE) surface was modified with as-fabricated Ni-Co LDHs to achieve a new sensing platform for determination of sumatriptan. The electrochemical behavior of the Ni-Co LDH-modified SPE (Ni-CO LDH/SPE) for sumatriptan determination was investigated using voltammetric methods. Compared with bare SPE, the presence of Ni-Co LDH was effective in the enhancement of electron transport rate between the electrode and analyte, as well as in the significant reduction of the overpotential of sumatriptan oxidation. Differential pulse voltammetry (DPV) was applied to perform a quantitative analysis of sumatriptan. The linearity range was found to be between 0.01 and 435.0 μM. The limits of detection (LOD) and sensitivity were 0.002 ± 0.0001 μM and 0.1017 ± 0.0001 μA/μM, respectively. In addition, the performance of the Ni-CO LDH/SPE for the determination of sumatriptan in the presence of naproxen was studied. Simultaneous analysis of sumatriptan with naproxen showed well-separated peaks leading to a quick and selective analysis of sumatriptan. Furthermore, the practical applicability of the prepared Ni-CO LDH/SPE sensor was examined in pharmaceutical and biological samples with satisfactory recovery results.

A Voltammetric Sensor for the Determination of Hydroxylamine Using a Polypyrrole Nanotubes-Modified Electrode

In this work, we develop an electrochemical sensor using a polypyrrole nanotubes-modified graphite screen-printed electrode (PPy NTs/GSPE) for sensing hydroxylamine. The PPy NTs/GSPE-supported sensor has an appreciable electrocatalytic performance and great stability for hydroxylamine oxidation. Compared to a bare graphite screen-printed electrode, we demonstrate that using the PPy NTs/GSPE leads to a significant reduction in the oxidation potential of hydroxylamine. The standard curve shows a linear relationship ranging from 0.005 to 290.0 μM (R2  =  0.9998), with a high sensitivity (0.1349 μA/μM) and a narrow limit of detection (LOD) of 0.001 μM. In addition, the PPy NTs/GSPE has satisfactory outcomes for hydroxylamine detection in real specimens.

Surface amplification of graphite screen printed electrode using reduced graphene oxide/polypyrrole nanotubes nanocomposite; a powerful electrochemical strategy for determination of sulfite in food samples

The present research presents synthesis and substantial utilization of a nanocomposite of reduced graphene oxide/polypyrrole nanotubes to modify graphite screen printed electrode (rGO/PPy NTs-GSPE) for detection of sulfite. The nanocomposite preparation was done by hydrothermal protocol, followed by characterization by energy-dispersive X-ray (EDX) and field emission-scanning electron microscopy (FE-SEM). Electrocatalytic sensing of sulfite is carried out using differential pulse voltammetric (DPV), linear sweep voltammetry (LSV), cyclic voltammetric (CV), and Chronoamperometry. Electrochemical behaviors of modified and unmodified electrodes were explored with CV method. In addition, DPV was employed for anodic peak and quantitatively detecting sulfite. The DPV results unveiled a linear response of the sensor to various sulfite contents (0.04-565.0 μM) with a narrow detection limit (0.01 μM) and admirable sensitivity (0.0483 μA/μΜ). The diffusion coefficient (D) for sulfite using rGO/PPy NTs-GSPE, 9.9 × 10^-6 cm ²/s was obtained. The sensor was also successful in the sulfite detection in real specimens.

Hydrothermal synthesis of CuFe2O4 nanoparticles for highly sensitive electrochemical detection of sunset yellow

The sunset yellow, as a synthetic food coloring azo dye, was detected in the present work using a new sensitive and selective sensor based on the modification of screen-printed electrode surface with Copper ferrite nanoparticles (CuFe₂O₄/SPE). Thus, a facile hydrothermal protocol was performed to prepare the CuFe₂O₄ nanoparticles, followed by characterization applying valid techniques, including Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and field-emission scanning electron microscopy (FE-SEM). Chronoamperometry, differential pulse voltammetry (DPV) and cyclic voltammetry (CV) were employed to determine the electrochemical behavior of as-fabricated sensor. According to the electrochemical findings, a greater anodic peak current was found for the sunset yellow oxidation on the CuFe₂O₄/SPE than that on the unmodified SPE. The electrocatalytic response for the sunset yellow oxidation on the CuFe₂O₄/SPE in phosphate buffer (0.1 M, pH = 7.0) was effective, with an excellent sensitivity (0.1919 μA μM^-1). There was a linear relationship between the voltammetric current and different sunset yellow concentrations (0.03-100.0 μM). The calculated limit of detection (LOD = 3Sb/m) for the sunset yellow was 0.009 μM.

Electrochemical sensors based on carbon nanostructures for the analysis of bisphenol A-A review

Overuse of Bisphenol A (BPA), a proven endocrine disruptor, has become a serious public health problem across the world. It has the potential to harm both the environment and human health, notably reproductive disorders, heart disease, and diabetes. Accordingly, much attention has been paid to the detection of BPA to promote food safety and environmental health. Carbon based nanostructures have proven themselves well in a variety of applications, such as energy storage, catalysis and sensors, due to their remarkable properties. Therefore, researchers have recently focused on fabricating electrochemical BPA sensors based on carbon nanostructures due to their unique advantages, such as real-time monitoring, simplicity, high selectivity, high sensitivity and easy operation. The purpose of the current review was to summarize the recent findings on carbon nanostructures for electrochemically sensing the BPA, as well as relevant future prospects and ongoing challenges.

Glassy Carbon Electrode Modified with N-Doped Reduced Graphene Oxide Sheets as an Effective Electrochemical Sensor for Amaranth Detection

Amaranth is one of the synthetic azo colorants used to improve the appearance and to increase the appeal of some foods and soft drinks. The excessive consumption of amaranth can be associated with health side effects, emphasizing the need to monitor this food dye. Accordingly, the present study aimed to introduce an electrochemical sensor of glassy carbon electrode (GCE) modified with N-doped reduced graphene oxide (N-rGO), N-rGO/GCE, to detect the amaranth sensitively and rapidly. Several electrochemical techniques such as differential pulse voltammetry (DPV), linear sweep voltammetry (LSV), chronoamperometry (CHA), and cyclic voltammetry (CV) are exploited for the evaluation of the efficiency of the developed electrode for the detection of amaranth. We found that N-rGO/GCE enhanced amaranth oxidation, thus significantly elevating the current signal. Amaranth showed that calibration curves ranged from 0.1 to 600.0 µM, and the limit of detection (LOD) (S/N = 3) was 0.03 μM. Finally, the developed sensor was effectively applied for real samples (tap water, apple juice, and orange juice) with acceptable recovery values from 96.0 to 104.3%.

Application of MnO2 Nanorod–Ionic Liquid Modified Carbon Paste Electrode for the Voltammetric Determination of Sulfanilamide

The current work introduced a convenient single-phase hydrothermal protocol to fabricate MnO₂ nanorods (MnO₂ NRs). Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDX) and field-emission scanning electron microscopy (FE-SEM) were used to determine the characteristics of MnO₂ NR. Then, ionic liquid (IL) and MnO₂ NRs were utilized to modify a carbon paste electrode (CPE) surface (MnO₂NR-IL/CPE) to voltammetrically sense the sulfanilamide (SAA). An enhanced voltammetric sensitivity was found for the as-developed modified electrode toward SAA when compared with a bare electrode. The optimization experiments were designed to achieve the best analytical behavior of the SAA sensor. Differential pulse voltammetry (DPV) in the optimized circumstances portrayed a linear dependence on various SAA levels (between 0.07 and 100.0 μM), possessing a narrow detection limit (0.01 μM). The ability of the modified electrode to be used in sensor applications was verified in the determination of SAA present in the actual urine and water specimens, with impressive recovery outcomes.