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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 treatment of wound inflammation is intricately linked to the concentration of reactive oxygen species (ROS) in the wound microenvironment. Among these ROS, H2O2 serves as a critical signaling molecule and second messenger, necessitating the urgent need for its rapid real-time quantitative detection, as well as effective clearance, in the pursuit of effective wound inflammation treatment. Here, we exploited a sophisticated 3D Cu2-xSe/GO nanostructurebased nanonzymatic H2O2 electrochemical sensor, which is further decorated with evenly distributed Pt nanoparticles (Pt NPs) through electrodeposition. The obtained Cu2-xSe/GO@Pt/SPCE sensing electrode possesses a remarkable increase in specific surface derived from the three-dimensional surface constructed by GO nanosheets. Moreover, the localized surface plasma effect of the Cu2-xSe nanospheres enhances the separation of photogenerated electron-hole pairs between the interface of the Cu2-xSe NPs and the Pt NPs. This innovation enables near-infrared light-enhanced catalysis, significantly reducing the detection limit of the Cu2-xSe/GO@Pt/SPCE sensing electrode for H2O2 (from 1.45 mM to 0.53mM) under NIR light. Furthermore, this biosensor electrode enables in-situ real-time monitoring of H2O2 released by cells. The NIR-enhanced Cu2-xSe/GO@Pt/SPCE sensing electrode provide a simple-yeteffective method to achieve a detection of ROS (H2O2-OH) with high sensitivity and efficiency. This innovation promises to revolutionize the field of wound inflammation treatment by providing clinicians with a powerful tool for accurate and rapid assessment of ROS levels, ultimately leading to improved patient outcomes. [ABSTRACT FROM AUTHOR]

This article is devoted to the study of the effect of ZnO nanoparticles on the development of tolerance to salt stress in rye samples. As a quantitative criterion for assessing the degree of oxidative stress, the amount of H2O2 released in the samples during growth was determined. For these purposes, an electrochemical sensor based on hydrothermally synthesized wall-shaped NiO nanostructures was developed. This sensor has been proven to demonstrate high sensitivity (2474 µA·mM−1), a low limit of detection (1.59 µM), good selectivity against common interferents, and excellent long-term stability. The investigation reveals that the incorporation of ZnO nanoparticles in irrigation water notably enhances rye's ability to combat salt stress, resulting in a decrease in detected H2O2 levels (up to 70%), coupled with beneficial effects on morphological traits and photosynthetic rates. [ABSTRACT FROM AUTHOR]

The use of hydrogen peroxide (produced in situ or ex situ) as the main agent in oxidative processes of environmental pollutant removal is widely studied. The degradation of water pollutants, such as dyes, pharmaceuticals, cosmetics, petroleum derivatives, and even pathogens, has been successfully obtained by different techniques. This review gives an overview of the more recent methods developed to apply oxidative processes mediated by H2O2 and other reactive oxygen species (ROS) in environmental catalysis, with particular attention to the strategies (Fenton-like and Bio-Fenton, photo- and electro-catalysis) and the materials employed. A wide discussion about the characteristics of the materials specifically studied for hydrogen peroxide activation, as well as about their chemical composition and morphology, was carried out. Moreover, recent interesting methods for the generation and use of hydrogen peroxide by enzymes were also presented and their efficiency and applicability compared with the Fenton and electro-Fenton methods discussed above. The use of Bio-Fenton and bi-enzymatic methods for the in situ generation of ROS seems to be attractive and scalable, although not yet applied in full-scale plants. A critical discussion about the feasibility, criticalities, and perspectives of all the methods considered completes this review. [ABSTRACT FROM AUTHOR]

The treatment of wound inflammation is intricately linked to the concentration of reactive oxygen species (ROS) in the wound microenvironment. Among these ROS, H2O2 serves as a critical signaling molecule and second messenger, necessitating the urgent need for its rapid real-time quantitative detection, as well as effective clearance, in the pursuit of effective wound inflammation treatment. Here, we exploited a sophisticated 3D Cu2-xSe/GO nanostructure-based nanonzymatic H2O2 electrochemical sensor, which is further decorated with evenly distributed Pt nanoparticles (Pt NPs) through electrodeposition. The obtained Cu2-xSe/GO@Pt/SPCE sensing electrode possesses a remarkable increase in specific surface derived from the three-dimensional surface constructed by GO nanosheets. Moreover, the localized surface plasma effect of the Cu2-xSe nanospheres enhances the separation of photogenerated electron-hole pairs between the interface of the Cu2-xSe NPs and the Pt NPs. This innovation enables near-infrared light-enhanced catalysis, significantly reducing the detection limit of the Cu2-xSe/GO@Pt/SPCE sensing electrode for H2O2 (from 1.45 μM to 0.53μM) under NIR light. Furthermore, this biosensor electrode enables in-situ real-time monitoring of H2O2 released by cells. The NIR-enhanced Cu2-xSe/GO@Pt/SPCE sensing electrode provide a simple-yet-effective method to achieve a detection of ROS (H2O2、-OH) with high sensitivity and efficiency. This innovation promises to revolutionize the field of wound inflammation treatment by providing clinicians with a powerful tool for accurate and rapid assessment of ROS levels, ultimately leading to improved patient outcomes.

Multifunctional materials based on carbon xerogel (CX) with embedded bismuth (Bi) and iron (Fe) nanoparticles are tested for ultrasensitive amperometric detection of lead cation (Pb2+) and hydrogen peroxide (H2O2). The prepared CXBiFe-T nanocomposites were annealed at different pyrolysis temperatures (T, between 600 and 1050 °C) and characterized by X-ray diffraction (XRD), Raman spectroscopy, N2 adsorption, dynamic light scattering (DLS), and electron microscopies (SEM/EDX and TEM). Electrochemical impedance spectroscopy (EIS) and square wave anodic stripping voltammetry (SWV) performed at glassy carbon (GC) electrodes modified with chitosan (Chi)-CXBiFe-T evidenced that GC/Chi-CXBiFe-1050 electrodes exhibit excellent analytical behavior for Pb2+ and H2O2 amperometric detection: high sensitivity for Pb2+ (9.2·105 µA/µM) and outstanding limits of detection (97 fM, signal-to-noise ratio 3) for Pb2+, and remarkable for H2O2 (2.51 µM). The notable improvements were found to be favored by the increase in pyrolysis temperature. Multi-scale parameters such as (i) graphitization, densification of carbon support, and oxide nanoparticle reduction and purification were considered key aspects in the correlation between material properties and electrochemical response, followed by other effects such as (ii) average nanoparticle and Voronoi domain dimensions and (iii) average CXBiFe-T aggregate dimension. [ABSTRACT FROM AUTHOR]

An exploratory analytical chemistry comprehensive experiment was designed based on Prussian blue analog-derived nanoenzymes. The experiment includes the preparation and characterization of three kinds of Prussian blue analog-derived nanoenzyme materials and the determination of their enzyme catalytic reaction rate constants. These nanomaterials were further applied to hydrogen peroxide detection. As this experiment features inexpensive reagents, mild reaction conditions, obvious experimental phenomena, and reasonable time allocation, it is suitable for undergraduate laboratory teaching to improve students' experimental skills and cultivate their scientific research and innovation ability. [ABSTRACT FROM AUTHOR]

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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]

This article is devoted to the study of the effect of ZnO nanoparticles on the development of tolerance to salt stress in rye samples. As a quantitative criterion for assessing the degree of oxidative stress, the amount of H2O2 released in the samples during growth was determined. For these purposes, an electrochemical sensor based on hydrothermally synthesized wall-shaped NiO nanostructures was developed. This sensor has been proven to demonstrate high sensitivity (2474 µA·mM−1), a low limit of detection (1.59 µM), good selectivity against common interferents, and excellent long-term stability. The investigation reveals that the incorporation of ZnO nanoparticles in irrigation water notably enhances rye’s ability to combat salt stress, resulting in a decrease in detected H2O2 levels (up to 70%), coupled with beneficial effects on morphological traits and photosynthetic rates.

Nanocomposite enzymes are attracting intensive attention worldwide. In the present study, a novel colorimetric H2O2 paper sensor was developed based on a new type of nanocomposites composed of Pd−Pt nanoparticles, hemin functionalized reduced graphene oxide (hemin‐rGO) and carboxylated carbon nanotubes (CNTs‐COOH). The proposed nanocomposites show a high peroxidase‐like activity. It provides a sensitive platform showing a linear response toward H2O2 in the range of 0.05–500 μM with a determination limit of 0.01 μM. Based on this, the composites were applied to construct a paper sensor for H2O2 detection in real samples. The cost‐effectiveness, simplicity and efficiency of this paper sensor could be developed for "point‐of‐care" analysis and other related areas. [ABSTRACT FROM AUTHOR]

Accurate detection of hydrogen peroxide (H 2 O 2) is crucial in health, food and environmental monitoring. In this research, 3D nanostructured indium tin oxide (ITO) electrodes, prepared by the glancing angle deposition technique, were coated with a thin layer of platinum via atomic layer deposition (ALD), and the novel core/shell structure was used for electrochemical detection of H 2 O 2. X-ray diffraction analysis confirmed the presence of crystalline Pt, and morphological assessments via scanning electron microscopy and energy dispersive x-ray spectroscopy revealed conformal deposition of Pt across the micron long ITO columns. The electrode prepared under optimized ALD conditions exhibited two contiguous ranges of linear H 2 O 2 sensitivity: a low concentration range from 1 to 10 μM H 2 O 2 with an outstanding sensitivity of 5400 ± 260 μA mM−1 cm−2 leading to a 0.9 µM limit of detection, and a higher concentration linear range from 10 μM to 8 mM H 2 O 2 with 330 μA mM−1 cm−2 sensitivity. The sensor was selective to H 2 O 2 in the presence of potential interferents found in local drinking water, and it maintained consistent sensing performance over a prolonged period of 50 days with a relative standard deviation of 3.5 %. This promising performance underscores the effectiveness of the deposition techniques employed in this study. [Display omitted] • High surface area ITO/Pt core/shell electrodes are formed by glancing angle deposition and atomic layer deposition. • Conformal Pt coating is confirmed by x-ray diffraction and energy-dispersive x-ray spectroscopy compositional mapping. • High performance H 2 O 2 sensing is demonstrated, with low detection limit, high sensitivity and wide linear ranges. [ABSTRACT FROM AUTHOR]

We herein describe a novel lateral flow assay (LFA) to detect H 2 O 2 by utilizing self-biotinylation of G-quadruplex (G4). In this strategy, the G4 strand promotes the self-biotinylation of G4 itself in the presence of H 2 O 2 , which is then allowed to bind to the FAM-labeled complementary detector probe. The resulting biotin-labeled G4/FAM-detector probe complex is captured on the test line, producing a red-colored band during lateral flow readout. Based on this unique approach, we achieved the naked-eye detection of target H 2 O 2 at concentrations as low as 1 μM, with reliable quantification down to 0.388 μM. This method also demonstrated exceptional specificity in distinguishing H 2 O 2 from other non-target molecules. We further verified its versatile applicability by reliably identifying another biomolecule, choline, by coupling with choline oxidase, which generates H₂O₂ during oxidation. This novel LFA strategy holds great promise as a powerful point-of-care testing (POCT) platform for detecting a large spectrum of target biomolecules by employing their corresponding oxidases. [ABSTRACT FROM AUTHOR]

• High selectivity and low detection limit for the recognition of H 2 O 2. • High solid-state fluorescence quantum yield and long fluorescence lifetime. • Excellent aggregation-induced emission (AIE) and twisted intramolecular charge transfer (TICT) properties. H 2 O 2 plays a key regulatory role as a bioendogenous reactive oxygen species in cells and organisms. However, excessive production or accumulation of H 2 O 2 during mitochondrial oxidative stress may lead to oxidative damage of cellular proteins and trigger rheumatic diseases, cancers, and a variety of neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. In addition, H 2 O 2 is a very useful chemical widely employed in the textile and chemical industries, and its excessive emission not only pollutes the environment but also jeopardizes human health. Therefore, the sensitive and specific detection and removal of H 2 O 2 is important for early diagnosis of diseases, treatment prognosis and environmental pollution monitoring. We have designed two novel triphenylamine-based AIEgens MOTPP and MOTPP-B , which each have a high solid-state fluorescence quantum yield and excellent aggregation-induced emission properties. MOTPP-B has high selectivity and anti-interference ability toward H 2 O 2 , a wide pH tolerance range, a sensing process that is complete in under 40 min, and a low detection limit of 120.77 nM. It has been successfully applied for the detection of low concentrations of H 2 O 2 in the environment and to dual-channel imaging of low concentrations of exogenous H 2 O 2 in living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • NH 2 -UiO-67(Zr/Cu) nanozyme synthesized using a classic solvothermal method. • Developed a dual-mode colorimetric/fluorescent sensor for sensitive H 2 O 2 detection. • Designed a smartphone-assisted portable device for on-site H 2 O 2 detection. • The sensor exhibits high selectivity and interference resistance in complex matrices. • Portable device enables rapid, reliable, and user-friendly H 2 O 2 monitoring. Hydrogen peroxide (H 2 O 2) is extensively used in water treatment and food preservation for its pathogen-killing efficacy. Excessive H 2 O 2 intake, however, can lead to poisoning with symptoms such as abdominal pain and breathing difficulties. Additionally, small amounts of H 2 O 2 may be generated during food preservation, necessitating careful control to meet safety regulations. Real-time detection of H 2 O 2 is crucial for process safety and compliance. In this study, a Zr-MOF-based colorimetric fluorescent nanozyme sensor (NH 2 -UiO-67(Zr/Cu)) along with a smartphone-assisted portable device were developed for detecting H 2 O 2. The sensor, NH 2 -UiO-67(Zr/Cu), combines the stable structural properties of Zr-MOF with ligand-generated fluorescence and exhibits peroxidase-like activity. The sensor demonstrated a detection range of 0–1000 μM, with limits of detection (LOD) of 0.0057 μM for the colorimetric assay and 0.0020 μM for the fluorescence assay. Additionally, we designed and developed a portable, smartphone-assisted device using 3D printing technology. This device offers a detection range of 0–750 μM, with LODs of 0.0093 μM in colorimetric mode and 0.0311 μM in fluorescence mode. The developed colorimetric fluorescent nanozyme sensor and portable device show significant potential for the rapid on-site detection of H 2 O 2 , offering a more convenient and reliable approach for quick identification of analytes in practical applications. [ABSTRACT FROM AUTHOR]

Introducing hollow structure by self-assembly and hard-templating methods enables the increase of specific surface areas and reaction sites toward boosting the electrochemical sensing performance of the manganese oxide-based materials. In this work, a strategy of synthesizing Mn3O4–CeO2 with nanosized hollow spheres was developed by employing cerium oxide as the support skeleton for a superior catalyzing effect toward hydrogen peroxide (H2O2) electroreduction. Herein, the effect of molar ratios of Ce and Mn on the structure and electrocatalytic property of synthesized Mn3O4–CeO2 hollow nanospheres was investigated. Profiting from abundant active sites, high porosity, large specific surface area, and the synergy of Mn3O4 and CeO2, the resulting Mn3O4–CeO2 hollow nanospheres display a wide linear range response (0.005–17 mM) with high sensitivity (176.4 μA mM–1 cm–2) for H2O2 determination. The developed sensor shows excellent stability, selectivity, and recovery for detecting H2O2 in actual samples. This work finds an efficient way to construct hollow structure through self-assembly on a hard-templating surface, providing special insight into the electrochemical properties of transition-metal oxides. [ABSTRACT FROM AUTHOR]

The lack of systematic structural resolution makes it difficult to build specific transition‐metal‐atom‐doped carbonized polymer dots (TMA‐doped CPDs). Herein, the structure‐activity relationship between Cu atoms and CPDs was evaluated by studying the peroxidase‐like properties of Glu−Cu−CPDs prepared by using copper glutamate (Glu) with a Cu−N2O2 initial structure. The results showed that the Cu atoms bound to Glu−Cu−CPDs in the form of Cu−N2C2, indicating that Cu−O bonds changed into Cu−C bonds under hydrothermal conditions. This phenomenon was also observed in other copper‐doped CPDs. Moreover, the carboxyl and amino groups content decreased after copper‐atom doping. Theoretical calculations revealed a dual‐site catalytic mechanism for catalyzing H2O2. The detection of intracellular H2O2 suggested their application prospects. Our study provides an in‐depth understanding of the formation and catalytic mechanism of TMA‐doped‐CPDs, allowing for the generation specific TMA‐doped‐CPDs. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) and their derivatives are emerging biosensing platforms due to their rational structural optimization. Herein, several metalloporphyrin–Porous Coordinated Network-222 (M-PCN-222) are developed for composition-dependent hydrogen peroxide (H2O2) sensing. A typical colorimetric sensing method (via a 3,3′,5,5′-tetramethylbenzidine-induced allochroic reaction) is employed to investigate the intrinsic peroxidase activity of M-PCN-222 (M = Mn, Fe, Co, and Ni). Fe-PCN-222 affords high sensitivity, good selectivity, robust stability, and a widely applicable concentration range. Theoretical investigations of active sites reveal that such different performances stem from the OH* binding on the M-PCN-222 surface. In addition, the adsorption energy of OH* on Fe-PCN-222 is similar to that of natural horseradish peroxidase. Molecular dynamics simulations are performed on Fe-PCN-222 nanorods to study the catalytic process of H2O2 based on their abundant micropores and mesopores. The obtained results suggest that the porphyrinic Fe-PCN-222 nanorod-based colorimetric sensing of H2O2 has great potential in catalysis, biosensors, and food industries. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H2O2), a double-edged sword, exists at all stages of proliferation, invasion, and metastasis of tumor cells; thus, it has become one of the most important markers for the diagnosis and treatment of cancer. Owing to its fast diffusion, natural decomposition, and ultralow level in the extracellular microenvironment, it still poses many challenges in distinguishing and quantifying H2O2 released from tumor cells. Therefore, it is of great importance to establish a fast-response and ultrasensitive method for real-time monitoring of intracellular H2O2 dynamic balance for the study of cancer mechanisms. In this study, a dual-mode electrochemical and electrochemiluminescence (ECL) biosensor was prepared using peroxidase-like N-doped carbon nanotubes loaded with NiCo-layered double-hydroxide (N-CNTs@NiCo-LDH) hollow tubular nanoflowers, which were synthesized using hollow N-CNTs as templates and ultrathin NiCo-LDH nanosheets (Ni/Co = 1:2) grown in situ on their surfaces. The thin and uniform nanopetals with the synergistic effect of Ni and Co make its catalytic performance comparable to that of noble-metal catalysts. Moreover, peroxidase mimics of N-CNTs@NiCo-LDHs serve not only as a redox mediator to H2O2 but also as a scaffold carrier to immobilize luminol to form a solid-state luminophore, which accelerates the generation of reactive oxygen species and decreases the distance between the luminophore and electrode. Furthermore, an electrochemical response speed of 4 s is consistent with the short half-life of H2O2. The experimental results show that electrochemistry with a wide detection range (2.5–187.5 and 187.5–16987.5 μM) can distinguish abundant cancer cells from normal cells, while ultrasensitive ECL (limit of detection of 8.72 nM) can detect H2O2 released from as low as 59 cancer cells per mL. [ABSTRACT FROM AUTHOR]

Photoacoustic (PA) imaging with much deeper tissue penetration and better spatial resolution had been widely employed for the prevention and diagnosis of many diseases. In this study, a new type of hydrogen peroxide (H2O 2) -activated photoacoustic nanoprobe [Mn-AH nanoscale coordination polymer nanodots (NCPs)] was successfully synthesized by a simple one-step method in water phase containing 2,2 ′ -azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), horse radish peroxidase (HRP), and manganese ion (Mn 2 +). After modification by polyethylene glycol (PEG), Mn-AH NCPs exhibited excellent stability and biocompatibility for in vivo H2O2-responsive chromogenic assay with great specificity and sensitivity. In the presence of H2O2, colorless ABTS would be converted by HRP into the oxidized form with strong near-infrared (NIR) absorbance, enabling photoacoustic detection of endogenous H2O2. Using H2O2-activated Mn-AH NCPs, we have successfully performed PA imaging and H2O2 detection of subcutaneous murine colon CT26 tumor and deep-seated orthotopic bladder tumor. Due to the inherent Mn element existence inside the Mn-AH, this nanoprobe also serves as a good T1-weighted magnetic resonance imaging (MRI) contrast agent simultaneously. Lastly, after accomplishing its imaging functions, the Mn-AH NCPs could be cleared out from the body without any long-term toxicity, providing a new opportunity for cancer diagnosis and treatment. [ABSTRACT FROM AUTHOR]

Single‐chain polymer nanoparticles (SCNPs) are soft matter constructed by intrachain crosslinks, with promising prospects in detection and catalysis. Herein, a fluorescent core (SCNPs) with aggregation‐induced emission (AIE) is prepared, applying for H2O2 detection through intermolecular heavy‐atom effect. In detail, the SCNPs precursors are synthesized by ring‐opening copolymerization. Then the SCNPs are prepared by intramolecularly cross‐linking via olefin metathesis. Imitating the structure of AIE dots, SCNPs are encapsulated by H2O2‐responsive polymers. Probably due to the stable secondary structure of SCNPs, the obtained micelles show stable fluorescence performance. Furthermore, as the heavy‐atom, tellurium is introduced into the carriers to construct the heavy‐atom effect. In this micelle‐based system, the SCNPs act as the fluorescent core, and the stimuli‐responsive polymer acts as the carrier and the fluorescent switch. The hydrophilicity of the tellurium‐containing segment is affected by the concentration of H2O2, resulting in a change in the distance from the SCNPs, which ultimately leads to a change in the fluorescence intensity. Furthermore, tellurium is particularly sensitive to H2O2, which can detect low concentrations of H2O2. The SCNPs are merged with AIE materials, with the hope of exploring new probe designs. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H 2 O 2) plays an important role in biology, and biomarker detection in skin interstitial fluid (ISF) has recently shown great promise. However, limited sensors were designed for H 2 O 2 detection in ISF. Therefore, a high-performance wearable H 2 O 2 microneedle sensor with a Prussian blue (PB)/carbon nanotube (CNT) composite electrode and a glucose microneedle sensor based on this electrode were developed. Two types of H 2 O 2 microneedle sensors with different CNT and PB ratios were prepared with ultra-wide detection ranges (1 μΜ–2800 mM/100 nΜ–2200 mM) in accordance with the Hill equation. Ultra-high sensitivity (954.1 μA mM−1 cm−2 and 451 μA mM−1 cm−2) and excellent linearity (R2=0.999) were exhibited in linear ranges of 1 μM to 10 mM and 100 nM to 10 mM, respectively·H 2 O 2 sensors exhibit good selectivity and essentially unattenuated detection signals in artificial ISF. The glucose enzyme-catalyzed microneedle sensor based on the CNT/PB composite electrode also exhibited a great detection range (0.5 mM–180 mM) in accordance with the Hill equation and ultra-wide linear range (0.5 mM–40 mM) with high sensitivity (16.56 μA mM−1 cm−2) and linearity (R2=0.995) in artificial ISF. To verify the practical applicability of the sensors, H 2 O 2 levels in normal and tumor cells were successfully detected by the H 2 O 2 sensor. The glucose levels in ISF before and after eating were successfully detected by the glucose sensor in vivo. The present work developed a low-cost, easy-to-prepare H 2 O 2 sensor and a related enzyme-catalyzed sensor with excellent performance, which hold promising prospects for application across diverse fields. • Highest sensitivity (954.1 μA mM−1 cm−2) in H 2 O 2 linear range of 1 μM to 10 mM. • Largest H 2 O 2 detection range in accordance with the Hill equation. • The released H 2 O 2 in different cells has been detected. • The glucose changes in human ISF in vivo have been detected. • Suitable combination of composite preparation and hollow microneedle modification. [ABSTRACT FROM AUTHOR]

Functionalized few-layer borophene (FFB) was prepared using gallnut extract and coffee waste extract as natural exfoliating and stabilizing agents in an environmentally friendly ultrasonic and high shear exfoliation. Here, a facile precipitation method was employed to grow iron oxide nanoparticles doped with cerium (Ce-FeONPs) onto the surface of FFB. This intriguing combination of materials yielded Ce-FeONPs nanoparticles that exhibited exceptional peroxidase-like activity, efficiently catalyzing the conversion of 3,3′,5,5′-tetramethylbenzidine (TMB) to a blue oxidized TMB (oxTMB) in the presence of hydrogen peroxide (H 2 O 2). Additionally, the introduction of FFB contributes a reducibility effect to the catalytic oxidation of TMB, facilitating the restoration of the oxTMB to TMB. Thus, FFB-Ce-FeONPs showcase intriguing properties encompassing both oxidative and reductive characteristics, suggesting their potential as a reagent for repeated detection of H 2 O 2. Moreover, a colorimetric sensing system enabled the liner detection of H 2 O 2 spanning a concentration range from 0.08 to 1 mM, with a detection limit of 0.03 mM. Noteworthily, FFB-Ce-FeONPs demonstrated sustained efficacy over ten successive recycling cycles, as indicated by consistent slopes and observable color changes. In summary, this work reports the first application of nanoenzymes in repetitive H 2 O 2 detection. Even after ten multiple cycles, the detection limit remains virtually unaltered, underscoring the robustness and enduring effectiveness of the engineered nanomaterial. The proposed simultaneous oxidation and reduction strategies for detecting H 2 O 2 showed a commendable capability in ten cycles of H 2 O 2 detection, thus providing a promising approach in the field of H 2 O 2 detection. [ABSTRACT FROM AUTHOR]

Coronavirus disease 2019 (COVID-19) is a highly contagious illness caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), resulting in a global health crisis. The primary diagnostic method for COVID-19 is quantitative reverse transcription PCR, which is time-consuming and requires expensive instrumentation. Here, we developed an electrochemical biosensor for detecting SARS-CoV-2 biomarkers using a 3D porous polyacrylamide/polyaniline hydrogel (PPG) electrode prepared by UV photopolymerization and in situ polymerization. The electrochemical immunosensor for detecting SARS-CoV-2 N protein via the immune sandwich principle demonstrated a lower detection limit of 42 pg/mL and comparable specificity to a commercial enzyme-linked immunosorbent assay, which was additionally validated in pseudoviruses. The electrochemical sensor for hydrogen peroxide showed a low detection limit of 0.5 μM and excellent selectivity, which was further confirmed in cancer cells under oxidative stress. The biomarkers of SARS-CoV-2 were successfully detected due to the signal amplification capability provided by 3D porous electrodes and the high sensitivity of the antigen-antibody specific binding. This study introduces a novel three-dimensional electrode with great potential for the early detection of SARS-CoV-2. [ABSTRACT FROM AUTHOR]

We aimed to synthesize sensitive electrochemical sensors for hydrogen peroxide sensing by using zinc oxide nanorods grown on a fluorine-doped tin oxide electrode by using the facial hydrothermal method. It was essential to keep the surface morphology of the material (nanorods structure); due to its large surface area, the concerned material has enhanced detection ability toward the analyte. The work presents a non-enzymatic H2O2 sensor using vertically grown zinc oxide nanorods on the electrode (FTO) surfaces with Cu nanoparticles deposited on zinc oxide nanorods to enhance the activity. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-Ray (EDX), X-ray diffraction (XRD), and electrochemical methods were used to characterize copper–zinc oxide nanorods. In addition to the high surface area, the hexagonal Cu-ZnO nanorods exhibited enhanced electrochemical features of H2O2 oxidation. Nanorods made from Cu-ZnO exhibit highly efficient sensitivity of 3415 μAmM−1cm−2 low detection limits (LODs) of 0.16 μM and extremely wide linear ranges (0.001–11 mM). In addition, copper-zinc oxide nanorods demonstrated decent reproducibility, repeatability, stability, and selectivity after being used for H2O2 sensing in water samples with an RSD value of 3.83%. Cu nanoparticles decorated on ZnO nanorods demonstrate excellent potential for the detection of hydrogen peroxide, providing a new way to prepare hydrogen peroxide detecting devices.

Silver nanoparticles (AgNPs)‐based nanozyme sensors are gaining attention for rapid on‐site H2O2 detection, which is beneficial to disease diagnosis and environmental monitoring. However, the severe agglomeration of AgNPs on the electrodes significantly reduced electrochemical catalytic activity. In this work, we fabricated N‐doped Ti3C2 MXene (named Ag/N−Ti3C2) deposited with three‐dimensional flower‐like AgNPs to achieve ultrasensitive H2O2 detection. N doping strategy is employed to improve the conductivity of MXene, and the corresponding catalytic activity of Ag/N−Ti3C2 is enhanced by optimizing the growth process and morphology. The Ag/N−Ti3C2/glassy carbon electrode (Ag/N‐Ti3C2/GCE) sensor exhibited a wide H2O2 detection range (0.05–35 mM), a low limit detection (1.53 μM), and 3.1 % relative standard deviation in 50 repeated cyclic voltammetry measurements. The results above indicate that catalytic activity of metal nanozymes could be influenced by the substrate and both materials jointly determine the sensor's performance. As a result, N‐doped MXene is an attractive candidate for biological sensing and other electrocatalytic applications. [ABSTRACT FROM AUTHOR]

Hydrogen evolution reaction (HER) and electrochemical analysis are two important fields of electrochemical research at present. We found that both HER and some electrochemical analytical reactions relied on the concentration of hydrogen ions (H+) in solution, so we intended to develop an electrode material that is sensitive to H+ and can be used for both HER and some electrochemical analyses. In this work, we synthesized Ni 3 Mo 3 N coupled with nitrogen-rich carbon microspheres (Ni 3 Mo 3 N@NC MSs) as highly efficient electrode material for HER and detection of Hydrogen peroxide (H 2 O 2), which plays an important role in physiological processes. Here the aniline was used as the nitrogen and carbon sources to synthesize Ni 3 Mo 3 N@NC. The Ni 3 Mo 3 N@NC MSs showed high performance for HER in 1 M KOH solution with a small overpotential of 51 mV at 10 mA cm−2 and superior stability. For H 2 O 2 detection, a detection limit of 1 μM (S/N = 3), sensitivity of 120.3 μA·mM−1 cm−2 and linear range of 5 μM–40 mM can be achieved, respectively. This work will open up a low-cost and easy avenue to synthesize transition metal nitrides coupled with N-doped carbon as bifunctional electrode material for HER and electrochemical detection. [Display omitted] • Bifunctional electrode material for HER and H 2 O 2 detection. • Using aniline as the nitrogen source to synthesize TMNs. • Low overpotential of 51 mV at 10 mA cm−2 for HER. • A sensitivity of 120.3 μA·mM−1 cm−2 for detection of H 2 O 2. [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]

Herein, an Au nanoparticles-polydopamine-poly acrylic acid-graphene (Au NPs-PDA-PAA-graphene) multicomponent nanohybrid is fabricated by surface functionalization of graphene alongside extensive in-situ growth of Au nanoparticles. The as-obtained nanocomposite possesses good hydrophilicity, excellent biocompatibility and high biomolecules loading capacity, which acts as an ideal platform for enzyme modification. Considering this fact, Horseradish peroxidase is expressively immobilized upon Au NPs-PDA-PAA-graphene surface, in order to lay the foundations of a biosensor that is majorly based on enzymatic activity. The biosensor exhibits higher sensitivity towards the determination of H2O2 with linearity ranging from 0.1 μm upto 20 mm, and the limit of detection going down to 0.02 μm. Encouraged by its acceptable electrocatalytic performance, this multicomponent system can also be easily employed for carrying out the real-time tracking of H2O2 coming out of Macrophage cells. Therefore, this work designs an extraordinarily updated platform for biosensing related applications, and also presents a reliable platform for the direct detection of H2O2in vivo and in vitro, which show great potential in bioelectroanalytical chemistry, cellular biology, and pathophysiology.

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]

[Display omitted] • An enzyme-free H 2 O 2 amperometric sensor was proposed based on PtPd/IL-CDs/ACF microelectrode. • PtPd/IL-CDs/ACF exhibit higher peak current and lower potential toward H 2 O 2 reduction. • The detection limit of H 2 O 2 was low down to 0.29 μM. • Such amperometric sensor was used for H 2 O 2 detection in living cancer cells successfully. Given the pivotal role of hydrogen peroxide (H 2 O 2) in numerous biological progresses, there has been a recent surge in the development of highly effective electrochemical sensors for H 2 O 2 detection. In this article, we propose an enzyme-free amperometric system for the sensitive and selective recognition of H 2 O 2 , leveraging ultrafine PtPd alloy/ionic liquid-carbon dots (IL-CDs) nanocomposites modified flexible carbon fiber. The IL-CDs were synthesized through the direct electrodeposition of ionic liquid [BMIM][PF 6 ] using Pt sheets as electrodes. Subsequently, a sequential electrodeposition of IL-CDs, H 2 PtCl 6 , and PdCl 2 onto the activated carbon fiber (ACF) yielded the PtPd/IL-CDs/ACF microelectrode. This microelectrode serves as an enzyme-free amperometric sensor for H 2 O 2 detection, exhibiting an improved response with a significantly lower detection limit of 0.29 μM and a relatively broad linear range spanning from 2 to 6561 μM. Furthermore, this enzyme-free amperometric H 2 O 2 sensor demonstrates remarkable stability over extended periods and exceptional performance in practical applications, such as the analysis of commercially available milk, human serum, human urine, and living cancer cells analysis. This study offers a fresh perspective on amperometric sensors based on metal alloys and CDs electrode, highlighting the potential of enzyme-independent detection for hydrogen peroxide in biological systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • SnO 2 -nanowire have been synthesized using PFG400 as a structural directing agent at room temperature. • The SnO 2 -nanowire/GCE sensor was first used to detect hydrogen peroxide. • Theoretical calculations indicate that the adsorption capacity of SnO 2 (1 1 0) crystal surface for H 2 O 2 is superior to that of SnO 2 (1 0 1) crystal surface. • This sensor has good practicality for detecting H 2 O 2 in orange juice and tap water. In this paper, SnO 2 -nanowire was synthesized and constructed as non enzymatic sensor to detect hydrogen peroxide (H 2 O 2). In 0.1 M PBS, the prepared SnO 2 -nanowire/GCE amperometric sensor exhibits a well performance against H 2 O 2 , with the linear detection range of 1.4 μM ∼ 6.66 mM and detection limit of 0.34 μ M. This superior electrochemical sensing performance is mainly due to the mesoporous structure, large specific surface area, and high conductivity of the SnO 2 nanowire. Theoretical calculations indicate that the adsorption capacity of SnO 2 (1 1 0) crystal surface for H 2 O 2 is superior to that of SnO 2 (1 0 1) crystal surface. In addition, the sensor can detect hydrogen peroxide in tap water and orange juice, showing its potential applications. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H 2 O 2) is an environmentally friendly intermediate in the environmental field and also plays an important role in human metabolism, but the production and accumulation of excessive H 2 O 2 will cause harm to the human body, resulting in serious damage to cells. Therefore, N-doped graphene quantum dots Fe 3 O 4 /Co 3 O 4 nanoparticles with core-shell structure were prepared by in-situ synthesis and precipitation. The experimental results show that the prepared Co 3 O 4 nanoparticles have more efficient peroxidase activity than Co 3 O 4 nanoparticles alone. It can catalyze the oxidation of 3, 3, 5, 5-tetramethylbenzidine (TMB) to produce a blue product (TMBox) in the presence of H 2 O 2. In addition, Co 3 O 4 with negative charge in the shell can produce a strong electrostatic driving coordination effect with positively charged TMB, which enhances the affinity between the nanoparticles and the substrate, and selectively catalyzes H 2 O 2 oxidation of colorless TMB to turn it blue. Based on these experimental results, a simple, low-cost, and efficient colorimetric method for H 2 O 2 detection was established, which showed a sensitive response to H 2 O 2 in the range of 0.02–2.5 μM with a detection limit of 2.3 nM. In addition, due to the magnetic properties of the prepared nanoparticles, they could be easily recovered by applying a magnetic field. This research provides a viable approach for magnetic nanomaterials with encouraging prospects for environmental monitoring, biosensing, and more. [Display omitted] [ABSTRACT FROM AUTHOR]

In the present study, we propose a scheme for detecting H 2 O 2 by using horseradish peroxidase (HRP) adsorbed onto single silica particles and fluorescence microspectroscopy. When the silica particles were immersed in an HRP solution, the HRP concentration in the silica particles increased by a factor of 690 compared to that in the bulk aqueous solution because HRP was adsorbed on the silica surface. When a single particle containing HRP was added to a mixed solution of H 2 O 2 and Amplex Red, fluorescence from resorufin, which was produced by the reaction of HRP, H 2 O 2 , and Amplex Red, was observed. The fluorescence from the resorufin in the particles increased after a single particle was added to the solution, and the release of resorufin was observed. As the concentration of H 2 O 2 (C H2O2) decreased, the time it takes for fluorescence intensity to reach its maximum was shorter. The detection limit for H 2 O 2 in the present system was 980 nM. The reaction behavior of a single silica particle was evaluated using a spherical diffusion model, which explains the approximate concentration change of resorufin in the silica particle. The proposed method has the advantages of simple sample preparation and detection, low sample consumption, and a short detection time. [Display omitted] • H 2 O 2 detection scheme in single silica particle. • 980 nM H 2 O 2 was detectable. • Reaction kinetics in the particle was explained based on a diffusion equation. [ABSTRACT FROM AUTHOR]

Although peroxidase-like nano-enzymes have been widely utilized in biosensors, nano-enzyme based biosensors are seldom used for both quantitative analysis of H 2 O 2 and differentiation of isomers of organic compounds simultaneously. In this study, a dual-functional mimetic enzyme-based fluorescent sensor was constructed using metal-organic frameworks (Bi-MOFs) with exceptional oxidase activity and fluorescence properties. This mimetic enzyme sensor facilitated quantitative analysis of H 2 O 2 and accurate discrimination of phenylenediamine isomers. The sensor exhibited a wide linear range (0.5–400 μM) and low detection limit (0.16 μM) for the detection of H 2 O 2. Moreover, the sensor can also be used for the discrimination of phenylenediamine isomers, in which the presence of o-phenylenediamine (OPD) leads to the appearance of a new fluorescence emission peak at 555 nm, while the presence of p-phenylenediamine (PPD) significantly quenched its fluorescence due to the internal filtration effect. The proposed strategy exhibited a commendable capability in distinguishing phenylenediamine isomers, thereby paving the way for novel applications of MOFs in the field of environmental science. [Display omitted] • A mimic enzyme fluorescent probe realized detection of H 2 O 2 and distinction of phenylenediamine isomers, simultaneously. • A green, simple and eco-friendly method is used to visual analysis. • H 2 O 2 in real samples was detected by the proposed fluorescent probe. [ABSTRACT FROM AUTHOR]

Flexible and portable film sensor (PLA@RPEG@TBSN) that embedded with AIE-featured nanoparticles is constructed for selective detection of gaseous H 2 O 2 using ratio fluorescence strategy. Moreover, effective photodynamic antimicrobial performance and multifunctional wearable applications can be realized for the film sensor. [Display omitted] • Flexible film sensor with H 2 O 2 detection and antibacterial characters is constructed. • Efficient fluorescence emission is ensured by the embedded AIE-active responder. • Sensitive H 2 O 2 vapor detection with visual color change is achieved by ratio method. • Photodynamic antimicrobial can be sufficiently realized by the film sensor. • Multifunctional wearable applications of the film sensor have been implemented. The development of portable flexible sensors for sensitive gas detection with antibacterial activity is of great significance for protecting human health and environment safety. In this paper, we designed a ratiometric sensing platform (PLA@RPEG@TBSN) for reliable and visual monitoring of gaseous H 2 O 2 by electrospinning technology, which reveals self-antibacterial function and highly photostability simultaneously. By employing the aggregation-induced emission (AIE) active nanoparticles (TBSN) as fluorescent responder and Rose Bengal modified photosensitive polymer (RPEG) as reference unit, accurate ratiometric sensing process of PLA@RPEG@TBSN film was realized based on the specific peroxide-mediated reaction between TBSN and H 2 O 2. The flexible film system demonstrated superior sensing performance toward H 2 O 2 vapor, including excellent selectivity, visualized color change and low detection limit (7 ppb). Additionally, benefitting from the photodynamic activity of RPEG, the PLA@RPEG@TBSN film exhibited highly effective antibacterial performance (killing 84 % of bacteria). Moreover, the multifunctional wearable potential is supported by employing film sensor onto the protective mask, which reveals dual capabilities of ratio sensing and resistance bacteria aerosols, encouraging the application of the sensor in complex practical scenario. [ABSTRACT FROM AUTHOR]

• Au hollow spheres (Au HS) decorate on rROGO-SH as electrocatalyst. • rROGO-S-Au HS/GCE exhibits wide linear detection range, low detection limit, and good sensitivity. • Sensitively detection of trace amount of H 2 O 2 released from living tumor cells. • Online monitoring of H 2 O 2 levels at tumor sites. In this work, graphene undergoes twice oxidization to produce reoxidized-graphene oxide (ROGO), and then ROGO reacts with thiourea to obtain thiol-functionalized reduced ROGO (rROGO-SH), achieving reduction and surface thiolation. Subsequently, Au hollow spheres (Au HS) are decorated on rROGO-SH, and an electrochemical sensor is therefore fabricated by coating rROGO-S-Au HS on a glassy carbon electrode (GCE). rROGO-S-Au HS/GCE exhibits attractive electrochemical performance for H 2 O 2 detection with a wide linear detection range (5 μM to 11.5 mM), low detection limit (5 μM), and good sensitivity (0.19 mA mM−1 cm−2). Due to its good performance for in-vivo detection, rROGO-S-Au HS/GCE can sensitively detect a trace amount of H 2 O 2 released from living tumor cells. Hence, the rROGO-S-Au HS based electrochemical sensing platform shows great potential for online monitoring of H 2 O 2 levels at tumor sites, which is beneficial for the rapid and sensitive diagnosis of cancer, as well as in vivo monitoring of tumor progression. [ABSTRACT FROM AUTHOR]

Herein, a mesoporous silica nanoparticle (MSN) based ratiometric fluorescence nanosensor (MSN-BA-SiCD) with improved performance was designed for monitoring hydrogen peroxide (H 2 O 2). Specifically, H 2 O 2 response molecule (BA) with AIE feature was synthesized and encapsulated into MSN channel as the fluoresent recognition site. Afterwards, silane-modified carbon dot (SiCD) was covalently connected to the MSN surface which can effectively prevent the leakage of BA and improve the water dispersibility of the nanosensor. The presence of H 2 O 2 could result in a "turn-on" fluorescence of BA as well as concurrent variation in the fluorescence resonance energy transfer (FRET) signal between SiCD and BA. MSN-BA-SiCD displays a specific blue-to-green resolved emission change in response to H 2 O 2 and the detection limit can be as low as 4.78 × 10−6 M. In addition, the nanosensor exhibited enhanced photostability due to the protection of the material framework. Moreover, the nanosensing system was successfully applied to detect H 2 O 2 in beer, orange juice and living cells. The excellent water dispersibility and photostability of the nanosensor, together with high specificity and biocompatibility, constituted an advanced set of characteristics among existing MSNs, which was expected to further promote the development of H 2 O 2 sensors in the environmental and biological fields. [Display omitted] • A ratio fluorescence nanosensor is designed based on carbon dot modified MSN. • Selective and sensitive detection of H 2 O 2 is achieved by FRET based ratio sensing. • Improved water dispersibility and photostability are exhibited for the nanosensor. • The nanosensor is successfully applied in drink samples and cell imaging. [ABSTRACT FROM AUTHOR]