Amperometric Detection Of H2O2 Research Articles

One‐Step Synthesis of Copper Single‐Atom Nanozymes for Electrochemical Sensing Applications

Single‐atom nanozymes (SANs) combine the natural enzymatic properties of nanomaterials with the atomic distribution of metallic sites over a suitable support. Unfortunately, their synthesis is complicated by some key factors, like poor metallic loading, aggregation, time consumption, and low yield. Herein, copper SANs, with a surface metal loading (1.47% ± 0.16%) are synthesized, through a green, facile, minimal solution processing, single‐step procedure, using a CO2 laser to promote the anchoring of the metallic precursor while simultaneously generating the laser‐scribed graphene (LSG) support out of a polyimide sheet. The presence of the atomic Cu on the LSG surface is verified using high‐angle‐annular dark‐field–scanning transmission electron microscopy and X‐ray photoelectron spectroscopy. To explore the advantages incurred by the incorporation of Cu SANs on LSG, the material is used as a working electrode on an electrochemical sensor for the amperometric detection of H2O2, achieving a detection limit of 2.40 μM. The findings suggest that CuSANs can confer enhanced sensitivity to H2O2, which is essential for oxidative stress assessment, reaching values up to 130.0 μA mM−1 cm−2.

Ultrasensitive Electroanalytical Detection of Pb2+ and H2O2 Using Bi and Fe-Based Nanoparticles Embedded into Porous Carbon Xerogel-The Influence of Nanocomposite Pyrolysis Temperatures.

Multifunctional materials based on carbon xerogel (CX) with embedded bismuth (Bi) and iron (Fe) nanoparticles are tested for ultrasensitive amperometric detection of lead cation (Pb2+) and hydrogen peroxide (H2O2). The prepared CXBiFe-T nanocomposites were annealed at different pyrolysis temperatures (T, between 600 and 1050 °C) and characterized by X-ray diffraction (XRD), Raman spectroscopy, N2 adsorption, dynamic light scattering (DLS), and electron microscopies (SEM/EDX and TEM). Electrochemical impedance spectroscopy (EIS) and square wave anodic stripping voltammetry (SWV) performed at glassy carbon (GC) electrodes modified with chitosan (Chi)-CXBiFe-T evidenced that GC/Chi-CXBiFe-1050 electrodes exhibit excellent analytical behavior for Pb2+ and H2O2 amperometric detection: high sensitivity for Pb2+ (9.2·105 µA/µM) and outstanding limits of detection (97 fM, signal-to-noise ratio 3) for Pb2+, and remarkable for H2O2 (2.51 µM). The notable improvements were found to be favored by the increase in pyrolysis temperature. Multi-scale parameters such as (i) graphitization, densification of carbon support, and oxide nanoparticle reduction and purification were considered key aspects in the correlation between material properties and electrochemical response, followed by other effects such as (ii) average nanoparticle and Voronoi domain dimensions and (iii) average CXBiFe-T aggregate dimension.

Amperometric Miniaturised Portable Enzymatic Nanobiosensor for the Ultrasensitive Analysis of a Prostate Cancer Biomarker.

Screen-printing technology is a game changer in many fields including electrochemical biosensing. Two-dimensional nanomaterial MXene Ti3C2Tx was integrated as a nanoplatform to immobilise enzyme sarcosine oxidase (SOx) onto the interface of screen-printed carbon electrodes (SPCEs). A miniaturised, portable, and cost-effective nanobiosensor was constructed using chitosan as a biocompatible glue for the ultrasensitive detection of prostate cancer biomarker sarcosine. The fabricated device was characterised with energy-dispersive X-ray spectroscopy (EDX), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Sarcosine was detected indirectly via the amperometric detection of H2O2 formed during enzymatic reaction. The nanobiosensor could detect sarcosine down to 7.0 nM with a maximal peak current output at 4.10 ± 0.35 × 10-5 A using only 100 µL of a sample per measurement. The assay run in 100 μL of an electrolyte showed the first linear calibration curve in a concentration window of up to 5 μM with a slope of 2.86 μA·μM-1, and the second linear calibration curve in the range of 5-50 μM with a slope of 0.32 ± 0.01 μA·μM-1 (R2 = 0.992). The device provided a high recovery index of 92.5% when measuring an analyte spiked into artificial urine, and could be used for detection of sarcosine in urine for at least a period of 5 weeks after the preparation.

Development of an Electrochemical CCL5 Chemokine Immunoplatform for Rapid Diagnosis of Multiple Sclerosis

Serum level of CCL5 chemokine is considered an emerging biomarker for multiple sclerosis (MS). Due to the lack of specific assays for this disease, the development of a point-of-care test for rapid detection of MS could lead to avoiding diagnostics delays. In this paper, we report the first electrochemical immunoplatform for quantification of the CCL5 biomarker at the clinically required levels, able to discriminate between patients diagnosed with MS and healthy individuals. The immunosensing device involves protein capture from biological samples by complexation with biotinylated specific antibodies immobilized onto neutravidin-functionalized microparticles and sandwich assay with anti-CCL5 antibody and IgG labelled with horseradish peroxidase (HRP) for the enzyme-catalyzed amperometric detection of H2O2 using hydroquinone (HQ) as the redox mediator. The method shows excellent analytical performance for clinical application with a wide linear range of concentrations (0.1–300 ng·mL−1 CCL5, R2 = 0.998) and a low detection limit (40 pg·mL−1 CCL5). The biosensing platform was applied to the determination of the CCL5 endogenous content in 100-fold diluted sera both from healthy individuals and patients diagnosed with MS, with no further sample treatment in just two hours. The results were successfully compared with those obtained by the ELISA methodology.

Enzyme-like activity of cobalt-MOF nanosheets for hydrogen peroxide electrochemical sensing

Metal-organic frameworks (MOFs) are receiving increased attention as new functional nanomaterials for the development of electrochemical sensors. Herein, we develop an electrochemical platform for non-enzymatic hydrogen peroxide detection built with a composite of two-dimensional cobalt MOF nanosheets and Nafion (2D-Co-MOF@Nafion). The feasibility of the 2D-Co-MOF@Nafion composite as active material for high performance hydrogen peroxide sensor was investigated by using cyclic voltammetry and chronoamperometry. Its voltammetric response reveals an efficient charge transport through the MOF composite, and rapid electron exchange between MOF and electrode. Notably, these MOF nanosheets exhibit enzyme-like activity for the non-common catalytic oxidation of hydrogen peroxide, leading to an electrochemical sensor with rapid quantitative detection, outstanding sensitivity, selectivity, stability, and durability at the desirable neutral pH. In particular, for a cobalt metal loading of 1.2 nanomol, the sensor yields amperometric H2O2 detection with characteristic electrocatalytic parameters of imax= 5.7 mA cm−2 and KM = 13 mM. Moreover, linear ranges of up to either 1 mM or 10 mM are achieved, with sensitivities as high as 570 ± 5 A cm−2 mM−1 or 395 ± 10 A cm−2 mM−1 for the low and high concentration ranges, respectively. The particular coordination chemistry of the MOF consisting of a regular arrangement of multiple Co(II) redox metal sites connected by appropriate organic ligands can provide inherent enzyme-mimicking properties, thereby explaining the higher oxidase-like activity of the present MOF. This work raises the new idea of using two-dimensional cobalt-based MOFs as active nanozymes, offering exciting opportunities in the design of non-enzymatic electrochemical sensing devices.

NiO-nanoflowers decorating a plastic electrode for the non-enzymatic amperometric detection of H2O2 in milk: Old issue, new challenge

In food supply chain, there are regulatory limitations on the use of chemicals for cleaning processing lines since the healthiness of the commodities must be guaranteed if accidently traces of these detergents and sanitizers pass to them. Hydrogen peroxide, is a commonly used sanitizer in the cleaning of the food processing lines having both bactericidal and bacteriostatic properties, however, it produces inflammatory effects on the human body. The availability of rapid systems to detect its accidental presence is therefore useful to speed up the control and apply corrective actions. In the present work, a drop casting and easily prepared plastic graphite/PVC electrode decorated with NiO nanostructures has been investigated as electrochemical sensor for the non-enzymatic amperometric determination of H2O2. The catalytic activity, dispersion, and stability of NiO nanostructures mixed with plastic nanocomposite electrode have been studied in detail. The preparation method, particularly the precipitating agents used in the synthesis of NiO nanostructures strongly influenced their morphology and porosity. Further, the electrochemical response of NiO-PE electrodes towards H2O2 resulted to be morphology-dependent. The non-enzymatic electrochemical sensor was optimized for the rapid and sensitive detection of H2O2 present in milk with no sample pre-treatments. NiO nanoflowers showed the best catalytic activity towards H2O2, a linear range that extends up to 4 mM and a LOD of 5 μM (3sd of the blank signal) were obtained.

Bimetallic MOFs-derived coral-like Ag-Mo2C/C interwoven nanorods for amperometric detection of hydrogen peroxide.

Coral-like Ag-Mo2C/C-I and blocky Ag-Mo2C/C-II composites were obtained from one-step in situ calcination of [Ag(HL)3(Mo8O26)]n·nH2O [L: N-(pyridin-3-ylmethyl) pyridine-2-amine] under N2/H2 and N2 atmospheres, respectively. The coral-like morphology of Ag-Mo2C/C-I is composed of interwoven nanorods embedded with small particles, and the nano-aggregate of Ag-Mo2C/C-II is formed by cross-linkage of irregular nanoparticles. The above composites are decorated on glassy carbon electrode (GCE) drop by drop to generate two enzyme-free electrochemical sensors (Ag-Mo2C/C/GCE) for amperometric detection of H2O2. In particular, the coral-like Ag-Mo2C/C-I/GCE sensor possesses rapid response (1.2 s), high sensitivity (466.2 μA·mM-1·cm-2), and low detection limit (25 nM) towards trace H2O2 and has wide linear range (0.08 μM~4.67 mM) and good stability. All these sensing performances are superior to Ag-Mo2C/C-II/GCE, indicating that the calcining atmosphere has an important influence on microstructure and electrochemical properties. Theexcellent electrochemical H2O2 sensing performance of Ag-Mo2C/C-I/GCE sensor is mainly attributed to the synergism of unique microstructure, platinum-like electron structure of Mo2C, strong interaction between Mo and Ag, as well as the increased active sites and conductivity caused by co-doped Ag and carbon. Furthermore, this sensor has been successfully applied tothe detection of H2O2 in human serum sample, contact lens solution, and commercial disinfector, demonstrating the potential in related fields of environment and biology. Graphical abstract.

Green and controllable synthesis of multi-heteroatoms co-doped graphene fiber as flexible and biocompatible microelectrode for in situ electrochemical detection of biological samples

Abstract In this work, we report a green and facile strategy to synthesize a new type of multi-heteroatoms co-doped graphene fiber (GF) using graphene nanosheets as the building block and eco-friendly ionic liquid (IL) molecules as the heteroatoms-containing precursor, where the type of heteroatoms doped in graphene can be adjusted by choosing different IL molecules. Among different multi-heteroatoms co-doped GF microelectrodes, N, B co-doped GF (NBGF) possesses the largest specific surface area and lowest charge transfer resistance, which gives rise to an improvement on the electrocatalytic activity towards H2O2 reduction. When used in amperometric detection of H2O2, NBGF microelectrode exhibits good sensing performance as well as unique flexibility and biocompatibility, these enable it to be used for real-time tracking H2O2 released from different colorectal cancer cells, which provide the possibility to distinguish different types of cancer cells and evaluate the efficacy of chemotherapy drugs by electrochemical sensing system. Moreover, the proposed NBGF microelectrode has been applied in in situ sensitive detection of H2O2 in tumor tissue from female Balb/c mice. Therefore, this study presents a new strategy for the rational design of functionalized GF based microelectrode with potential widespread use in implantable sensor devices for clinic application.

Fabrication of Cu-hemin metal-organic-frameworks nanoflower supported on three-dimensional reduced graphene oxide for the amperometric detection of H2O2.

A novel electrochemical sensor based on Cu-hemin metal-organic-frameworks nanoflower/three-dimensional reduced graphene oxide (Cu-hemin MOFs/3D-RGO) was constructed to detect H2O2 released from living cells. The nanocomposite was synthesized via a facile co-precipitation method using hemin as the ligand, then decorated with 3D-RGO. The prepared Cu-hemin MOFs showed a 3D hollow spherical flower-like structure with a large specific surface area and mesoporous properties, which could load more biomolecules and greatly enhance the stability by protecting the activity of hemin. In addition, the introduction of 3D-RGO effectively enhanced the conductivity of Cu-hemin MOFs. Thus, the proposed sensor (Cu-hemin MOFs/3D-RGO/GCE) showed excellent electrochemical performances towards H2O2 with a wide linear range (10-24,400μM), high sensitivity (207.34μAmM-1cm-2), low LOD (0.14μM), and rapid response time (less than 3s). Most importantly, we prepared a Cu-hemin MOFs/3D-RGO/ITO electrode with cells growing on it. Compared with detecting H2O2 in cell suspension by GCE-based electrode, adhesion of cells on ITO could shorten the diffusion distance of H2O2 from solution to the surface of the electrode and achieve in situ and a real-time monitor of H2O2 released by living cells. This self-supported sensing electrode showed great potential applications in monitoring the pathological and physiological dynamics of cancer cells.

Preparation and Characterization of Carbon Xerogel Based Composites for Electrochemical Sensing and Photocatalytic Degradation.

In order to obtain a multifunctional nanocomposite material-for electrochemical sensors and photocatalytic applications, structures based on Bi, Fe and TiO₂ were grown inside carbon xerogel supports (BiFeCX and BiFeCX-TiO₂). First, a wet polymer containing Bi and Fe salts was obtained by following a modified resorcinol-formaldehyde based sol-gel route, followed by drying in ambient conditions, and pyrolysis under inert atmosphere. Then, through TiCl₄ hydrolysis, TiO₂ nanoparticles were deposited on the BiFeCX xerogel leading to BiFeCX-TiO₂. The morphological and structural characterization of the investigated nanocomposites consisted in X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and N₂ adsorption measurements, revealing porous carbon structures with embedded nanoparticles and the particularities driven by the pyrolysis and TiCl₄ treatment. The new modified electrodes based on BiFeCX or BiFeCX-TiO₂ nanocomposite materials, kept in a chitosan matrix (Chi) and deposited on a glassy carbon (GC) electrode surface (GC/Chi-BiFeCX or GC/Chi-BiFeCX-TiO₂), were obtained and investigated for Pb(II) voltammetric detection and H₂O₂ amperometric detection. Moreover, the BiFeCX-TiO₂ nanocomposite was tested for the photocatalytic degradation of methyl orange. The great potential of BiFeCX nanocomposite material for developing electrochemical sensors, or BiFeCX-TiO₂ for sensors application and photocatalytic application was demonstrated.

Cu/Electrochemically reduced graphene oxide layered nanocomposite for non-enzymatic H2O2 sensor

In this present study, we modified the Au surface with nanocomposite containing Cu nanoparticles and electrochemically reduced graphene oxide (ERGO) to increase the electrocatalytic performance of Au electrode for nonenzymatic amperometric detection of H2O2. The morphology and structural properties of the Cu/ERGO nanocomposites were investigated by XPS, XRD, STM and SEM techniques. The Cu/ERGO nanocomposite electrode displayed good performance for the electrochemical detection of H2O2, compared to naked Au and Cu-modified Au electrodes, in terms of low working potential (at around −0.2 V), high sensitivity (20 μA cm−2 mM−1), and low detection limit (1.87 × 10−9 mol.L−1).

A green approach for hybrid material preparation based on carbon nanotubes/lignosulfonate decorated with silver nanostructures for electrocatalytic sensing of H2O2

We present a green and simple approach for the fabrication of multi-walled carbon nanotubes decorated with silver nanoparticles (MWCNT/LS/NAg) via lignosulfonate assisted synthesis. Due to reducing and stabilizing properties of lignosulfonate, silver nanoparticles were produced in a facile synthetic route without the addition of any reductant or toxic solvents. The existence of silver nanoparticles was confirmed through X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) was employed to investigate the morphologies and structures of prepared functional nanomaterials. Cyclic voltammograms of the MWCNT/LS/NAg nanomaterial presented, revealed well-defined and sharp redox peaks recorded in phosphate buffer (pH = 7.4) corresponding to silver nanoparticles electroactivity. The obtained data proved that the hybrid material exhibits persistent reversible redox behavior. The hybrid nanomaterial possesses strong electrocatalytic properties toward hydrogen peroxide reduction. Based on the electrocatalytic properties of the material, the amperometric detection of H2O2 at −0.2 V demonstrated a wide linear range of 6.00–486 μM. The limit of detection (LOD) and limit of quantitation (LOQ) were 1.169 μM and 3.543 μM, respectively. Substantial electrochemical performance shows the proposed material as a promising electrochemical sensing platform for the detection of hydrogen peroxide.

A novel nonenzymatic hydrogen peroxide amperometric sensor based on AgNp@GNR nanocomposites modified screen-printed carbon electrode

Abstract A nonenzymatic hydrogen-peroxide sensor was developed by utilization of silver nanoparticles and graphene nanoribbons. The mentioned composite was inflicted on a screen-printed carbon electrode which provides disposable, ready-to-use sensor. The structure and morphology of the nanocomposite were analyzed by scanning electron microscopy and X-ray diffraction. The sensor has excellent performance toward H2O2 amperometric detection. Figures of merit include dynamic response range from 0.05 to 5 mM and detection limit of 20 μM (at S/N = 3). The fabricated sensor was used for the determination of H2O2 in milk samples. The obtained results showed that the proposed AgNp@GNR/SPCE sensor can be used for the determination of hydrogen peroxide in real samples.

Fabrication of efficient nanostructured Co3O4-Graphene bifunctional catalysts: Oxygen evolution, hydrogen evolution, and H2O2 sensing

Nanostructured Co3O4-graphene hybrid catalysts are fabricated by a one-step vacuum kinetic spray technique from microparticles of Co3O4 and graphite powders. The Co3O4-graphene hybrid catalysts with various Co3O4 contents are studied concerning the oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) in 1.0 M KOH, as well as, H2O2 sensing in 0.1 M NaOH. We find that increasing graphene content in the hybrid catalysts results in an overall improvement of the OER electrocatalytic activity due to the enhancement in the charge transfer kinetics. The hybrid catalyst with 25 wt% Co3O4 reveals the optimum electrocatalytic activity toward the OER with the lowest overpotential (η) of 283 mV@ 10 mA cm−2 and superior reaction kinetics with a low Tafel slope of 25 mV dec−1. Besides, the OER stability at 50 mA cm−2 for 50 h in 1.0 M KOH was verified. The hybrid catalyst with 50 wt% Co3O4 revealed the highest activity toward the HER with η of 108 mV@ 10 mA cm−2, Tafel slope of 90 mV.dec−1, and stability at 50 mA cm−2 for nearly 30 h. Moreover, it reveals ultrahigh H2O2 amperometric detection with superior sensitivity of 18,110 μA mM−1 cm−2, linear detection range from 20 μM to 1 mM, and a limit of detection of 0.14 μM.

Electrochemical synthesis of Prussian blue from iron impurities in 3D-printed graphene electrodes: Amperometric sensing platform for hydrogen peroxide

This communication shows the electrochemical synthesis of Prussian blue (PB) films on additive manufactured (3D-printed) electrodes from iron impurities found at the graphene-polylactic acid (G/PLA) substrate and its application as a highly selective sensor for H2O2. The 3D-printed G/PLA electrode was immersed in dimethylformamide for 30 min to exposure the iron impurities within the PLA matrix. Next, cyclic voltammograms (200 cycles) in the presence of potassium ferricyanide in 0.1 mol L−1 KCl + 0.01 mol L−1 HCl were performed to grow the PB films. The sensing properties of this novel PB/G/PLA platform were evaluated for the amperometric detection of H2O2 using batch-injection analysis, with a limit of detection of 0.56 μmol L−1 under the application of 0.0 V (vs Ag/AgCl/KClsat.). The applicability of the sensor was demonstrated for the analysis of milk samples (10-fold diluted in the supporting electrolyte), resulting in proper recovery values (94–101%).

Electrodeposition of pore-confined cobalt in metal–organic framework thin films toward electrochemical H2O2 detection

In this study, cobalt is electrodeposited within solvothermally grown thin films of a zirconium-based metal–organic framework, MOF-808, to obtain electrochemically active cobalt confined in the pore of MOF-808 crystals. With the help of the highly porous but electrically insulating MOF-808 thin film and a step-wise electrodepositing technique, cobalt can be mainly deposited within the pore of MOF-808 crystals. The resulting Co@MOF-808 thin film is applied for electrochemical H2O2 sensor in aqueous electrolytes, and its electrocatalytic activity toward H2O2 significantly outperforms that of the electrodeposited cobalt on a bare substrate. The electrochemical behavior of Co@MOF-808 thin films and the corresponding electrocatalytic mechanism toward H2O2 are investigated. The material is further used for amperometric H2O2 detection, and a sensitivity, limit of detection, and linear range of 382.27 μA/mM-cm2, 1.3 μM, and 10–450 μM can be achieved, respectively.

Influence of buffer solution on structure and electrochemical properties of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) hydrogels

Numerous advantages of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT-PSS) hydrogel make this material appropriable for biosensors developing. Among many of them, it may be exploited as an immobilization matrix for binding bioreceptors. Porous 3-D structure facilitates high loading of the enzyme and extends surface area, what results in better biosensor performance and signal increase. High water content generates hydrophilic environment, thus biocompatibility is greatly enhanced. Citrate or phosphate buffers are typically used to provide optimal pH for the immobilized enzyme. The present work reports on the development of the PEDOT-PSS hydrogels synthesized in phosphate buffer or citrate buffer solutions at pH = 5 to verify the influence of the anion present in the polymerization environment on the molecular structure and electrochemical properties of the hydrogel. The water content in each hydrogel sample is estimated by weighting the swelled and dried samples and termogravimetric analysis. It is shown that PEDOT-PSS obtained in phosphate buffer solution comprises much more water than hydrogel synthesized in citrate buffer. This property is of great importance for the electrocatalytic properties of immobilized horseradish peroxidase (HRP). Wherefore, the PEDOT-PSS/HRP modified electrode has been used for the amperometric detection of H2O2 at pH = 6. The phosphate containing ph-PEDOT-PSS/HRP biosensor is characterized by a good linear relation with the concentrations of H2O2 with a linear range from 0.0088 to 0.15 mM and from 0.4 to 10 mM and a low detection limit of 9.4∙10-7 M and 4.5∙10−5 M (S/N = 3), respectively. While the citrate containing cit-PEDOT-PSS/HRP sensor shows worse analytical parameters - linear range from 0.05 to 0.25 mM and detection limit of 1∙10−5 M (S/N = 3).

Functionalized graphene fiber modified by dual nanoenzyme: Towards high-performance flexible nanohybrid microelectrode for electrochemical sensing in live cancer cells

The development of flexible miniaturized electrochemical sensors based on functionalized microelectrode systems has gained numerous attentions for their promising application in potable, implantable and wearable medical devices. In this work, we report a facile strategy to construct a new type of high-performance microelectrode based on wet-spinning graphene fiber (GF) functionalized by dual nanoenzyme composed of ultrafine Au nanoparticles (Au-NPs) wrapped flower-like MnO2 nanowires (MnO2-NWs) assembly (MnO2-NWs@Au-NPs), and explore its practical application in electrochemical detection of biomarker hydrogen peroxide (H2O2) released from live cancer cells. Benefiting from the advantage of the unique hierarchical nanohybrid structure and dual nanoenzyme activity, the resultant MnO2-NWs@Au-NPs modified GF microelectrode shows superior catalytic activity towards the electrochemical redox reaction of H2O2. When used in amperometric detection of H2O2, the nanohybrid microelectrode exhibits high sensitivity and selectivity as well as good mechanical stability and biocompatibility, and can be used in real-time in situ detection of H2O2 released from human breast cancer cells, which contributes to the development of high-performance hierarchically nanostructured microelectrode in electrochemical sensing system for sensitive detection of various targets in biological samples.

Electrochemical Studies of Hydrogen Peroxide Oxidation on a Nanoporous Gold Surface: Fundamental and Analytical Applications

A nanoporous gold (NPG) surface with high electroactive surface area and roughness factor was prepared via anodization-electrochemical reduction method and was used as a new platform to study the electrochemical oxidation of hydrogen peroxide (H2O2). Field-emission scanning electron microscopy (FE-SEM) analysis, cyclic voltammetry, and amperometry techniques were employed for structural morphology and electrochemical studies. The H2O2 oxidation peak potential was significantly shifted (∼0.23 V) towards a less positive direction with increased current response at the NPG surface compared to that of a bare gold electrode. The mechanism for the H2O2 anodic oxidation at the NPG surface was proposed based on the calculated transfer coefficient (α = 0.32) and the total number of electrons involved (n = 2.0) in the electrochemical process. Besides, the diffusion coefficient (D) of H2O2 in PBS solution was also calculated using the Randles-Sevcik equation (2.18 × 10−5 cm2 s−1). In addition, the analytical application of the NPG electrode was demonstrated by amperometric detection of H2O2 at a relatively less positive potential (0.57 V). The current increased proportionally to H2O2 concentration in the linear range of 0.01 to 1.8 mM and the detection limit was found to be 0.6 μM (S/N = 3).

Screen-Printed Soft-Nitrided Carbon Electrodes for Detection of Hydrogen Peroxide.

Nitrogen-doped carbon materials have garnered much interest due to their electrocatalytic activity towards important reactions such as the reduction of hydrogen peroxide. N-doped carbon materials are typically prepared and deposited on solid conductive supports, which can sometimes involve time-consuming, complex, and/or costly procedures. Here, nitrogen-doped screen-printed carbon electrodes (N-SPCEs) were fabricated directly from a lab-formulated ink composed of graphite that was modified with surface nitrogen groups by a simple soft nitriding technique. N-SPCEs prepared from inexpensive starting materials (graphite powder and urea) demonstrated good electrocatalytic activity towards hydrogen peroxide reduction. Amperometric detection of H2O2 using N-SPCEs with an applied potential of −0.4 V (vs. Ag/AgCl) exhibited good reproducibility and stability as well as a reasonable limit of detection (2.5 µM) and wide linear range (0.020 to 5.3 mM).