Non-enzymatic Hydrogen Peroxide Research Articles

Changes in antioxidant properties of pepper leaves (Capsicum annuum L.) upon UV radiation

Bell pepper (Capsicum annuum) is one of the most popular vegetables consumed worldwide. The leaves of pepper are rich in phenolics, including phenolic acids and flavonoids. These compounds are well known for their ultraviolet (UV) absorbing and antioxidant properties. While the change of the phenolic pattern is an intensive research subject, it is not yet well-known in pepper leaves, particularly in outdoor conditions. In this experiment, we examined the effect of UV radiation on the leaves of outdoor grown peppers, focusing on the UV-absorbing properties and antioxidant capacities. Three different total antioxidant capacity (TAC) measurements have been compared: (I) Folin-Ciocalteu Reactivity (FC), (II) Ferric Reducing Antioxidant Power (FRAP) and (III) Trolox Equivalent Antioxidant Capacity (TEAC). Moreover, non-enzymatic hydrogen peroxide scavenging antioxidant capacity was measured. Significant increase was detected only in FRAP, suggesting an elevation exclusively in the level of phenolic acids in case of UV exposed outdoor grown pepper leaves.

A Non-Disposable Electrochemical Sensor Based on Laser-Synthesized Pd/LIG Nanocomposite-Modified Screen-Printed Electrodes for the Detection of H2O2.

There have been many studies on the significant correlation between the hydrogen peroxide content of different tissues or cells in the human body and the risk of disease, so the preparation of biosensors for detecting hydrogen peroxide concentration has been a hot topic for researchers. In this paper, palladium nanoparticles (PdNPs) and laser-induced graphene (LIG) were prepared by liquid-phase pulsed laser ablation and laser-induced technology, respectively. The complexes were prepared by stirring and used for the modification of screen-printed electrodes to develop a non-enzymatic hydrogen peroxide biosensor that is low cost and mass preparable. The PdNPs prepared with anhydrous ethanol as a solvent have a uniform particle size distribution. The LIG prepared by laser direct writing has good electrical conductivity, and its loose porous structure provides more adsorption sites. The electrochemical properties of the modified electrode were characterized by cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Compared with bare screen-printed electrodes, the modified electrodes are more sensitive for the detection of hydrogen peroxide. The sensor has a linear response range of 5 µM-0.9 mM and 0.9 mM-5 mM. The limit of detection is 0.37 µM. The above conclusions indicate that the hydrogen peroxide electrochemical biosensor prepared in this paper has great advantages and potential in electrochemical catalysis.

Spherical nickel boride nanoparticles anchored on a carbon nanofiber composite for efficient sensing of non-enzymatic hydrogen peroxide in biological samples

Spherical nickel boride nanoparticles (Ni3B NPs) were grown firmly on surface-functionalized carbon nanofibers (ƒ-CNFs) using a simple and convenient synthesis strategy and their application as enzyme-free electrochemical sensors for hydrogen peroxide (H2O2) were examined. The Ni3B NPs/ƒ-CNFs composite was characterized by the crystalline structure, surface morphology, and surface chemical states using a range of techniques. The sensing efficiency of the as-prepared composite was also examined using various voltammetry techniques. The structural and morphological characterization results showed that the Ni3B NPs could be effectively anchored in the ƒ-CNFs matrix and the average particle size of the anchored Ni3B NPs is 15.9 nm. The electrochemical studies suggested that the small Ni3B NPs could enhance the electrocatalytic activity for the reduction of H2O2 via the ƒ-CNFs because of the synergistic effects of ƒ-CNFs and Ni3B NPs. The kinetic parameters, such as the catalytic rate constant and diffusion coefficient of the Ni3B NPs/ƒ-CNFs composite modified electrode, were calculated to be 30.9 × 105 mol−1s−1 and 4.48 × 10-6 cm2s−1, respectively. Under the optimal conditions, the enzyme-free H2O2 sensor showed a more comprehensive linear range (0.083 µM – 12.6 mM and 14.2 – 39.5 mM), low detection limit (21 nM), high sensitivity (59 µA mM−1 cm−2), and negligible interference from glucose, dopamine, uric acid, and ascorbic acid. Moreover, the prepared electrode showed good repeatability, reproducibility, stability, and suitability for real sample analysis. These results highlight a method to develop high-performance sensing materials and a great candidate for practical application.

Carbon Nitride Quantum Dots: A Novel Fluorescent Probe for Non-Enzymatic Hydrogen Peroxide and Mercury Detection

Carbon Nitride Quantum Dots: A Novel Fluorescent Probe for Non-Enzymatic Hydrogen Peroxide and Mercury Detection

Graviola Protects Against Hepatic Toxicity Associated with DMBA induced Breast Cancer via Restoration of Antioxidants and Attenuation of Inflammatory Pathways

Aims: This study documented hepatic tissue's protective activity against oxidative damage mediated experimental models of breast cancer. Background: Gaviola has a long history of improving the protection mechanism against many diseases as an antioxidant and anticancer dietary agent. Objective: The purpose of this study is to establish changes in hepatic profiling, antioxidants, inflammatory cytokine expression, and DMBA-induced hepatic histopathology of mammalian rats. Methods: 7,12-dimethylbenz[a] anthracene (DMBA), PAHs, used orally in female Sprague Dawley rats Fifty-seven days-old with breast cancer single-dose diluted in sesame oil of 20 mg/kg/body weight. The cancer-bearing animals had 45 days gastrogavagated at 200 mg/kg/body weight with Graviola. The serum samples were taken at the end of the experiment. The rats were sacrificed to establish the hepatic protective activity of the Graviola by testing hepatic and oxidative stress markers. Results: Graviola therapy shows that enzymatic and non-enzymatic antioxidants and lipid peroxide levels have increased efficiency and have restored the high activity of hepatic marker enzymes such as ALT, AST, ALP, and GGT. To date, hepatic expression of nuclear factor erythroid 2-like 2 (Nfe2l2) and nuclear factor kappa B subunit 1 (Nfkb1) mediated rats have normalized. In addition, histological observations have demonstrated that Graviola's treatment effectively protects the liver from the oxidative damage caused by DMBA, reinforcing its hepatic defensive nature. Conclusion: Graviola therapy improves the efficiency of both enzymatic and non-enzymatic antioxidants and lipid peroxide levels. It also helps in the restoration of other liver enzymes.

Non-enzymatic hydrogen peroxide detection on a novel nanohybrid composite of chitosan and grafted graphene oxide

Hydrogen peroxide (H2O2) is a significant constituent of several biological and industrial processes; however, as it is malignant to human health, the ability to detect its presence is indispensable. From the various H2O2 detection methods, enzyme-free electrochemical detection method is thriving in research, as it is economical, easy-to-use, stable, and provides repeatable platforms. Herein, we report on a metal-free, novel, biopolymer-based low-cost, stable, and easy-to-operate, conducting nanohybrid composite for the non-enzymatic detection of H2O2. This nanohybrid composite consists of a novel crosslinked chitosan (CS) and polyaniline (PANI) grafted graphene oxide (GO) (GOP) composite. In the first step, a gamma-irradiated GO (γGO) substrate is used for the in-situ graft polymerization of aniline, and following the grafted nanohybrid was incorporated in a CS matrix and crosslinked with tetraethylorthosilicate (TEOS) to form CS and GO composites. The sensor, fabricated by coating the newly prepared composite on a glassy carbon electrode, was tested for hydrogen peroxide detection in an alkaline solution, showing a low detection limit of 17.3 μM, a linear range up to 200 μM, and a sensitivity of 0.77 μA μM−1 cm−2. These notable results and comparable performance with the literature suggest that the electrochemical biosensor exhibit promising potential for a wide range of H2O2 detection.

Synthesis of CuxO/Ag nanoparticles on exfoliated graphene: application for enhanced electrochemical detection of H2O2 in milk

In this paper, a novel composite is constructed as a non-enzymatic hydrogen peroxide (H2O2) sensor by liquid-phase exfoliation method, which is composed of copper oxide, cuprous oxide and silver nanoparticles doped few-layer-graphene (CuxO/Ag@FLG). Its surface morphology and composition were characterized by scanning electron microscopy (SEM) and X-ray photo spectroscopy (XPS), and its H2O2 sensing performances include catalytic reduction and quantitative detection were studied with electrochemical methods. Our sensor had a high sensitivity of 174.5 μA mM−1 cm−2 (R2 = 0.9978) in an extremely wide range of concentrations from 10 μM to 100 mM, a fast response (about 5 s) and a low limit of detection (S/N = 3) of 2.13 μM. The sensor exhibits outstanding selectivity in the presence of various biological interference, such as dopamine, ascorbic acid, uric acid, citric acid, etc. In addition, the constructed sensor continued 95% current responsiveness after 1 month of storage further points to its long-term stability. Last but not least, it has a good recovery rate (90.12–102.00%) in milk sold on the open market, indicating that it has broad application possibilities in the food industry and biological medicine.

Ru doping induced lattice distortion of Cu nanoparticles for boosting electrochemical nonenzymatic hydrogen peroxide sensing

In this paper, we report a new strategy to activate the electrocatalytic activity of Cu to realize the non-enzymatic detection of hydrogen peroxide. The Ru-doped copper nanoparticles were prepared on the surface of carbon materials by direct pyrolysis of Ru in exchange for Cu-BTC metal-organic framework. The materials were characterized by transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD). Surprisingly, Ru doping induced obvious lattice distortion of Cu nanoparticles, which made Cu nanoparticles exhibit excellent electrocatalytic activity for hydrogen peroxide reduction. The sensor based on Ru-doped Cu nanoparticles can detect hydrogen peroxide in a wide linear range from 0.01 mM to 5.55 mM. Moreover, as a hydrogen peroxide sensor, it has a high sensitivity of 327.14 µA·mM−1·cm−2 and a low detection limit of 8.9 µM. Therefore, Cu nanoparticles with the lattice distortion was demonstrated to be a potential material for hydrogen peroxide electrochemical sensor.

Synthesis of Ag Nanoparticles Dispersed on Co3O4–3D Porous Reduced Graphene Oxide and their Application for Electrochemical Sensing of Hydrogen Peroxide

Ag nanoparticles dispersed on Co3O4/3D porous reduced graphene oxide (Ag/Co3O4/rGO) were successfully synthesized through sol–gel method and used for fabricating a novel nonenzymatic hydrogen peroxide (H2O[Formula: see text] sensor. The structure and morphology of anocomposites were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The electrochemical properties of the sensor were investigated by cyclic voltammetry and amperometry. The experimental results suggest that the composites have an excellent catalytic property toward dopamine with a wide linear range from 0.5[Formula: see text][Formula: see text]M–6.48[Formula: see text]mM, a low detection limit of 0.17[Formula: see text][Formula: see text]M ([Formula: see text]) and high sensitivity of 413.72[Formula: see text][Formula: see text]A[Formula: see text]mM[Formula: see text] cm[Formula: see text]. In addition, the sensor exhibits long-term stability, good reproducibility and anti-interference.

Green facile synthesis of biowaste-converted Cu-Cu2O/BPC for non-enzymatic hydrogen peroxide sensing

Despite the rapid development of non-enzyme sensors, there is an urgent need for a sensor that can produce sensing materials without the use of reducing agents. Herein，a green biowaste conversion strategy is elaborately developed to fabricate advanced Cu-based sensing material, in which the Cu-Cu 2 O/BPC-1 was obtained by facilely carbonizing the bamboo powder soaked with Cu (NO 3 ) 2 without using any reduction agents. Particularly, the Cu-Cu 2 O particles were uniformly anchored on the mesoporous carbon plate. Profited from the synergistic effect between biomass carbon plate and Cu-Cu 2 O particles, electrochemical measurements showed that the prepared Cu-Cu 2 O/BPC-Y/GCE sensor demonstrated prominent catalytic activity for H 2 O 2 . In particular, the Cu-Cu 2 O/BPC-1/GCE sensor displayed a wide linear range (1–8330 μM), a low detection limit (0.35 μM) (S/N = 3), and excellent selectivity, reproducibility and stability. This work provides a cost-effective and environmentally friendly strategy to fabricate the non-enzymatic H 2 O 2 sensor. • Cu-CuO/BPC-1 was obtained by adjusting the mass ratio of bamboo powder to copper nitrate. • Non-enzyme H 2 O 2 sensors were prepared from waste biomass materials without using any reducing agents. • The as-prepared sensor displayed a wide linear range and a low detection limit.

High-performance non-enzymatic hydrogen peroxide electrochemical sensor prepared with a magnetite-loaded carbon nanotube waterborne ink

• Magnetite-loaded carbon nanotube waterborne ink with peroxidase-like activity. • Mechanical stability allowing determinations in forced convection/quiescent conditions. • Ease of preparation, suitable for inkjet and screen-printing methods. • Remarkable analytical figures of merit towards the detection of hydrogen peroxide. • Composite’s formulation optimized to maximize its catalytic properties. In this study, a non-enzymatic hydrogen peroxide sensor was developed employing a waterborne carbon nanotube ink containing catalytic submicrometric particles of magnetite. Magnetite particles were synthesized via a solvothermal method and characterized by scanning electron microscopy (SEM) and powder X-ray diffraction measurements (XRD). For the ink preparation, Fe 3 O 4 particles were incorporated into a waterborne carbon nanotube ink and the mixture was drop casted onto a glassy carbon and used for coating Valox TM strips to fabricate standalone electrodes. As a non-enzymatic amperometric sensor, the resulting Fe 3 O 4 /CNT ink coated electrodes exhibited high-performance values towards the detection of H 2 O 2 , presenting a limit of detection of 0.5 µM, a linear detection range up to 2 mM, a sensitivity of 1040 µA cm −2 mM −1 and tolerance to common interfering agents like ascorbic acid, glucose and Cl - /SO4 -2 ions. Moreover, the Fe 3 O 4 /CNT electrodes presented a high stability, losing only 20% of their catalytic performance after three weeks.

Enzyme-like activity of cobalt-MOF nanosheets for hydrogen peroxide electrochemical sensing

Metal-organic frameworks (MOFs) are receiving increased attention as new functional nanomaterials for the development of electrochemical sensors. Herein, we develop an electrochemical platform for non-enzymatic hydrogen peroxide detection built with a composite of two-dimensional cobalt MOF nanosheets and Nafion (2D-Co-MOF@Nafion). The feasibility of the 2D-Co-MOF@Nafion composite as active material for high performance hydrogen peroxide sensor was investigated by using cyclic voltammetry and chronoamperometry. Its voltammetric response reveals an efficient charge transport through the MOF composite, and rapid electron exchange between MOF and electrode. Notably, these MOF nanosheets exhibit enzyme-like activity for the non-common catalytic oxidation of hydrogen peroxide, leading to an electrochemical sensor with rapid quantitative detection, outstanding sensitivity, selectivity, stability, and durability at the desirable neutral pH. In particular, for a cobalt metal loading of 1.2 nanomol, the sensor yields amperometric H2O2 detection with characteristic electrocatalytic parameters of imax= 5.7 mA cm−2 and KM = 13 mM. Moreover, linear ranges of up to either 1 mM or 10 mM are achieved, with sensitivities as high as 570 ± 5 A cm−2 mM−1 or 395 ± 10 A cm−2 mM−1 for the low and high concentration ranges, respectively. The particular coordination chemistry of the MOF consisting of a regular arrangement of multiple Co(II) redox metal sites connected by appropriate organic ligands can provide inherent enzyme-mimicking properties, thereby explaining the higher oxidase-like activity of the present MOF. This work raises the new idea of using two-dimensional cobalt-based MOFs as active nanozymes, offering exciting opportunities in the design of non-enzymatic electrochemical sensing devices.

A non-enzymatic electrochemical hydrogen peroxide sensor based on copper oxide nanostructures.

This article describes the synthesis of nanostructured copper oxide on copper wires and its application for the detection of hydrogen peroxide. Copper oxide petal nanostructures were obtained by a one-step hydrothermal oxidation method. The resulting coating is uniform and dense and shows good adhesion to the wire surface. Structure, surface, and composition of the obtained samples were studied using field-emission scanning electron microscopy along with energy-dispersive spectroscopy and X-ray diffractometry. The resulting nanostructured samples were used for electrochemical determination of the H2O2 content in a 0.1 M NaOH buffer solution using cyclic voltammetry, differential pulse voltammetry, and i–t measurements. A good linear relationship between the peak current and the concentration of H2O2 in the range from 10 to 1800 μM was obtained. The sensitivity of the obtained CuO electrode is 439.19 μA·mM−1. The calculated limit of detection is 1.34 μM, assuming a signal-to-noise ratio of 3. The investigation of the system for sensitivity to interference showed that the most common interfering substances, that is, ascorbic acid, uric acid, dopamine, NaCl, glucose, and acetaminophen, do not affect the electrochemical response. The real milk sample test showed a high recovery rate (more than 95%). According to the obtained results, this sensor is suitable for practical use for the qualitative detection of H2O2 in real samples, as well as for the quantitative determination of its concentration.

Tantalum nitride nanotube structured electrode for non-enzymatic hydrogen peroxide sensing via photoelectrochemical route

• A non-enzymatic photoelectrochemical (PEC) H 2 O 2 sensor has been constructed. • The sensor consists of Ta 3 N 5 nanotube electrode, without any other catalysts. • High sensitivity of 167.9 uA cm −2 mM −1 has been obtained for H 2 O 2 sensing. • The work expands the application of Ta 3 N 5 in the field of chemical analysis. Photoelectrochemical (PEC) sensing holds great promise in the field of analytical chemistry owing to its high sensitivity, low cost and simple equipment. In this paper, tantalum nitride (Ta 3 N 5 ) photoanode is fabricated for PEC H 2 O 2 sensor through an anodization procedure combined with subsequent nitridation in NH 3 atmosphere. The crystalline phase, morphology and light adsorption property of Ta 3 N 5 are characterized by X-ray diffraction, scanning electron microscope and UV–vis diffuse reflectance spectrophotometer, the results show that Ta 3 N 5 has nanotube structure and can absorb light to 620 nm. The PEC tests exhibit Ta 3 N 5 photoelectrode has much higher current and lower onset potential for hydrogen peroxide (H 2 O 2 ) oxidation than H 2 O oxidation, indicating H 2 O 2 possesses faster reaction kinetics over Ta 3 N 5 surface. Furthermore, the Ta 3 N 5 photoelectrode exhibited a high sensitivity of 167.9 μA cm −2 mM −1 for H 2 O 2 determination in the concentration range of 0.1 ∼ 2.6 mM. It is supposed that the fast extraction of hole by H 2 O 2 on the Ta 3 N 5 electrode surface is the key for the high sensing performance achieved in our fabricated PEC sensor.

Aluminosilicate nanoparticles decorated by copper hexacyanoferrate as a good electrocatalyst for non-enzymatic hydrogen peroxide sensing

In this work, porous amorphous aluminosilicates nanoparticles (PAS NPs) have been synthesized by the sol-gel method. The crystals particle sizes of PAS NPs were about 90 nm by SEM. Carbon paste modified PAS NPs/Cu (CPE/PAS NPs/Cu) was placed into a potassium hexacyanoferrate solution by continuous cycling of the potential for deposition of copper hexacyanoferrate (CuHCF) at the surface of CPE/PAS NPs/Cu. The cyclic voltammograms of CPE/PAS NPs/CuHCF show two pairs (Fe(CN)6 3−/Fe(CN)6 4− and Cu2+/Cu+) of redox couples due to the system. The total surface coverage of immobilized CuHCF was calculated at about 1.65 × 10−7 mol cm−2. Finally, this modified electrode responded to the different concentrations of hydrogen peroxide. The linear range and limit of detection (LOD) were 0.8–1.8 × 102 μmol L−1 and 0.65 μmol L−1, respectively. The fabrication of this electrode is easy and it is simple and low-cost. The stability, reproducibility, and repeatability of this modified electrode are acceptable.

Highly Sensitive Amperometric Detection of Hydrogen Peroxide in Saliva Based on N-Doped Graphene Nanoribbons and MnO2 Modified Carbon Paste Electrodes.

Four different graphene-based nanomaterials (htGO, N-htGO, htGONR, and N-htGONR) were synthesized, characterized, and used as a modifier of carbon paste electrode (CPE) in order to produce a reliable, precise, and highly sensitive non-enzymatic amperometric hydrogen peroxide sensor for complex matrices. CPE, with their robustness, reliability, and ease of modification, present a convenient starting point for the development of new sensors. Modification of CPE was optimized by systematically changing the type and concentration of materials in the modifier and studying the prepared electrode surface by cyclic voltammetry. N-htGONR in combination with manganese dioxide (1:1 ratio) proved to be the most appropriate material for detection of hydrogen peroxide in pharmaceutical and saliva matrices. The developed sensor exhibited a wide linear range (1.0–300 µM) and an excellent limit of detection (0.08 µM) and reproducibility, as well as high sensitivity and stability. The sensor was successfully applied to real sample analysis, where the recovery values for a commercially obtained pharmaceutical product were between 94.3% and 98.0%. Saliva samples of a user of the pharmaceutical product were also successfully analyzed.

HCN-derived polymers from thermally induced polymerization of diaminomaleonitrile: A non-enzymatic peroxide sensor based on prebiotic chemistry

HCN-derived polymers have recently attracted considerable attention due to their promising applications as multifunctional materials. This study, inspired by plausible early Earth geochemical conditions, describes a strategy to synthesize them from the self-initiated thermal bulk polymerization of the HCN tetramer, diaminomaleonitrile (DAMN), with outstanding sensing properties. These conjugated polymers were obtained through noncatalysed and simple isothermal reactions at 170 °C in the solid-state, and experiments at 190 °C permitted polymerization in the melt. Both processes are highly efficient, allowing quantitative yields of the end products. The conductivity properties of both polymers have been explored to show their high potential, especially DAMN polymers synthesized in melt, as nonenzymatic peroxide sensors. To better understand the differences found between the two series, structural characterisation was carried out using compositional data, Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) and X-ray photoelectron (XPS) spectroscopies, and X-ray diffraction (XRD) measurements. The interpretation of the structural data suggests that a two-dimensional (2-D) macrostructure based on N-heterocyclics is predominant regardless of the state of monomer aggregation during the course of polymerization, but preferably formed in the melt. The morphological and thermal stability properties of the polymers based on DAMN were also evaluated. Finally, the most likely mechanisms based on the dehydrocyanation and deamination reactions that take place during the polymerization reaction are proposed. This study demonstrates the robust and straightforward character of these thermally activated polymerizations, which are of interest to chemical evolution research and to current materials and surface science.

Photolithographic 3D microarray electrode-based high-performance non-enzymatic H2O2 sensor

In recent years, electrochemical biosensors have been widely used in health care, and, due to the increasing demand for their use, new sensing performance requirements have been proposed. Widening detection range and speeding up response rate while improving the sensitivity of these sensors is a major current challenge. In this study, a high-performance three-dimensional (3D) non-enzymatic hydrogen peroxide biosensor was fabricated based on a simple photolithographic process. Neatly arranged cylindrical microarrays (MA) with clear edges were fabricated using SU-8 photoresist. Subsequently, a gold thin film was sputtered onto the MA to form a 3D Au/microarray electrode (Au/MAE). Additionally, we investigated the optimal size of the MA (aspect ratio = 2, diameter = 30 µm) required to obtain an Au/MAE with the best electron transfer properties. Based on these results, a 3D CuNPs/Au/MAE sensor was constructed via the electrochemical in-situ reduction of copper nanoparticles (CuNPs). Due to its increased specific surface area and contact sites, this 3D sensor with high stability and good selectivity for detecting hydrogen peroxide exhibited higher sensitivity and wider range of detection than 2D CuNPs/AuE sensor. Consequently, the design of 3D microarray structure provides a new strategy for the fabrication of high-performance sensors that can be used in clinical applications.

A Two-step Electrodeposition of Pd-Cu/Cu2O Nanocomposite on FTO Substrate for Non-enzymatic Hydrogen Peroxide Sensor

Background: Hydrogen peroxide (H2O2) is a common reagent in the production and living, but excessive H2O2 may enhance the danger to the human body. Consequently, it is very important to develop economical, fast and accurate techniques for detecting H2O2. Methods: A simple two-step electrodeposition process was applied to synthesize Pd-Cu/Cu2O nanocomposite for non-enzymatic H2O2 sensor. Cu/Cu2O nanomaterial was firstly electrodeposited on FTO by potential oscillation technique, and then Pd nanoparticles were electrodeposited on Cu/Cu2O nanomaterial by cyclic voltammetry. The chemical structure, component, and morphology of the synthesized Pd-Cu/Cu2O nanocomposite were characterized by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. The electrochemical properties of Pd-Cu/Cu2O nanocomposite were studied by cyclic voltammetry and amperometry. Results: Under optimal conditions, the as-fabricated sensor displayed a broad linear range (5-4000 μM) and low detection limit (1.8 μM) for the determination of H2O2. The proposed sensor showed good selectivity and reproducibility. Meanwhile, the proposed sensor has been successfully applied to detect H2O2 in milk. Conclusion: The Pd-Cu/Cu2O/FTO biosensor exhibits excellent electrochemical activity for H2O2 reduction, which has great potential application in the field of food safety.

Nonenzymatic Hydrogen Peroxide Detection Using Surface-Enhanced Raman Scattering of Gold-Silver Core-Shell-Assembled Silica Nanostructures.

Hydrogen peroxide (H2O2) plays important roles in cellular signaling and in industry. Thus, the accurate detection of H2O2 is critical for its application. Unfortunately, the direct detection of H2O2 by surface-enhanced Raman spectroscopy (SERS) is not possible because of its low Raman cross section. Therefore, the detection of H2O2 via the presence of an intermediary such as 3,3,5,5-tetramethylbenzidine (TMB) has recently been developed. In this study, the peroxidase-mimicking activity of gold–silver core–shell-assembled silica nanostructures (SiO2@Au@Ag alloy NPs) in the presence of TMB was investigated using SERS for detecting H2O2. In the presence of H2O2, the SiO2@Au@Ag alloy catalyzed the conversion of TMB to oxidized TMB, which was absorbed onto the surface of the SiO2@Au@Ag alloy. The SERS characteristics of the alloy in the TMB–H2O2 mixture were investigated. The evaluation of the SERS band to determine the H2O2 level utilized the SERS intensity of oxidized TMB bands. Moreover, the optimal conditions for H2O2 detection using SiO2@Au@Ag alloy included incubating 20 µg/mL SiO2@Au@Ag alloy NPs with 0.8 mM TMB for 15 min and measuring the Raman signal at 400 µg/mL SiO2@Au@Ag alloy NPs.