A novel application of iron oxide nanoparticles for detection of hydrogen peroxide in acid rain

Determining the concentration of hydrogen peroxide (H₂O₂) is of great importance in food, pharmaceutical, environmental and clinical analyses. Horseradish peroxidase (HRP), an enzyme specifically catalyzing the oxidative reaction of H₂O₂ to develop color reaction, has been widely used for measuring H₂O₂ concentration. However, owing to the instability and high cost of this enzyme, discovering efficient mimics of peroxidase has been important to conquer these disadvantages of protein catalyst. Recently we have found that Fe₃O₄ magnetic nanoparticles (Fe₃O₄ MNPs) possess intrinsic peroxidase-like activity, which can catalyze oxidation of various peroxidase substrates in the presence of H₂O₂. Based on this finding, we developed a spectrometric method using Fe₃O₄ MNPs as a catalyst to determine H₂O₂ in rainwater. Our data show that the Fe₃O₄ MNPs are efficient catalysts to determine H₂O₂ in rainwater. Compared to HRP, the Fe₃O₄ MNPs are reusable and economical and these characteristics make the particles a board range of applications in determining H₂O₂ in the rainwater.     

A novel approach to hydrogen sensing

A novel sensor for the selective detection of hydrogen in the presence of other reducing gases is presented. The device comprises a commercially available non- or partially-selective semiconductor gas sensor and an air filled centimeter-long capillary tube. The attachment is so that upon exposure, the target gas diffuses in air through the length of the capillary before affecting the sensor. The hydrogen component of the gas mixture diffuses much faster than other components, and is sensed at an earlier stage of the sensor response. The response of a capillary-attached gas sensor (CGS) to a gas mixture containing hydrogen is mathematically analyzed. The results indicate that the hydrogen concentration can readily be extracted from certain mathematical features of the transient response. The fabrication of a prototype CGS and experimental verification of the analytical results are reported. The prototype can measure hydrogen concentration at the presence of other reducing and combustible gases exceeding its concentration by two orders of magnitude.     

Horseradish peroxidase functionalized fluorescent gold nanoclusters for hydrogen peroxide sensing

The fluorescence of metal nanoclusters provides an amusing optic feature to be applied in various fields. However, rational design of dual functional fluorescent metal nanoclusters directed by active enzyme with targeted application remains little explored. In this work, we report a new strategy to construct enzyme functionalized fluorescent gold nanoclusters via a biomineralization process for the detection of hydrogen peroxide. Horseradish peroxidase (HRP) was used as a model functional template to direct the synthesis of fluorescent gold nanoclusters (Au NCs) at physiological conditions to form HRP-Au NCs bioconjugates. We found that the fluorescence of HRP-Au NCs can be quenched quantitatively by adding H(2)O(2), indicating that HRP enzyme remains active and enables catalytic reaction of HRP-Au NCs and H(2)O(2). Upon the addition of H(2)O(2) under optimal conditions, the fluorescence intensity quenched linearly over the range of 100 nM to 100 μM with high sensitivity (LOD = 30 nM, S/N = 3). This study would be potentially extended to other functional proteins to generate dual functional nanoclusters and applied to real time monitoring of biologically important targets in living cells.     

Electrospun carbon nanofibers with manganese dioxide nanoparticles for nonenzymatic hydrogen peroxide sensing

Carbon nanofibers (CNFs) decorated by manganese dioxide nanoparticles (MnO₂NPs) are prepared by an electrospinning technique, followed by thermal treatments in different environments. The obtained MnO₂NPs–CNFs composite was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). SEM images showed that the surface of the CNFs was decorated with homogeneously dispersed nanoparticles with narrow size distribution. XRD and XPS characterizations confirmed the main composition of the nanoparticles was MnO₂. Furthermore, for the strong catalytic oxidation ability of MnO₂ toward hydrogen peroxide, the composite material was used as the matrix for nonenzymatic sensor construction. Cyclic voltammetry and amperometric response were applied to investigate the performance of the sensor. Under the optimum conditions, a wide linear range from 10 μM to 15 mM (R = 0.9994, R represents the correlation coefficient) with a low detection limit of 1.1 μM was obtained. The proposed sensor also displayed short response time, high sensitivity, good reproducibility and stability. These superior performances could be attributed to the large surface area and excellent electrocatalytic activity of the MnO₂NPs–CNFs.     

Gold nanoparticles/graphene oxide composite for electrochemical sensing of hydroxylamine and hydrogen peroxide

It has been discovered that the complex formed by cetyltrimethyl ammonium bromide (CTAB) and graphene oxide (GO) is highly stable in aqueous solution and adhesive to the glassy carbon electrode (GCE) surface in our previous research. In this work, the film of CTAB/GO complex was directly formed on GCE and gold nanoparticles were facilely incorporated into the matrix of CTAB/GO complex at the same time. Scanning electron microscopic (SEM) investigation shows that gold nanoparticles were distributed uniformly on the sheets of graphene. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and amperometry were used to investigate the electrochemical behaviors of AuNP/CTAB/GO. The obtained AuNP/CTAB/GO presents excellent catalytic capabilities towards the oxidation of hydroxylamine (HA) and the reduction of H₂O₂. The oxidation current of HA and the reduction current of H₂O₂ are linear with their concentrations in the range of 10～1000 μM and 1.0～5000 μM, respectively. The detection limits for HA and H₂O₂ are 3.5 μM and 0.67 μM, respectively. The mechanism of the oxidation of HA on AuNP/CTAB/GO modified GCE was also studied.     

Paper-based vapor detection of hydrogen peroxide: colorimetric sensing with tunable interface

Vapor detection of hydrogen peroxide still remains challenging for conventional sensing techniques, though such vapor detection implies important applications in various practical areas, including locating IEDs. We report herein a new colorimetric sensor system that can detect hydrogen peroxide vapor down to parts per billion level. The sensory materials are based on the cellulose microfibril network of paper towels, which provide a tunable interface for modification with Ti(IV) oxo complexes for binding and reacting with H(2)O(2). The Ti(IV)-peroxide bond thus formed turns the complex from colorless to bright yellow with an absorption maximum around 400 nm. Such complexation-induced color change is exclusively selective for hydrogen peroxide, with no color change observed in the presence of water, oxygen, common organic reagents or other chelating reagents. This paper-based sensor material is disposable and one-time use, representing a cheap, simple approach to detect peroxide vapors. The reported sensor system also proves the technical feasibility of developing enhanced colorimetric sensing using nanofibril materials that will provide plenty of room to enlarge the surface area (by shrinking the fiber size), so as to enhance the surface interaction with gas phase.     

A novel potentiometric hydrogen peroxide sensor based on pKa changes of vinylphenylboronic acid membranes

A potentiometric hydrogen peroxide (H₂O₂) sensing scheme was developed using arylboronic acid as the electrode modifier. It is well-known that both aliphatic and aryl boronic acid undergo electrophilic displacement reaction with H₂O₂. This reaction involves replacement of boronic acid by the hydroxyl group of peroxide resulting in a change in pK_a value that can be exploited for sensing of H₂O₂. Vinylphenylboronic acid (VPBA) ink was prepared using Nafion as the binder and it was drop cast on an electrode surface. Morphology of the modified electrode was analysed using scanning electron microscopy (SEM). The present modifier exhibited a linear relationship between the difference in electrode potential (?Ep) vs. [H₂O₂] with a Nernstian slope of 26 ± 2 mV in the concentration range of 10^? 1–10^? 5 M. Application of the VPBA modified electrode for hydrogen peroxide sensing was studied in an industrial dye-bleach effluent.     

Fabrication of a novel hydrogen peroxide biosensor based on C@Au composite

A promising hydrogen peroxide (H2O2) biosensor was fabricated by the immobilization of hemoglobin (Hb) on C@Au composite surface. The composite with carbon spheres and gold shell (C@Au) was synthesized via the seed-growth assembly technique. The assembly of the gold shell on carbon sphere surfaces was characterized by scanning electron miscroscopy (SEM). Owing to the unique structure and large surface area of the gold shell, the composite offered an effective interface for the immobilization of hemoglobin to fabricate a H2O2 biosensor. The obtained biosensor showed a wide linear range from 5.0 microM to 135 microM with a detection limit of 1.67 microM at 3sigma, and the apparent Michaelis-Menten constant (Km(app)) of the immobilized Hb was calculated to be 88.6 microM. Moreover, the biosensor also exhibited good reproducibility and long-term stability. Therefore, this kind of composite can provide an ideal matrix for protein immobilization and biosensor fabrication.     

Olive mill wastewater degradation by Fenton oxidation with zero-valent iron and hydrogen peroxide

The degradation of olive mill wastewater (OMW) with hydroxyl radicals generated from zero-valent iron and hydrogen peroxide has been investigated by means of chemical oxygen demand (COD) and phenolic compounds analyses. The effects of the H2O2 dose, the pH and the organic matter concentration have been studied. The optimal experimental conditions were found to have continuous presence of iron metal, acid pH (2.0-4.0), and relatively concentrated hydrogen peroxide (9.5M). Coloration of OMW disappeared and phenolic compound decreased to 50% of initial concentration after 3h reaction time. The application of zero-valent Fe/H2O2 procedure permitted high removal efficiencies of pollutants from olive mill wastewater. The results show that zero-valent Fe/H2O2 could be considered as an effective alternative solution for the treatment of OMW or may be combined with a classical biological process to achieve high quality of effluent water.     

Iron oxide particles are the active sites for hydrogen peroxide sensing at multiwalled carbon nanotube modified electrodes

We demonstrate that the "electrocatalytic" hydrogen peroxide detection reported at multiwalled carbon nanotube modified electrodes is due to iron oxide particles arising from the chemical vapor deposition nanotube fabrication process rather than due to intrinsic catalysis attributable to the carbon nanotubes arising, for example, from edge plane-like sites/defects.     

A mechanochemical synthesis of nanostructured zinc oxide via acetate route for LPG sensing

This article reports the liquefied petroleum gas (LPG) sensing of nanostructured zinc oxide (ZnO) synthesised via zinc acetate [Zn(CH₃COO)₂·2H₂O] as precursor. The structural and morphological characterisations of the material were analysed by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). Structural analysis showed that material was highly crystalline having minimum crystallite size 15?nm. Surface morphological studies show nanospheres of ZnO throughout the surface, however not distributed uniformly. Optical characterisation of the sensing material was carried out by UV-Visible spectroscopy and FTIR spectroscopy. By Tauc plot, the estimated value of band gap of film was found 3.45?eV. The LPG-sensing properties of the ZnO pellet were investigated at room temperature for different vol.% of LPG. The variations in electrical resistance of the sensing pellet were measured with the exposure of LPG as a function of time. The maximum values of average sensitivity and sensor response factors were found ～5 and 396, respectively, for 5 vol.% of LPG. The activation energy calculated from Arrhenius plot was found 0.61?eV. The response and recovery time of sensing pellet were found ～90 and 110?s, respectively. These experimental results show that nanostructured ZnO is a promising material as LPG sensor.     

A pulse amperometric sensor for the measurement of atmospheric hydrogen peroxide

Gaseous H(2)O(2) is sampled through a Nafion membrane diffusion scrubber while 1 mM HCl is maintained stationary in the scrubber. After a preselected preconcentration time (typically, 5-10 min), a valve is opened to allow the scrubber liquid to flow by gravity over an electrochemical H(2)O(2) sensor for a brief period. The miniature flow-over sensor consists of a Pt/Rh wire working electrode and a Pt wire counter electrode wound respectively on separate segments of a Nafion solid polymer electrolyte tubing supported on a Ag/AgCl wire reference electrode. A simple electronic interface and a personal computer are used to control and record the electrochemical measurement. The liquid phase detection limit for this sensor is ～30 nM H(2)O(2) in the anodic oxidation mode. For a 9 min gas sample preconcentration period, the LOD (S/N = 3 criterion) is 0.11 ppbv H(2)O(2)(g). Ambient H(2)O(2) data obtained with this instrument were in excellent agreement with those obtained by an established fluorometric technique in a blind intercomparison.     

A novel magnetic trap for spin-polarized hydrogen

A microwave trap for spin-polarized atomic hydrogen has the important advantage of trapping very cold atoms in the ground hyperfine states at the high densities necessary for BEC. By first cooling atoms in a static trap the shallow microwave trap can be loaded. We report the construction of such a hybrid trap in this article.     

An electrochemical sensing platform based on a new copper complex for the determination of hydrogen peroxide and nitrite

Abstract

A new copper(II) complex [Cu(C₁₂H₂₃N₃)₄Br₂·2H₂O] was synthesized and its structure was characterized by x-ray crystallography and elemental analysis. The copper atom had a distorted octahedron coordination involving two bromide anions and four nitrogen atoms from the 1-decyl-1H-[1,2,4]triazole ligands. Moreover, the electrochemical behavior and electrocatalysis of the carbon paste electrode (Cu-CPE) bulk-modified by the complex have been studied in detail. The Cu-CPE showed excellent electrocatalytic activities toward the reduction of hydrogen peroxide and nitrite, and the detection limit was much lower than that mentioned in earlier reports. This bulk-modified CPE has good reproducibility, long-term stability and surface renewability, which appear promising for constructing chemical sensors.     

Use of an amorphous iron oxide hydrated as catalyst for hydrogen peroxide oxidation of ferulic acid in water

The abatement of ferulic acid (FA), a polyphenolic constituent of olive mill wastewater, is studied in the pH range 5.0-7.0 by using hydrogen peroxide and an amorphous iron oxide as catalyst. The effect of pH, catalyst load, hydrogen peroxide and substrate starting concentrations is assessed during the investigation. A suitable reaction scheme is developed and used to build a mathematical model which satisfactorily describes the system's behavior. Kinetic constants for the proposed scheme as well as the total active site concentration of the catalyst in the studied pH range are estimated. The occurrence of internal mass-transfer limitation for the adopted granulometric fraction of the catalyst is demonstrated.     

Polypyrrole-based optical probe for a hydrogen peroxide assay

An optical sensing probe has been developed by taking advantage of the polypyrrole (PPy) chromophore. The absorbance of the oxidation product of pyrrole, i.e., solubilized PPy colloids, is shown to be directly proportional to the concentration of hydrogen peroxide, when H2O2 is used as an oxidant for pyrrole in the presence of a surfactant, sodium dodecyl sulfate, and Fe(II) in a slightly acidic aqueous solution. Based on this result, a new optical sensing method has been developed for the determination of H2O2. The probe has also been applied to optical sensing of ethanol by biocatalyzed generation of H2O2 in the presence of O2, ethanol, and alcohol oxidase. The novel methodology is expected to provide a general protocol for the determination of H2O2 as well as for numerous other oxidase-based reactions producing H2O2 as a product.     

碳基电催化材料选择性合成过氧化氢研究进展

过氧化氢(H2O2)作为一种环境友好型绿色氧化剂,在健康护理、污水处理和化学合成等领域均有广泛应用.近年来,其作为零碳型储氢材料在长期储能领域的应用前景也广受关注.当前H2O2的工业化生产主要依赖蒽醌工艺,步骤复杂、废水废气排放量大,且生产和运输过程存在安全隐患.电催化合成H2O2是近年来兴起的研究热点,通过利用清洁能...     

A novel ultrasonic sensing system for autonomous mobile systems

This paper presents a novel ultrasonic sensing system for autonomous mobile systems. We describe how wide-angled ultrasonic transducers can be used to obtain substantial information from the environment. This can be achieved by exploiting the overlapping of detection cones from neighbor sensors and by receiving cross echoes between them. The ultrasonic sensing system also allows the detection of multiple echoes from different echo paths for each sensor. In this way, a significantly higher number of echoes can be obtained in comparison to conventional ultrasonic sensing systems for mobile robots. In order to benefit from the increased sensor information, algorithms for adequate data post-processing are required. In this context, we describe how an environment model can be created from ultrasonic sensor data.     

A novel solid-stabilized emulsion approach to CuO nanostructured microspheres

Nanostructured CuO microspheres were prepared by a novel solid-stabilized emulsion for the first time. SEM, TEM, XRD, size analysis and BET measurement were used to characterize the CuO microspheres. The average diameter of the CuO microspheres was 2.8 μm. The surfaces of the CuO microspheres were made of pin-like nanostructures with a pin diameter of 95 nm and a pin length of at least 600 nm. The XRD analysis indicated that the CuO nanostructured microspheres were of monoclinic lattice. The specific surface area of the CuO nanostructured microspheres was about 56.8 m²/g. A mechanism for the formation of the CuO microspheres with nanostructured surfaces was proposed.