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Nanosized materials acting as substitutes of natural enzymes are currently attracting significant research due to their stable enzyme-like characteristics, but some flaws of these nanozymes, including their limited catalytic rate and efficiency, need to be remedied to enable their wider applications. In this work, we verify for the first time the catalytic behavior of uncapped nanobranch-based CuS clews as a peroxidase mimic. XRD, XPS, SEM, and TEM proofs demonstrate that high-purity CuS clews composed of intertwined wires with abundant nanodendrites outside are successfully produced via a facile one-pot hydrothermal synthesis approach, with thiourea as both the sulfion source and the structure-directing agent. The synthesized CuS can catalytically oxidize 3,3',5,5'-tetramethylbenzidine (TMB) by H 2 O 2 to trigger a visible color reaction with rapid response (reaching a maximum change within 5 min). The proposed CuS nanozyme exhibits preferable catalytic kinetics over natural horseradish peroxidase (HRP). This outstanding activity primarily results from the large surface area and rich sites exposed by the uncapped unique structure. Under optimized conditions, the fabricated sensing system provides linear absorbance (652 nm) changes in the H 2 O 2 concentration range of 0.2˜130 μM, with a detection limit of as low as 63 nM. When coupled with glucose oxidase (GOD), the system is demonstrated to be capable of monitoring glucose in blood samples with excellent performance., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Novel snowflake-like Pt-Pd bimetallic nanoclusters (Pt-PdBNC) were synthesized on a screen-printed gold nanofilm electrode (SPGFE) substrate by electrochemically reducing precursors with a new constant potential/multi-potential step deposition strategy. The electrocatalytic behavior of the modified electrode (SPGFE/Pt-PdBNC) towards H(2)O(2) was investigated. The results indicate that the as-prepared Pt-PdBNC significantly enhances the electrochemical reduction of H(2)O(2) in neutral media, exhibiting preferable electrocatalytic performance compared to Pt and Pd monometallic nanoclusters. Under optimum conditions, SPGFE/Pt-PdBNC offers linear responses for H(2)O(2) in the concentration range from 0.005 to 6 mM with an ultrahigh sensitivity of 804 mA M(-1) cm(-2) and excellent selectivity. Furthermore, glucose oxidase was immobilized on the Pt-PdBNC structure, and the fabricated biosensor presents favorable properties for glucose sensing., (Copyright © 2012 Elsevier B.V. All rights reserved.)

A sensitive and selective amperometric H2O2 biosensor was obtained by utilizing the electrodeposition of Pt flowers on iron oxide-reduced graphene oxide (Fe3O4/rGO) nanocomposite modified glassy carbon electrode (GCE). The morphology of Fe3O4/rGO and Pt/Fe3O4/rGO was characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. The step-wise modification and the electrochemical characteristics of the resulting biosensor were characterized by cyclic voltammetry (CV) and chronoamperometry methods. Thanks to the fast electron transfer at the Pt/Fe3O4/rGO electrode interface, the developed biosensor exhibits a fast and linear amperometric response upon H2O2. The linear range of Pt/Fe3O4/rGO is 0.1∼2.4 mM (R2=0.998), with a sensitivity of 6.875 μA/mM and a detection limit of 1.58 μM (S/N=3). In addition, the prepared biosensor also provides good anti-interferent ability and long-term stability due to the favorable biocompatibility of the electrode interface. The proposed sensor will become a reliable and effective tool for monitoring and sensing the H2O2 in complicate environment. [ABSTRACT FROM AUTHOR]

The cover picture shows a sensitive and selective amperometric H2O2 biosensor which was obtained by utilizing the electrodeposition of Pt flowers on iron oxide‐reduced graphene oxide (Fe3O4/rGO) nanocomposite modified glassy carbon electrode (GCE). Details are discussed in the article by Xueling Zhao et al. on page 1518. [ABSTRACT FROM AUTHOR]

In analytical science, it is always of great scientific and practical significances to explore convenient, rapid, and reliable methods/devices to trace the H 2 O 2 level in various matrices. Herein, we fabricated a ready-to-use paper-based chemosensor by using mesoporous carbon-dispersed Pd nanoparticles (Pd NPs/meso-C) as a promising peroxidase mimic for the visual determination of H 2 O 2 . Thanks to the large exposed surface of the meso-C support and the highly dispersed active Pd NPs, the synthesized Pd NPs/meso-C exhibited favorable catalytic performance to trigger the chromogenic reaction of colorless TMB to blue TMBox mediated by H 2 O 2 , providing a K cat of 326.67 s −1 for H 2 O 2 and 0.55 s −1 for TMB, larger than the bare Pd NPs and even comparable to the activity of natural horse radish peroxidase. As demonstrated, this principle could be employed to colorimetrically detect H 2 O 2 in the linear scope of 5–300 μM. By simply immobilizing the Pd NPs/meso-C mimic and the TMB substrate onto a common filter paper, ready-to-use paper-based sensors were further prepared. By combining these test strips with a smartphone and an easy-to-access color-scanning APP together, the integrated platform could be used for the quantitative analysis of H 2 O 2 with advantages of simple operation, fast response, low cost, and good selectivity and repeatability. Furthermore, reliable sensing of the target in milk matrices suggested great promise of the integrated platform in practical applications. [ABSTRACT FROM AUTHOR]

In this work, an ultrasensitive microelectrode for hydrogen peroxide (H 2 O 2 ) detection was constructed. The carbon fiber microelectrode (CFME) was modified with Pt-Pd nanocoral (Pt-Pd/CFME) by using a one-step electrochemical deposition method. Compared to Pt/CFME and Pd/CFME, the Pt-Pd/CFME has larger active surface area and faster electron transfer efficiency, thus exhibiting higher electrocatalytic activity for H 2 O 2 sensing. Under the optimal condition, the Pt-Pd/CFME presents fast response time (≤5 s), high selectivity (11.6 mA mM −1  cm −2 ), wide linear range (5–3920 μM) and low detection limit (0.42 μM, S/N = 3) for H 2 O 2 detection. Furthermore, the proposed sensor was successfully employed to monitor H 2 O 2 released from A549 living cells, and the detection of H 2 O 2 in milk was also realized. With the above attractive electrocatalytic properties and convenient fabrication process, the as-prepared microelectrode provides unique advantages in the monitor of H 2 O 2 in biological samples, especially in cellular environment. [ABSTRACT FROM AUTHOR]

The trend of developing electrochemical sensors toward cellular level detection put forward higher requirements of the electrodes in the detection performance. However, common disk electrodes or conventional screen printing electrodes meet up with some limitations in the electrocatalytic activity and electron transfer capability. In this work, we applied inkjet printing technology to fabricate electrodes to make some improvements. Highly conductive Ag nanoparticles based electrodes were obtained on plastic substrate by inkjet printing technology followed by a sintering process at room temperature. The resistivity of IPAgE is determined to be 64.0 ± 5.3 μΩ cm. With better conductivity and the nanoparticle-based interface, superb electrochemical response of IPAgE for H 2 O 2 was obtained, nearly 300-fold higher than the conventional screen printed Ag electrode. Moreover, high sensitivity of 287 μA mM −1 cm −2 with a LOD of 5.0 μM was obtained under the optimized 20 printed layers. The inkjet printed Ag electrodes were also credibly applied in the detection of H 2 O 2 release from living cells. This work demonstrates inkjet printing is a promising method for the high performance electrochemical sensors. [ABSTRACT FROM AUTHOR]

Quantifying biomarkers at the early stage of the disease is challenging due to the low abundance of biomarkers in the sample and the lack of sensitive techniques. This article reports the development of a novel microfluidic electrochemical biosensing platform to address this challenge. The electrochemical sensing is achieved by utilizing a micropillar array electrode (μAE) coated with 3D bimetallic Pt–Pd nanotrees to enhance the sensitivity. A bubble-based acoustic microstreaming technique is integrated with the device to increase the contact of analyte molecules with the surface of electrodes to further enhance the electrochemical performance. The current density of Pt–Pd NTs/μAE with acoustic microstreaming is nearly 22 times that of the bare planar electrode in potassium ferrocyanide solution. The developed biosensor has demonstrated excellent sensing performance. For hydrogen peroxide detection, both the Pt–Pd NTs/μAE and acoustic microstreaming contribute to the sensitivity enhancement. The current density of the Pt–Pd NTs/μAE is approximatively 28 times that of the bare μAE. With acoustic microstreaming, this enhancement is further increased by nearly 1.6 times. The platform has a linear detection range of 5–1000 μM with a LOD of 1.8 μM toward hydrogen peroxide detection, while for sarcosine detection, the linear range is between 5 and 100 μM and LOD is 2.2 μM, respectively. Furthermore, the sarcosine biosensing shows a high sensitivity of 667 μA mM−1∙cm−2. Such a sensing platform has the potential as a portable device for high sensitivity detection of biomarkers. [ABSTRACT FROM AUTHOR]

Nanosized metallic particles are commonly used as an electrode modifier to catalyze various species, yet some of their physico-chemical characters, such as size, morphology, immobilization mode, and modification density, might affect the electrocatalytic properties of these particles. Here we engineer the diverse assemblies of silver nanoparticles on screen-printed carbon electrodes via the versatile vacuum sputtering approach, and evaluate their voltammetric behavior toward hydrogen peroxide reduction in pH 7.4. By simply modulating the sputtering time from 10 s to 200 s, silver assemblies with different surface coverages (defined as the ratio of the particle occupied surface area to the substrate geometric surface area) in the range of 0.38∼0.99 are exquisitely obtained. It is interestingly found that the surface coverage of the assembled silver on the disposable substrate exhibits a significant impact on the voltammetry of hydrogen peroxide electroreduction. The cathodic peak potential keeps shifting positively along with the surface coverage increasing, and the apparent peak current density normalized to the substrate surface area undergoes a volcano-type variation. When the overall peak current is normalized to the metal occupied surface area/loading content, a decreasing tendency of the specific/mass current is observed. These results suggest that the effect of the modification surface coverage should be taken into consideration when evaluating the contribution of nanosized materials to a given electrocatalytic reaction. When an appropriate compromise of the catalytic overpotential and the apparent current as well as the catalyst amount is desired for electrocatalysis, modulation of the modification surface coverage may be utilized to realize this compromise. [ABSTRACT FROM AUTHOR]

Highlights: [•] A Nafion-PB-MWCNTs/SPCE-IL sensor for nonenzymatic H2O2 detection. [•] Doping of IL promotes the electron transfer and provides enhanced performance for H2O2 sensing. [•] Outstanding sensitivity and excellent selectivity for enzyme-free H2O2 determination. [Copyright &y& Elsevier]

[Display omitted] • PtCu-rGO/CFME could be facilely proposed via a stepwise electrodeposition method. • It is featured with cost-effective, high sensitivity and good biocompatibility. • This microsensor can real-time monitor H 2 O 2 generated from living cells. Hydrogen peroxide (H 2 O 2) is an important biomarker for recognition of multiple diseases, the construction of nonenzymatic miniaturized sensors that capable to real-time monitor H 2 O 2 is tremendously significant. Here, we developed a high-performance microelectrode based on carbon fiber via a facile stepwise electrodeposition method, which could realize the high-sensitivity detection of the target H 2 O 2. Carbon fiber was decorated by reduced graphene oxide supported PtCu bimetallic cluster nanocomposite (PtCu-rGO), in which rGO as catalyst support had a thin layer, which could realize the uniform loading of the other material. Meanwhile, in virtue of the low cost and synergistic effect, PtCu bimetallic cluster nanoparticles exhibited great potential in electrocatalytic of H 2 O 2. The PtCu-rGO modified microelectrode displayed outstanding electrochemical behavior to H 2 O 2 sensing, including a broad working range of 5 μM-1270 μM (R2 = 0.991), 1270 μM-3920 μM (R2 = 0.998) with high sensitivity (15079.9 μA mM-1cm−2, 5–1270 μM; 10319.8 μA mM−1 cm−2, 1270–3920 μM), an appreciable detection limit of 0.60 μM, as well as good selectivity, reproducibility and stability. Additionally, this easy-to-interpret sensor enabled real-time monitoring of H 2 O 2 generated from living cells and could further recognize cancer cells and normal cells. This newly proposed microsensor could be a promising tool for clinic diagnosis. [ABSTRACT FROM AUTHOR]

Abstract: Novel snowflake-like Pt–Pd bimetallic nanoclusters (Pt–PdBNC) were synthesized on a screen-printed gold nanofilm electrode (SPGFE) substrate by electrochemically reducing precursors with a new constant potential/multi-potential step deposition strategy. The electrocatalytic behavior of the modified electrode (SPGFE/Pt–PdBNC) towards H2O2 was investigated. The results indicate that the as-prepared Pt–PdBNC significantly enhances the electrochemical reduction of H2O2 in neutral media, exhibiting preferable electrocatalytic performance compared to Pt and Pd monometallic nanoclusters. Under optimum conditions, SPGFE/Pt–PdBNC offers linear responses for H2O2 in the concentration range from 0.005 to 6mM with an ultrahigh sensitivity of 804mAM−1 cm−2 and excellent selectivity. Furthermore, glucose oxidase was immobilized on the Pt–PdBNC structure, and the fabricated biosensor presents favorable properties for glucose sensing. [Copyright &y& Elsevier]

Abstract: In the present study the electrocatalytic behavior of platinum nanoparticle-decorated multi-walled carbon nanotube clusters vertically aligned on a screen-printed gold nanofilm electrode substrate (SPGFE/MWCNTC/PtNP) toward hydrogen peroxide was intensively investigated. Oriented multi-walled carbon nanotube clusters (MWCNTC) were firstly well-organized onto the screen-printed gold film electrode (SPGFE) surface by covalent immobilization, and then platinum nanoparticles (PtNPs) dispersed on the MWCNTC structure were in situ synthesized by electrochemically reducing chloroplatinic acid. It was demonstrated that the MWCNTC/PtNP hybrid structure on the SPGFE substrate could significantly enhance the electrochemical reduction of hydrogen peroxide in neutral solutions. Compared with platinum nanoparticles loading on disordered multi-walled carbon nanotubes (SPGFE/MWCNT/PtNP), the proposed SPGFE/MWCNTC/PtNP exhibited more sensitive responses for hydrogen peroxide reduction. The fabricated electrode provided linear current responses for hydrogen peroxide in the concentration range from 5 to 2000μM with a detection limit of 1.23μM. The non-enzymatic sensor also offered good reproducibility and high selectivity for hydrogen peroxide detection. The carbon nanotube cluster/platinum nanoparticle hybrid system holds great promise as a scaffold to fabricate enzyme biosensors. [Copyright &y& Elsevier]

Abstract: A disposable hydrogen peroxide biosensor was developed based on the direct electron transfer of myoglobin (Mb) on mesopores KIT-6 modified screen-printed electrode (SPE) which was manually performed to fabricate the planar carbon electrodes. KIT-6 is a new material which can absorb abundant of Mb molecules. A mixture of Mb and KIT-6 was immobilized with nafion on electrode. The cyclic voltammetry experiment indicated that a pair of stable and well-defined reduction peaks with a formal potentials of −0.35, and −0.28V versus saturated calomel electrode (SCE) was obtained, using the present modified electrode in phosphate buffer saline (0.05M, pH 7.0) at scan rate of 100mVs−1, characteristic of Mb heme Fe(III)/Fe(II) redox couple. The heterogeneous electron transfer rate constant k s was estimated to be 16.93s−1. And the formal potential was pH-dependent, having two slopes of −54.7 and −49.3mV/pH which illustrated one electron transfer. This modified electrode was applied to detect H2O2 with sensitivity of 55.68mAM−1 cm−2. Infrared spectrum and UV–vis absorption spectra of immobilized Mb film were recorded. In conclusion, KIT-6 increases the electron transfer activity of Mb and this kind of H2O2 biosensor is low cost for using disposable. [Copyright &y& Elsevier]

• MnFe 2 O 4 nanoparticles were evenly distributed on the rGO via a facile solvothermal method. • Synergetic effect of MnFe 2 O 4 and rGO provided enhanced performance for H 2 O 2 sensing. • MnFe 2 O 4 /rGO nanocomposites exhibited high current response with a LOD of 0.528 nM. Hydrogen peroxide (H 2 O 2) is a common oxidant and major active oxygen species in organisms. There is a great requirement for the accurate and rapid determination of H 2 O 2 in the fields of environmental analysis, clinical treatment, food safety, pharmaceuticals, etc. The electrochemical method is considered an ideal analytical technology due to its high sensitivity, fast response and low detection limit. Herein, a one-pot solvothermal synthesis method was used to prepare a manganese ferrite/reduced graphene oxide (MnFe 2 O 4 /rGO) composite, which was modified on the surface of home-made screen-printed electrodes to construct a new type of electrochemical sensor for the determination of H 2 O 2 , subsequently. Cyclic voltammetry and chronoamperometry were used to study the electrocatalytic performance of H 2 O 2 reduction in neutral conditions. The results showed that the sensor had good electrocatalytic activity for the reduction of H 2 O 2. The response time of the sensor is 5 s, and the linear detection range is 0.1 ~ 4.0 mM (R2 = 0.9991) with a low detection limit of 0.528 nM. Such sensor exhibited good long-term stability, and good anti-interfering ability from potential interfering species of glucose, ascorbic acid, dopamine, fructose and uric acid during the determination. This study thus provides a potential method to construct novel type of H 2 O 2 for practical application. [ABSTRACT FROM AUTHOR]