H2O2 Sensitivity Research Articles

Hydrogen peroxide residue determination in food samples by a glassy carbon electrode modified with CuO-SWCNT-PDDA nanocomposites

Copper oxide-single walled carbon nanotube (CuO-SWCNT) hybrid nanostructure and poly-(diallyldimethylammonium chloride) (PDDA) modified glassy carbon electrode (GCE) for sensitive enzyme-free H2O2 detection has been fabricated via electrostatic interaction strategies. Characterization by XRD, IR and SEM showing that CuO was coated on SWCNT molecular wires, and positively charged PDDA attached to the negatively charged SWCNT, thus CuO-SWCNT-PDDA was constructed. The reduction peak current of H2O2 was significantly increased due to the catalytic property of CuO, which was further enhanced by the synergic effect of SWCNT due to its improvement of electron transfer rate. The calibration curve was linear in the range of 1–1150 µM with a detection limit of 0.39 µM. The electrode coupled with amperometric measurement was successfully applied in H2O2 residue determination in milk and the soaking solutions of chicken paw samples. The results have no remarkable difference compared with the reference UV–Vis method.

Nafion-coated copper oxide porous hollow structures modified glassy carbon electrode for non-enzymatic detection of H2O2

Metal-oxide nano-porous microstructures have shown high electrocatalytic activity toward hydrogen peroxide oxidation. In this paper, we establish the copper oxide (CuO) porous hollow structures via the hydrothermal method using pluronic F-127 as a surfactant. The electrochemical performance involves the oxidation between Cu(I) and Cu(II) at room temperature. For verifying the formation of the desired morphology of CuO porous hollow structures, the scanning electron microscopy, Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction spectroscopy and H2-temperature-programmed reduction (TPR) were applied. The synthesized samples are hollow microstructures which are formed by CuO nanoparticles. The achieved CuO hollow structures exhibit excellent H2O2 detection properties such as a very low detection limit of 141.1 nM, an extremely wide dynamic detection range of 50 nM–70 mM, an outstanding sensitivity of 13.7 µA µM−1 cm−2 and satisfactory stability in alkaline solution. The good tolerance toward interfering species, the satisfactory behaviour in repeatability and reproducibility and favourable stability verified the promising performance of the proposed sensor. The results of the study on sensing low levels of H2O2 concentrations by using a modified glassy carbon electrode as an optimized electrochemical sensor have been reported. The proposed synthesized nanostructures (CuO porous hollow structures) can be used as sensitive H2O2 biosensors. Essential characterizations and measurements have been performed. The constructed sensor shows acceptable electrocatalytic activity for detecting H2O2. High sensitivity, very low LOD, wide dynamic range, excellent tolerance toward interfering agents, favorable stability and satisfactory reproducibility and repeatability of the sensor have made it suitable for practical applications.

Fe3C-Assisted Single Atomic Fe Sites for Sensitive Electrochemical Biosensing.

The rational construction of advanced sensing platforms to sensitively detect H2O2 produced by living cells is one of the challenges in both physiological and pathological fields. Owing to the extraordinary catalytic performances and similar metal coordination to natural metalloenzymes, single atomic site catalysts (SASCs) with intrinsic peroxidase (POD)-like activity have shown great promise for H2O2 detection. However, there still exists an obvious gap between them and natural enzymes because of the great challenge in rationally modulating the electronic and geometrical structures of central atoms. Note that the deliberate modulation of the metal-support interaction may give rise to the promising catalytic activity. In this work, an extremely sensitive electrochemical H2O2 biosensor based on single atomic Fe sites coupled with carbon-encapsulated Fe3C crystals (Fe3C@C/Fe-N-C) is proposed. Compared with the conventional Fe SASCs (Fe-N-C), Fe3C@C/Fe-N-C exhibits superior POD-like activity and electrochemical H2O2 sensing performance with a high sensitivity of 1225 μA/mM·cm2, fast response within 2 s, and a low detection limit of 0.26 μM. Significantly, sensitive monitoring of H2O2 released from living cells is also achieved. Moreover, the density functional theory calculations reveal that the incorporated Fe3C nanocrystals donate electrons to single atomic Fe sites, endowing them with improved activation ability of H2O2 and further enhancing the overall activity. This work provides a new design of synergistically enhanced single atomic sites for electrochemical sensing applications.

Electrochemical behavior of CuO/rGO nanopellets for flexible supercapacitor, non-enzymatic glucose, and H2O2 sensing application

In the present article, graphene oxide (GO) sheets and monoclinic copper oxide (CuO) nanocrystals are connected with each other and result in the formation of CuO/rGO nanopellets, and these nanopellets synthesized using coprecipitation method. The nanopellet structured CuO/rGO composite on carbon cloth, which act as current collector exhibits specific capacitance of 188 F g−1 at a current density of 0.2 A g−1 and up to 96.3% capacity retention after 2000 charge-discharge cycles. It shows a maximum energy density of 7.32 Wh kg−1 and power density of 53 W kg−1. The glucose sensing characteristics of CuO/rGO nanopellet is investigated on carbon cloth and ITO substrate. It shows glucose sensitivity of 0.805 mA mM−1 cm−2 and 0.2982 mA mM−1 cm−2 for a bundle like structured CuO/rGO composite on carbon cloth and ITO substrate, respectively. Further H2O2 sensing is studied on ITO substrate, which manifests H2O2 sensitivity of 84.39 μA mM−1 cm−2. The results indicate that nanopellet structured CuO/rGO composite could be a promising electrode material for supercapacitor, glucose, and H2O2 sensor.

A Nonenzymatic Hydrogen Peroxide Electrochemical Sensing and Application in Cancer Diagnosis.

The diagnosis of malignant tumors is essential for informing clinical decisions regarding therapeutic options. Current imaging and pathological diagnostic methods do not provide quantitative molecular information that is important in tumor identification. Moreover, pathological tissue analysis is dependent on unevenly distributed pathological features. The tumor microenvironment has been documented to have hydrogen peroxide (H2 O2 ). This study presents a biologically sensitive and efficient H2 O2 electrochemical sensor based on PtNi nanoparticle-doped N-reduced graphene oxide (PtNi-N-rGO) with a low detection limit (2.8× 10-9 m), a fast response time (<6 s) and desirable anti-interference characteristics. Herein, H2 O2 is used as molecular biomarker. The sensor successfully captures H2 O2 from cancer cells. In addition, it efficiently detects tumor tissues, adjacent tissues, and normal tissues. This study demonstrates the H2 O2 sensor potential to rapidly detect tumor tissues. This technique provides a complementary method for pathological tumor diagnosis that is independent of the traditional pathology labs.

Voltage-Switchable Biosensor with Gold Nanoparticles on TiO2 Nanotubes Decorated with CdS Quantum Dots for the Detection of Cholesterol and H2O2.

A thin layer of gold nanoparticles (Au NPs) sputtered on cadmium sulfide quantum dots (CdS QDs) decorated anodic titanium dioxide nanotubes (TNTs) (Au/CdS QDs/TNTs) was fabricated and explored for the nonenzymatic detection of cholesterol and hydrogen peroxide (H2O2). Morphological studies of the sensor revealed the formation of uniform nanotubes decorated with a homogeneously dispersed CdS QDs and Au NPs layer. The electrochemical measurements showed an enhanced electrocatalytic performance with a fast electron transfer (∼2 s) between the redox centers of each analyte and electrode surface. The hybrid nanostructure (Au/CdS QDs/TNTs) electrode exhibited about a 6-fold increase in sensitivity for both cholesterol (10,790 μA mM-1 cm-2) and H2O2 (78,833 μA mM-1 cm-2) in analyses compared to the pristine samples. The hybrid electrode utilized different operational potentials for both analytes, which may lead to a voltage-switchable dual-analyte biosensor with a higher selectivity. The biosensor also demonstrated a good reproducibility, thermal stability, and increased shelf life. In addition, the clinical significance of the biosensor was tested for cholesterol and H2O2 in real blood samples, which showed maximum relative standard deviations of 1.8 and 2.3%, respectively. These results indicate that a Au/CdS QDs/TNTs-based hybrid nanostructure is a promising choice for an enzyme-free biosensor due to its suitable band gap alignment and higher electrocatalytic activities.

Expanding Horizon: Controllable Morphology Design of an Ecofriendly Tamarind Seedcase-Derived Porous Carbonaceous Biomass as a Versatile Electrochemical Biosensor Platform for Reactive Oxygen Species

Novel, uniform, and ordered biomass carbon materials using the skin tissue of tamarind seedcase (TS) as the carbon source were first synthesized by one-step carbonization or hydrothermal carbonization (HTC) without being template-assisted and are further explored for highly sensitive H₂O₂ biosensing. The results demonstrated that the obtained biomass carbonaceous materials (TS-C, TS powder (TSP), TSP-C, TS-HTC, and TSP-HTC) with obviously different morphologies, absorption characteristics, and pore size distributions showed variable electrocatalytic properties. TS-HTC with promising pitaya flower-like structures and a high specific surface area of 436.425 m² g–¹ presented the optimized catalytic performance for H₂O₂ detecting at the peak potential of −0.38 V. The corresponding H₂O₂ sensor displayed an outstanding sensitivity of 122.02 μA mM–¹ cm–² at the H₂O₂ concentration range of 0.05–0.5 mM and 80.79 μA mM–¹ cm–² (0.5–2.7 mM), respectively. The response time was short at 3.61 s, indicating that TS-HTC has turned out to be an attractive material for designing H₂O₂ biosensors, with a promising internally interlinked reticulate-like structure for capturing biomolecules. Moreover, the direct detection of H₂O₂ released from Hep3B cells is demonstrated on TS-HTC-based sensors, being effective to detect H₂O₂ activity in situ for the early diagnosis of liver cancer, suggesting its potential application for efficient recognition and determination of H₂O₂ in fields of life science, clinics, disease prevention, and so on.

Reasonable design of an MXene-based enzyme-free amperometric sensing interface for highly sensitive hydrogen peroxide detection

Sensitive detection of H2O2 in the nano- to micromolar range is critical for health monitoring and disease diagnosis. Two-dimensional transition metal carbides or/and nitrides (called MXenes, MXs) have excellent potential applications in the electrochemical field due to their outstanding electrical conductivity and catalytic properties. In this work, Ti3C2Tx (MX) was employed for the construction of a sensitive and enzyme-free electrochemical sensing interface for the detection of hydrogen peroxide (H2O2) through a simple and effective method. Prussian blue (PB) was electrochemically deposited on the surface of a glassy carbon electrode (GCE). Chitosan (CS) and MX were sequentially dripped onto the PB modified GCE surface. The reasonable fabrication of the MX/CS/PB/GCE sensing interface presented good electrochemical sensing performance towards H2O2 with a low limit of detection (4 nM), a wide linear range from 50 nM to 667 μM and good selectivity. The proposed MX/CS/PB/GCE has been proven to monitor H2O2 in food samples and biological samples with recoveries between 94.7% and 100.3%. This work has made a beneficial attempt and research for exploring and expanding the application of MXs in the field of electrochemical sensing.

CdZnSeS quantum dots condensed with ordered mesoporous carbon for high-sensitive electrochemiluminescence detection of hydrogen peroxide in live cells

The accurate and rapid determination of hydrogen peroxide (H2O2) levels is of great significance because of the far-ranging impacts of H2O2 homeostasis on human health. In this work, we developed an enhanced electrochemiluminescence (ECL) biosensor based on CdZnSeS quantum dots (QDs) condensed with ordered mesoporous carbon (OMC) for high-sensitive detection of H2O2 in live cells. Benefiting from the combination of QDs with the highly conductive OMC materials, the prepared ECL biosensor exhibited outstanding ECL signal. We then assessed the analytical performance of the ECL biosensor for H2O2 detection, and found that the biosensor possessed low detection limit, wide linear range, desirable selectivity, and long-time stability. By the detection of H2O2 in different live cells, the ECL biosensor platform shows its potential for reliable and sensitive H2O2 detection in diagnostic applications and physiological research.

Hierarchical MnS@MoS2 architectures on tea bag filter paper for flexible, sensitive, and selective non-enzymatic hydrogen peroxide sensors

We report here the rational development of MnO2 nanorods coated tea bag filter paper (TBFP) as a self-standing, bendable, and disposable electrochemical probe for the sensitive and selective H2O2 detection and addresses their challenges in H2O2 sensing via the replacement of ‘O’ with ‘S’ in the form of MnS microcubes and its core@shell architecture with MoS2. The as-configured MnS@MoS2/TBFP overwhelms the constrains of conventional electrochemical probes including time and cost consumed electrode surface renewability and catalyst loading progression, and the practice of an insulating binder. The hierarchical open porous architectures of MoS2-shell favour the diffusion of H2O2 into the core-MnS microcubes, facilitating an analyte utilization efficacy at both the core and shell architectures. The impacts of core@shell morphological features, replacement of ‘O’ with ‘S’, surface defects, and lattice distribution of MnS@MoS2 toward non-enzymatic H2O2 sensing performances are elucidated using variant electrochemical techniques. With the synergism of uniformly implanted and exposed metallic active sites, efficient electron transfer rate, and high analyte utilization efficiency, MnS@MoS2/TBFP exposes the low detection limit (120 nM), excellent sensitivity (650 μA mM−1 cm−2), and wide linear range (500 nM-5 mM) on H2O2 detection. Furthermore, the scrutinized non-enzymatic H2O2 detection concerts of MnS/MoS2/TBFP are selective, decisive, repeatable, and stable, constructing the excellent recovery rates in human urine sample analyses. Thus, the collective benefits of free-standing, flexible, binder-less, re-functional, and cost-efficient MnS@MoS2/TBFP probe actualize the evolution of affordable and high performance H2O2 sensors.

Synthesis, optical properties of a new 4-substituted pyrene and its application for H2O2 detection in living cells

A new 4-substituted pyrene derivative 4,4,5,5-tetramethyl-2-(4-((pyren-4- yloxy)methyl)phenyl)-1,3,2-dioxaborolane (4-PYB) has been designed and synthesized by introducing phenyl boronic ester to the precursor 4-hydroxylpyrene. Compound 4-PYB with large Stokes shift displays relatively outstanding sensitivity and selectivity for H2O2, which is successfully applied to detect H2O2 in living cells. The fluorescent properties of probe 4-PYB displays significantly different properties from its derivative Py-Boe based on 1-hydroxylpyrene, further indicating the functionalization of pyrene on the different position is still an effective strategy to develop novel pyrene-based functional materials.

Peroxiredoxin promotes longevity and H2O2-resistance in yeast through redox-modulation of protein kinase A.

Peroxiredoxins are H2O2 scavenging enzymes that also carry out H2O2 signaling and chaperone functions. In yeast, the major cytosolic peroxiredoxin, Tsa1 is required for both promoting resistance to H2O2 and extending lifespan upon caloric restriction. We show here that Tsa1 effects both these functions not by scavenging H2O2, but by repressing the nutrient signaling Ras-cAMP-PKA pathway at the level of the protein kinase A (PKA) enzyme. Tsa1 stimulates sulfenylation of cysteines in the PKA catalytic subunit by H2O2 and a significant proportion of the catalytic subunits are glutathionylated on two cysteine residues. Redox modification of the conserved Cys243 inhibits the phosphorylation of a conserved Thr241 in the kinase activation loop and enzyme activity, and preventing Thr241 phosphorylation can overcome the H2O2 sensitivity of Tsa1-deficient cells. Results support a model of aging where nutrient signaling pathways constitute hubs integrating information from multiple aging-related conduits, including a peroxiredoxin-dependent response to H2O2.

MOF-Derived Bimetallic CoFe-PBA Composites as Highly Selective and Sensitive Electrochemical Sensors for Hydrogen Peroxide and Nonenzymatic Glucose in Human Serum.

The fabrication of two-dimensional (2D) metal-organic frameworks (MOFs) and Prussian blue analogues (PBAs) combines the advantages of 2D materials, MOFs and PBAs, resolving the poor electronic conductivity and slow diffusion of MOF materials for electrochemical applications. In this work, 2D leaflike zeolitic imidazolate frameworks (Co-ZIF and Fe-ZIF) as sacrificial templates are in situ converted into PBAs, realizing the successful fabrication of PBA/ZIF nanocomposites on nickel foam (NF), namely, CoCo-PBA/Co-ZIF/NF, FeFe-PBA/Fe-ZIF/NF, CoFe-PBA/Co-ZIF/NF, and Fe/CoCo-PBA/Co-ZIF/NF. Such fabrication can effectively reduce transfer resistance and greatly enhance electron- and mass-transfer efficiency due to the electrochemically active PBA particles and NF substrate. These fabricated electrodes as multifunctional sensors achieve highly selective and sensitive glucose and H2O2 biosensing with a very wide detective linear range, extremely low limit of detection (LOD), and good stability. Among them, CoFe-PBA/Co-ZIF/NF exhibits the best sensing performance with a very wide linear range from 1.4 μM to 1.5 mM, a high sensitivity of 5270 μA mM-1 cm-2, a low LOD of 0.02 μM (S/N = 3), and remarkable stability and selectivity toward glucose. What is more, it can realize excellent detection of glucose in human serum, demonstrating its practical applications. Furthermore, this material as a multifunctional electrochemical sensor also manifests superior detection performance against hydrogen peroxide with a wide linear range of 0.2-6.0 mM, a high sensitivity of 196 μA mM-1 cm-2, and a low limit of detection of 1.08 nM (S/N = 3). The sensing mechanism for enhanced performance for glucose and H2O2 is discussed and proved by experiments in detail.

Three Human Pol ι Variants with Impaired Polymerase Activity Fail to Rescue H2O2 Sensitivity in POLI-Deficient Cells.

Human Y-family DNA polymerase (pol) ι is involved in translesion DNA synthesis (TLS) and base excision repair (BER) of oxidative DNA damage. Genetic variations may alter the function of pol ι and affect cellular susceptibility to oxidative genotoxic agents, but their effects remain unclear. We investigated the impacts of 10 human missense germline variations on pol ι function by biochemical and cell-based assays. Both polymerase and deoxyribose phosphate (dRP) lyase activities were determined utilizing recombinant pol ι (residues 1-445) proteins. The K209Q, K228I, and Q386R variants showed 4- to 53-fold decreases in specificity constants (kcat/Km) for dCTP insertion opposite G and 8-oxo-7,8-dihydroguanine compared to the wild-type. The R126C and K345E variants showed wild-type-like polymerase activity, although these two variants (as well as the R209Q, K228I, and Q386R variants) showed greater than 6-fold decreases in dRP lyase activity compared to the wild-type. A CRISPR/Cas9-mediated POLI knockout conferred higher sensitivity to H2O2 in human embryonic kidney (HEK293) cells. Exogenous expression of the full-length wild-type, R126C, and K345E variants fully rescued the H2O2 sensitivity in POLI-deficient cells, while full-length R209Q, K228I, and Q386R variants did not rescue the sensitivity. Our results indicate that the R126C and K345E variants (having wild-type-like polymerase activity, albeit impaired in dRP lyase activity) could fully rescue the H2O2 sensitivity in POLI-deficient cells, while the R209Q, K228I, and Q386R variants, all impaired in polymerase and dRP lyase activity, failed to rescue the sensitivity, indicating the relative importance of TLS-related polymerase function of pol ι rather than its BER-related dRP lyase function in protection from oxidative stress. The possibility exists that the hypoactive pol ι variants increase the individual susceptibility to oxidative genotoxic agents.

A hybrid composite of recycled popcorn-shaped MnO2 microsphere and Ox-MWCNTs as a sensitive non-enzymatic amperometric H2O2 sensor

Taking full advantage of the manganese (Mn) species which were produced in the fabrication of graphene oxide (GO) using modified Hummers method, loosely popcorn-shaped MnO2 microspheres were synthesized accordingly. A network composite of oxidized multi-walled carbon nanotubes (Ox-MWCNTs) and MnO2 (MnO2-Ox-MWCNTs) was assembled by a facile ultrasound-assisted approach. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) confirmed the successful preparation of MnO2 and the assembly of MnO2-Ox-MWCNTs. Based on drop-casting route, MnO2-Ox-MWCNTs composite modified glassy carbon electrode (GCE) (MnO2-Ox-MWCNTs/GCE) was constructed. The electrochemical performances of the proposed electrode were investigated by cyclic voltammetry (CV) and amperometric method. Due to the synergistic effect between loosely popcorn-shaped MnO2 microspheres and Ox-MWCNTs, the proposed electrode showed high peroxidase-like electrocatalysis activity for H2O2 detection. The peak currents linearly increased with H2O2 concentrations in the range 0.80–1000 μM, and limit of detection (LOD) was 0.38 μM. The proposed electrode could be employed for qualitative detection and quantitative determination of H2O2 in milk samples.

Iron sulfide nanosheets supported 3D foam: A binder-free electrocatalyst for sensitive and selective electrochemical H2O2 detection

Electrochemical nonenzymatic sensor has achieved numerous attentions from analytical chemistry communities. A facile and direct synthesis route for developing high-performance electrocatalyst is essential to improve efficiency of sensor in terms of cost and catalytic activities for reliable analysis applications. In this research, we introduced an easy synthesis approach for the in-situ fabrication of iron sulfide nanosheets (Fe–S NSs) vertically grown on a nickel foam (NF) via an electrodeposition step. Such a self-supported Fe–S NSs/NF demonstrated sensitive and selective determination towards hydrogen peroxide (H2O2) with a wide sensing region ranging from 10 μM to 3.3 mM in 0.1 M KOH medium. Besides, it’s excellent sensitivity of 4.48 μA μM−1 cm−2, low detection limit of 7.9 μM, good reproducibility, and stability have been successfully demonstrated as well. The facile fabrication process of Fe–S NSs/NF opened a novel and effective avenue for the development of non-precious metal-based electrocatalysts in analytical chemistry.

Monitoring Plant Health with Near Infrared Fluorescent H2O2 Nanosensors

Nanotechnology-based sensors are promising tools for optimizing plant performance and use of resources in agriculture by equipping plants with capabilities to report when they are under stress and require intervention. Herein, we interfaced near infrared (nIR) fluorescent nanosensors with plant leaves that report hydrogen peroxide (H2O2), a key signaling molecule associated with the onset of plant environmental and pathogen stresses. For this purpose, we used single-walled carbon nanotubes (SWCNT) as non-photobleaching fluorescent building blocks for H2O2 nanoscale sensors with a nIR fluorescent emission (> 800 nm) in a ultra-low background region that is ideal for high-sensitivity remote sensing and imaging. SWCNTs were functionalized with a DNA aptamer that binds to hemin, resulting in nIR fluorescence nanosensor response that is quenched by H2O2 in a dose dependent way within the plant physiological range (10-100 H2O2 µM). The in vivo sensor sensitivity for H2O2 (10 µM) allows it to reversibly report signs of stress in plants exposed to UV-B, high light, and a microbial pathogen related peptide (flg 22), but not mechanical leaf wounding. The sensor response was imaged in leaves by a standoff nIR camera, which reported remotely changes in sensor nIR emission up on stress. Such nanotechnology-based sensors report plant signaling molecules associated with early signs of stress and will impact our understanding of plant stress communication, provide novel tools for precision agriculture, and reduce undesirable losses of agrochemicals in the environment.

Solution processed, vertically aligned, AZO nanocolumn array for chemiresistive sensor application with UV-enhanced sensitivity

In this work, a wide and highly sensitive chemiresistive sensor has been developed based on the AZO nanocolumn array film. This is meant for the room detection of H2O2 under UV illumination. A cost-effective one step multi-layers growth process was adopted for the synthesis of the AZO nanocolumn array. The experimental studies were done by scanning electron microscopy (SEM), transmission and electron microscopy (TEM).Then X-ray diffraction confirmed that the AZO column array was closely packed, connected, vertically aligned, and polycrystalline, with a high surface area. This structure ensures better electrical conduction over random and separated nanostructures. The hall-effect measurement indicates that the AZO film was n-type, with high conductivity (3.60 × 103 Ωcm), high carrier density (11.3 × 1020cm−3) and with acceptable mobility (0.95 cm2/Vs). The x-ray photoemission spectroscopy suggests that the AZO film consists of a large amount of adsorbed oxygen-related species at the sheath layer of the thin-film, which is vital for sensors. By the UV light activation, sensors based on the AZO nanocolumn array exhibited enhanced H2O2 detection properties at room temperature. At a concentration from 15 μM to 30 mM, H2O2 sensitivity evaluated by relative response was remarkably increased from 15% to 36%. The operation under ambient conditions and wide range sensing shows that this chemiresistive AZO sensor is adequate for biomedical and environmental applications.

A highly sensitive nonenzymatic H2O2 sensor based on 3D N-doped porous graphene aerogel decorated with AuPd alloy nanoparticles

3D N-doped porous graphene aerogel (3D NPGA) was facilely prepared through a one-step hydrothermal reduction by mixing graphene oxide (GO) and p-phenylenediamine with ammonia solution, followed by a freeze-drying process. Then, the AuPd alloy nanoparticles were deposited on the 3D NPGA to synthesize AuPd/NPGA by reduction of HAuCl4 and PdCl2 using NaBH4 as a reducing agent. NPGA composite shows a microporous with 3D structure, a large specific surface area and reveals edge plane like-sites/defects and can act as support sites for nanoparticles. The obtained AuPd/NPGA exhibits better catalytic activity towards H2O2 reduction compared with Pd/NPGA, Au/NPGA, and 3D NPGA composites. The improved performance of AuPd/NPGA attributed to the 3D porous structure of NPGA and the synergistic effect between Au and Pd NPs in the AuPd alloy as well as between 3D NPGA and AuPd NPs. In the 0.1 M PBS pH 7 electrolyte, the AuPd/NPGA electrode displays a linear response towards H2O2 reduction in the range of 1–1000 μM, high sensitivity of 12,235 μA mM−1 cm−2, low LOD 0.038 μM (S/N = 3) and quick response time (<1 s). This nonenzymatic H2O2 sensor was also displays satisfying selectivity, good reproducibility, and excellent long-term stability. In addition, the AuPd/NPGA electrode can also be employed for H2O2 detection in human serum samples. These results confirm that the AuPd/NPGA composite would be a promising catalytic material to construct sensors in different fields.

Hierarchical 0D-2D bio-composite film based on enzyme-loaded polymeric nanoparticles decorating graphene nanosheets as a high-performance bio-sensing platform

Herein, we developed a hierarchical bio-composite sensing film by facile one-step electro-deposition of 0D enzyme-polymer nanoparticles (NPs) with 2D graphene oxide nanosheets as conductive supports and nanofillers, based on which an effective and robust enzymatic biosensor platform was constructed. Horseradish peroxidase (HRP) as a model enzyme was co-assembled with a photo-cross-linkable polypeptide of 2-hydroxyethyl methacrylate modified poly(γ-glutamic acid) (γ-PGA-HEMA), generating hybrid HRP@γ-PGA-HEMA nanoparticles (HRP@PGH NPs). Then HRP@PGH NPs and graphene oxide nanosheets (GO NSs) were simultaneously electrodeposited onto the electrode surface, obtaining a hierarchical 0D-2D bio-composite film. After subsequent electrochemical reduction of GO NSs into graphene nanosheets (GNSs) and following photo-cross-linking, the resultant nanostructured HRP@PGH/GNSs sensing film was successfully applied to construct an enzymatic biosensor for hydrogen peroxide (H2O2). The biosensor exerted high sensitivity, fast response, and good stability for H2O2 sensing. Satisfactory results were also demonstrated for its practical application in human serum samples, suggesting a promising application potential in biomedical diagnostics. The one-step generated 0D-2D bio-composite sensing film demonstrates synergetic effects from both the soft nanoparticles and hard conductive nanosheets, which would enlighten the innovative construction of composite nanomaterials and nanoarchitectonics for bio-sensing systems.