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.

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).

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).

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.

Electrochemical sensing of hydrogen peroxide using metal nanoparticles: a review

We are reviewing the state of electrochemical sensing of H₂O₂ based on the use of metal nanoparticles. The article is divided into subsections on sensors based on nanoparticles made from Ag, Pt, Pd, Cu, bimetallic nanoparticles and other metals. Some sensors display high sensitivity, fast response, and good stability. The review is subdivided into sections on sensors based on heme proteins and on nonenzymatic sensors. We also discussed the challenges of nanoscaled sensors and their future aspects.

Direct Detection of Solid Inorganic Mercury Salts at Ambient Pressure by Electron-Capture and Reaction-Assisted HePI Mass Spectrometry

Solid HgCl₂ is readily detected at ambient conditions by electron capture in a HePI-MS source. The captured electron occupies the empty 6 s orbital of the Hg atom. The resulting radical-anion HgCl₂ ^?? can exist as three “flexomers” of different Cl-Hg-Cl angle. The facile in-source formation of HgCl₂ ^?? and the adduct [HgCl₃]^–- is exploited to detect other solid Hg compounds by exposing them to an external chloride source, such as HCl, NaCl, or vapors emanating from solid TiCl₃. In situ oxidation of Hg₂Cl₂ with H₂O₂ generated signals for HgCl₂ ^?? and [HgCl₃] ^–, suggesting that oxidation makes Hg 6 s orbital available for electron capture.

Electrochemical sensors based on graphene materials

Single?Clayered graphene, emerging as a true two?Cdimensional nanomaterial, has tremendous potential for electrochemical catalysis and biosensing as a novel electrode material. Considering the excellent properties of graphene, such as large surface?Cto?Cvolume ratio, high conductivity and electron mobility at room temperature, low energy dynamics of electrons with atomic thickness, robust mechanical and flexibility, we give a general view of recent advances in electrochemical sensors based on graphene. We are highlighting here important applications of graphene and graphene nanocomposites, and the assay strategies in electrochemical sensors for DNA, proteins, neurotransmitters, phytohormones, pollutants, metal ions, gases, hydrogen peroxide, and in medical, enzymatic and immunosensors.

Voltammetric and amperometric determination of hydrogen peroxide using a carbon-ceramic electrode modified with a nanohybrid composite made from single-walled carbon nanotubes and silver nanoparticles

A nanohybrid composite material was prepared from single-walled carbon nanotubes and silver nanoparticles, and used to fabricate a modified carbon-ceramic electrode. The preparation of the composite is facile and efficient. The nanohybrid composite deposited on the carbon-ceramic electrode was characterized by X-ray diffraction and cyclic voltammetry. The new electrode displays favorable electrocatalytic ability towards hydrogen peroxide (H₂O₂) and can be used to electrocatalytically reduce this species. Under the optimum conditions, the current measured during hydrodynamic amperometry is linearly related to the concentration of H₂O₂ over the concentration range from 0.01 to 8 mM, with a detection limit of 2?×?10^?7 M at a signal-to-noise ratio of 3 and sensitivity of 3.23 μA/mM. The electrode exhibits good reproducibility, long-term stability and negligible interference by dopamine, uric acid, and other important biological compounds. The electrode was successfully applied to the determination of H₂O₂ in honey samples, and the recovery was 101.2%.

A highly sensitive nonenzymatic glucose sensor based on CuO nanowires

We report on the sensitive determination of glucose using a glassy carbon electrode modified with CuO nanowires and a Nafion film. The structure and morphology of CuO nanowires were established by scanning electron microscopy and X-ray diffraction. The electrochemical performance of the modified electrode was investigated by cyclic voltammetry and chronoamperometry. Compared to a bare glassy carbon electrode, a substantial increase in efficiency of the electrocatalytic oxidation of glucose can be observed. The new glucose sensor displays two useful linear ranges of response towards glucose, is not affected by commonly interfering species, and displays a detection limit as small as 45?nM. The response time is <2?s towards 0.5?mM of glucose. Additional features include high electrocatalytic activity, high sensitivity, excellent selectivity, and good stability.

Determination of hydrogen peroxide and glucose using a novel sensor platform based on Co0.4Fe0.6LaO3 nanoparticles

We report on a novel nonenzymatic sensor platform for the determination of hydrogen peroxide and glucose. It is based on a carbon paste electrode that was modified with Co_0.4Fe_0.6LaO₃ nanoparticles synthesized by the sol–gel method. The structure and morphology of Co_0.4Fe_0.6LaO₃ nanoparticles were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The electrochemical performance of this sensor was evaluated by cyclic voltammetry and amperometry, and the results demonstrated that it exhibits strong electrocatalytical activity towards the oxidation of H₂O₂ and glucose in an alkaline medium. The sensor has a limit of detection as low as 2.0 nM of H₂O₂ and a linear range that extends from 0.01 to 800 μM. The response to glucose is characterized by two analytical ranges of different slope, viz. from 0.05 to 5 μM and from 5 to 500 μM, with a 10 nM limit of detection. The glucose sensor has a fast response and good long term stability.

Electrochemical synthesis of a novel platinum nanostructure on a glassy carbon electrode, and its application to the electrooxidation of methanol

We show that the addition of white dextrin during the electrochemical deposition of platinum nanostructures (nano-Pt) on a glassy carbon electrode (GCE) results in an electrochemically active surface that is much larger than that of platinum microparticles prepared by the same procedure but in the absence of dextrin. The nano-Pt deposits are characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy, and electrochemical methods. The SEM images reveal deposits composed of mainly nanoparticles and short nanorods. The GCE was applied as a novel and cost-effective catalyst for methanol oxidation. The use of nano-Pt improves the electrocatalytic activity and the stability of the electrodes.

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.

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.

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.

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.

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).

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).

Titanium dioxide nanorod-based amperometric sensor for highly sensitive enzymatic detection of hydrogen peroxide

Titanium dioxide nanorods (TNR) were grown on a titanium electrode by a hydrothermal route and further employed as a supporting matrix for the immobilization of nafion-coated horseradish peroxidase (HRP). The strong electrostatic interaction between HRP and TNR favors the adsorption of HRP and facilitates direct electron transfer on the electrode. The electrocatalytic activity towards hydrogen peroxide (H₂O₂) was investigated via cyclic voltammetry and amperometry. The biosensor exhibits fast response, a high sensitivity (416.9 μA·mM^?1), a wide linear response range (2.5 nM to 0.46 mM), a detection limit as low as 12 nM, and a small apparent Michaelis-Menten constant (33.6 μM). The results indicate that this method is a promising technique for enzyme immobilization and for the fabrication of electrochemical biosensors.

Luminescent probes for detection and imaging of hydrogen peroxide

The relevance of hydrogen peroxide (H₂O₂) in biological processes has been underestimated for a long time. In recent years, various reports showed that H₂O₂ not only acts as a cytotoxic compound appearing in the course of oxidative stress, but also functions as an important signaling molecule. Fluorescent probes (or indicators) and nanoparticles that respond selectively to hydrogen peroxide can be applied for intracellular measurements or in vivo imaging, and are superior to electrochemical methods, e.g. in terms of spatial resolution. In contrast to previous reviews that concentrated on the adoption of different probes for certain applications, this survey highlights the basic principles of different probes in terms of their chemical design, structures and functionalities. Thus, the probes are classified according to the underlying reaction mechanism: oxidation, hydrolysis, photoinduced electron transfer, and lanthanide complexation. Other assays are based on fluorescent proteins and nanoparticles, and chemi- or bioluminescent reagents. We confine this review to probes that display a more or less distinct selectivity to hydrogen peroxide. Indicators responding to reactive oxygen species (ROS) in general, or to particular other ROS, are not covered. Finally, we briefly discuss future trends and perspectives of these luminescent reporters in biomedical research and imaging.