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.     

Electrochemical Determination of Hydrogen Peroxide Using a Glassy Carbon Electrode Modified with Three-Dimensional Copper Hydroxide Nanosupercages and Electrochemically Reduced Graphene Oxide

Three-dimensional copper hydroxide nanosupercages and electrochemically reduced graphene oxide were used to modify the glassy carbon electrode for the selective determination of hydrogen peroxide. The morphology and electrochemistry properties of copper hydroxide nanosupercage/electrochemically reduced graphene oxide/glassy carbon electrode were characterized using transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectra, Raman spectra, cyclic voltammetry, and electrochemical impedance spectroscopy. The resulting copper hydroxide nanosupercage/electrochemically reduced graphene oxide/glassy carbon electrode showed favorable performance for the electrocatalytic reduction of hydrogen peroxide. The amperometric current–time curve of the electrochemical sensor exhibited a wide linear range from 0.5 to 1030?µM with a limit of detection of 0.23?µM at a signal-to-noise ratio of three. Moreover, the sensor provided favorable selectivity, reproducibility, and stability and was used for the determination of H₂O₂ in tap water.     

A Non‐Enzymatic Hydrogen Peroxide Sensor Based on Ag/MnOOH Nanocomposites

A novel non‐enzymatic sensor based on Ag/MnOOH nanocomposites was developed for the detection of hydrogen peroxide (H₂O₂). The H₂O₂ sensor was fabricated by immobilizing Ag/MnOOH nanocomposites on a glassy carbon electrode (GCE). The morphology and composition of the sensor surface were characterized using scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, transmission electron microscopy and X‐ray diffraction spectroscopy. The electrochemical investigation of the sensor indicates that it possesses an excellent electrocatalytic property for H₂O₂, and could detect H₂O₂ in a linear range from 5.0 µM to 12.8 mM with a detection limit of 1.5 µM at a signal‐to‐noise ratio of 3, a response time of 2 s and a sensitivity of 32.57 µA mM^?1 cm^?2. Additionally, the sensor exhibits good anti‐interference. The good analytical performance, low cost and straightforward preparation method made this novel electrode material promising for the development of effective non‐enzymatic H₂O₂ sensor.     

Graphene–Pt nanocomposite for nonenzymatic detection of hydrogen peroxide with enhanced sensitivity

A sensitive hydrogen peroxide (H₂O₂) sensor was fabricated based on graphene–Pt (GN–Pt) nanocomposite. The GN–Pt was synthesized by photochemical reduction of K₂PtCl₄ on GNs, and characterized by atomic force microscope (AFM), transmission electron microscope (TEM), and energy-dispersive X-ray spectroscopy (EDS). Electrochemical investigations indicated that the GN–Pt exhibited a high peak current and low overpotential towards the reduction of H₂O₂. The GN–Pt modified glass carbon electrode displayed a wide linear range (2–710 μM), low limit of detection (0.5 μM) and good selectivity for detection of H₂O₂ with a much higher sensitivity than that of Pt nanoparticles or graphene modified electrode.     

Nonenzymatic amperometric sensor of hydrogen peroxide and glucose based on Pt nanoparticles/ordered mesoporous carbon nanocomposite

A simple and facile synthetic method to incorporate Pt nanoparticles inside the mesopores of ordered mesoporous carbons (OMCs) is reported. The Pt/OMCs nanocomposite was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and nitrogen adsorption-desorption. The results show that the incorporation of Pt nanoparticles inside the pores of OMCs does not change the highly ordered two-dimensional hexagonal mesostructure of OMCs matrix. Nonenzymatic amperometric sensor of hydrogen peroxide and glucose based on the Pt/OMCs nanocomposite-modified glassy carbon (GC) electrode is developed. Compared with the original OMCs-modified electrode, the Pt/OMCs-modified electrode displays improved current response towards hydrogen peroxide and gives linear range from 2 to 4212 μM. At an applied potential of −0.08 V, the Pt/OMCs nanocomposite gives linearity in the range of 0.5-4.5 mM glucose in neutral buffered saline solution. This glucose sensor also exhibits good ability of anti-interference to electroactive molecules. The combination the unique properties of Pt nanoparticles and the ordered mesostructure of OMCs matrix guarantees the enhanced response for hydrogen peroxide and glucose.     

Sensitive Electrochemical Determination of Hydrogen Peroxide Using Copper Nanoparticles in a Polyaniline Film on a Glassy Carbon Electrode

Rapid and accurate determination of hydrogen peroxide is necessary in biochemistry and environmental science. In this paper, a sensitive hydrogen peroxide electrochemical sensor was developed by cyclic voltammetry deposition of polyaniline–copper nanocomposite film on a glassy carbon electrode. The synthesized polyaniline/Cu composites were characterized by scanning electron microscopy and X-ray diffraction. With a typical working potential of 0.4?V (versus Ag/AgCl) and a pH value of 6.0, the prepared electrochemical sensor achieved linear range of 1.0–500?µM for hydrogen peroxide detection. A relative standard deviation of 4.9% for n?=?7 and 10.0?µM of H₂O₂ and a limit of detection of 0.33?µM at a signal-to-noise ratio?=?3 were observed. The sensor was successfully used for the analysis of tap water, and a spiked recovery of 93.0?±?2.1% was obtained, further confirming the sensor’s accuracy and feasibility.     

Nickel oxide hydroxide/platinum double layers modified n-silicon electrode for hydrogen peroxide determination

A novel photo-electrochemical and non-enzymatic hydrogen peroxide (H₂O₂) sensor was fabricated by electrochemically cathodic plating nickel hydroxide (Ni(OH)₂) on platinum films coated n-silicon (Pt/n-n⁺-Si electrode). Nickel oxide hydroxide (Ni(OH)₂-NiOOH) films on the Pt/n-n⁺-Si electrode were formed by cyclic voltammetry in 0.2 M KOH solution. The morphology and composition of Ni(OH)₂-NiOOH film were characterized via scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. A two-electrode cell based on Ni(OH)₂-NiOOH/Pt/n-n⁺-Si electrode and a platinum counter has been used for determination of H₂O₂ in the absence of reference electrode by photocurrent measurement at a zero bias. In these conditions a sensitivity of 96.9 μA mM^?1 cm^?2 and a linear response range from 0.02 up to 0.16 mM with a determination limit (S/N?=?3) of 5.4 μM were achieved in KOH solution at pH 13.3. In addition, the electrode also exhibited superior stability, anti-interference and selectivity.     

Hydrogen peroxide sensor based on a stainless steel electrode coated with multi-walled carbon nanotubes modified with magnetite nanoparticles

Multi-walled carbon nanotubes (MWCNTs) were decorated with magnetite (Fe₃O₄) nanoparticles and then used to modify a stainless steel electrode. The Fe₃O₄/MWCNTs composite was characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and X-ray diffraction patterns. Electrochemical properties of the modified electrode revealed a substantial catalytic activity for the reduction of hydrogen peroxide. The relationship between peak current and the concentration of hydrogen peroxide was linear in the range from 0.06?mmol?L^?1 to 0.36?mmol?L^?1, and the lowest detectable concentration is 0.01?mmol·L^?1 (S/N?=?3). The modified stainless steel electrode displays excellent stability.

Ag nanoparticles decorated Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/chitosan nanocomposite: synthesis,characterization and application toward electrochemical sensing of hydrogen peroxide

We studied a rapid, sensitive and selective amperometric sensor for determination of hydrogen peroxide by electrodeposited Ag NPs on a modified glassy carbon electrode (GCE). The modified GCE was constructed through a step by step modification of magnetic chitosan functional composite (Fe₃O₄–CH) and high-dispersed silver nanoparticles on the surface. The resulted Ag@Fe₃O₄–CH was characterized by various analytical methods including Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy and cyclic voltammetry. The proposed sensor employed Ag@Fe₃O₄–CH/GCE as the working electrode with a linear current response to the hydrogen peroxide concentration in a wide range from 0.01 to 400 µM with a low limit of detection (LOD = 0.0038 µM, S/N = 3). The proposed sensor showed superior reproductivity, sensitivity and selectivity for the detection of hydrogen peroxide in environmental and clinical samples.     

A general electrochemical approach to deposition of metal hydroxide/oxide nanostructures onto carbon nanotubes

This communication describes a new and relatively general electrochemical approach to the deposition of transition metal hydroxide/oxide nanostructures onto multi-walled carbon nanotubes (MWNTs) based on the precipitation of metal hydroxide/oxide nanostructures onto MWNTs by increasing the local pH values at the electrode/electrolyte interface induced by the proton-consuming electrochemical reduction of hydrogen peroxide (H₂O₂). The results obtained with cyclic voltammetry, scanning electron microscopy, and X-ray photoelectron spectroscopy of the synthetic nanocomposites substantially suggest the deposition of the metal hydroxides/oxides onto MWNTs induced by the electrochemical reduction of H₂O₂. This study essentially offers a facile but effective and relatively general electrochemical approach to the synthesis of the nanocomposites consisting of metal hydroxides/oxides and MWNTs.     

A novel photoelectrochemical hydrogen peroxide sensor based on nickel(II)-potassium hexacyanoferrate-graphene hybrid materials modified n-silicon electrode

A platinum (Pt) film coated n-silicon (Pt/n-n⁺-Si) was modified with nickel(II)-potassium hexacyanoferrate (NiHCF)-graphene sheets (GS) hybrid and used as a photo-electrochemical (PEC) sensor for non-enzyme hydrogen peroxide (H₂O₂) detection. A NiHCF film was deposited on the surface of GS/Pt/n-n⁺-Si electrode by chemical method. The structure and composition of the NiHCF film was characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). PEC behavior of the NiHCF-GS/Pt/n-n⁺-Si electrode was investigated using cyclic voltammetry (CV) under illumination. The modified electrode has been used as PEC sensor for H₂O₂ detection with a linear range of 2.0 × 10^?6–2.9 × 10^?3 M and a detection limit of 1.0 × 10^?6 M at a signal-to-noise ratio of 3 in a two-electrode cell with a Pt plate as counter electrode. The characteristics of GS layer have been discussed in both the improvement of sensibility and selectivity.     

MnO2/Graphene Nanocomposites for Nonenzymatic Electrochemical Detection of Hydrogen Peroxide

MnO₂/graphene nanocomposites with different morphologies were synthesized and the petal‐shaped nanosheet MnO₂/graphene composite was developed as an electrode material for nonenzymatic hydrogen peroxide (H₂O₂) sensor. The morphology, structure, composition, and hydrophilicity of the resulting products were characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), and the contact angle tests. In addition, the fabricated MnO₂/graphene composites could be used as catalysts for the electrochemical oxidation of H₂O₂. Cyclic voltammogram (CV) experiments indicated that MnO₂/graphene‐modified electrode showed good electrocatalytic activity towards both the oxidation and reduction of H₂O₂ in a neutral environment. Amperometric response results illustrated that this nonenzymatic sensor had excellent anti‐interference ability and displayed two linear ranges from 10 to 90 µM and from 0.2 to 0.9 mM with a detection limit of 2 µM.     

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.

Highly accessible Pt nanodots homogeneously decorated on Au nanorods surface for sensing

Some nanostructures are reported to possess enzyme-mimetic activities similar to those of natural enzymes. Herein, highly-dispersed Pt nanodots on Au nanorods (HD- PtNDs@AuNRs) with mimetic peroxidase activity were designed as an active electrode modifier for fabrication of a hydrogen peroxide (H₂O₂) electrochemical sensor. The HD-PtNDs@AuNRs were synthesized by a seed-mediated growth approach and confirmed by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and UV–vis spectroscopy. The electrochemical and catalytical performances of HD-PtNDs@AuNRs towards H₂O₂ reduction were investigated in detail by cyclic voltammetry and amperometry. The HD-PtNDs@AuNRs modified electrode displayed a high catalytic activity to H₂O₂ at −0.10 V (versus SCE), a rapid response within 5 s, a wide linear range of 2.0–3800.0 μM, a detection limit of 1.2 μM (S/N = 3), and a high sensitivity of 181 μA mM⁻¹ cm⁻². These results suggested a promising potential of fabricating H₂O₂ electrochemical sensor using HD- PtNDs@AuNRs.     

A novel hydrogen peroxide sensor based on Ag nanoparticles electrodeposited on chitosan-graphene oxide/cysteamine-modified gold electrode

A novel strategy to fabricate a hydrogen peroxide sensor based on Ag nanoparticles electrodeposited on chitosan-graphene oxide nanocomposites/cysteamine-modified gold (Au) electrode was reported. The chitosan-graphene oxide nanocomposites were first assembled on a cysteamine-modified Au electrode to produce chitosan-graphene oxide/cysteamine/Au electrode. Then Ag nanoparticles were electrodeposited on the modified Au electrode and formed Ag nanoparticles/chitosan-graphene oxide/cysteamine/Au electrode. The chitosan-graphene oxide nanocomposites and the electrodeposited Ag nanoparticles were characterized by atomic force microscopy and scanning electron microscopy. The results showed the Ag nanoparticles were uniformly dispersed on the chitosan-graphene oxide/cysteamine/Au electrode. The cyclic voltammagrams and amperometric method were used to evaluate electrocatalytic properties of the Ag nanoparticles/chitosan-graphene oxide/cysteamine/Au electrode. The results showed that the modified electrode displayed good electrocatalytic activity to the reduction of hydrogen peroxide with a detection limit of 0.7 μM hydrogen peroxide based on a signal-to-noise ratio of 3. The sensor has good reproducibility, wide linear range, and long-term stability.     

Development of Nonenzymatic Hydrogen Peroxide Sensor Based on Successive Pd‐Ag Electrodeposited Nanoparticles on Glassy Carbon Electrode

A novel strategy to fabricate hydrogen peroxide (H₂O₂) sensor was developed by electrodepositing palladium? silver nanoparticles (NPs) on a glassy carbon electrode. The morphology of the modified electrode was characterized by Scanning electron microscopy (SEM). The result of electrochemical experiments showed that such constructed sensor had a favorable catalytic ability, high sensitivity, excellent selectivity towards reduction of hydrogen peroxide (H₂O₂). The response to H₂O₂ is linear in the range between 0.30 μM to 2.50 mM, and the detection limit is 0.1 μM (at an S/N of 3).     

Influences of Mesoporous Structure on the NO+H2+O2 Low Temperature Reaction over Pt/Si-MCM-41 Catalyst

It was found that Si-MCM-41 mesoporous molecular sieves as a support of noble metal Pt could be used for the selective catalytic reduction of NO by hydrogen (H₂-SCR) under lean-burn conditions. Pt/Si-MCM-41, together with Pt/Si-ZSM-5 and Pt/SiO₂, was characterized by X-ray diffraction analysis (XRD), nitrogen adsorption/desorption, hydrogen adsorption, and transmission electron microscopy (TEM). The results indicated that Pt/Si-MCM-41 had the best H₂-SCR activity in comparison with Pt/Si-ZSM-5 and Pt/SiO₂ catalysts and that the maximum conversion of NO was up to 60.1% at 100 °C and a gas hourly space velocity (GHSV) of 80000 h_-1 under lean-burn conditions. Characterization showed that the large surface area and pore volume of MCM-41 favored the dispersion of Pt. The maximum NO conversion of Pt/Si-MCM-41 catalyst decreased obviously to 15% at 120 °C when the pore structure of Si-MCM-41 support was destroyed. The reaction mechanism over Pt/Si-MCM-41 was investigated using in situ diffuse reflectance infrared spectroscopy (DRIFTS), which revealed that the main reaction intermediates should be nitrate species during NO reduction.     

Effect of Bimetallic Pd/Pt Clusters on the Sensing Properties of Nanocrystalline SnO<Subscript>2</Subscript> in the Detection of CO

Nanocrystalline tin dioxide modified by Pd and Pt clusters or by bimetallic PdPt nanoparticles was synthesized. Distribution of the modifers on the SnO₂ surface was studied by high-resolution transmission electron microscopy and energy dispersive X-ray microanalysis with element distribution mapping. It was shown that the Pd/Pt ratio in bimetallic particles varies over a broad range and does not depend on the particle diameter. The effect of platinum metals on the reducibility of nanocrystalline SnO₂ by hydrogen was determined. The sensing properties of the resulting materials towards 6.7 ppm CO in air were estimated in situ by electrical conductivity measurements. The sensor response of SnO₂ modified with bimetallic PdPt particles was a superposition of the signals of samples with Pt and Pd clusters.     

Heterostructural NiCo2O4 Nanocomposites for Nonenzymatic Electrochemical Glucose Sensing

Hierarchical nanocomposites consisting of NiCo₂O₄ nanorods and NiCo₂O₄ nanoparticles through a straightforward two-step hydrothermal process was employed as a working electrode to examine the electrochemical behavior of glucose. The NiCo₂O₄@NiCo₂O₄ heterostructures was confirmed by the scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffractometer (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemistry analysis. Results indicated that glucose is electrochemically oxidized with improved sensitivity at the NiCo₂O₄@NiCo₂O₄ sensor, compared to NiCo₂O₄ sensors. Analytical parameters such as the optimal potential (0.45 V), linear range from 0.4 μM to 5.2 mM, limit of detection (1.1 μΜ) (S/N=3), stability and repeatability (2.7 %) demonstrate the suitability of the prepared sensor for glucose analysis. Moreover, the proposed sensor could be used for actual samples analysis in complex matrices.     

Graphene oxide–MnO_2 nanocomposite-modified glassy carbon electrode as an efficient sensor for H_2O_2

In this study, a new facile preparation method of nanocomposites consisting of graphene oxide and manganese dioxide nanowires(GO/MnO_2 NW_s) was developed. The morphology, structure and composition of the resulted products were characterized by transmission electron microscopy, X-ray diffraction and N_2 adsorption and desorption. The GO/MnO_2 nanocomposite was used as an electrode material for non-enzymatic determination of hydrogen peroxide. The proposed sensor exhibits excellent electrocatalytic performance for the determination of hydrogen peroxide in phosphate buffer solution(PBS, pH7) at an applied potential of 0.75 V. The non-enzymatic biosensor for determination of hydrogen peroxide displayed a wide linear range of 4.90 mmol L~(-1)–4.50 mmol L~(-1)with a correlation coefficient of 0.9992, a low detection limit of 0.48 mmol L~(-1) and a high sensitivity of 191.22μA(mmol L~(-1))~(-1)cm~(-2)(signal/noise, S/N = 3). Moreover, the non-enzymatic biosensor shows an excellent selectivity.