Nanomolar amperometric sensing of hydrogen peroxide using a graphite pencil electrode modified with palladium nanoparticles

We report on a simple and rapid method for the preparation of a disposable palladium nanoparticle-modified graphite pencil electrode (PdNP-GPE) for sensing hydrogen peroxide (H₂O₂). The bare and PdNP-modified GPEs were characterized by cyclic voltammetry and SEM. The two electrodes displayed distinct electrocatalytic activities in response to the electrochemical reduction of H₂O₂. The amperometric detection limits were 45 nM and 0.58 mM, respectively, for the PdNP-GPE and bare-GPE, at an S/N of 3. The electrodes can be prepared simply and at low cost, and represent a promising tool for sensing H₂O₂.

A novel non-enzyme hydrogen peroxide sensor based on an electrode modified with carbon nanotube-wired CuO nanoflowers

We have prepared a novel sensor for hydrogen peroxide that is based on a glassy carbon electrode modified with a film containing multi-walled carbon nanotubes wired to CuO nanoflowers. The nanoflowers were characterized by X-ray powder diffraction, and the electrode was characterized by cyclic voltammetry (CV) and scanning electron microscopy. The response of the modified electrode towards hydrogen peroxide was investigated by CV and chronoamperometry and showed it to exhibit high electrocatalytic activity, with a linear range from 0.5?μM to 82?μM and a detection limit of 0.16?μM. The sensor also displays excellent selectivity and stability.

Enhanced stability of a Prussian blue/sol-gel composite for electrochemical determination of hydrogen peroxide

We have prepared a sol–gel that incorporates Prussian Blue (PB) as a redox mediator. It is shown that the PB in the pores of the sol–gel retains its electrochemical activity and is protected from degradation at acidic and neutral pH values. TEM and EDX studies revealed the PB nanoparticles to possess a cubic crystal structure and to be well entrapped and uniformly dispersed in the pores of the matrix. The electrocatalytic activity of the materials toward hydrogen peroxide (H₂O₂) was studied by cyclic voltammetry and amperometry. The modified electrode displays good sensitivity for the electrocatalytic reduction of H₂O₂ both in acidic (pH 1.4) and neutral media. The sensor has a dynamic range from 3 to 210 μM of H₂O₂, and the detection limit is 0.6 μM (at an SNR of 3).

Sensitive electrochemical sensor for hydrogen peroxide using Fe3O4 magnetic nanoparticles as a mimic for peroxidase

A sensor for hydrogen peroxide is described that is based on an indium tin oxide electrode modified with Fe₃O₄ magnetic nanoparticles which act as a mimic for the enzyme peroxidase and greatly improve the analytical performance of the sensor. The amperometric current is linearly related to the concentration of H₂O₂ in the range from 0.2 mM to 2 mM, the regression equation is y?=?-0.5–1.82x, the correlation coefficient is 0.998 (n?=?3), and the detection limit is 0.01 mM (S/N?=?3). The sensor exhibits favorable selectivity and excellent stability.

Highly sensitive detection of hydrogen peroxide at a carbon nanotube fiber microelectrode coated with palladium nanoparticles

We report on a carbon nanotube (CNT) fiber microelectrode coated with palladium nanoparticles (PdNPs) and enabling electrochemical sensing of hydrogen peroxide (H₂O₂). The synergistic effects of the CNT fibers (good mechanical strength and large surface area) and of the PdNPs (high electrocatalytic activity) result in a microelectrode for H₂O₂ that exhibits a 2-s response time, a detection limit as low as 2 μM, a sensitivity of 2.75 A cm^?2 M^?1, and a linear response range from 2 μM to 1.3 mM (R?=?0.9994). The sensor is also selective and not interfered by potentially competing species in biological fluids, thus representing an inexpensive but highly sensitive and selective microsensor for H₂O₂.

Amperometric biosensor for hydrogen peroxide based on the co-electrodeposition of horseradish peroxidase and methylene blue on an ITO electrode modified with an anodic aluminum oxide template

We report on a nano-array sensor for hydrogen peroxide (H₂O₂) that is based on a nanoporous anodic aluminum oxide template. This was used as a matrix for the co-immobilization of horseradish peroxidase (HRP) and methylene blue (MB) on the surface of an indium tin oxide electrode. The immobilized HRP retained its natural activity and MB is capable of efficiently shuttle electrons between HRP and the electrode. The new electrode was characterized by SEM and electrochemical methods. It exhibits fast response, long-term stability, high sensitivity and good selectivity to H₂O₂. Under optimized conditions, it linearly responds to H₂O₂ in the concentration range from 1.0?μM to 26?mM, with a detection limit of 0.21?μM (at S/N?=?3).

Synthesis of multi-branched gold nanoparticles by reduction of tetrachloroauric acid with Tris base, and their application to SERS and cellular imaging

A biosensor for hydrogen peroxide was constructed by immobilizing horseradish peroxidase on chitosan-wrapped NiFe₂O₄ nanoparticles on a glassy carbon electrode (GCE). The electron mediator carboxyferrocene was also immobilized on the surface of the GCE. UV?Cvis spectra, Fourier transform IR spectra, scanning electron microscopy, and electrochemical impedance spectra were acquired to characterize the biosensor. The experimental conditions were studied and optimized. The biosensor responds linearly to H₂O₂ in the range from 1.0?×?10^?5 to 2.0?×?10^?3?M and with a detection limit of 2.0?×?10^?6?M (at S/N?=?3).

Amperometric hydrogen peroxide biosensor based on a glassy carbon electrode modified with polythionine and gold nanoparticles

We report on a novel hydrogen peroxide biosensor that was fabricated by the layer-by-layer deposition method. Thionine was first deposited on a glassy carbon electrode by two-step electropolymerization to form a positively charged surface. The negatively charged gold nanoparticles and positively charged horseradish peroxidase were then immobilized onto the electrode via electrostatic adsorption. The sequential deposition process was characterized using electrochemical impedance spectroscopy by monitoring the impedance change of the electrode surface during the construction process. The electrochemical behaviour of the modified electrode and its response to hydrogen peroxide were studied by cyclic voltammetry. The effects of the experimental variables on the amperometric determination of H₂O₂ such as solution pH and applied potential were investigated for optimum analytical performance. Under the optimized conditions, the biosensor exhibited linear response to H₂O₂ in the concentration ranges from 0.20 to 1.6?mM and 1.6 to 4.0?mM, with a detection limit of 0.067?mM (at an S/N of 3). In addition, the stability and reproducibility of this biosensor was also evaluated and gave satisfactory results.

Nonenzymatic hydrogen peroxide sensor based on a glassy carbon electrode modified with electrospun PdO-NiO composite nanofibers

A glassy carbon electrode was modified with PdO-NiO composite nanofibers (PdO-NiO-NFs) and applied to the electrocatalytic reduction of hydrogen peroxide (H₂O₂). The PdO-NiO-NFs were synthesized by electrospinning and subsequent thermal treatment, and then characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Factors such as the composition and fraction of nanofibers, and of the applied potential were also studied. The sensor exhibits high sensitivity for H₂O₂ (583.43 μA?·?mM^?1?·?cm^?2), a wide linear range (from 5.0 μM to 19 mM), a low detection limit (2.94 μM at an SNR of 3), good long term stability, and is resistant to fouling.

Peroxidase-like activity of magnetoferritin

Magnetoferritin is a spherical biomacromolecule with a diameter of about 12 nm. It consists of a protein shell composed of apoferritin that is surrounding magnetic nanoparticles of magnetite (Fe₃O₄) or maghemite (γ-Fe₂O₃). Magnetoferritins with various iron content (loading factor) were synthetically prepared and their peroxidase-like activities studied via the oxidation of the chromogenic substrate N,N-diethyl-p-phenylenediamine sulfate by hydrogen peroxide to give a purple product with an absorption maximum at 551 nm. Magnetoferritin with higher loading factor exhibits a higher peroxidase-like activity. The catalytic activity was successfully applied to the determination of hydrogen peroxide in the 5.8 to 88.2 mM concentration range.

A study on the direct electrochemistry and electrocatalysis of microperoxidase-11 immobilized on a porous network-like gold film: Sensing of hydrogen peroxide

We have prepared porous and network-like nanofilms of gold by galvanic replacement of a layer of copper particles acting as a template. The films were first characterized by scanning electron microscopy and X-ray diffraction, and then modified with cysteamine so to enable the covalent immobilization of the enzyme microperoxidase-11. The immobilized enzyme undergoes direct electron transfer to the underlying electrodes, and the electrode displays high electrocatalytic activity towards the reduction of oxygen and hydrogen peroxide, respectively, owing to the largely enhanced electroactive surface of the porous gold film. The detection limit of H₂O₂ is 0.4 μM (3 S/N).

Electrochemistry and biosensing activity of cytochrome c immobilized in macroporous materials

An amperometric biosensor for hydrogen peroxide (H₂O₂) has been constructed by immobilizing cytochrome c on an indium/tin oxide (ITO) electrode modified with a macroporous material. Cyclic voltammetry showed that the direct and quasi-reversible electron transfer of cytochrome c proceeds without the need for an electron mediator. A surface-controlled electron transfer process can be observed with an apparent heterogeneous electron-transfer rate constant (k_s) of 29.2?s^?1. The biosensor displays excellent electrocatalytic responses to the reduction of H₂O₂ to give amperometric responses that increase steadily with the concentration of H₂O₂ in the range from 5???M to 2?mM. The detection limit is 0.61???M at pH?7.4. The apparent Michaelis-Menten constant (K_m) of the biosensor is 1.06?mM. This investigation not only provided a method for the direct electron transfer of cytochrome c on macroporous materials, but also established a feasible approach for durable and reliable detection of H₂O₂.

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.

Optical determination of glucose and hydrogen peroxide using a nanocomposite prepared from glucose oxidase and magnetite nanoparticles immobilized on graphene oxide

Fe₃O₄ nanoparticles were deposited on sheets of graphene oxide (GO) by a precipitation method, and glucose oxidase (GOx) was then immobilized on this material to produce a GOx/Fe₃O₄/GO magnetic nanocomposite containing crosslinked enzyme clusters. The 3-component composite functions as a binary enzyme that was employed in a photometric method for the determination of glucose and hydrogen peroxide where the GOx/Fe₃O₄/GO nanoparticles cause the generation of H₂O₂ which, in turn, oxidize the substrate N,N-diethyl-p-phenylenediamine to form a purple product with an absorption maximum at 550 nm. The absorbance at 550 nm can be correlated to the concentration of glucose and/or hydrogen peroxide. Under optimized conditions, the calibration plot is linear in the 0.5 to 600 μM glucose concentration range, and the detection limit is 0.2 μM. The respective plot for H₂O₂ ranges from 0.1 to 10 μM, and the detection limit is 0.04 μM. The method was successfully applied to the determination of glucose in human serum samples. The GOx/Fe₃O₄/GO nanoparticles are reusable.

A silica-dextran nanocomposite as a novel matrix for immobilization of horseradish peroxidase, and its application to sensing hydrogen peroxide

We report on a novel matrix of solgel organic–inorganic nanocomposite that was fabricated from silica sol gel and dextran. It was used for the immobilization of horseradish peroxidase (HRP) to give a biosensor for hydrogen peroxide (H₂O₂). The sensor film was characterized by Fourier transform infrared and UV–vis spectroscopy with respect to structural features and the conformation of the enzyme. The topographies of the surface of the electrode were investigated by field emission scanning electron microscopy. The biosensor was used to determine H₂O₂ quantitatively in the presence of Methylene blue as a mediator with high electron transfer efficiency. A pair of stable and well defined quasi-reversible redox peaks of the HRP [Fe (III)]/HRP [Fe (II)] redox couple was observed at pH 7.0. The biosensor responds to H₂O₂ in the 0.5 mM to 16.5 mM concentration range, and the limit of detection is 0.5 mM.

Non-enzymatic hydrogen peroxide sensor based on a gold electrode modified with granular cuprous oxide nanowires

Granular nanowires with a diameter of about 60 nm were fabricated from cuprous oxide (Cu₂O) by an electrochemical method using anodic aluminium oxide as the template. A non-enzymatic sensor for hydrogen peroxide (H₂O₂) was then developed on the basis of a gold electrode modified with Cu₂O nanowires and Nafion. The resulting sensor enables the determination of H₂O₂ with a sensitivity of 745 μA?mM^?1?cm^?2, over a wide linear range (0.25 μM to 5.0 mM), and with a low detection limit (0.12 μM). The results demonstrate that the use of such granular nanowires provides a promising tool for the design of non-enzymatic chemical sensors.

Carbon nanofibers decorated with platinum nanoparticles: a novel three-dimensional platform for non-enzymatic sensing of hydrogen peroxide

We have developed a 3-dimensional (3-D) electrochemical sensor for highly sensitive detection of hydrogen peroxide (H₂O₂). Porous 3-D carbon nanofibers (CNFs), prepared by electrospinning, served as scaffold on a glassy carbon electrode. The 3-D CNFs were functionalized with platinum nanoparticles (Pt-NPs) by in-situ gas-phase decomposition of platinum salts at high temperature. The Pt-NPs act as an electrocatalyst for the decomposition of H₂O₂. TEM revealed that large amounts of Pt-NPs are deposited in the electrospun CNFs electrode even without using any stabilizer or reducing reagent. The sensor was investigated by cyclic voltammetry and amperometry and displays a good response to H₂O₂ with a linear range between 10 μM and 15 mM (R?=?0.9994), a low detection limit (3.4 μM at a signal-to-noise ratio of 3), and a response time of 3 s. The sensor shows excellent stability and selectivity.

A glassy carbon electrode modified with a film composed of cobalt oxide nanoparticles and graphene for electrochemical sensing of H2O2

We have prepared a graphene-based hybrid nanomaterial by electrochemical deposition of cobalt oxide nanoparticles (CoO_xNPs) on the surface of electrochemically reduced graphene oxide deposited on a glassy carbon electrode (GCE). Scanning electron microscopy and cyclic voltammetry were used to characterize the immobilized nanoparticles. Electrochemical determination of H₂O₂ is demonstrated with the modified GCE at pH 7. Compared to GCEs modified with CoO_xNPs or graphene sheets only, the new electrode displays larger oxidative current response to H₂O₂, probably due to the synergistic effects between the graphene sheets and the CoO_xNPs. The sensor responds to H₂O₂ with a sensitivity of 148.6 μA mM^?1 cm^?2 and a linear response range from 5 μM to 1 mM. The detection limit is 0.2 μM at a signal to noise ratio (SNR) of three. The method was successfully applied to the determination of H₂O₂ in hydrogen peroxide samples.

Sensitive detection of hydrogen peroxide in foodstuff using an organic�Cinorganic hybrid multilayer-functionalized graphene biosensing platform

We report on a new electrochemical biosensing strategy for the sensitive detection of hydrogen peroxide (H₂O₂) in foodstuff samples. It is based on a gold electrode modified with layer of graphene patterned with a multilayer made from an organic?Cinorganic hybrid nanomaterial. Initially, a layer of thionine (Th) was assembled on the surface of the graphene nanosheets, and these were then cast on the surface of the electrode for the alternate assembly of gold nanoparticles and horseradish peroxidase. The large surface-to-volume ratio and high conductivity of the nanosheets provides a benign microenvironment for the construction of the biosensor. The use of such a multilayer not only shortens the electron transfer pathway of the active center of the enzyme due to the presence of gold nanoparticles, but also enhances the electrocatalytic efficiency of the biosensor toward the reduction of H₂O₂. The electrochemical characteristics of the biosensor were studied by cyclic voltammetry and chronoamperometry. The number of layers, the operating potential, and the pH of the supporting electrolyte were optimized. Linear response is obtained for the range from 0.5???M to 1.8?mM of H₂O₂, the detection limit is 10 nM (at S/N?=?3), and 95% of the steady-state current is reached within 2?s. The method was applied to sense H₂O₂ in spiked sterilized milk and correlated excellently with the permanganate titration method.

A glassy carbon electrode modified with poly(anthranilic acid), poly(diphenylamine sulfonate) and CuO nano-particles for the sensitive determination of hydrogen peroxide

We report on a modified glassy carbon electrode (GCE) for sensing hydrogen peroxide (H₂O₂). It was constructed by consecutive electrochemical deposition of poly(anthranilic acid) and poly(diphenylamine sulfonate) on the GCE, followed by the deposition of copper oxide (CuO). The morphology and electrochemistry of the modified electrode was characterized by atomic force microscopy, X-ray diffraction, cyclic voltammetry, and electrochemical impedance spectroscopy. The catalytic performance of the sensor was studied with the use of differential pulse voltammetry under optimized conditions. This sensor displayed significantly better electrocatalytic activity for the reduction of H₂O₂ in comparison to a GCE without or with modification with CuO or polymer films alone. The response to H₂O₂ is linear in the range between 0.005 to ~11 mM, and the detection limit is 0.18 μM (at an S/N of 3).