Detection Limit Of H2O2 Research Articles

Kinetic detection of hydrogen peroxide in single horseradish peroxidase-concentrated silica particle using confocal fluorescence microspectroscopic measurement

In the present study, we propose a scheme for detecting H2O2 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 H2O2 and Amplex Red, fluorescence from resorufin, which was produced by the reaction of HRP, H2O2, 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 H2O2 (CH2O2) decreased, the time it takes for fluorescence intensity to reach its maximum was shorter. The detection limit for H2O2 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.

Visual detection of H2O2 and glucose by HBcAb-HRP fluorescence-enhanced CdTe QDs/CDs ratiometric fluorescence sensing platform

This study presents the development of a sensitive and simple enhanced ratiometric fluorescence sensing platform in the consist of CdTe quantum dots (QDs), carbon dots (CDs), and hepatitis B core antibody labeled with horseradish peroxidase (HBcAb-HRP) for the visual analysis of H2O2 and glucose. The sulfur atoms in HBcAb-HRP have a strong affinity for Cd(II), which effectively enhances the fluorescence intensity of the CdTe QDs due to the generation of more radiative centers at the CdTe/Cd-SR complex. In the presence of H2O2, the Cd-S bonds are oxidized to form disulfide products and results in linear fluorescence quenching, while CDs maintain stable. Becasue glucose can be converted into H2O2 with the aid of glucose oxidase, this sensing platform can also be used for analyzing glucose. The detection limits for H2O2 and glucose are 2.9 μmol L−1 with RSD of 2.6% and 1.6 μmol L−1 with RSD of 2.4% respectively. In addition, under UV lamp irradiation, the orange-yellow CdTe QDs gradually quench with increasing H2O2 and glucose, while the blue CDs remain unchanged. A color change from orange-yellow to blue enables a visual semi-quantitative determination of H2O2 in commercial contact lens solution and glucose in human serum without any pretreatment. Thus, this CdTe QDs/CDs ratiometric sensing platform has significant potential for the rapid analysis of H2O2 and glucose in actual application.

CNTs/Graphene Oxide‐Nickel Phosphate Nanocomposite‐Based Electrochemical Sensor for Detecting H2O2 in Human Serum

AbstractMonitoring H2O2 levels in human serum is vital as it is a biomarker for oxidative stress‐induced diseases and neurodegenerative disorders. Thus, an efficient electrochemical sensor is developed for detecting H2O2 in real human serum samples. The sensor is fabricated by modifying the GC surface with two consecutive thin layers namely carbon nanotubes (CNTs), and graphene oxide‐nickel phosphate composite (GRO‐NIPO). Under optimized conditions, the H2O2 sensor in human serum shows excellent catalytic effect in the concentration range (7 nM to 600 μM) with low detection limit 0.55 nM in the low range (7 nM to 1 μM). The combined effect of the catalytic activity of GRO‐NIPO nanocomposite and the large conductive surface area of CNTs improve the sensor's performance. The negative reduction potential of H2O2 at −570 mV improves the anti‐interference ability of the H2O2 sensor toward common interfering species in biological fluids. The layered modified electrode offers good sensitivity and low detection limit for H2O2 compared to other modified electrodes and some methods cited in the literature. Besides, the H2O2 sensor exhibits stable response over four weeks, excellent selectivity, reproducibility, repeatability, and steadiness. The reliability test of the sensor in serum sample shows good recovery of H2O2.

Hydrogel-Based Electrodeposition of Copper Nanoparticles for Selective Detection for Hydrogen Peroxide

A copper-modified indium tin oxide (ITO) electrode was utilized as an electrocatalytic sensing platform for hydrogen peroxide (H2O2) detection. In this study, instead of conventional solution-phase electrodeposition, electrochemical deposition was used to deposit Cu on an ITO electrode with agarose hydrogel. The hydrogel-based Cu nanoparticles exhibited a more evenly dispersed distribution compared to those in the solution phase. Additionally, by incorporating agarose hydrogel as a solid electrolyte, the overall active surface area of Cu nanoparticles on the electrode surface was increased, mainly resulting from a decrease in the aggregation of Cu nanoparticles. Cyclic voltammetry and chronoamperometry confirmed that the resulting Cu nanoparticles possessed distinct electrocatalytic activity for H2O2 reduction and good selectivity for various interfering substances. The chronocoulometry response of the fabricated sensor obtained at −0.6 V (vs. Ag/AgCl) increased linearly with a dynamic range of 1–500 μM, and the limit of detection for H2O2 was 1.73 μM. Our research provides new possibilities for the electrochemical synthesis of metal nanoparticles for non-enzymatic sensing applications.

Polymeric Composite including Magnetite Nanoparticles for Hydrogen Peroxide Detection

The combination of a biopolymer and a conductive polymer can produce new materials with improved physico-chemical and morphological properties that enhance their use as sensors. Magnetite nanoparticles (MN) can be further introduced to these new matrices to improve the analytical performance. This study aimed to evaluate the electrocatalytic response of nanocomposites formed by the introduction of MN to polypyrrole (PPy) doped in the presence of cashew gum polysaccharide (CGP) and in the presence of carboxymethylated cashew gum polysaccharide (CCGP). Characterization of the nanocomposites was carried out via transmission electron microscopy (TEM) and infrared spectroscopy (FTIR) and showed that the absorption band of the blend was shifted to a higher frequency in the nanocomposites, indicating the intermolecular interaction between the blend and nanoparticles. The electrocatalytic performance of the nanocomposites was evaluated by applying a constant potential of −0.7 V with successive additions of H2O2 (1 mmol L−1) in 10 mmol L−1 phosphate buffer under agitation at pH 7.5. The nanocomposite formed by the introduction of MN to polypyrrole doped with cashew gum polysaccharide (PPy(cgp)–MN) displayed excellent electrocatalytic surface properties, with high H2O2 specificity, a linear response (R2 = 0.99), high sensitivity (0.28 µmol L−1), and a low H2O2 detection limit (0.072 mmol L−1).

Dual-mode colorimetric and homogeneous electrochemical detection of intracellular/extracellular H2O2 based on FeSx/SiO2 nanoparticles with high peroxidase-like activity

Abnormal expression of hydrogen peroxide (H2O2) elucidates cell dysfunctions and might induce the occurrence and deterioration of various diseases. However, limited by its ultralow level under pathophysiological conditions, intracellular and extracellular H2O2 was difficult to be detected accurately. Herein, a colorimetric and homogeneous electrochemical dual-mode biosensing platform was constructed for intracellular/extracellular H2O2 detection based on FeSx/SiO2 nanoparticles (FeSx/SiO2 NPs) with high peroxidase-like activity. In this design, FeSx/SiO2 NPs were synthesized with excellent catalytic activity and stability compared to natural enzymes, which improved the sensitivity and stability of sensing strategy. 3,3′,5,5′-Tetramethylbenzidine (TMB), as a multifunctional indicator, was oxidized in the presence of H2O2, generated color changes and realized visual analysis. In this process, the characteristic peak current of TMB decreased, which could realize the ultrasensitive detection of H2O2 by homogeneous electrochemistry. Accordingly, by integrating visual analysis ability of colorimetry and the high sensitivity of homogeneous electrochemistry, the dual-mode biosensing platform exhibited high accuracy, sensitivity and reliability. The detection limits of H2O2 were 0.2 μM (S/N = 3) for the colorimetric method and 2.5 nM (S/N = 3) for the homogeneous electrochemistry assay. Therefore, the dual-mode biosensing platform provided a new opportunity for highly accurate and sensitive detection of intracellular/extracellular H2O2.

Amorphization-Modulated Metal Sulfides with Boosted Active Sites and Kinetics for Efficient Enzymatic Colorimetric Biodetection.

Colorimetric biosensing has become a popular sensing method for the portable detection of a variety of biomarkers. Artificial biocatalysts can replace traditional natural enzymes in the fields of enzymatic colorimetric biodetection; however, the exploration of new biocatalysts with efficient, stable, and specific biosensing reactions has remained challenging so far. Here, to enhance the active sites and overcome the sluggish kinetics of metal sulfides, the creation of an amorphous RuS2 (a-RuS2 ) biocatalytic system is reported, which can dramatically boost the peroxidase-mimetic activity of RuS2 for the enzymatic detection of diverse biomolecules. Due to the existence of abundant accessible active sites and mildly surface oxidation, the a-RuS2 biocatalyst displays a twofold Vmax value and much higher reaction kinetics/turnover number (1.63 × 10-2 s-1 ) compared to that of the crystallized RuS2 . Noticeably, the a-RuS2 -based biosensor shows an extremely low detection limit of H2 O2 (3.25× 10-6 m), l-cysteine (3.39× 10-6 m), and glucose (9.84× 10-6 m), respectively, thus showing superior detection sensitivity to many currently reported peroxidase-mimetic nanomaterials. This work offers a new path to create highly sensitive and specific colorimetric biosensors in detecting biomolecules and also provides valuable insights for engineering robust enzyme-like biocatalysts via amorphization-modulated design.

Oxygen vacancy-rich Bi2WO6 nanocrystals for fast and wide-range photoelectrochemical sensing of hydrogen peroxide

Improper treatment of highly active natural or edible water will cause environmental pollution, and hydrogen peroxide (H2O2) is a common pollutant. Wide-range concentrations and short half-lift time of H2O2 in different sample conditions make it a challenge for its accurate and fast detection. We present here the use of Bi2WO6 nanocrystal with rich oxygen vacancy (Bi2WO6-V) to construct a photoelectrochemical (PEC) sensor for fast and wide-range qualification of H2O2. Under visible light irradiation, the H2O2 detection limit of the Bi2WO6-V PEC sensor reaches 0.5 μM, which is 10 times that without light. The mechanism of PEC sensing performance toward H2O2 was studied by UV–vis, Mott-Schottky characterization and PEC measurements, finding that the driving force of photogenerated electrons (−0.627 V) caused by energy level difference between Bi2WO6-V and the reduction of H2O2 ensures that the visible light can be effectively absorbed to reduce H2O2 to H2O. The calibration curve of H2O2 obtained by the proposed PEC sensor regions from 1.5 μ M to 230 mM, with high response time and good selectivity. In addition, the sensor can detect H2O2 in actual samples-milk and lake water, which has broad prospects in environmental monitoring.

Synthesis of MnS/MnO Decorated N, S‐Doped Carbon Derived from a Mn(II)‐Coordinated Polymer for the Catalytic Oxidation of H2O2 and Bisphenol A

AbstractA way to synthesize a Mn2+‐ coordinated polymer precursor ligated by sulfur atoms with acetate counter ions (Mn‐DTOGA) is proposed, which is achieved by an imine formation reaction between dithiooxamide and glutaraldehyde in the presence of manganese (II) acetate. MnS/MnO decorated N, S‐doped carbon nanoparticles (MnS/O‐SNC) are then prepared by calcination of the Mn ion‐coordinated polymer for the practical applications of catalytic reactions. The Mn‐DTOGA and MnS/O‐SNC structures prepared at different temperatures (700, 800, and 900 °C) are characterized using various physical and electrochemical and chemical analyses. The nanoparticles prepared at 900 °C reveal the best performance for the catalytic oxidation of Hydrogen peroxide (H2O2) and bisphenol A. The decomposition potentials of H2O2 (1.0 mm) and bisphenol A (100.0 µm) on the catalyst modified electrode are observed to be +0.40 and +0.15 V (versus Ag/AgCl), respectively. It is observed that the catalytic performances to the oxidation reactions are mainly related to MnO decorated outside the SNC particles compared to MnS formed inside the particles. The electrode reveals a wide dynamic range with the low detection limits for H2O2 (0.08 (±0.02) µm) and bisphenol A (0.17 (±0.04) µm). This study will provide essential clues for the future catalyst design.

Silk fibroin based wearable electrochemical sensors with biomimetic enzyme-like activity constructed for durable and on-site health monitoring

Flexible biomimetic sensors have encountered a bottleneck of sensitivity and durability, as the sensors must directly work within complex body fluid with ultra-trace biomarkers. In this work, a wearable electrochemical sensor on a modified silk fibroin substrate is developed using gold nanoparticles hosted into N-doped porous carbonizated silk fibroin (AuNPs@CSF) as active materials. Taking advantage of the inherent biocompatibility and flexibility of CSF, and the high stability and enzyme-like catalytic activity of AuNPs, AuNPs@CSF-based sensor exhibits durable stability and superior sensitivity to monitor H2O2 released from cancer cell (4T1) and glucose in sweat. The detection limits for H2O2 and glucose are low to be 1.88 μM and 23 μM respectively, and the sensor can be applied in succession within 30 days at room temperature. Further, physical cross-linking of polyurethane (PU) with SF well matches with the skin tissue mechanically and provides a flexible, robust and stable electrode-tissue interface. AuNPs@CSF is applied successfully for wearable electrochemical monitoring of glucose in human sweat.The present AuNPs@CSF will possess a potential application in clinical diagnosing of H2O2- or glucose-related diseases in future.

Design of an Electrochemical Biosensor for the Quantification of H2O2 for Application to Cardiovascular Diseases

Electrochemical biosensors, which are fast and reliable analytical tools, have attracted particular attention in recent years for their ability to incorporate biomolecules into nanomaterial-designed electrodes. In this study, an electrochemical biosensor for the detection of hydrogen peroxide (H2O2) was developed using a multi-walled carbon nanotube (EPMWC) platform electrochemically modified with poly [Fe (III)-5-Aphen] and using an oxide-reductase enzyme as recognition agent. Amperometry was applied to obtain the calibration curves for H2O2 at the reduction process. The analytical parameters such as sensitivity, linear range, and low detection limits for H2O2 were obtained. A sensitivity of 26.51µA/mM, linear range from (0.4 to 4.5) H2O2 mM and a LOD of 0.761 µM. The advance of this measurement system is the first step in the development process of an electrochemical biosensor for cardiovascular diseases applications.

A sensitive fluorescence detection strategy for H2O2 and glucose by using aminated Fe-Ni bimetallic MOF as fluorescent nanozyme.

Anaminated Fe-Ni bimetallic metal-organic framework (Fe3Ni-MOF-NH2) with both peroxidase-like activity and fluorescence properties was developed. Fe3Ni-MOF-NH2 possessed the enhanced peroxidase-like activity through the enhanced electron transfer process and hydroxyl radical (·OH) generation. It was found that the amino group endowed the material with fluorescent property and the metal site Ni in Fe3Ni-MOF-NH2 could also enhance the fluorescence emission intensity (Ex = 345nm, Em = 452nm). Based on the dual excellent performance of Fe3Ni-MOF-NH2, a novel sensitive fluorescence detection strategy for H2O2 and glucose was designed and achieved. First, Fe3Ni-MOF-NH2 converted H2O2 to ·OH by exerting peroxidase-like activity, and ·OH converts catechol to o-benzoquinone. Then, the amino group in Fe3Ni-MOF-NH2 connected to o-benzoquinone, which resulted in its fluorescence quenching. The detection limit of H2O2 was as low as 5nM. Combined with glucose oxidase which can oxidize glucose and produce H2O2 the glucose could be indirectlydetermined with a detection limit of 40nM. The method was applied to the detection of low-level glucose in human urine samples with good recoveries and reproducibilities.

Electrodeposition of Silver Nanoparticles on Indium-Doped Tin Oxide Using Hydrogel Electrolyte for Hydrogen Peroxide Sensing

Nanoparticles are used in various fields, including fuel cells, energy conversion devices, and sensors, because of their large surface area and excellent catalytic properties. Although various methods of synthesizing nanoparticles are available, the most popular is the solution-phase reduction of metal ions. Electrodeposition is a method of reducing metal ions in solution and is widely used because of its various advantages. In this study, Ag nanoparticles with a narrow size distribution were evenly dispersed on the surface of an electrode by applying electrodeposition in an agarose hydrogel medium instead of in solution, confirming the feasibility of Ag deposition in agarose hydrogel, even at a lower reduction potential than that in solution. These results are attributed to the electrolyte effect owing to the hydrophilic backbone of the agarose hydrogel and the gel effect, which reduces unexpected convection. H2O2 was detected by using the Ag nanoparticles synthesized in agarose hydrogel, and the limit of detection for H2O2 was found to be 4.82 µM, with a dynamic range of 1-500 µM. The nanoparticle synthesis platform proposed in this study is expected to be actively used for the synthesis of other metal/nonmetal nanoparticles.

A Non‐Enzymatic and Electrochemical‐Based Sensor using a Prussian Blue‐Gold Nanoparticle‐Reduced Graphene Oxide Ternary Nanocomposite for Efficient Hydrogen Peroxide Detection.

AbstractAn electrochemical sensor has been developed using PBNCs/AuNPs/RGO ternary nanocomposite, in which gold nanoparticles (AuNPs) are deposited on Prussian blue nanocubes (PBNCs) and reduced graphene oxide (RGO) using two‐step in‐situ synthetic approach. The synthesized ternary nanocomposite shows high catalytic activity towards H2O2 sensing due to the synergistic effect of gold nanoparticles and RGO. The material was prepared by the co‐precipitation method, and the morphology of the synthesized composites was characterized using X‐Ray diffraction (XRD), scanning electron microscopy (SEM), and High‐resolution Transmission electron microscopy (HR‐TEM). Electrochemical measurements were performed by modifying glassy carbon electrodes (GCE) with bare PBNCs, PBNCs/RGO, and PBNCs/AuNPs/RGO for low‐level detection of H2O2 using Cyclic Voltammetry (CV) and Chronoamperometry. The interference property was analyzed using ascorbic acid (AA), uric acid (UA), and glucose as interfering agents. The modified electrode shows high sensitivity of 5.47 nA/nM and a limit of detection of 260 pM for H2O2 at (S/N=3). This electrochemical sensor observed a linear range of detection from 0.66 nM to 10.53 nM. The proposed sensor exhibits good stability, better selectivity, and a picomolar concentration detection limit for H2O2.

Iron porphyrin-based porous organic polymer with high peroxidase-like activity as colorimetric sensor for glutathione and ascorbic acid assay.

A new iron porphyrin-based organic polymer (Fe-POP) was synthesized through the William ether reaction. The as-prepared Fe-POP presented high chemical stability, wide pore distribution, high iron content, and strong affinity with 3,3',5,5'-tetramethylbenzidine (TMB) and hydrogen peroxide (H2O2), which contributed to its excellent peroxidase-mimicking performance. In the presence of H2O2, Fe-POP could catalyze the transparent TMB into blue ox-TMB, which could be easily distinguished by the naked eyes. Moreover, glutathione (GSH) and ascorbic acid (AA) could convert blue ox-TMB into colorless TMB due to the inhibitory effect of GSH/AA to the catalytic oxidation of TMB. Based on this phenomenon, a rapid and sensitive colorimetric method for the assay of H2O2, GSH, and AA was developed using Fe-POP as sensor. The detection limits of H2O2, GSH, and AA were 1.37, 0.44, and 0.33μM, respectively. Finally, the colorimetric method based on Fe-POP was used to evaluate the GSH and AA content in real samples, which provided the guidance for GSH and AA supplements in our daily diet, suggesting the significant potential of Fe-POP in practical applications.

Chitosan coated fluorescent mesoporous silica for the sensitive and selective detection of H2O2

A novel turn-on fluorescent sensor for hydrogen peroxide (H2O2) was prepared from chitosan (CS) coating mesoporous silica nanoparticles (MSNs) loaded with 1-(4-Aminophenyl)-1,2,2-triphenylethene (TPE-NH2) and silver nanoparticles (AgNCs). The surface of MSNs was coated by CS as the gatekeeper and the template for loading of AgNCs. Because of the surface plasmon-enhanced energy transfer (SPEET), AgNCs effectively quenched the fluorescence emission of nanoparticles. In the presence of H2O2, AgNCs can be oxidized to Ag+, resulting in the recovery of fluorescence. This fluorescent sensor was characterized with respect to its chemical composition, morphological features and optical properties by means of FTIR, XRD, TGA, SEM, TEM, XPS, UV–Vis and fluorescence spectroscopy. The MSN/TPE-CS@Ag nanoparticles showed good sensitivity and selectivity for H2O2 even with various interfering ions and agents. Under optimized conditions, the detection limit for H2O2 was 0.64 μM in the rage of 1–300 μM. The feasibility of the practical application of this probe was confirmed by accurate quantitative of H2O2 in practical samples.

Investigation of the chemical effect of pilot injection on main combustion in a gasoline controlled auto-ignition engine by in-cylinder measurements and numerical simulation of H2O2, HO2, and OH radicals

Compared to conventional combustion in gasoline engines, Gasoline Controlled Auto-Ignition (GCAI) has the potential to significantly reduce both fuel consumption and nitrogen oxides (NOX) raw emissions. However, GCAI combustion still has a limited operating range due to limitations in combustion stability at low loads and high rates of cylinder pressure rise at high engine loads. Previous research identified hydrogen peroxide (H2O2) decomposition as an effective means to control GCAI, which is formed among other species with pilot fuel injection during the negative valve overlap (NVO) phase. Since the chemical effect of H2O2 on the main combustion has not been experimentally confirmed so far, the aim of the experimental study described in this paper is to detect H2O2 during early compression using optical methods. This is approached by conducting Photofragmentation Laser-Induced Fluorescence (PFLIF) of H2O2 by a pump laser and simultaneous hydroxyl radical Laser-Induced Fluorescence (OH-LIF) detection in the combustion chamber of a dedicated GCAI single-cylinder research engine at low loads after NVO with pilot injection (PI). Thereto, the pilot injection strategy as well as the global air/fuel ratio (AFR) are varied. Interestingly, no H2O2, hydroxyl (OH) or hydroperoxyl (HO2) constituents were detected under the operating conditions studied, despite relatively high pilot injection fuel masses and a highly accurate H2O2 detection limit of about 1 ppm. Numerical three-dimensional computational fluid dynamics (3D-CFD) combustion simulations using a semi-detailed reaction kinetic mechanism predicted 5–8 times higher H2O2 concentrations than the detection limit, yielding an uncertainty estimate of the numerical methods. Furthermore, the 3D-CFD simulations showed a significant mixture stratification which is a possible reason for the lack of H2O2 detection under these operating conditions.

CeO2/Co3O4@N-doped hollow carbon microspheres with improved peroxidase-like activity for the determination of quercetin.

Nanozymes, as substitutes for natural enzymes, have been used to construct some fast cheap sensing platforms by virtue of the high catalytic activity. Herein, we firstly study the peroxidase-like activity of CeO2/Co3O4@N-doped hollow carbon microspheres as nanozymes. In the presence of H2O2, CeO2/Co3O4@NCH exhibits high peroxidase-like activity evaluated by the catalytic oxidation of the chromogenic substrate, 3,3',5,5'-tetramethylbenzidine (TMB) into a blue oxTMB visually in 1min. The larger surface area, pore-like structure, and oxygen vacancies contribute to the enhanced peroxidase-like activity of CeO2/Co3O4@NCH. The active species •O2- is detected during the catalytic process. Thus, based on the excellent peroxidase-like activity of CeO2/Co3O4@NCH, a facile and effective biosensor is fabricated for sensitive and selective determination of H2O2 and quercetin, respectively. CeO2/Co3O4@NCH shows high affinity towards H2O2 (Km = 4.001mM) and TMB (Km = 0.086mM). The detection limit of H2O2 and quercetin is as low as 0.086mM and 1.19μM (3σ/slope), respectively. This work remarkably extends the utilization of CeO2/Co3O4@NCH in designing a colorimetric sensing platform related to biosensing, food, and environmental monitoring. A fast colorimetric sensing platform for quercetin based on the excellent peroxidase-like activity of CeO2/Co3O4@NCH.

Quantifying H2O2 by ratiometric fluorescence sensor platform of N-GQDs/rhodamine B in the presence of thioglycolic acid under the catalysis of Fe3+

In the presence of thioglycolic acid (TGA) and under the catalysis of Fe3+, a simple, rapid, sensitive, selective and effective ratiometric fluorescence sensor platform based on the mixed physically blue nitrogen-doped graphene quantum dots (N-GQDs) as probe signals and orange rhodamine B as internal standard signals has been constructed for analysis of H2O2 in human serum. TGA is the key factor for fluorescence response toward H2O2 by N-GQDs and the mechanism is H2O2 reacts speedily with TGA under the catalysis of Fe3+, and produces intermediate of superoxide anions (O2−), which accepts electrons from N-GQDs, and generates graphene oxide, causing the fluorescence quench of N-GQDs. Compared with N-GQDs probe, the sensitivity of the ratiometric fluorescence sensor platform of N-GQDs/rhodamine B for analysis of H2O2 has been improved by nearly 5-folds. Under the optimum conditions, Fλ=580nm/Fλ=440nm has a good linear relationship with the concentration of H2O2 and the detection limit of H2O2 is 0.46 μmol/L with 3.5% RSD. The established sensor platform has been successfully used for probing H2O2 in human serum with satisfactory results. The superior performance of the probe lies in its high selectivity and can be directly employed in detecting H2O2 in serum samples without any sample pretreatment procedures.

Fabrication of nonenzymatic electrochemical interface for ratiometric and simultaneous detection of hydrogen peroxide, dopamine, and ascorbic acid

In this work, a novel electrochemical platform of boronic acid pinacol ester compound modified carbon nanotubes (CNTs) coupled methylene blue (MB) was developed for ultrasensitive and simultaneous determination of hydrogen peroxide (H2O2), dopamine (DA), and ascorbic acid (AA). MB and CNTs were used as internal reference and signal amplification medium, respectively, for accurate and rapid detection of H2O2, DA and AA in complex environments. A turn-on electrochemical probe of 4-(pyren-4-yl)-N-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl) butanamide (BP) modified on CNTs via π-π stacking was designed for the nonenzymatic detection of H2O2 based on the oxidation of phenol groups. When simultaneous detection of H2O2, DA, and AA, the oxidation peak potentials of the three compounds on the electrode could be well separated and the electrochemical platform showed excellent linear range and ultrasensitive response to the three components, and the detection limits for H2O2, DA, and AA were estimated to be as low as 0.62, 0.15, and 3.8 μM, respectively (S/N = 3). The fabricated sensor also exhibited excellent stability and reproducibility. More importantly, we had successfully utilized this strategy for the detection of three analytes in real samples and satisfactory results were obtained.