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The H2 production using N2H4 splitting (OHzS) was often constrained by the requirement for insufficient stability, distinct catalysts at the anode and cathode, and the high-cost electrocatalyst associated with confined activity. This work verified the efficacy of surfactant-free branched CuAu nano-alloy as a bifunctional electrocatalyst for H2 production. Benefiting from its favorable electronic structure and surfactant-free surface, surfactant-free CuAu nano-alloy demonstrated a reduced over-potential compared with pure Cu, pure Au, and CuAu nano-alloy prepared by surfactant. When using branched CuAu nano-alloy as both cathodic and anodic electrodes, a cell voltage of 0.768 V was required to drive a current density of 10 mA/cm2. After 2550 min of H2 generation, the amplitude of the working potential for anodic reactions was found to be less than 0.92%. The enhanced electrocatalytic activity could be also applied to H2O2 and NaNO2 sensors. The CuAu nano-alloy exhibited a 2.35-folds increase in sensitivity compared to pure Au nano-crystals in the detection of H2O2. Moreover, the detection of NaNO2 in water solution has been successfully achieved. The detection range 0–175.0 mM was much wider than that of sensors in previous works. [ABSTRACT FROM AUTHOR]

The NiAlO@PPy-Ag sensing material was designed and prepared via in-situ oxidative polymerization of pyrrole monomer on the NiAl-oxide (NiAlO), and then anchoring Ag nanoparticles (NPs) on the surface of the NiAlO@PPy carrier. It was determined that the NiAlO particles were encased by PPy chains and Ag NPs were homogeneously distributed on the NiAlO@PPy based on various structural characterization. Subsequently, the NiAlO@PPy-Ag was directly fabricated into a non-enzymatic sensor for the detection of H2O2, which sensor showed a high sensitivity and selectivity toward H2O2 with a low detection limit of 0.03 μmol∙L−1 and high sensitivity of 346.50 μA∙mmol−1∙cm−2, and excellent repeatability and reproducibility. The results demonstrated that the NiAlO@PPy-Ag was a promising electrocatalytic material for H2O2 detection in the biological, clinical and environmental fields. [ABSTRACT FROM AUTHOR]

This study is focused on synthesizing environmentally friendly nano-probes for rapid and sensitive detection of H2O2. Biogenic manganese oxide nanoparticles were prepared and capped with two different types of nitrogen doped carbon dots. Nanocomposites are designated as NC1 (semicarbazide hydrochloride as a dopant source) and NC2 (urea as a dopant source). Synthesized nanocomposites (NC1 and NC2) were characterized by different techniques. UV-visible spectra depicted peaks at 298 nm (NC1) and 299 nm (NC2). FTIR confirmed the presence of different functional groups at the surface of nanocomposites. XRD showed the amorphous carbon structure of nanocomposites with particle size of 7 nm (NC1) and 6 nm (NC2). Raman spectra showed the graphitic carbon structure. In both cases, D and G bands were observed with ID/IG ratio equal to 0.76 for NC1 and 0.16 for NC2. NC1 depicted linearity for the concentration range of 10–40 µM with LOD and LOQ of 7 and 24 µM, respectively, while NC2 exhibited linearity over the concentration range of 50–80 µM with LOD of 12 µM and LOQ of 40 µM. Percentage recoveries for spiked samples were calculated to be 99.8–101.8 and 98.5–99.1% for NC1 and NC2, respectively. [ABSTRACT FROM AUTHOR]

Ce-based nanomaterials have been widely studied as catalyst for their unique electronic structure, but there are few reports on the combination of cerium catalytic activity and photoluminescence performance. In this paper, by adjusting the molar ratio of Ce/P, CeO2/CePO4 nanocrystal were synthesized in one-step, which integrated the enzyme activities of CeO2 and CePO4, as well as the optical property of CePO4 together. Taking H2O2 as analyte model, utilizing the catalase oxidization activity of CeO2/CePO4, TMB molecule can be oxidized, leading to the increased absorption intensity of 652 nm, realizing the colorimetric assay of H2O2. On the other hand, using the fluorescence of CeO2/CePO4 at 338 nm as output signal, which can be quenched by H2O2 since Ce3+ ions were oxidized into Ce4+, realizing H2O2 fluorescence detection. Compared with the single-signal probe, CeO2/CePO4 provides two sensing modes of fluorescence and colorimetry for H2O2 discrimination to obtain different test results, which can be mutually verified and effectively improve the detection accuracy. [ABSTRACT FROM AUTHOR]

Research into metal nanoparticles has increased, and they have been increasingly used in non-enzymatic sensor applications. However, there have been few reports on the use of natural products to prepare non-precious metal nanoparticles in an eco-friendly (green) manner. Studies were conducted on Cu nanoparticles (Cu NPs) prepared by the use of natural gallic acid (GA). This method is environmentally friendly and can be applied to H2O2 detection. As-obtained Cu NPs were characterized by x-ray photoelectron spectroscopy (XPS), powder x-ray diffraction (XRD), and transmission electron microscopy (TEM). When applied to H2O2 detection, Cu NPs had good sensitivity, stability, and anti-interference properties. Its electrochemical performance is no less than that of precious metal nanomaterials. Cu NPs mainly exhibit good sensitivity, reaching 5.74 μA mM-1 cm-2; the concentration range thereof is 1–20 mM. The process of constructing nanoparticles in this work used natural products, making it environmentally friendly and proving the practicality of constructing non-precious metal nanoparticles and the feasibility of their application to H2O2 detection. [ABSTRACT FROM AUTHOR]

As an important detection technology, how to realize the rapid detection of H2O2 is very important for the early diagnosis of some diseases. Herein, octahedral porous carbon composites containing Cu and MoO2 are prepared by using bimetallic metal–organic frame (MOF) NENU-5 as precursor. It is found that Cu and MoO2 nanoparticles of Cu-MoO2-C are uniformly dispersed in the porous carbon framework. For the electrochemical detection of H2O2, compared with the Cu-C composite without MoO2, Cu-MoO2-C shows stronger redox ability, higher sensitivity (121 μA mM−1 cm−2), and lower detection limit (95.5 nM). In addition, Cu-MoO2-C also shows strong anti-interference ability and H2O2 detection sensitivity in the presence of a variety of interference substances. Our work proves that MoO2 has a good H2O2 reduction ability, and it also proves that the H2O2 detection performance of the sensors can be improved by using the constructed metal–metal oxide-porous frame materials. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H2O2), as a signaling molecule, plays a vital role in a wide variety of signaling transduction processes, aging, and diseases. However, the excessive production of H2O2 causes various diseases. Herein, we develop a novel method for H2O2 detection in live cells via dark-field scattering spectroscopy with gold triangular nanoprisms (AuTNPs) as probes. The corners of AuTNPs would be gradually oxidatively etched by the strong coordination of Br• which is generated by enzymatic reactions in the presence of horseradish peroxidase (HRP), bromide ion and trace hydrogen peroxide. Benefitting from the morphological change, the single AuTNP based plasmonic nanoprobe shows notable blueshifts and scattering color changes which could be real-time monitored under the dark-field microscopy. The peak position in the scattering spectra of individual AuTNP blueshifts linearly with the increase of H2O2 concentration, and exhibits high sensitivity to H2O2 in a large range from 2.5 to 100 µM with a low detection limit (LOD) of 0.74 µM. Moreover, the experimental results were supported by the simulated results via the finite-difference time-domain (FDTD) method. The nanoprobes have been further used for intracellular H2O2 detection in live cells. Besides, the etching of AuTNP also provides an alternative method to design novel plasmonic logic chips and write-once plasmonic memories. [ABSTRACT FROM AUTHOR]

The successful synthesis is reported of Mn, Fe, Co, Ni, Cu-doped g-C3N4 nanoflakes via a simple one-step pyrolysis method, respectively. Among them, the Fe-doped g-C3N4 nanoflakes exhibited the highest peroxidase-like activity, which can be used for colorimetric detection of hydrogen peroxide (H2O2) and sarcosine (SA), within the detection ranges of 2–100 μM and 10–500 μM and detection limits of 1.8 μM and 8.6 μM, respectively. The catalytic mechanism of the Fe-doped g-C3N4 nanoflake was also explored and verified the generation of hydroxyl radical (•OH) through fluorescence method. It is believed that the Fe-doped g-C3N4 nanoflakes as enzyme mimics will greatly promote the practical applications in a variety of fields in the future including biomedical science, environmental governance, antibacterial agent, and bioimaging due to their extraordinary catalytic performance and stability. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks with diverse structures and unique properties have demonstrated that can be an ideal substitute for natural enzymes in colorimetric sensing platform for analyte detection in various fields such as environmental chemistry, biotechnology and clinical diagnostics, which have attracted the scientist's attention, recently. In this study, a porous coordination network (denoted as PCN-222) was synthesized as a new biomimetic material from an iron linked tetrakis (4-carboxyphenyl) porphyrin (named as Fe-TCPP) as a heme-like ligand and Zr6 linker as a node. This catalyst shows the peroxidase and catalase activities clearly. The mechanism of peroxidase activity for PCN-222 was investigated using the spectrophotometric methods and its activity was compared with the other nanoparticles which, the results showed a higher activity than the other catalysts. Also, the hydrogen peroxide was detected by PCN-222(Fe) based on the peroxidase-like activity. For detection of hydrogen peroxide a linear range of 3–200 µM and detection of limit (LOD) 1 µM (3σ/slope), under optimal conditions were obtained. Moreover, based on the high tendency of PCN-222(Fe) to combine with the TMB as a chromogenic substrate in the peroxidase-like activity, we developed the sensitive and selective colorimetric assay for glucose detection that was found a detection limit (LOD) of 2.2 µM in the linear range from 12 to 75 µM. Finally due to the good catalytic activity of PCN-222(Fe), it was used to detection of glucose and hydrogen peroxide in real samples. [ABSTRACT FROM AUTHOR]

The mechanism behind the variation in the photoluminescence (PL) of a MoS2 nanohybrid material with pH was investigated. Highly fluorescent MoS2 quantum dots dispersed across MoS2 nanosheets (MoS2 QDNS) were synthesized by a hydrothermal route in the presence of NaOH. Upon reducing the pH from 13 to 6.5, the PL intensity was markedly quenched. The removal of dangling sulfur atoms by adding mineral acids could be a plausible mechanism for this PL quenching, together with the inner filter effect and Förster resonance energy transfer due to the resulting species. A label-free turn-on fluorescence sensor for H2O2 was developed using this hybrid material. The PL of the acidified MoS2 QDNS at pH 6.5 increased (i.e., recovered) linearly with the concentration of H2O2. The dynamic range of the sensor was found to be 2–94 μM with a limit of detection (LOD) of 2 μM. This sensing strategy was also extended for the detection of glucose by appending glucose oxidase (GOx) as a catalyst. In the presence of GOx, glucose oxidizes to gluconic acid and H2O2, so the original level of glucose can be estimated by determining the H2O2 present. The absence of a complicated enzyme immobilization step is the prime advantage of the present glucose sensor. The current work exemplifies the utility of MoS2-based nanoparticle systems in the biological sensor domain. [ABSTRACT FROM AUTHOR]

The mechanism behind the variation in the photoluminescence (PL) of a MoS2 nanohybrid material with pH was investigated. Highly fluorescent MoS2 quantum dots dispersed across MoS2 nanosheets (MoS2 QDNS) were synthesized by a hydrothermal route in the presence of NaOH. Upon reducing the pH from 13 to 6.5, the PL intensity was markedly quenched. The removal of dangling sulfur atoms by adding mineral acids could be a plausible mechanism for this PL quenching, together with the inner filter effect and Förster resonance energy transfer due to the resulting species. A label-free turn-on fluorescence sensor for H2O2 was developed using this hybrid material. The PL of the acidified MoS2 QDNS at pH 6.5 increased (i.e., recovered) linearly with the concentration of H2O2. The dynamic range of the sensor was found to be 2–94 μM with a limit of detection (LOD) of 2 μM. This sensing strategy was also extended for the detection of glucose by appending glucose oxidase (GOx) as a catalyst. In the presence of GOx, glucose oxidizes to gluconic acid and H2O2, so the original level of glucose can be estimated by determining the H2O2 present. The absence of a complicated enzyme immobilization step is the prime advantage of the present glucose sensor. The current work exemplifies the utility of MoS2-based nanoparticle systems in the biological sensor domain. [ABSTRACT FROM AUTHOR]

The detection of hydrogen peroxide (H2O2) is essential due to its extensive application in bio-medical and environment. Herein, we synthesized a novel polyethyleneimine-Au nanoparticle-copper protoporphyrin (PEI-AuNPs-CuPP) nanocomposite toward H2O2 detection. Ultraviolet-visible spectrometry (UV-vis), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR) were used to characterize this nanomaterial. Analytical performance of this proposed sensor was evaluated through differential pulse voltammetry (DPV) and cyclic voltammetry (CV). It was found surprisingly that the PEI-AuNPs-CuPP-based sensor exhibited sensing for H2O2 with a detection limit of 91.74 aM. In addition, this sensor displayed superb selectivity in the presence of dopamine (DA), ascorbic acid (AA), uric acid (UA), and glucose (Glu), which held satisfactory analytical performance for the detection of H2O2 in human serum samples, indicating a promising application in biological sample analysis. [ABSTRACT FROM AUTHOR]

Highly sensitive, selective, and stable hydrogen peroxide (H2O2) detection using nanozyme-based catalysts are desirable for practical applications. Herein, vertical α-FeOOH nanowires were successfully grown on the surface of carbon fiber paper (CFP) via a low-temperature hydrothermal procedure. The formation of vertical α-FeOOH nanowires is ascribed to the structure-directing role of sodium dodecyl sulfate. The resulting free-standing electrode with one-dimensional (1D) nanowires offers oriented channels for fast charge transfer, excellent electrical contact between the electrocatalyst and the current collector, and good mechanical stability and reproducibility. Thus, it can serve as an efficient electrocatalyst for the reduction and sensitive detection of H2O2. The relation of the oxidation current of H2O2 with the concentration is linear from 0.05 to 0.5 mM with a sensitivity of -0.194 mA/(mM·Lcm2) and a low detection limit of 18 μM. Furthermore, the portability in the geometric tailor and easy device fabrication allow extending the general applicability of this free-standing electrode to chemical and biological sensors. [ABSTRACT FROM AUTHOR]

A bio-mediated route for the synthesis of silver nanoparticles (AgNPs) is an area of interest in research of many scientists, and this work aims to study the electrocatalytic activity of these particles during electrochemical sensing of H2O2 in a phosphate buffer media. The composite electrodes were fabricated using nearly spherical AgNPs and reduced graphene oxide (rGO) with the graphite (99.999% purity) support made of graphite paste. Graphene oxide (GO) was first synthesized using the modified Hummers method followed by rGO synthesis by chemical reduction of GO. rGO is consisting of about nine layers of rGO sheets of a wrinkled surface morphology with an intensity ratio of D to G band (ID/IG) of 1.17 and an interplanar d-spacing of 0.36 nm as evidenced by HRTEM micrograph. There was about 10 times increase in the cell current with the AgNPs-impregnated composite-electrode compared to without AgNPs impregnation, and an overpotential of H2O2 reduction was found to be -1.373 V with a detection limit of 19.04 μM and 95.3% electrode stability with the graphite-rGO-AgNPs composite electrode. A nafion membrane cast on the rGO-AgNPs prevented the leakage of this composite from the electrode surface. The interference of various electroactive compounds on the amperometric response of the graphite-rGO-AgNPs electrode was also investigated. [ABSTRACT FROM AUTHOR]