Synthesis of Ag Nanoparticle Doped MnO2/GO Nanocomposites at a Gas/Liquid Interface and its Application in H2O2 Detection

Ag/MnO₂/GO nanocomposites were synthesized via the method of gas/liquid interface based on silver mirror reaction, and a non‐enzymatic H₂O₂ sensor was fabricated through immobilizing Ag/MnO₂/GO nanocomposites on GCE. The composition and morphology of the nanocomposites were studied by energy‐dispersive X‐ray spectroscopy (EDS), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Electrochemical investigation indicated that it exhibited a favorable performance for the H₂O₂ detection. Its linear detection range was from 3 μM to 7 mM with a correlation coefficient of 0.9960; the sensitivity was 105.40 μA mM^?1 cm^?2 and the detection limit was estimated to be 0.7 μM at a signal‐to‐noise ratio of 3.     

Synthesis of Functionalized MWCNTs Decorated with Copper Nanoparticles and Its Application as a Sensitive Sensor for Amperometric Detection of H2O2

Functionalized‐multiwall carbon nanotubes decorated with redox active copper nanoparticles have been fabricated for sensitive enzyme‐less H₂O₂ detection. The new nanocomposite was characterized by Transmission electron microscopy, energy dispersive X‐ray analysis and cyclic voltammetry. The response of the modified electrode to H₂O₂ was examined using amperometry at ?0.45 V vs. Ag/AgCl in a buffer solution at pH 10.0. The developed sensor displayed linear concentration ranges of 0.5–10.0 and 10.0–10000.0 µmol L^?1 with a detection limit of 0.3 µmol L^?1. The proposed sensor displayed good selectivity for H₂O₂ detection in the presence of common interferences such as ascorbic acid.     

Trace Level Determination of Hydrogen Peroxide at a Carbon Ceramic Electrode Modified with Copper Oxide Nanostructures

An electrochemical sensor was developed for determination of hydrogen peroxide based on nanocopper oxides modified carbon sol‐gel or carbon ceramic electrode (CCE). The modified electrode was prepared by electrodeposition of metallic copper on the CCE surface and derivatized in situ to copper oxides nanostructures and characterized by scanning electron microscopy (SEM) and X‐ray diffraction (XRD) techniques. The modified electrode responded linearly to the hydrogen peroxide (H₂O₂) concentration over the range 0.78–193.98 µmol L^?1 with a detection limit of 71 nmol L^?1 (S/N=3) and the sensitivity of 0.697 A mol^?1 L cm^?2. This electrode was used as selective amperometric sensor for determination of H₂O₂ contents in hair coloring creams.     

A Non‐Enzymatic Hydrogen Peroxide Sensor Based on Gold Nanoparticles/Carbon Nanotube/Self‐Doped Polyaniline Hollow Spheres

In this study, a novel non‐enzymatic hydrogen peroxide (H₂O₂) sensor was fabricated based on gold nanoparticles/carbon nanotube/self‐doped polyaniline (AuNPs/CNTs/SPAN) hollow spheres modified glassy carbon electrode (GCE). SPAN was in‐site polymerized on the surface of SiO₂ template, then AuNPs and CNTs were decorated by electrostatic absorption via poly(diallyldimethylammonium chloride). After the SiO₂ cores were removed, hollow AuNPs/CNTs/SPAN spheres were obtained and characterized by transmission electron microscopy (TEM), field‐emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FTIR). The electrochemical catalytic performance of the hollow AuNPs/CNTs/SPAN/GCE for H₂O₂ detection was evaluated by cyclic voltammetry (CV) and chronoamperometry. Using chronoamperometric method at a constant potential of ?0.1 V (vs. SCE), the H₂O₂ sensor displays two linear ranges: one from 5 µM to 0.225 mM with a sensitivity of 499.82 µA mM^?1 cm^?2; another from 0.225 mM to 8.825 mM with a sensitivity of 152.29 µA mM^?1 cm^?2. The detection limit was estimated as 0.4 µM (signal‐to‐noise ratio of 3). The hollow AuNPs/CNTs/SPAN/GCE also demonstrated excellent stability and selectivity against interferences from other electroactive species. The sensor was further applied to determine H₂O₂ in disinfectant real samples.     

Novel Nonenzymatic Hydrogen Peroxide Sensor Based on Ag/Cu2O Nanocomposites

The nanocomposites of Ag nanoparticles supported on Cu₂O were prepared and used for fabricating a novel nonenzymatic H₂O₂ sensor. The morphology and composition of the nanocomposites were characterized using the scanning electron microscope (SEM), transmission electron microscope (TEM), energy‐dispersive X‐ray spectrum (EDX) and X‐ray diffraction spectrum (XRD). The electrochemical investigations indicate that the sensor possesses an excellent performance toward H₂O₂. The linear range is estimated to be from 2.0 μM to 13.0 mM with a sensitivity of 88.9 μA mM^?1 cm^?2, a response time of 3 s and a low detection limit of 0.7 μM at a signal‐to‐noise ratio of 3. Additionally, the sensor exhibits good anti‐interference.     

A Nonenzymatic Hydrogen Peroxide Sensor Based on Silver Nanowires and Chitosan Film

A nonenzymatic amperometric electrochemical sensor for the detection of hydrogen peroxide (H₂O₂) was fabricated based on highly dense silver nanowires (Ag NWs) and chitosan (CS) film. Ag NWs were synthesized by a poly(vinyl pyrrolidone) (PVP)‐mediated polyol process in the presence of manganese chloride (MnCl₂), and were characterized by scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDS), and X‐ray diffraction (XRD). Under the optimal conditions, the proposed nonenzymatic sensor exhibited good electrocatalytic activity towards the reduction of H₂O₂, and could detect H₂O₂ in the linear range of 0.008–1.35 mM, with a detection limit of 2 µM (S/N=3).     

A MnOOH‐Polyaniline Nanocomposite Modified Gold Electrode for Electrochemical Sensing of Nitrite

A novel non‐enzymatic nitrite sensor was fabricated by immobilizing MnOOH‐PANI nanocomposites on a gold electrode (Au electrode). The morphology and composition of the nanocomposites were investigated by transmission electron microscopy (TEM ) and Fourier transform infrared spectrum (FTIR ). The electrochemical results showed that the sensor possessed excellent electrocatalytic ability for NO₂⁻ oxidation. The sensor displayed a linear range from 3.0 μmol•L⁻¹ to 76.0 mmol•L⁻¹ with a detection limit of 0.9 μmol•L⁻¹ (S/N = 3), a sensitivity of 132.2 μA •L•mol⁻¹•cm⁻² and a response time of 3 s. Furthermore, the sensor showed good reproducibility and long‐term stability. It is expected that the MnOOH‐PANI nanocomposites could be applied for more active sensors and used in practice for nitrite sensing.     

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.     

Gold Nanoparticles Electrodeposited on Ordered Mesoporous Carbon as an Enhanced Material for Nonenzymatic Hydrogen Peroxide Sensor

A facile and controllable electrodeposition method was developed to directly attach gold nanoparticles (GNPs) on ordered mesoporous carbon (OMC). The GNPs on OMC substrate were characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD) and X‐ray photoelectron spectrometer (XPS), respectively. A nonenzymatic hydrogen peroxide (H₂O₂) sensor was fabricated on GNPs‐OMC/GCE. The sensor demonstrated a fast amperometric response (2.5 s), a wide linear range toward H₂O₂ concentrations between 2.0×10^?6 and 3.92×10^?3 M (R=0.999), and a low detection limit of 0.49 µM (S/N=3). Moreover, it exhibited good reproducibility and long‐term stability. The excellent electrocatalytical activity might be attributed to the synergistic effect of OMC and GNPs.     

A Novel Hydrogen Peroxide Amperometric Sensor Based on Hierarchical 3D Porous MnO2−TiO2 Composites

A novel nanocomposite electrode based on hierarchical 3D porous MnO₂?TiO₂ for the application in hydrogen peroxide (H₂O₂) sensors has been explored. This electrode was fabricated by growing TiO₂ cross‐linked nanowires on a commercial fluorine tin oxide (FTO) glass via a hydrothermal process and subsequent deposition of 3D honeycomb‐like MnO₂ nanowalls using an electrodeposition method (denoted as 3D MNS‐TNW@FTO). The obtained 3D MNS‐TNW@FTO electrode was characterized by scanning electron microscopy (SEM), Raman spectroscopy, X‐ray diffraction (XRD), and X‐ray photoelectron spectroscopy (XPS). Based on such a unique 3D porous framework and the existence of MnO₂, the electrode demonstrates a good performance in the detection of H₂O₂, with two linear ranges from 9.8 to 125 μM and 125 μM–1.0 mM, a good selectivity of 8.02 μA mM^?1 cm^?2, and a low detection limit of 4.5 μM. In addition, the simplicity of the developed low‐cost fabrication process provides an efficient method for the mass production of electrocatalytical MnO₂?TiO₂ nanocomposites on commercial FTO glass for H₂O₂ sensing applications and can be adapted for other electrochemical sensors for various biochemical targets. It thus is beneficial for the practical usage in bioanalysis.     

An Enzyme‐free H2O2 Sensor Based on Poly(2‐Aminophenylbenzimidazole)/Gold Nanoparticles Coated Pencil Graphite Electrode

A poly(2‐aminophenylbenzimidazole)/gold nanoparticles (P2AB/AuNPs) coated disposable pencil graphite electrode (PGE) was fabricated as an enzyme‐free sensor for the H₂O₂ determination. P2AB/AuNPs and P2AB were successfully synthesized electrochemically on PGE in acetonitrile for the first time. The coatings were characterized by scanning electron microscopy, X‐ray diffraction spectroscopy, Energy‐dispersive X‐ray spectroscopy, Surface‐enhanced Raman spectroscopy, and UV‐Vis spectroscopy. AuNPs interacted with P2AB as carrier enhances the electrocatalytic activity towards reduction of H₂O₂. The analytical performance was evaluated in a 100 mM phosphate buffer solution at pH 6.5 by amperometry. The steady state current vs. H₂O₂ concentration is linear in the range of 0.06 to 100 mM (R²=0.992) with a limit of detection 3.67×10^?5 M at ?0.8 V vs. SCE and no interference is caused by ascorbic acid, dopamine, uric acid, and glucose. The examination for the sensitive determination of H₂O₂ was conducted in commercially available hair oxidant solution. The results demonstrate that P2AB/AuNPs/PGE has potential applications as a sensing material for quantitative determination of H₂O₂.     

Improvement of Selectivity and Stability of Amperometric Detection of Hydrogen Peroxide Using Prussian Blue‐PAMAM Supramolecular Complex Membrane as a Catalytic Layer

A novel hydrogen peroxide (H₂O₂) sensor was fabricated by using a submonolayer of 3‐mercaptopropionic acid (3‐MPA) adsorbed on a polycrystalline gold electrode further reacted with poly(amidoamine) (PAMAM) dendrimer (generation 4.0) to obtain a film on which Prussian Blue (PB) was later coordinated to afford a mixed and stable electrocatalytic layer for H₂O₂ reduction. On the basis of the electrochemical behaviors, atomic force microscopy (AFM) and X‐ray photoelectron spectra (XPS), it is suggested that the PB molecules are located within the dendritic structure of the surface attached PAMAM dendrimers. It was found that the PB/PAMAM/3‐MPA/Au modified electrode showed an excellent electrocatalytic activity for H₂O₂ reduction. The effects of applied potential and pH of solution upon the response of the modified electrode were investigated for an optimum analytical performance. Even in the presence of dissolved oxygen, the sensor exhibited highly sensitive and rapid response to H₂O₂. The steady‐state cathodic current responses of the modified electrode obtained at ?0.20 V (vs. SCE) in air‐saturated 0.1 mol L^?1 phosphate buffer solution (PBS, pH 6.50) showed a linear relationship to H₂O₂ concentration ranging from 1.2×10^?6 mol L^?1 to 6.5×10^?4 mol L^?1 with a detection limit of 3.1×10^?7 mol L^?1. Performance of the electrode was evaluated with respected to possible interferences such as ascorbic acid and uric acid etc. The selectivity, stability, and reproducibility of the modified electrode were satisfactory.     

A Non‐Enzymatic Glucose Sensor Based on Ni/MnO2 Nanocomposite Modified Glassy Carbon Electrode

A novel flower like 3D nickel/manganese dioxide (Ni/MnO₂) nanocomposite was synthesized by a kind of simple electrochemical method and the formation mechanism of flower like structure was also researched. In addition, morphology and composition of the nanocomposite were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), and X‐ray photoelectron spectroscopy (XPS). Then the Ni/MnO₂ nanocomposites were applied to fabricate electrochemical non‐enzymatic glucose sensor. The electrochemical investigation for the sensor indicated that it possessed an excellent electrocatalytic property for glucose, and could applied to the quantification of glucose with a linear range from 2.5×10^?7 to 3.5×10^?3 M, a sensitivity of 1.04 mA mM^?1 cm^?2, and a detection limit of 1×10^?7 M (S/N=3). The proposed sensor also presented attractive features such as interference‐free, and long‐term stability. The present study provided a general platform for the one‐step synthesis of nanomaterials with novel structure and can be extended to other optical, electronic and magnetic nanocompounds.     

Synthesis of MnO2/MWNTs Nanocomposites Using a Sonochemical Method and Application for Hydrazine Detection

A sonochemical method has been successfully used to synthesize MnO₂/MWNTs nanocomposites. The structure and nature of the resulting MnO₂/MWNTs composite were characterized by scanning electron microscopy (SEM), energy‐dispersive X‐ray diffraction (EDX), X‐ray photoelectron spectroscopy (XPS).The results show that the sonochemically synthesized MnO₂ nanoparticles were homogeneously dispersed on the modified MWNT surfaces. The performance of the MnO₂/MWNTs nanocomposites modified electrode was characterized using cyclic voltammetry (CV) and Nyquist plots. The electrode exhibits efficient electron transfer ability and high electrochemical response towards hydrazine. This may be attributed to the small particle size, high dispersion of MnO₂ particles. The fabricated hydrazine sensor showed a wide linear range of 5.0×10^?7–1.0×10^?3 M with a response time less than 5 s and a detection limit of 0.2 μM. Taking the advantage of the unique properties of both MWNTs and MnO₂, it would greatly broaden the applications of MWNTs and MnO₂.     

Synthesis of Ferrocene Based Naphthoquinones and its Application as Novel Non‐enzymatic Hydrogen Peroxide

At present, a highly sensitive hydrogen peroxide (H₂O₂) sensor is fabricated by ferrocene based naphthaquinone derivatives as 2,3‐Diferrocenyl‐1,4‐naphthoquinone and 2‐bromo‐3‐ferrocenyl‐1,4‐naphthoquinone. These ferrocene based naphthaquinone derivatives are characterized by H‐NMR and C‐NMR. The electrochemical properties of these ferrocene based naphthaquinone are investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) on modified glassy carbon electrode (GCE). The modified electrode with ferrocene based naphthaquinone derivatives exhibits an improved voltammetric response to the H₂O₂ redox reaction. 2‐bromo‐3‐ferrocenyl‐1,4‐naphthoquinone show excellent non‐enzymatic sensing ability towards H₂O₂ response with a detection limitation of 2.7 μmol/L a wide detection range from 10 μM to 400 μM in H₂O₂ detection. The sensor also exhibits short response time (1 s) and good sensitivity of 71.4 μA mM^?1 cm^?2 and stability. Furthermore, the DPV method exhibited very high sensitivity (18999 μA mM^?1 cm^?2) and low detection limit (0.66 μM) compared to the CA method. Ferrocene based naphthaquinone derivative based sensors have a lower cost and high stability. Thus, this novel non‐enzyme sensor has potential application in H₂O₂ detection.     

Magnetite Nanorods Stabilized by Polyaniline/Reduced Graphene Oxide as a Sensing Platform for Selective and Sensitive Non‐enzymatic Hydrogen Peroxide Detection

In this study, magnetite nanorods stabilized on polyaniline/reduced graphene oxide (Fe₃O₄@PANI/rGO) was synthesized via a wet‐reflux strategy. The possible formation of Fe₃O₄@PANI/rGO was morphologically and structurally verified by field emission scanning electron microscopy (FE‐SEM), Fourier transform infrared (FT‐IR) spectroscopy, Raman spectroscopy, X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). Furthermore, the thermal stability of Fe₃O₄@PANI/rGO was measured by a thermogravimetric analyzer (TGA); the composite had good thermal stability owing to the ceramic nature of Fe₃O₄. The Fe₃O₄@PANI/rGO has been applied as a potential sensing platform for electrochemical detection of hydrogen peroxide (H₂O₂). By the combined efforts of extended active surface area, active carbon support, more catalytic active sites and high electrical conductivity, the Fe₃O₄@PANI/rGO exhibited an improved performance toward the non‐enzymatic detection of H₂O₂ in 0.5 M KOH with a fast response time (5 s), high sensitivity (223.7 μA mM^?1 cm^?2), low limit of detection (4.45 μM) and wide linear range (100 μM–1.5 mM). Furthermore, the fabricated sensor exhibited excellent recovery rates (94.2–104.0 %) during real sample analysis.     

Cauliflower‐like NiCo2O4−Zn/Al Layered Double Hydroxide Nanocomposite as an Efficient Electrochemical Sensing Platform for Selective Pyridoxine Detection

In the present study, a cauliflower‐like NiCo₂O₄?Zn/Al layered double hydroxide (NiCo₂O₄?Zn/Al LDH) nanocomposite was used as a novel electrode material for the sensitive and selective determination of pyridoxine (vitamin B₆). The structure and morphology of the as‐prepared nanocomposite were characterized by X‐ray diffraction (XRD), FT‐IR, field emission scanning electron microscopy (FESEM) and energy dispersive X‐ray spectroscopy (EDX). The NiCo₂O₄?Zn/Al LDH nanocomposite exhibited excellent electrocatalytic ability in the oxidation of pyridoxine, which could result from the synergistic effect of the two components. The developed sensor also provided a selective determination of pyridoxine in the presence of other species such as vitamins (B₁, B₂, B₁₂ and ascorbic acid), inorganic ions and biomolecules. The fabricated sensor showed a good linear response for pyridoxine over the concentration ranges 2×10^?7–2.0×10^?4 mol L^?1 with a low detection limit of 8.6×10^?8 mol L^?1. Finally, the proposed method was successfully applied for the determination of pyridoxine in commercial tablets and plasma samples with satisfactory results. Furthermore, this novel sensor displayed superior benefits in terms of stability, sensitivity, repeatability and cost. The present work aims to expand NiCo₂O₄ based nanocomposites to sensor fields and promote the development of pyridoxine sensors.     

Highly Sensitive Electrochemiluminescent Insecticide Sensor Based on ZnO Nanocrystals Anchored Nickel Foam for Determination of Imidacloprid in Real Samples

In this work, a novel electrochemiluminescent (ECL) pesticide sensor based on zinc oxide nanocrystals decorated nickel foam is proposed for determination of imidacloprid for the first time. The silica film was used as a morphology‐controlling factor for modification of the electrode with zinc oxide nanocrystals. Zinc oxide was selected as luminescent material due to its cheapness, non‐toxicity, high thermal stability and excellent luminescence properties which truly adhered on the surface of nickel foam. The K₂S₂O₈ was used as strong co‐reactant for this purpose. The silica template plays an important role in controlling the size of ZnO nanocrystals. The Physical morphology of the ZnO/Ni‐foam electrode was performed by electrochemical impedance spectroscopy, Brunauer‐Emmett‐Teller (BET), X‐Ray diffraction analysis, field emission scanning electron microscopy, and energy‐dispersive X‐ray analysis. The ultra‐sensitive electrochemiluminescence method was successfully used for ultra‐trace determination of imidacloprid. The linear dynamic range and low detection limit were obtained 3×10^?14 ?8×10^?8 M and 4.4×10^?15 M, respectively. Also, the relative standard deviation for 15 repetitive optical signals was calculated 1.09 %.The present ECL sensor exhibited superior performance toward the accurate determination of imidacloprid with good reproducibility and stability.     

Electrocatalytic Activity of Nanocomposites of Sulphur Doped Graphene Oxide and Nanosized Cobalt Phthalocyanines

In this work we explore the electrocatalytic activity of nanocomposites of reduced sulphur doped graphene oxide nanosheets (rSDGONS) and cobalt phthalocyanine (CoPc) or cobalt tetra amino phthalocyanine (CoTAPc) towards hydrogen peroxide. Transmission electron microscopy, scanning electron microscopy, X‐ray photon spectroscopy, X‐ray diffraction, chronoamperometry, linear scan voltammetry and cyclic voltammetry were used to characterize the nanocomposites. Nanosized CoPc showed superior (in terms of currents) electrocatalytic oxidation and reduction of hydrogen peroxide compared to CoTAPc nanoparticles (CoTAPc NP ). The lowest detection limit was obtained for hydrogen peroxide oxidation on electrodes modified with CoPc NP ‐rSDGONS at 1.49 µM. The same electrode gave a high adsorption equilibrium constant of 1.27×10³ mol^?1 and a Gibbs free energy of ?17.71 kJ/mol, indicative of a spontaneous reaction on the electrode surface.     

A Novel Enzymatic Glucose Biosensor and Nonenzymatic Hydrogen Peroxide Sensor Based on (3‐Aminopropyl) Triethoxysilane Functionalized Reduced Graphene Oxide

In the present study, a novel enzymatic glucose biosensor using glucose oxidase (GOx) immobilized into (3‐aminopropyl) triethoxysilane (APTES) functionalized reduced graphene oxide (rGO‐APTES) and hydrogen peroxide sensor based on rGO‐APTES modified glassy carbon (GC) electrode were fabricated. Nafion (Nf) was used as a protective membrane. For the characterization of the composites, Fourier transform infrared spectroscopy (FTIR), X‐ray powder diffractometer (XRD), and transmission electron microscopy (TEM) were used. The electrochemical properties of the modified electrodes were investigated using electrochemical impedance spectroscopy, cyclic voltammetry, and amperometry. The resulting Nf/rGO‐APTES/GOx/GC and Nf/rGO‐APTES/GC composites showed good electrocatalytical activity toward glucose and H₂O₂, respectively. The Nf/rGO‐APTES/GC electrode exhibited a linear range of H₂O₂ concentration from 0.05 to 15.25 mM with a detection limit (LOD) of 0.017 mM and sensitivity of 124.87 μA mM⁻¹ cm⁻². The Nf/rGO‐APTES/GOx/GC electrode showed a linear range of glucose from 0.02 to 4.340 mM with a LOD of 9 μM and sensitivity of 75.26 μA mM⁻¹ cm⁻². Also, the sensor and biosensor had notable selectivity, repeatability, reproducibility, and storage stability.