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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]

We have synthesized nitrogen-doped graphene nanoribbons (N-GrNRs) by unzipping multi-walled carbon nanotubes (CNTs) under strongly oxidizing conditions and subsequent doping with nitrogen by a low-temperature hydrothermal method. The N-GNRs were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy, and assembled on a disposable screen-printed carbon electrode to give a sensor for HO that was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, chronocoulometry and chronoamperometry. The nano-modified electrode displays enhanced electron transfer ability, and has a large active surface and a large number of catalytically active sites that originate from the presence of nitrogen atoms. This results in a catalytic activity towards HO reduction at near-neutral pH values that is distinctly improved compared to electrodes modified with CNTs or unzipped (non-doped) CNTs only. At a working potential of −0.4 V (vs. Ag/AgCl), the amperometric responses to HO cover the 5 to 2785 μM concentration range, with a limit of detection as low as 1.72 μM. This enzyme-free electrochemical sensor exhibits outstanding selectivity and long-term stability for HO detection. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The investigation of highly efficient catalysts for the electrochemical oxidation of glucose is the most critical challenge to commercialize nonenzymatic glucose sensors, which display a few attractive superiorities including the sufficient stability of their properties and the desired reproducibility of results over enzyme electrodes. Herein we propose a new and very promising catalyst: Pt cubes well-dispersed on the porous Cu foam, for the the electrochemical oxidation reaction of glucose in neutral media. The catalyst is fabricated in situ on a homemade screen-printed carbon electrode (SPCE) substrate through initially synthesizing the three-dimensional (3D) porous Cu foam using a hydrogen evolution assisted electrodeposition strategy, followed by electrochemically reducing the platinic precursor simply and conveniently. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) proofs demonstrate that Pt cubes, with an average size (the distance of opposite faces) of 185.1 nm, highly dispersed on the macro/nanopore integrated Cu foam support can be reproducibly obtained. The results of electrochemical tests indicate that the cubic Pt-based catalyst exhibits significant enhancement on the catalytic activity towards the electrooxidation of glucose in the presence of chloride ions, providing a specific activity 6.7 times and a mass activity 5.3 times those of commercial Pt/C catalysts at −0.4 V (vs. Ag/AgCl). In addition, the proposed catalyst shows excellent stability of performance, with only a 2.8 % loss of electrocatalytic activity after 100 repetitive measurements. [ABSTRACT FROM AUTHOR]

Prussian blue (PB)-multi-walled carbon nanotubes (MWCNTs) modified screen-printed electrodes (SPEs) were used to immobilize enzyme acetylcholinesterase (AChE) for carbamate insecticide sensing. The synthesized hybrid PB-MWCNTs had high stability at pH values in the range of 5–10 and presented a porous and homogeneous microenvironment to entrap enzyme molecules. The generated hybrids not only acted as carriers of acetyl cholinesterase, but also promoted electron-transfer reactions because of the synergistic effects between MWCNTs and PB. Under the optimal conditions, the response of the sensor was proportional to acetylthiocholine (ATCh) concentrations ranging from 0.1 mM to 0.6 mM, with a sensitivity of 21.97 µA · mM−1 · cm−2. The sensors were further used to detect pesticides, and the inhibition rate of pirimicarb was proportional to the logarithm of its concentration ranging from 1.0 × 10−6to 1.0 g · L−1, with a limit of detection (LOD) equal to 5.32 × 10−8 g · L−1. In order to evaluate the performance of the detection system, the sensors were applied to determine pirimicarb in water samples and exhibited high sensitivity and good stability. The detection system is fast, simple for analysis of pirimicarb in environmental samples, and could provide a semi-automated analytical system through further improvement in biosensor arrays. [ABSTRACT FROM PUBLISHER]

Two kinds of carbon-based nanozymes were constructed from the same precursor of zeolitic imidazolate framework-8 (ZIF-8) for O2•− determination. Hollow carbon cubic nanomaterial (labelled as HCC) was obtained by chemically etching ZIF-8 with tannic acid and a subsequent calcination. A porous carbon cubic nanomaterial (labelled as PCC) was prepared by directly pyrolysis. Then HCC and PCC were immobilized on the surface of screen printed carbon electrodes (SPCE), fabricating HCC and PCC modified electrodes (denoted as HCC/SPCE and PCC/SPCE). HCC/SPCE, best operated at −0.5 V (vs. Ag/AgCl), has a sensitivity of 6.55 × 102 nA μM−1 cm−2 with a detection limit of 207 nM (at S/N = 3) for O2•− sensing. And PCC/SPCE, best operated at −0.4 V (vs. Ag/AgCl), exhibited a superior performance for O2•− detection with a sensitivity of 1.14 × 103 nA μM−1 cm−2 and a low detection limit of 140 nM (at S/N = 3). The two sensors possess excellent reproducibility and stability. They were used to sense O2•− released from HeLa cells. [ABSTRACT FROM AUTHOR]

Abstract Here we present a new method to fabricate enzyme-mimic metal-free catalysts for electrochemical detection of superoxide anion (O 2 •−) by introducing phosphate groups into graphene-based foam. Through a template-free hydrothermal process, graphene oxide (GO) was treated with different amount of phytic acid (PA) to obtain 3D porous graphene-based foam (PAGF). Characterizations demonstrate that phosphate groups were successfully modified on the surface and inter layer structure of PAGF materials and the defects and disorder degree of PAGF could be controlled by adjusting the addition of PA precursors. Meanwhile, the synthesized PAGF was successfully immobilized on screen printed carbon electrodes (SPCEs) and employed in O 2 •− detection. With PA treated on graphene structure, the resulted PAGF/SPCEs exhibit distinct characteristic redox peaks, showing enzyme-mimic catalytic activity toward O 2 •− dismutation. Also, the amount of modified phosphate groups has caused a considerable variety on the performance of PAGF-based electrodes. Apart from high sensitivity, wide liner range, low detection limit, good selectivity and long-term stability, our sensors also present satisfying performance in the real-time monitoring of drug-induced O 2 •− released from Hela cells. The reliability of the biological measurement was further demonstrated via electron paramagnetic resonance (EPR) to characterize the released O 2 •− from stimulated cells by using 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL) to trap the transient O 2 •−. The above results indicate that our established sensors hold potential application in the real-time detection of O 2 •− in biological samples. Highlights • A facile method to fabricate carbon-based Nanozyme with SOD-mimic activity. • The recommended sensor exhibit stable current steps toward cell-released O 2 •−. • The electrochemical determination of cell-released O 2 •− was further confirmed by using EPR. [ABSTRACT FROM AUTHOR]

• CeO 2 /Co 3 O 4 materials with porous structure by calcination of ZIF-67. • The CeO 2 /Co 3 O 4 nanocomposites show high electrochemical activity towards DA. • The synergistic effect of CeO 2 /Co 3 O 4 enhances the electrocatalytic properties. • Sensor has excellent selectivity and reproducibility for dopamine in real samples. In the field of biosensing and disease diagnosis, rapid and sensitive detection of dopamine (DA) is essential. In this work, Co 3 O 4 with a porous structure was prepared by temperature-controlled calcination of the precursor template zeolite imidazole framework-67 (ZIF-67), and CeO 2 /Co 3 O 4 composites with a porous framework structure were prepared by hydrothermal methods. The porous structure of the Co 3 O 4 prevented the aggregation of the CeO 2 nanoparticles and allowed them to be dispersed in a uniform manner on the surface. The CeO 2 introduction led to changes in the specific surface area and pore size of the calcined Co 3 O 4 material, and more active sites were exposed, allowing better binding with CeO 2 thus achieving good catalytic performance and excellent synergistic properties. The CeO 2 /Co 3 O 4 modification on the surface of glassy carbon electrodes (GCE) showed good electrocatalytic activity, which was superior to that of pure Co 3 O 4 and CeO 2 , as determined by electrochemical methods, thanks to. The results show that CeO 2 /Co 3 O 4 /GCE has a limit of detection (LOD) of 0.13 μM for DA (S/ N = 3) and a linear range of 0.13 μM-60 μM, as well as good interference resistance and reproducibility. This work provides a new solution for excellent dopamine sensors in Co 3 O 4 and CeO 2 composites, which can be extended to other biosensing applications. Schematic diagram of a glassy carbon electrode based on CeO 2 /Co 3 O 4 nanocomposite for DA determination. [Display omitted] [ABSTRACT FROM AUTHOR]

The determination of cardiac troponin I (cTnI) and myoglobin (Myo) is increasingly significant considering their potential in acute myocardial infarction (AMI) diagnosis. Here, we constructed a sandwich-type electrochemical aptasensor for the simultaneous detection of cTnI and Myo. The polydopamine-Au-metal ions (PDA-Au-Pb2+/Cu2+) were synthesized and used as the labels of second aptamers (TrO6 and S232). The labels displayed different peaks at different potential sites, thus making the simultaneous detection method available. Meanwhile, the synthesized zirconium-based carbon architecture (CC) was well-conductive originating from the annealing process. After the modification of CC on the bare electrode (screen-printed carbon electrode, SPCE), the coralloid Au (CAu) was further decorated on the electrode by electro-deposition, thus forming CAu/CC/SPCE with high conductivity. Hence, the aptasensor proposed here showed admirable simultaneous quantitative analysis performance towards cTnI and Myo with wide linear ranges (1 μg/mL-0.01 pg/mL, 1 μg/mL-0.1 pg/mL) and low detection limits (3.8 fg/mL, 35 fg/mL). These results demonstrated that the aptasensor held the potential application in clinical diagnosis. ● An electrochemical aptasensor was fabricated based on CAu/CC and PDA-Au-Pb2+/Cu2+. ● The CAu/CC exhibited high electronic conductivity, thus improving sensitivity. ● The labels PDA-Au-Pb2+/Cu2+ made the simultaneous detection available. ● The aptasensor showed good performance for the simultaneous detection of cTnI+Myo. ● The portable aptasensor further showed its potential application in on-site analysis. [ABSTRACT FROM AUTHOR]

Quantification of superoxide anions (O 2 •− ) is significant in the monitoring of many serious diseases and the design of enzyme-mimic catalysts plays the main role in the development of non-enzymatic O 2 •− sensors. Herein, we proposed a facile self-assembly process to synthesize manganese phosphate modified carbon networks using three kinds of widely-used carbon materials (MWCNTs, NGS and GO) as pillar connectors. Characterizations demonstrate that manganese phosphate is widely dispersed inside and on the surface of carbon networks without visible morphology. Meanwhile, all three kinds of synthesized catalysts were successfully immobilized on the screen-printed carbon electrodes to evaluate the electrochemical performance of fabricated sensors. The results indicate that sensors based on Mn x (PO 4 ) y modified MWCNTs exhibit high sensitivity with an extremely low detection limit of 0.127 μM (S/N = 3) and a wide liner range of 0–1.817 mM (R 2 = 0.998). We further employed the recommended sensors in the real-time monitoring of HepG2 cells released O 2 •− under the stimulating of Zymosan (20 mg/mL). Noticeably, the proposed sensors exhibit not only sensitive response but also stable current steps upon different addition of Zymosan. The calculated concentrations of cell-released O 2 •− vary from 6.772 to 24.652 pM cell −1 for the Zymosan amount used in this work. The established novel sensors display low background current and signal noises, thus holding unique advantages in the trace analysis of O 2 •− in biological samples and in vivo environment. [ABSTRACT FROM AUTHOR]

Undoubtedly, electrocatalyzing the hydrogen evolution reaction (HER) is now becoming the subject of extensive studies due to its crucial role in harvesting clean energy. In general, bare screen-printed carbon electrodes (SPCEs) have negligible ability to catalyze the HER due to the lack of effective sites. Here we find that: 1) a facile anodization treatment can improve the electrocatalytic activity of home-made SPCEs with apparently reduced overpotential and increased current density for the HER; 2) the activity enhancement of SPCEs is highly dependent on anodization conditions including electrolyte, treatment time, and anodization potential; 3) the introduction of negatively charged oxygen-containing functional groups during anodization, together with the increased defect sites and hydrophilicity on electrode surface, leads to the promoted activity of anodized SPCEs synergistically. Similar phenomena are also found in other carbon-based electrodes including glassy carbon electrode and carbon nanotube-modified electrode. These findings reported in this work are expected to guide the future design of advanced electrode systems for efficient hydrogen evolution. [ABSTRACT FROM AUTHOR]

In this work, a highly sensitive enzyme- and metal-free electrochemical method for superoxide anion (O 2 − ) detection has been developed by employing screen-printed carbon electrodes (SPCE) modified by nitrogen doped hollow mesoporous carbon spheres (N-HMCS). For comparison, solid carbon spheres (SCS) and hollow mesoporous carbon spheres (HMCS) were also synthesized to fabricate the modified SPCE. Compared with SCS/SPCE and HMCS/SPCE, N-HMCS/SPCE displayed a higher electrochemical performance. When applied for electrochemical detection of O 2 − , N-HMCS/SPCE exhibited a high sensitivity of 1.49 μA cm −2 μM −1 , better than SCS/SPCE and HMCS/SPCE and many of enzyme- or metal-based superoxide anion sensors. N-HMCS is expected to become a new generation of sensing materials for electrochemical analysis of O 2 − . [ABSTRACT FROM AUTHOR]

Rapid and accurate detection of nicotine is important due to its detrimental effects on human beings and recent surge in the usage of electronic cigarettes. In this paper, we report an electrochemical sensor for nicotine detection by using screen-printed carbon electrodes (SPCE) modified with nitrogen-doped graphene sheets (NGS). NGS was synthesized and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectrometry. Due to the superior electron transfer capability and the doped nitrogen atoms, NGS shows high catalytic activity for the electro-oxidation of nicotine, with a significant decrease in the overpotential. Using the NGS-based nicotine sensor, we obtained detection sensitivity at 0.627 mA·cm − 2 mM − 1 with the limit of detection at 47 nM nicotine. Moreover, the sensor shows favorable selectivity and long-term stability for detecting nicotine in urine and tobacco samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • A biosensor for simultaneous detection of ascorbic acid (AA), dopamine (DA) and uric acid (UA). • The nanocomposites of MnFe 2 O 4 /MoS 2 showed high electrocatalytic activity for AA, DA and UA. • MMF nanocomposite with excellent oxidase like activity. • MMF biosensor has very good anti-interference and reproducibility. In this paper, we adopt a one-pot solvothermal synthesis method to prepare MnFe 2 O 4 /MoS 2 nanocomposite (MMF) as an artificial enzyme for simultaneous electrochemical detection of ascorbic acid (AA), dopamine (DA) and uric acid (UA) by screen-printed carbon electrode (SPCE). The exfoliated MoS 2 surface contains numerous S defects and the spinel MnFe 2 O 4 possesses non-homogeneous catalystic properties, high abundance of oxygen vacancies and surface. It provides high adsorption properties through the replacement of cations with large amounts of active clusters on the surface of nano-impurity composites, as well as the high surface activity of MoS 2. Finally, we found that MMF can effectively and sensitively detect AA, DA and UA, and the peak current increases significantly in a certain scanning speed range. The electrochemical sensing performance of the synthetic nanocomposite for the analytes was better than that of individually synthesized MoS 2 and MnFe 2 O 4 , respectively. The obtained limit of detection (LOD) of MMF for AA, DA and UA were 0.17 mM, 0.41 μM and 0.14 μM, respectively. In addition, the LOD for simultaneous detection of AA, DA and UA were as low as 0.90 mM, 0.16 μM and 3.05 μM, respectively. The prepared MMF showed good anti-interference ability and reproducibility for the analytes sensing. [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]

Abstract: It is widely thought in electro-biochemical analysis that the sensing interfaces play a key role in the enzymeless detection of biomolecules like glucose, ascorbic acid, dopamine and uric acid. On the way to maximize the anti-poisoning sensitivity of nonenzymatic electrochemical glucose sensors as well as achieve favorable selectivity, we propose here a porous interface fabricated by a facile but effective approach for glucose monitoring in alkaline media containing dissolved oxygen. The sensing interface based on porous Cu foams is directly formed on a homemade disposable screen-printed carbon electrode (SPCE) substrate by electrodeposition assisted with hydrogen evolution simultaneously, and its porosity can be easily tailored through adjusting deposition conditions for the optimal electrocatalytic oxidation of glucose molecules. SEM and BET studies show that the generated Cu foam possesses robust hierarchical porous architectures with greatly enhanced surface area and pore volume, beneficial for the unimpeded mobility of glucose and reaction products. Cyclic voltammetric tests indicate that a diffusion-controlled glucose electro-oxidation reaction occurs at the Cu foam electrode at around +0.35V vs. Ag/AgCl in 0.1M NaOH. Chronoamperometric results obtained under optimized conditions reveal that the proposed sensor exhibits desired poison resistance ability in the presence of chloride ions and significant selectivity to glucose, providing fascinating sensitivities of 2.57 and 1.81mAcm−2 mM−1 for glucose in the linear concentration ranges of 2–80μM and 0.1–5mM, respectively. The limit of detection is calculated to be as low as 0.98μM according to the signal-to-noise ratio of three. In addition, the fabricated sensing interface shows attractive reproducibility (RSD of 5.1% and 7.0% for 15 repeated measurements on a sensor and for measurements on 15 prepared sensors, respectively) and outstanding long-term stability (less than 5% loss in sensitivity over 1 month) for glucose detection. The application of the Cu foam based sensor for monitoring glucose in practical samples is also successfully demonstrated. [Copyright &y& Elsevier]

Abstract: Here we report a new disposable bismuth-coated porous screen-printed carbon electrode (Bi-P-SPCE) for trace heavy metal ions detection. The Bi-P-SPCE was fabricated by two processes: firstly, the porous screen-printed carbon electrode (P-SPCE) was prepared by combing a printing procedure of a graphite-based layer doped with CaCO3 powders with a subsequent dissolution of these powders; secondly, a Bi film layer was formed on the P-SPCE by in situ electrodepositing Bi(III) along with accumulating analytes. Due to the rough surface, large active area and low background noise of P-SPCE, the electrode exhibited significantly enhanced sensitivity for lead(II) and cadmium(II) detection compared to screen-printed carbon electrode (SPCE) and glassy carbon electrode (GCE). With a preconcentration at −1.2V (vs. Ag/AgCl) for 300s, the detection limits obtained on the proposed Bi-P-SPCE are 0.03μg/L and 0.34μg/L (S/N=3) for lead(II) and cadmium(II), respectively. This easy-to-prepare and low-cost electrode was also successfully applied to real water sample analysis. [Copyright &y& Elsevier]

Abstract: A new screen-printed carbon electrode with porous architectures prepared using an extremely facile and low-cost approach is introduced. The preparation mainly involved a printing procedure of a graphite-based layer doped with CaCO3 powders and a subsequent dissolution of these powders. The resulting porous screen-printed carbon electrode (P-SPCE) can offer large surface, broad potential window, low background current and high electrochemical reactivity. Moreover, the proposed P-SPCE provides enhanced performance for enzyme-free H2O2 sensing compared to conventional glassy carbon electrodes and screen-printed carbon electrodes. These attractive properties of the P-SPCE are expected to be of wider applications. [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]

[Display omitted] • A kind of hydrogel based on dopamine polymer doped polypyrrole (PDA-PPy) was synthesized in rapid one-pot method. • PDA-PPy hydrogel exhibited selective adsorption capacity for Pb(II). • PDA-PPy/SPCE showed good sensing performance for Pb(II) detection. Lead is one of the most common toxic heavy metals in the environment and it is easily accessible by the human body because there are residues in daily necessities and food. Therefore, it is significant to develop the high-performance detection method of lead ion (Pb(II)) in the environment and food. In this work, a sensitive and selective electrochemical sensing platform of Pb(II) was successfully constructed based on dopamine polymer doped polypyrrole (PDA-PPy) hydrogel modified screen-printed carbon electrode (SPCE) (noted as PDA-PPy/SPCE). PDA-PPy hydrogel was prepared by the hybridization of dopamine hydrochloride and pyrrole through a rapid and eco-friendly one-step synthesis method. Combined the selective adsorption capacity and good conductivity of PDA-PPy hydrogel, it was employed as the modified material for electrodes to achieve signal amplification. The result showed that PDA-PPy/SPCE exhibited excellent sensing performance towards Pb(II) with low detection limit of 0.15 μg L-1 and high sensitivity of 0.17 μg L-1 μA-1. Besides, acceptable recoveries were shown in real sample analysis, indicating that it has application prospects. [ABSTRACT FROM AUTHOR]