Silver microspheres for application as hydrogen peroxide sensor

In this paper, we synthesized flowerlike silver microspheres with nanostructures by simply reducing silver nitrate by ascorbic acid in the presence of PVP. The structure was investigated by SEM. The chemical composition was determined by EDX, XRD and XPS. Recent studies on hydrogen peroxide sensor based on silver nanoparticles inspired us to examine the electrocatalytic activity of prepared microspheres. This electrochemical sensor exhibited good electrocatalytic activity towards the reduction of H₂O₂ in 0.2 M phosphate buffer solution (pH 7.0), and the detection limit of H₂O₂ was found to be 1.2 μM, which was lower than certain enzyme-based biosensors.     

Activation of titanium electrodes for voltammetric detection of oxygen and hydrogen peroxide in alkaline media

Bright, freshly-polished Ti electrodes give minimal cathodic response for O₂ and H₂O₂ in 1.0 M NaOH. However, the response is increased gradually by repeated application of a triangular waveform within the approximate potential limits of O₂ response (ca. −1.5 to −0.7 V vs. SCE). This same voltammetric pretreatment applied for excessive periods results in formation of golden films on the Ti surfaces that are active for reduction of O₂ and H₂O₂. Levich plots of cathodic current for O₂ and H₂O₂ at rotated golden-Ti disk electrodes in 1.0 M NaOH (−1.35 V) are linear over a large range of rotational velocity (42 to 513 rad s⁻¹), a behavior considered to be indicative of fast heterogeneous kinetics. Ring-disk data demonstrate that a small amount of H₂O₂ is produced throughout the potential region for O₂ reduction and H₂O₂ is concluded to be an intermediate product in the O₂-reduction mechanism. These observations are consistent with those reported previously for single-crystal TiO₂ electrodes.     

A novel nonenzymatic hydrogen peroxide sensor based on multi-wall carbon nanotube/silver nanoparticle nanohybrids modified gold electrode

A novel strategy to fabricate hydrogen peroxide (H₂O₂) sensor was developed based on multi-wall carbon nanotube/silver nanoparticle nanohybrids (MWCNT/Ag nanohybrids) modified gold electrode. The process to synthesize MWCNT/Ag nanohybrids was facile and efficient. In the presence of carboxyl groups functionalized multi-wall carbon nanotubes (MWCNTs), silver nanoparticles (Ag NPs) were in situ generated from AgNO₃ aqueous solution and readily attached to the MWCNTs convex surfaces at room temperature, without any additional reducing reagent or irradiation treatment. The formation of MWCNT/Ag nanohybrids product was observed by transmission electron microscope (TEM), and the electrochemical properties of MWCNT/Ag nanohybrids modified gold electrode were characterized by electrochemical measurements. The results showed that this sensor had a favorable catalytic ability for the reduction of H₂O₂. The resulted sensor could detect H₂O₂ in a linear range of 0.05-17 mM with a detection limit of 5 × 10⁻⁷ M at a signal-to-noise ratio of 3. The sensitivity was calculated as 1.42 μA/mM at a potential of −0.2 V. Additionally, it exhibited good reproducibility, long-term stability and negligible interference of ascorbic acid (AA), uric acid (UA), and acetaminophen (AP).     

Electrode modified with a composite film of ZnO nanorods and Ag nanoparticles as a sensor for hydrogen peroxide

A conducting fluorine-doped tin oxide (FTO) electrode, first modified with zinc oxide nanorods (ZnONRs) and subsequently attached with photosynthesized silver nanoparticles (AgNPs), designated as AgNPs/ZnONRs/FTO electrode, was used as an amperometric sensor for the determination of hydrogen peroxide. The first layer (ZnONRs) was obtained by chemical bath deposition (CBD), and was utilized simultaneously as the catalyst for the photoreduction of Ag ions under UV irradiation and as the matrix for the immobilization of AgNPs. The aspect ratio of ZnONRs to be deposited was optimized by controlling the number of their CBDs to render enough surface area for Ag deposition, and the amount of AgNPs to be attached was controlled by adjusting the UV-irradiation time. The immobilized AgNPs showed excellent electrocatalytic response to the reduction of hydrogen peroxide. The resultant amperometric sensor showed 10-fold enhanced sensitivity for the detection of H₂O₂, compared to that without AgNPs, i.e., only with a layer of ZnONRs. Amperometric determination of H₂O₂ at −0.55 V gave a limit of detection of 0.9 μM (S/N = 3) and a sensitivity of 152.1 mA M⁻¹ cm⁻² up to 0.983 mM, with a response time (steady-state, t₉₅) of 30-40 s. The selectivity of the sensor was investigated against ascorbic acid (AA) and uric acid (UA). Energy dispersive X-ray (EDX) analysis, transmission electron microscopic (TEM) image, X-ray diffraction (XRD) patterns, cyclic voltammetry (CV), and scanning electron microscopic (SEM) images were utilized to characterize the modified electrode. Sensing properties of the modified electrode were studied both by CV and amperometric analysis.     

Probing traces of hydrogen peroxide by use of a biosensor based on mediator-free DNA and horseradish peroxidase immobilized on silver nanoparticles

A new electrochemical biosensor for determination of hydrogen peroxide (H₂O₂) has been developed by immobilizing horseradish peroxidase (HRP) on silver colloids (nanosilver) and use of a DNA-functionalized interface. In the presence of the DNA and the nanosilver the immobilized HRP gives a pair of well-defined redox peaks with an electron-transfer rate constant of 3.27 ± 0.91 s⁻¹ in pH 7.0 PBS. The presence of DNA also provides a biocompatible microenvironment for enzyme molecules, greatly amplifies the amount of HRP molecules immobilized on the electrode surface, and improves the sensitivity of the biosensor. Under optimum conditions the biosensor has electrocatalytic activity in the reduction of hydrogen peroxide with linear dependence on H₂O₂ concentration in the range 1.5 × 10⁻⁶ to 2.0 × 10⁻³ mol L⁻¹; the detection limit is 5.0 × 10⁻⁷ mol L⁻¹ at a signal-to-noise ratio of 3. The value of HRP in the composite membrane was found to be 1.62 mmol L⁻¹. These results suggest that the properties of the complex film, with its bioelectrochemical catalytic activity, could make it useful for development of bioelectronic devices and for investigation of protein electrochemistry at functional interfaces.     

Biosensor for determination of hydrogen peroxide based on catalase activity of human erythrocytes

A hydrogen peroxide biosensor based on human erythrocytes is described. Erythrocytes are retained on the surface of an oxygen electrode by a semipermeable membrane. The response is based on the catalase activity of the erythrocytes. The sensitivity of 10^?4 mol 1^?1 and linearity from 1.5×10^?4 to 5×10^?3 mol^?1 are comparable to those of analogous enzyme biosensors for hydrogen peroxide determination. The greatest advantages of this biosensor are its easy preparation and a lifetime of 2 months together with good reproducibility (relative standard deviation <5%) and selectivity; only ascorbic acid appeared to interfere with the measurements.     

Dendrimer-rhodium nanoparticle modified glassy carbon electrode for amperometric detection of hydrogen peroxide

Metallic nanoparticles of rhodium were prepared by using the newly synthesized N,N-bis-succinamide-based dendrimer as stabilizers. The Rh nanoparticles were spherical shaped with a particle size of ∼2 nm. The dendrimer Rh-encapsulated nanoparticles (Rh-DENs) were immobilized on glassy carbon electrode (GCE) and their electrocatalytic activity towards hydrogen peroxide reduction was investigated using cyclic voltammetry and chronoamperometry. The Rh-DENs modified GCE showed excellent electrocatalytic activity for hydrogen peroxide reduction reactions. The steady-state cathodic current response of the modified electrode at −0.3 V (vs SCE) in phosphate buffer (pH 7.0) showed a linear response to hydrogen peroxide concentration ranging from 8 to 30 μM with a detection limit and sensitivity of 5 μM and 0.03103 × 10⁻⁶ A μM⁻¹, respectively.     

Polyethyleneimine-capped silver nanoclusters as a fluorescence probe for sensitive detection of hydrogen peroxide and glucose

In this work, we utilized polyethyleneimine-capped silver nanoclusters (PEI-Ag nanoclusters) to develop a new fluorometric method for the determination of hydrogen peroxide and glucose with high sensitivity. The PEI-Ag nanoclusters have an average size of 2 nm and show a blue emission at 455 nm. The photostable properties of the PEI-Ag nanoclusters were examined. The fluorescence of the PEI-Ag nanoclusters could be particularly quenched by H₂O₂. The oxidization of glucose by glucose oxidase coupled with the fluorescence quenching of PEI-Ag nanoclusters by H₂O₂ can be used to detect glucose. Under optimum conditions, the fluorescence intensity quenched linearly in the range of 500 nM–100 μM with high sensitivity. The detection limit for H₂O₂ was 400 nM. And a linear correlation was established between fluorescence intensity (F₀ − F) and concentration of glucose in the range of 1.0 × 10⁻⁶ to 1.0 × 10⁻⁵ M and 1.0 × 10⁻⁵ to 1.0 × 10⁻³ M with a detection limit of 8.0 × 10⁻⁷ M. The method was used for the detection of glucose in human serum samples with satisfactory results. Furthermore, the mechanism of sensitive fluorescence quenching response of Ag nanoclusters to glucose and H₂O₂ has been discussed.     

Effects of microstructure of carbon nanofibers for amperometric detection of hydrogen peroxide

Carbon nanofibers (CNFs) with three microstructures, including platelet-carbon nanofibers (PCNFs), fish-bone-carbon nanofibers (FCNFs), and tube-carbon nanofibers (TCNFs), were synthesized, characterized, and evaluated for electrochemical sensing of hydrogen peroxide. The CNFs studied here show microstructures with various stacked morphologies. The sizes and graphite-layer ordering of the CNFs can be well controlled. Glassy carbon (GC) electrodes modified by CNFs were fabricated and compared for amperometric detection of hydrogen peroxide. Sensors based on PCNFs/GC, FCNFs/GC, and TCNFs/GC were used in the amperometric detection of H₂O₂ in solution by applying a potential of +0.65 V versus Ag/AgCl at the working electrode. The highest electrocatalytic performance was observed for PCNFs/GC among the three types of hydrogen peroxide sensors. The amperometric response of PCNFs/GC retained over 90% of the initial current of the first day up to 21 days. The linear range is from 1.80 × 10⁻⁴ to 2.62 × 10⁻³ M with a correlation coefficient larger than 0.999 and with a detection limit of 4.0 μM H₂O₂ (S/N = 3). The relative standard deviation for detecting 1.80 × 10⁻⁴ M H₂O₂ (N = 8) is 2.1% with an average response of 0.64 μA. The significant diversity of electrocatalytic activity of the CNFs toward the oxidation of hydrogen peroxide may result from the difference of morphologies, textural properties, and crystalline structures.     

Fabrication of Pt/polypyrrole hybrid hollow microspheres and their application in electrochemical biosensing towards hydrogen peroxide

Pt/polypyrrole (PPy) hybrid hollow microspheres were successfully prepared by wet chemical method via Fe₃O₄ template and evaluated as electrocatalysts for the reduction of hydrogen peroxide. The as-synthesized products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD), inductive coupled plasma emission spectrum (ICP) and Fourier-transform infrared spectra (FTIR) measurements. The results exhibited that ultra-high-density Pt nanoparticles (NPs) were well deposited on the PPy shell with the mean diameters of around 4.1 nm. Cyclic voltammetry (CV) results demonstrated that Pt/PPy hybrid hollow microspheres, as enzyme-less catalysts, exhibited good electrocatalytic activity towards the reduction of hydrogen peroxide in 0.1 M phosphate buffer solution (pH = 7.0). The composite had a fast response of less than 2 s with linear range of 1.0-8.0 mM and a relatively low detection limit of 1.2 μM (S/N = 3). The sensitivity of the sensor for H₂O₂ was 80.4 mA M⁻¹ cm⁻².     

Ferricyanide immobilized within organically modified MCM-41; application for electrocatalytic reduction of hydrogen peroxide

Carbon paste electrode modified with aminated Mobil Catalytic Material Number 41 (MCM-41) was prepared and used for immobilization of K₃[Fe(CN)₆] in acidic medium, and then electrochemical behavior of modified electrode containing ferricyanide was studied in detail, including pH-dependence and scan rate effect. Cyclic voltammetry studies showed that the electrode reaction is a surface-controlled process at the scan rate range from 5 to 60 mV s⁻¹. Also, the electrocatalytic behavior of modified electrode toward the reduction of H₂O₂ is reported and the effect of pH on catalytic peak current was discussed. According to experimental results, with increasing solution pH, the catalytic effect of this modified electrode is decreased. Catalytic reduction current of H₂O₂ increases linearly with its concentration. It has been demonstrated that ferricyanide immobilized on the aminated MCM-41 is a stable catalyst for the electrocatalytic reduction of H₂O₂.     

Indirect catalytic epoxidation with hydrogen peroxide electrogenerated in ionic liquids

Hydrogen peroxide was generated in room temperature ionic liquids by electrolysis, which was then used for the epoxidation of lipophilic alkenes under a carbon dioxide-saturated environment and in the presence of catalytic amount of manganese salt. ¹³C NMR showed that the active peroxymonocarbonate (HCO₄⁻) was generated from the mixture of H₂O₂, CO₂, and water in the ionic liquids. Most lipophilic alkenes were selectively epoxidized within 4-5 h. The ionic liquids can be recovered and reused without any deterioration in the performance.     

Grape tissue-based electrochemical sensor for the determination of hydrogen peroxide

The use of grape tissue as a source of catalase for the determination of hydrogen peroxide is reported. A slice of grape tissue attached to the membrane of a Clark-type oxgen sensor was used to monitor the oxidation of hydrogen peroxide by catalase. At the steady state, the sensor responds linearly to hydrogen peroxide in the concentration range 1 × 10^?5–5 × 10^?4 M. The response time (T₉₀) was of the order of 1 min for this sensor. No interference was observed from ethanol, amino acids, glucose and lactic acid. The long-term stability of the grape tissue sensor was much better than previously reported immobilized enzyme and liver tissue-based hydrogen peroxide sensors.     

Immobilization of horseradish peroxidase to a nano-Au monolayer modified chitosan-entrapped carbon paste electrode for the detection of hydrogen peroxide

A procedure for fabricating an enzyme electrode has been described based on the effective immobilization of horseradish peroxidase (HRP) to a nano-scaled particulate gold (nano-Au) monolayer modified chitosan-entrapped carbon paste electrode (CCPE). The high affinity of chitosan entrapped in CCPE for nano-Au associated with its amino groups has been utilized to realize the use of nano-Au as an intermediator to retain high bioactivity of the enzyme. Hydrogen peroxide (H₂O₂) was determined in the presence of hydroquinone as a mediator to transfer electrons between the electrode and HRP. The HRP immobilized on nano-Au displayed excellent electrocatalytical activity to the reduction of H₂O₂. The effects of experimental variables such as the operating potential of the working electrode, mediator concentration and pH of measuring solution were investigated for optimum analytical performance by using an amperometric method. The enzyme electrode provided a linear response to hydrogen peroxide over a concentration range of 1.22×10⁻⁵-2.43×10⁻³ mol l⁻¹ with a sensitivity of 0.013 A l mol⁻¹ cm⁻² and a detection limit of 6.3 μmol l⁻¹ based on signal per noise =3. The apparent Michaelis-Menten constant (K_m^app) for the sensor was found to be 0.36 mmol l⁻¹. The lifetime, fabrication reproducibility and measurement repeatability were evaluated with satisfactory results. The analysis results of real sample by this sensor were in satisfactory agreement with those of the potassium permanganate titration method.     

Electrodeposited Silver Nanoparticles on Carbon Ionic Liquid Electrode for Electrocatalytic Sensing of Hydrogen Peroxide

Silver nanoparticles (narrowly dispersed in diameter) were electrodeposited on carbon ionic liquid electrode (CILE) surface using a two‐step potentiostatic method. Potentiostatic double pulse technique was used as a suitable and simple method for controlling the size and morphologies of silver nanoparticles electrodeposited on CILE. The obtained silver nanoparticles deposited on CILE surface showed excellent electrocatalytic activity (low overpotential of ?0.35 V vs. Ag/AgCl) towards reduction of hydrogen peroxide. A linear dynamic range of 2–200 μM with an experimental detection limit of 0.7 μM (S/N=3) and reproducibility of 4.1% (n=5) make the constructed sensor suitable for peroxide determination in aqueous solutions.     

Viologen-terminated polyamidoamine (PAMAM) dendrimer encapsulated with gold nanoparticles for nonenzymatic determination of hydrogen peroxide

The development of an accurate and low-cost monitoring technique for hydrogen peroxide (H₂O₂) is a crucial demand in environment, food industry, medicine and biology. Herein, we report the design and synthesis of viologen terminated second (G2.0) and third generation (G3.0) poly(amidoamine) PAMAM dendrimers, followed by encapsulation with gold nanoparticles to form G2.0 and G3.0 Vio-PAMAM-AuNPs. The G2.0 and G3.0 Vio-PAMAM-AuNPs were deposited over glassy carbon electrode (GCE) to form G2.0 and G3.0 Vio-PAMAM-AuNPs/GCE modified electrodes, respectively. The electrochemical behavior of G2.0 and G3.0 Vio-PAMAM-AuNPs/GCEs were investigated using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Both the G2.0 and G3.0 Vio-PAMAM-AuNPs/GCEs showed a pair of well-defined redox peaks in 0.1 M phosphate buffer corresponding to the redox behavior of viologen V²⁺?V^?+ radical. G3.0 Vio-PAMAM-AuNPs/GCE has shown a higher current response than that of the G2.0 Vio-PAMAM-AuNPs/GCE and further the G3.0 Vio-PAMAM-AuNPs/GCE demonstrated impressive electrocatalytic activity towards reduction of H₂O₂, based on which a nonenzymatic sensor for the detection of H₂O₂ has been developed. The developed nonenzymatic sensor has displayed excellent performance towards H₂O₂ detection in the broad linear range of 0.1 mM – 6.2 mM with a low detection limit of 27 μM and high sensitivity of 202.7 μA mM^?1 cm^?2. The G3.0 Vio-PAMAM-AuNPs/GCE modified electrode with its extensive dendritic structure creating tailored sanctuary to accommodate a large number of viologen mediator and AuNPs exhibited good operational and long term stability and further the quantification of H₂O₂ in real samples has been verified by standard addition method.     

GO-PtNi hybrid nanoenzyme mimics for the colorimetric detection of hydrogen peroxide

GO-PtNi nanocomposites with intrinsic peroxidase-like activity were obtained through one-pot synthesis. The hybrid nanomaterial was characterized by transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). The peroxidase-like activity of GO-PtNi nanocomposites was found to be dependent on pH, temperature, the concentration of enzyme and substrates. The optimal conditions for the catalytic activity of GO-PtNi nanocomposites were determined. Based on these findings, a simple and sensitive colorimetric method for the detection of H₂O₂ by using GO-PtNi nanocomposites and 3,3′,5,5′-tetramethylbenzidine (TMB) was developed. The linear range was from 0.08 to 1.5 mM with a detection limit of 5 μM.     

Localized surface plasmon resonance sensor for simultaneous kinetic determination of peroxyacetic acid and hydrogen peroxide

A new sensor for simultaneous determination of peroxyacetic acid and hydrogen peroxide using silver nanoparticles (Ag-NPs) as a chromogenic reagent is introduced. The silver nanoparticles have the catalytic ability for the decomposition of peroxyacetic acid and hydrogen peroxide; then the decomposition of them induces the degradation of silver nanoparticles. Hence, a remarkable change in the localized surface plasmon resonance absorbance strength could be observed. Spectra-kinetic approach and artificial neural network was applied for the simultaneous determination of peroxyacetic acid and hydrogen peroxide. Linear calibration graphs were obtained in the concentration range of (8.20 × 10⁻⁵ to 2.00 × 10⁻³ mol L⁻¹) for peroxyacetic acid and (2.00 × 10⁻⁵ to 4.80 × 10⁻³ mol L⁻¹) for hydrogen peroxide. The analytical performance of this sensor has been evaluated for the detection of simultaneous determination of peroxyacetic acid and hydrogen peroxide in real samples.     

A peroxidase-tetrathiafulvalene biosensor based on self-assembled monolayer modified Au electrodes for the flow-injection determination of hydrogen peroxide

The construction and performance under flow-injection conditions of an integrated amperometric biosensor for hydrogen peroxide is reported. The design of the bioelectrode is based on a mercaptopropionic acid (MPA) self-assembled monolayer (SAM) modified gold disk electrode on which horseradish peroxidase (HRP, 24.3 U) was immobilized by cross-linking with glutaraldehyde together with the mediator tetrathiafulvalene (TTF, 1 μmol), which was entrapped in the three-dimensional aggregate formed.

The amperometric biosensor allows the obtention of reproducible flow injection amperometric responses at an applied potential of 0.00 V in 0.05 mol L⁻¹ phosphate buffer, pH 7.0 (flow rate: 1.40 mL min⁻¹, injection volume: 150 μL), with a range of linearity for hydrogen peroxide within the 2.0 × 10⁻⁷–1.0 × 10⁻⁴ mol L⁻¹ concentration range (slope: (2.33 ± 0.02) × 10⁻² A mol⁻¹ L, r = 0.999). A detection limit of 6.9 × 10⁻⁸ mol L⁻¹ was obtained together with a R.S.D. (n = 50) of 2.7% for a hydrogen peroxide concentration level of 5.0 × 10⁻⁵ mol L⁻¹. The immobilization method showed a good reproducibility with a R.S.D. of 5.3% for five different electrodes. Moreover, the useful lifetime of one single biosensor was estimated in 13 days.

The SAM-based biosensor was applied for the determination of hydrogen peroxide in rainwater and in a hair dye. The results obtained were validated by comparison with those obtained with a spectrophotometric reference method. In addition, the recovery of hydrogen peroxide in sterilised milk was tested.     

Reduction of oxygen and hydrogen peroxide on electrodes with adsorbed monolayer of aliphatic compounds

Cathodic reduction of oxygen and hydrogen peroxide on amalgamated platinum electrodes, which are coated with monolayers of long-chain aliphatic compounds cetyl alcohol (CA) and stearic acid (SA), is retarded as compared with the same reactions on clean mercury (or amalgam) surface. The oxygen reduction kinetics differ from that on mercury. The difference is explained by that oxygen diffuses into the monolayer and is reduced in it at a certain distance from the metal surface and only at the limiting current the reaction is forced onto the monolayer surface. In contrast to the oxygen reduction, the hydrogen peroxide reduction kinetics on electrodes with SA and CA monolayers is much closer to that on mercury, but with some quantitative distinctions. All results favor the H₂O₂ reduction at the monolayer/solution interface. The difference in the behavior of O₂ and H₂O₂ is explained by different polarity of these molecules: it is significantly more difficult to penetrate the hydrocarbon monolayer for polar H₂O₂ molecule than for nonpolar O₂ molecule.