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Simultaneous electrochemical determination of 4-aminophenol (4-AP) and acetaminophen (ACOP) is crucial due to their high toxicity when are overused. Herein, a novel electrocatalyst of nitrogen-doped carbon coated CoNi alloy (CoNi@CN) is derived from bimetallic CoNi(BDC) 2 (DABCO) for the first time. A series of characterizations demonstrate that composite has been successfully synthesized, and all elements are evenly distributed in the catalyst. The optimal sensor based on Co 1 Ni 1 @CN-700 exhibits two wide linear responses for 4-AP (0.05–60 μM and 60–250 μM) and ACOP (0.05–40 μM and 40–150 μM) with the lowest detection limit of 5.2 nM and 3.8 nM compared with current known reports. Moreover, the sensor has superior reproducibility, selectivity and stability. In addition, the wonderful recoveries also are obtained when sensor is used to detect 4-AP and ACOP in real samples, illustrating that electrochemical sensor has great prospect in the clinical application. Image 1 • A novel nitrogen-doped carbon coated CoNi alloy (Co 1 Ni 1 @CN-700) is derived from bimetallic CoNi(BDC) 2 (DABCO). • Co 1 Ni 1 @CN-700 has large surface area, many catalytic sites, unique electronic effect and synergistic effect. • Co 1 Ni 1 @CN-700 shows high electrocatalytic activities towards oxidation of 4-aminophenol and acetaminophen. • Co 1 Ni 1 @CN-700 shows utra-low limit of detection for simultaneous determination of 4-aminophenol and acetaminophen. [ABSTRACT FROM AUTHOR]

Nickel‐based metal‐organic framework (Ni‐MOF) embedded in tubular poly(3,4‐ethylenedioxythiophene) (T‐PEDOT) composites was first synthesized through the in situ growth of Ni‐MOF with T‐PEDOT. The incorporation of T‐PEDOT and Ni‐MOF enhances the conductivity of Ni‐MOF/T‐PEDOT, reduces aggregation and restricts the size of Ni‐MOF, and exposes more active sites of the Ni‐MOF. Compared with Ni‐MOF, Ni‐MOF/T‐PEDOT manifests improved electrocatalytic activity toward the oxidation and reduction of gallic acid and tinidazole, respectively. The Ni‐MOF/T‐PEDOT‐2/glassy carbon electrode (GCE) as a novel electrochemical sensor was constructed to detect two antibacterial drugs. Ni‐MOF/T‐PEDOT‐2/GCE shows two linear responses to gallic acid in the range of 0.8–25.5 μM and 25.5–150 μM, with a high sensitivity of 0.559 μA μM−1. At the same time, Ni‐MOF/T‐PEDOT‐2/GCE exhibits two linear responses to tinidazole in the range of 0.7–35 μM and 35–255 μM. Therefore, Ni‐MOF/T‐PEDOT‐2/GCE could be used to detect gallic acid and tinidazole in real samples with satisfactory results. Recovery values varied from 95.1 to 104.2 % for gallic acid sensing and 94.2 to 104.2 % for tinidazole sensing, which demonstrates that the sensor has practical application for gallic acid and tinidazole detection. Our work offers an efficient strategy for fabricating a new electrocatalysts based on MOFs and tubular conductive polymer. [ABSTRACT FROM AUTHOR]

The cross-linked network of DUT-67/tubular polypyrrole (T-PPY) composites was first synthesized by in-situ growth zirconium - based metal-organic frameworks (DUT-67) with T-PPY. The introduction of T-PPY effectively increases conductivity of DUT-67/T-PPY composites, weakens accumulation of the DUT-67, and exposes more active sites of DUT-67. DUT-67/T-PPY/GCE manifests increased electrocatalytic activity toward reduction of nitrofurazone and ornidazole compared with DTU-67. A novel electrochemical sensor based on DUT-67/T-PPY was established to effectively detect two anti-infective drugs, respectively. Under optimized experimental conditions, the proposed sensor shows a wider linear range for nitrofurazone that is composed by two line segments (9.08–354.08 μM and 354.08–1004.04 μM). Meanwhile, the sensor also displays a linear response to ornidazole in the range of (0.7–100.5 μM and 100.5–250.4 μM) as well as a low LOD as 0.25 μM (S/N = 3). The proposed sensor was used for the detection of nitrofurazone and ornidazole in actual samples, and the satisfactory results were acquired. This research provides an efficient strategy for fabricating novel electrochemical sensor based on cross-linked network structure of T-PPY and MOFs. Image 1 • Constructing the electrocatalyst based on DUT-67/T-PPY with situ growth method for the first time. • Improved electrocatalytic properties due to the cross-linking between DTU-67 and T-PPY. • Low detection limit and the widest linear range for ornidazole and a wider linear range for nitrofurazone in pH = 6.0. • Satisfactory results for nitrofurazone and ornidazole in real samples. [ABSTRACT FROM AUTHOR]

As a novel single-atom-thick sheet of sp 2 hybridized carbon atoms, graphene (GR) has attracted extensive attention in recent years because of its unique and remarkable properties, such as excellent electrical conductivity, large theoretical specific surface area, and strong mechanical strength. However, due to the π-π interaction, GR sheets are inclined to stack together, which may seriously degrade the performance of GR with the unique single-atom layer. In recent years, an increasing number of GR-based electrochemical sensors and biosensors are reported, which may reflect that GR has been considered as a kind of hot and promising electrode material for electrochemical sensor and biosensor construction. However, the active sites on GR surface induced by the irreversible GR aggregations would be deeply secluded inside the stacked GR sheets and therefore are not available for the electrocatalysis. So the alleviation or the minimization of the aggregation level for GR sheets would facilitate the exposure of active sites on GR and effectively upgrade the performance of GR-based electrochemical sensors and biosensors. Less aggregated GR with low aggregation and high dispersed structure can be used in improving the electrochemical activity of GR-based electrochemical sensors or biosensors. In this review, we summarize recent advances and new progress for the development of electrochemical sensors based on less aggregated GR. To achieve such goal, many strategies (such as the intercalation of carbon materials, surface modification, and structural engineering) have been applied to alleviate the aggregation level of GR in order to enhance the performance of GR-based electrochemical sensors and biosensors. Finally, the challenges associated with less aggregated GR-based electrochemical sensors and biosensors as well as related future research directions are discussed. [ABSTRACT FROM AUTHOR]

In this work, Pd nanoparticles/porous graphene (Pd/PGR) is prepared by simultaneous reduction of graphene oxide (GO) and Pd precursor in sodium borohydride (NaBH 4 ) solutions at the electrode surface. In this preparation, the positively charged ZnO with high isoelectric point is used as templates for the adsorption of negatively charged GO in water. Then, the poly(diallyldimethylammonium chloride) (PDDA) is added into the ZnO/GO through the electrostatic interaction between the negative charge of GO and positive charge of PDDA. Subsequently, PDDA/ZnO/GO is employed as a support material for the adsorption of chloropalladic acid ions (PdCl 4 2 − ), via the self-assembly between the negative Pd precursor and positively charged functional groups of PDDA. One-step reduction of Pd precursor/PDDA/ZnO/GO in NaBH 4 solutions and the subsequent removal of the ZnO produce Pd/PDDA/PGR with a porous structure at the electrode surface. With a porous morphology and large surface area for both efficient exposure of Pd nanoparticles and enhanced electrolyte-reactant diffusion, a sensitive enzymeless sensor of hydrogen peroxide (H 2 O 2 ) is constructed. Compared with the nonporous Pd/PDDA/GR, the Pd/PDDA/PGR displays high electrocatalytic activity towards H 2 O 2 , exhibiting a high sensitivity of 57.7 μA mM − 1 and low detection limit of 0.9 μM towards the reduction of H 2 O 2 . The improved activity and simple preparation method makes Pd/PDDA/PGR promising for being developed as an attractive robust and new electrode material for electrochemical sensor and biosensor fabrication. [ABSTRACT FROM AUTHOR]

In this study, we developed a novel biosensor based on highly exposed Pt nanoparticles (Pt NPs) decorated porous graphene (PG) for the reliable detection of extracellular hydrogen peroxide (H 2 O 2 ) released from living cells. The commercially available low-cost hydrophilic CaCO 3 spheres were used as template for preparing PG. The porous structure provided larger surface area and more active sites. Due to the porous structure of PG, the Pt NPs supported on PG were not secluded by aggregated graphene layers and were highly exposed to target molecules. Ultrafine Pt NPs were well dispersed and loaded on PG by a method of microwave assistance. Electrochemical performances of the Pt/PG nanocomposites modified glassy carbon electrode (GCE) were investigated. The electrocatalytic reduction of H 2 O 2 showed a wide linear range from 1 to 1477 μM, with a high sensitivity of 341.14 μA mM −1 cm −2 and a limit of detection (LOD) as low as 0.50 μM. Moreover, the Pt/PG/GCE exhibited excellent anti-interference property, reproducibility and long-term storage stability. Because of these remarkable analytical advantages, the constructed sensor was used to determine H 2 O 2 released from living cells with satisfactory results. The superior catalytic activity makes Pt/PG nanocomposites a promising candidate for electrochemical sensors and biosensors design. [ABSTRACT FROM AUTHOR]

In this paper, porous reduced graphene oxide (P-rGO) was synthesized by electrochemical reduction method using ZnO as template. P-rGO was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The electrochemical oxidation of hydroquinone (HQ), catechol (CC), and resorcinol (RC) was investigated using cyclic and differential pulse voltammetry at P-rGO modified electrode. P-rGO electrode exhibited high current sensitivity for these analytes compared to bare glassy carbon electrode (GCE) and electrochemically reduced graphene oxide (ERGO) modified electrodes, which is due to porous structure. In addition, three isomers can be simultaneously determined at P-rGO modified electrode by using differential pulse voltammetry without any separation step. The P-rGO also exhibits superior stability, reproducibility, and good anti-interference properties. Therefore, the remarkable electrochemical advantage of P-rGO makes it a promising material in electrochemical biosensing field. [ABSTRACT FROM AUTHOR]

Abstract: Two-dimensional ordered mesoporous carbon nitride (OMCN) has been successfully prepared for the first time using SBA-15 mesoporous silica and melamine as template and precursor respectively, by a nano hard-templating approach. A series of OMCN-x samples with different pyrolysis temperatures have been reported. The formation of these composite materials was verified by detailed characterization (e.g., Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, N2 adsorption, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy). The results showed that the materials were structurally well ordered with two-dimensional porous structure, high surface area and large pore volume. The influence of BET surface area and different amounts of N-bonding configurations formed at different pyrolysis temperatures of OMCN-x for the electrocatalysis towards hydrogen peroxide, nitrobenzene, and nicotinamide adenine dinucleotide were investigated in detail. Results indicated that OMCN treated at 800°C with largest BET surface area and highest amounts of pyrindinic N showed improved electrocatalytic activity for H2O2, nitrobenzene, and NADH in neutral solution. [Copyright &y& Elsevier]

Abstract: In the present work, using copper as an etching agent, a novel and easy method to prepare porous graphene nanosheet (P-GR) was reported. With a large number of pores, more acidic groups and edge defect sites (EDSs) compared with graphene (GR), the prepared P-GR was used as an electrochemical biosensing platform for the first time. Using voltammetry and amperometry as detection methods, some important electroactive compounds, including dopamine (DA), ascorbic acid (AA), uric acid (UA), epinephrine (EP), guanine (G), adenine (A), xanthine (XA), hypoxanthine (HX), hydrogen peroxide and β-nicotinamide adenine dinucleotide (NADH) were employed to study their electrochemical responses on P-GR modified glassy carbon electrode (P-GR/GCE). The results show that P-GR/GCE exhibits better electrochemical performance to these substances compared with GR modified glassy carbon electrode (GR/GCE) and edge plane pyrolitic graphite electrode (PGE). The remarkable electrochemical advantage of P-GR makes it a promising material in electrochemical biosensing field. [Copyright &y& Elsevier]

Today's rampant abuse of antibiotics and lean meat powder disturbs environment and threatens public human health. Therefore, fast in-site detection of antibiotics or lean meat powder residue could avoid potential risks. In this work, flexible graphene electrodes (FGE) were easily and facilely patterned and prepared by CO 2 laser at room environment, which was coupled with a portable electrochemical analyzer for electronic signal transmission. Laser-enabled flexible electrochemical sensor on finger can be used for rapid real-time in-site electrochemical identification of chloramphenicol (CAP), clenbuterol (CLB) and ractopamine (RAC) in meat. The electrochemical response of CAP, CLB and RAC is investigated with the limit of detection of 2.70, 1.29 and 7.81 μM and the linear range of 10–200, 5–80 and 25–250 μM in phosphate buffer saline (PBS) pH 7.0, correspondingly. The minimum detection concentrations of CAP, CLB and RAC were 20, 10 and 30 μM, respectively, in actual samples of pork. And the minimum detection concentrations of CAP, CLB and RAC were 10, 5 and 25 μM in milk, respectively. Such an integrated sensing platform enriches application of sensors on finger in food security and provides information that prevents drug containments from entering food chain. [Display omitted] • Laser preparation of flexible patterned graphene electrode at room environment. • Construction of electrochemical sensor on finger. • Quick in-situ qualitative tracking of antibiotic and lean meat powder. [ABSTRACT FROM AUTHOR]

Abstract: A chiral electrochemical sensor has been prepared via cysteic acid modified glassy carbon (CyA-GC) electrode to discriminate tyrosine (Tyr) enantiomers. Sweep cycles of CyA-GC in modification process and pH of solution were investigated to obtain optimum experimental conditions. Electrochemical impedance spectroscopy was employed to characterize the electrical conductivity of the modified electrode. For the first time, different oxidation peak potentials (E p) of l- and d-Tyr were observed in the differential pulse voltammograms obtained in the solution containing l- or d-Tyr. Further study showed that only one peak appeared in mixture solution containing l- and d-Tyr and E p of that peak shifted positively and linearly with an increasing percentage of l-isomer of Tyr racemic mixture. [Copyright &y& Elsevier]

Abstract: A facile and fast microwave irradiation method was developed to prepare PtPd bimetallic alloy nanoparticles on onion-like mesoporous carbon vesicle (MCV). With MCV acts as a template, its high surface area favors the formation of nanosized PtPd particles. The PtPd/MCV nanocomposite was characterized by transmission electron microscopy (TEM), scanning electron micrographs (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). A nonenzymatic amperometric sensor of glucose based on the PtPd/MCV modified glassy carbon (GC) electrode is developed. Compared with the Pt/MCV nanocomposite, the PtPd/MCV modified electrode displays enhanced current response towards glucose and gives linear range from 1.5 to 12mM. The particular lamellar structure of the MCV results in favorable transport passage for glucose. The modified electrode achieves 95% of the steady-current within 3s. This nonenzymatic glucose sensor also exhibits good ability of anti-interference to electroactive molecules. The fast response and facile preparation method make PtPd/MCV nanocomposite promising for the development of enzyme-free sensor for glucose. [Copyright &y& Elsevier]

Abstract: Onion-like mesoporous carbon vesicle (MCV) with multilayer lamellar structure was synthesized by a simply aqueous emulsion co-assembly approach. Palladium (Pd) nanoparticles were deposited on the MCV matrix (Pd/MCV) by chemical reduction of H2PdCl4 with NaBH4 in aqueous media. Pd(X)/MCV (X wt.% indicates the Pd loading amount) nanocomposites with different Pd loading amount were obtained by adjusting the ratio of precursors. The particular structure of the MCV results in efficient mass transport and the onion-like layers of MCV allows for the obtainment of highly dispersed Pd nanoparticles. The introduction of Pd nanoparticles on the MCV matrix facilitates hydrazine oxidation at more negative potential and delivers higher oxidation current in comparison with MCV. A linear range from 2.0×10−8 to 7.1×10−5 M and a low detection limit of 14.9nM for hydrazine are obtained at Pd(25)/MCV nanocomposite modified glassy carbon (GC) electrode. A nonenzymatic amperometric sensor for hydrogen peroxide based on the Pd(25)/MCV nanocomposite modified GC electrode is also developed. Compared with MCV modified GC electrode, the Pd(25)/MCV nanocomposite modified GC electrode displays enhanced amperometric responses towards hydrogen peroxide and gives a linear range from 1.0×10−7 to 6.1×10−3 M. The Pd(25)/MCV nanocomposite modified GC electrode achieves 95% of the steady-current for hydrogen peroxide within 1s. The combination of the unique properties of Pd nanoparticles and the porous mesostructure of MCV matrix guarantees the improved analytical performance for hydrazine and hydrogen peroxide. [ABSTRACT FROM AUTHOR]

Abstract: A simple and facile synthetic method to incorporate Pt nanoparticles inside the mesopores of ordered mesoporous carbons (OMCs) is reported. The Pt/OMCs nanocomposite was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and nitrogen adsorption–desorption. The results show that the incorporation of Pt nanoparticles inside the pores of OMCs does not change the highly ordered two-dimensional hexagonal mesostructure of OMCs matrix. Nonenzymatic amperometric sensor of hydrogen peroxide and glucose based on the Pt/OMCs nanocomposite-modified glassy carbon (GC) electrode is developed. Compared with the original OMCs-modified electrode, the Pt/OMCs-modified electrode displays improved current response towards hydrogen peroxide and gives linear range from 2 to 4212μM. At an applied potential of −0.08V, the Pt/OMCs nanocomposite gives linearity in the range of 0.5–4.5mM glucose in neutral buffered saline solution. This glucose sensor also exhibits good ability of anti-interference to electroactive molecules. The combination the unique properties of Pt nanoparticles and the ordered mesostructure of OMCs matrix guarantees the enhanced response for hydrogen peroxide and glucose. [Copyright &y& Elsevier]

Abstract: A simple and facile synthetic method to incorporate copper sulfide (Cu2S) nanoparticles inside the mesopores of ordered mesoporous carbons (OMCs) is reported. The Cu2S/OMCs nanocomposite was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption–desorption. The results show that the incorporation of Cu2S nanoparticles inside the pores of OMCs does not change the highly ordered two-dimensional hexagonal mesostructure of OMCs matrix. Nonenzymatic amperometric sensor of hydrogen peroxide based on the Cu2S/OMCs nanocomposite modified glassy carbon (GC) electrode is developed. Compared with the pristine OMCs modified electrode, the Cu2S/OMCs modified electrode displays high electrocatalytic activity towards hydrogen peroxide and gives linear range from 1 to 3030μM (R =0.9986). The sensor also exhibits good ability of anti-interference to electroactive molecules. The combination of the unique properties of Cu2S nanoparticles and the ordered mesostructure of OMCs matrix guarantee the excellent electrocatalysis for hydrogen peroxide. The good analytical performance and low-cost make Cu2S/OMC nanocomposite promising for the development of effective sensor for hydrogen peroxide. [Copyright &y& Elsevier]

The authors describe a method for synthesis of a three-dimensional (3D) interconnected carbon nanorod aerogel (3D-ICNA) starting from wax gourd (Benincasa hispida) which is a low-cost biomass. The 3D-ICNA possesses unique 3D interconnected and porous nanostructure, with abundant edge-plane-like defective sites, a large specific surface area (823 m2 g−1) and a large pore volume (0.12 cm3 g−1). This makes the material attractive in terms of electrochemical sensing. To validate the feasibility, the voltammetric response towards ferricyanide, hydrogen peroxide (H2O2), acetaminophen, ascorbic acid (AA), dopamine, uric acid and epinephrine was investigated by using a glassy carbon electrode (GCE) modified with 3D-ICNA. The modified GCE shows higher electron-transfer capacity than a conventional GCE. In addition, as an electrochemical sensor for AA or H2O2, the electrode exhibits better analytical performance with lower detection limit [3.5 μM for AA or 0.68 μM for H2O2 based on 3σ/m criterion (where σ is the standard deviation of the blank and m is the slope of the calibration plot)], wider linear range and higher sensitivity (0.14, 0.11 and 0.080 μA μM−1 cm−2 for AA or 0.24 and 0.20 μA μM−1 cm−2 for H2O2) compared to a plain GCE or a carbon nanotube-modified GCE. The modified GCE exhibits a large potential for the amperometric determination of AA or H2O2 in real samples.By employing the biomass of wax gourd (Benincasa hispida) as the precursor, a three-dimensional interconnected carbon nanorod aerogel was prepared. It is shown to be a viable material for the construction of an advanced electrochemical sensor for H2O2 and ascorbic acid. [ABSTRACT FROM AUTHOR]

In this work, porphyrin-based 2D MOF CuTCPP/platelet ordered mesoporous carbon (pOMC) composites were successfully synthesized by conventional solvothermal reaction. The introduction of pOMC increases conductivity of CuTCPP/pOMC composites, weakens accumulation of the CuTCPP layers, and exposes active sites of CuTCPP. CuTCPP/pOMC composites show high electro-catalytic activity to the oxidation of hydroxylamine and the redox of chlorogenic acid. An electrochemical sensor based on CuTCPP/pOMC was constructed for quantitative determination of hydroxylamine and chlorogenic acid, and relevant mechanisms were discussed. Under optimized conditions, the fabricated sensor displays two wide linear responses in the ranges of 5.8–733.8 μM and 733.8–2933.8 μM for hydroxylamine, with a rapid response time about 1 s. For chlorogenic acid, the sensor presents linear responses in the ranges of 0.1–2 μM and 2–15 μM, with a high sensitivity of 10.18 μA/μM. The sensor was used to detect hydroxylamine and chlorogenic acid in real samples, and satisfactory results were obtained. The synthesis of CuTCPP/pOMC composites provides new strategy for designing electrochemical sensors based on 2D MOFs. Image 1 • 2D CuTCPP nanosheets and platelet OMC composites were synthesized for the first time. • CuTCPP/pOMC sensor shows enhanced electro-catalytic activity compared to CuTCPP. • The linear range is wide and the response time is fast for hydroxylamine. • The sensitivity of chlorogenic acid is the highest in non-noble metal materials. • CuTCPP/pOMC composites provide new strategy for electrochemical sensors based on 2D MOFs. [ABSTRACT FROM AUTHOR]

In this work, we reported a novel, facile and effective strategy by using hydrothermal reaction and following high-temperature pyrolysis under the ammonia flow to fabricate the molybdenum nitride nanosheets/N-doped multi-walled carbon nanotubes (MoN/N-MWNTs) hybrid nanocomposite. MoN/N-MWNTs nanocomposite was characterized via X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and electrochemical methods. This nanocomposite exhibits excellent electrocatalytic oxidation of l -cysteine ( l -CySH). An amperometric l -CySH sensor was constructed based on the MoN/N-MWNTs modified glassy carbon electrode. The as-prepared MoN/N-MWNTs nanocomposite has favourable conductivity, large surface area due to the MWNTs as supporter and highly exposed active sites of MoN. Moreover, the influence of different loading amounts of MoN was researched. The optimized MoN/N-MWNTs catalyst showed a wide detection range that was composed by two line segments (5 μM– 0.79 mM and 0.79 mM–12.60 mM), a sensitivity of 198.59 nA μM −1 cm −2 in the low concentration range, a rapidly response within 1.5 s as well as good reproducibility and stability. [ABSTRACT FROM AUTHOR]

Abstract: Gold nanoparticles/macroporous carbon (GNPs–MPC) composites were simply fabricated by electrodepositing GNPs film on MPC using cyclic voltammetry (CV). The prepared composites were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectra (XPS) and X-ray diffraction (XRD). Glassy carbon electrode (GCE) modified with GNPs–MPC was used as electrochemical sensor of l-tryptophane (l-Trp) and l-tyrosine (l-Tyr) for the first time. In 0.1M PBS (pH=7.4), the GNPs–MPC/GCE exhibited satisfactory electrocatalytic activity by significantly decreasing the oxidation potentials and increasing the peak currents of the oxidation of l-Trp and l-Tyr when compared with those modified electrodes. More importantly, the present electrode gave a wide linear range from 1.0×10−5 M to 1.0×10−3 M, 5.0×10−6 M to 1.0×10−3 M, a very low detection limit of 2.4×10−8 M, 7.4×10−8 M and a high sensitivity of 41μAmM−1, 13μAmM−1 for l-Trp and l-Tyr, respectively. Moreover, the electrode displayed a good reproducibility, a long-term stability and a favorable ability of anti-interference to electroactive-molecules. [Copyright &y& Elsevier]

Abstract: Free-standing few-layer graphene (FFG) were electrochemical-exfoliated from a graphite column via oxidation–reduction cycling (ORC). FFG with the width up to 500nm, and length up to 800nm were successfully obtained. The atom layers, crumpled morphology and scroll that concerned with structure defect of FFG were found through transmission electron microscope (TEM). The presence of defects on FFG was proved by Raman spectroscopy, and the surface chemistry informations about oxygen-containing groups were collected from XPS and FTIR data. For the potential applications of this FFG, the capability of electron transfer was studied by AC impedance and the electro-catalytic oxidation of nicotinamide adenine dinucleotide (NADH) was investigated. The results showed that this method can provide valuable protocol for preparation free-standing few-layer graphene, which may facilitate both its synthesis and applications. [Copyright &y& Elsevier]

Abstract: This article reports on the electrochemical property of large mesoporous carbons (LMC) synthesized using nano-CaCO3 as a template and sucrose as a carbon precursor. Though a simple preparation method for LMC, the LMC modified glassy carbon electrode (LMC/GCE) exhibited good electrochemical activity for some common electroactive compounds, such as ascorbic acid (AA), uric acid (UA), epinephrine (EP) and tryptophan (Trp). The unique properties of LMC were also compared with those of carbon nanotubes (CNT), and the results showed that the LMC possessed a much better property than CNT. In addition, the LMC/GCE was also used to analyze the β-nicotinamide adenine dinucleotide (NADH) and hydrogen peroxide (H2O2) and showed a high sensitivity and low detection limit. Based on a simple preparation method and good electrochemical property, the LMC represents a new class of carbon electrode for electrochemical sensor applications. [ABSTRACT FROM AUTHOR]

The zirconium fumarate metal-organic framework (MOF-801) and mesoporous carbon (MC) composite was prepared by a conventional method. Compared with MOF-801, MOF-801/MC has a larger specific surface area, pore volume, improved conductivity, and better electrocatalytic performance. The new electrochemical sensor based on MOF-801/MC exhibits significant electrocatalytic activity for the oxidation of GA and the redox of luteolin. And the mechanisms of these two substances are discussed. Under the optimum test conditions, the detection of GA displays a wider linear range, consisted of two linear segments (0.2–5 and 5–100 μM) and the limit of detection (LOD) is 0.15 μM (S/N = 3). At the same time, the detection of luteolin also exhibits two linear relationships, 0.02–0.2 and 0.2–10 μM with LOD of 2.90 nM (S/N = 3). In addition, the MOF-801/MC sensor has good stability, selectivity and reproducibility. MOF-801/MC/GCE sensor was also used for detection of GA and luteolin in green tea and urine with satisfactory results. Unlabelled Image • Mesoporous carbon and Zr-MOF-801 were combined for the first time. • MOF-801/MC shows larger specific surface area, pore volume and improved conductivity. • MOF-801/MC has wider linear range and comparable sensitivity for the oxidation of GA. • MOF-801/MC exhibits higher sensitive to the oxidation of luteolin. • Satisfactory results for the detection of actual samples. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The carbon nanoballs aggregation networks-based aerogels for electrochemical sensing. • The hydrogen peroxide determination in real samples. • Multifunctional electrochemical sensing platform. Abstract In this work, we reported the synthesis of carbon nanoballs aggregation networks-based aerogels (CNANAs) from the biomass waste of shaddock (Citrus maxima) peels for the first time. On the basis of the unique nanostructure of CNANAs with large surface area (446.39 m2 g−1), hierarchical pores (centered at 2, 12 and 87 nm) and high density of edge-plane-like defective sites (EPDSs), the CNANAs as a kind of advanced electrode material exhibited remarkable performance in electrocatalysis. Compared to carbon nanotubes modified glassy carbon electrode (CNTs/GCE) and glassy carbon electrode (GCE), the CNANAs modified GCE (CNANAs/GCE) showed higher electrocatalytic activities towards some important inorganic and organic molecules, such as the probe molecule of potassium ferricyanide, the oxidase-related molecule of hydrogen peroxide (H 2 O 2) and the neurotransmitters of dopamine (DA), ascorbic acid (AA) and uric acid (UA). Based on the superior electrocatalytic activities, the CNANAs/GCE exhibited a wider determination linear range (5–1760 μmol L−1), a higher sensitivity (42.4 μA mmol L−1 cm−2) and a lower detection limit (3.53 μmol L−1) than those at CNTs/GCE and GCE for H 2 O 2 detection. Especially, the CNANAs/GCE also showed great potential for the H 2 O 2 determination in human urine and serum samples. The utilization of environmentally-friendly biomass waste of the shaddock peels as the raw material is a promising way to synthesize low-cost and advanced carbon based electrode material for electrochemical sensors construction. [ABSTRACT FROM AUTHOR]

In this work, the three-dimensional nitrogen-doped nanostructured carbons with hierarchical architectures (3D-NNCsHAs) with high density of defective sites, high surface area and pluralities of pore size distributions was prepared through the pyrolysis of sea-tangle ( Laminaria japonica ), an inexpensive, eco-friendly and abundant precursor. Benefitting from their structural uniqueness, a selective and sensitive ascorbic acid (AA) sensor based on 3D-NNCsHAs was developed. Compared to the glassy carbon electrode (GCE) and the carbon nanotubes modified GCE (CNTs/GCE), the 3D-NNCsHAs modified GCE (3D-NNCsHAs/GCE) presents higher performance towards the electrocatalysis and detection of AA, such as lower detection limit (1 μM), wider linear range (10–4410 μM) and lower electrooxidation peak potential (−0.02 V vs. Ag/AgCl). In addition, 3D-NNCsHAs/GCE also exhibits high anti-interference and anti-fouling abilities for AA detection. Particularly, the fabricated 3D-NNCsHAs/GCE is able to determine AA in real samples and the results acquired are satisfactory. Therefore, the 3D-NNCsHAs can be considered as a kind of novel electrode nanomaterial for the fabrication of selective and sensitive AA sensor for the extensive practical applications ranging from food analysis, to pharmaceutical industry and clinical test. [ABSTRACT FROM AUTHOR]

In this paper, kelp ( Laminaria japonica ), as a kind of abundant biomass, is used as the precursor for the preparation of kelp-derived hierarchical meso-macroporous carbons (K-dHMMCs) through the carbonization under nitrogen (N 2 ) atmosphere at high temperature. The K-dHMMCs exhibits the unique structure with high specific surface area of 416.02 m 2  g −1 , large pore volume of 0.24 cm 3  g −1 , the hierarchical meso-macroporous size distribution centered at 2, 12 and 82 nm and high density of defective sites, enabling K-dHMMCs attractive for the electrocatalysis. Drop-casting K-dHMMCs on the glassy carbon (GC) surface allows the construction of K-dHMMCs based electrochemical sensing platform, which shows electrocatalytic activities towards many electroactive molecules, such as potassium ferricyanide, nicotinamide adenine dinucleotide (NADH), hydrogen peroxide (H 2 O 2 ), dopamine (DA), uric acid (UA), ascorbic acid (AA), epinephrine (EP), l -tyrosine (Tyr) and acetaminophen (APAP). Especially, the K-dHMMCs modified GC (K-dHMMCs/GC) electrode exhibits higher sensitivity, wider linear range, and lower detection limit than both carbon nanotubes modified GC (CNTs/GC) and GC electrodes for H 2 O 2 detection, which makes the K-dHMMCs/GC electrode to be able to determine the H 2 O 2 levels in human urine sample and monitor the H 2 O 2 released from human cancer cells. These results demonstrate that K-dHMMCs/GC possesses a great potential for conventional electrochemical sensing applications. [ABSTRACT FROM AUTHOR]

Graphene (GR) is one of the most promising candidates for utilization in the electroanalytical field because of its superior electrocatalytic activity, excellent electronic conductivity, and high chemical stability. However, the GR sheets usually tend to stack together with π-π interaction. The spontaneous stacking leads to the aggregation of the GR sheets and imposes a negative feedback in the surface area of the GR, which obviously limits its electrochemical application. In this study, nitrogen-doped porous GR (NPGR) with different pore sizes is prepared by using silica (SiO 2 ) as a template. The NPGR exhibits high surface area and porous structure, fulfilling the requirement for supporting materials. Being a support, the structural uniqueness and N dopants of NPGR facilitate the deposition of Pt nanoparticles (Pt NPs). The Pt NPs/NPGR composites integrate the structural properties of NPGR and catalytic properties of Pt NPs. A selective and sensitive electrochemical sensor was successfully developed for sensitive determination of Tadalafil (TAD), showing a concentration range of 1.30–488.9 μM and limit of detection of 0.268 μM. [ABSTRACT FROM AUTHOR]

For the first time, the carbon nanoplates with high density of defective sites derived from the biomass of ground cherry ( Physalis peruviana ) husks was synthesized for the construction of an advanced electrochemical sensing platform. Electrochemical responses of different molecules (potassium ferricyanide, β-nicotinamide adenine dinucleotide, hydrogen peroxide, epinephrine and dopamine, the mixture of four free DNA bases (guanine, thymine, cytosine and adenine), cysteine, ascorbic acid, L-tryptophan, uric acid and acetaminophen) were studied at the biomass derived ground cherry husks derived carbon nanoplates (BG-CNPs) modified glassy carbon (GC) (BG-CNPs/GC) electrode, which shows higher electrocatalytic activities than GC electrode. Especially, the BG-CNPs/GC electrode exhibits remarkably strong electrocatalytic response toward hydrogen peroxide (H 2 O 2 ) compared with carbon nanotubes modified GC (CNTs/GC) and GC electrodes, indicating the great potential feasibility in the detection of H 2 O 2 in human urine as well as the monitoring of H 2 O 2 released from the living cells. All the results indicate that BG-CNPs is a promising carbon material which could be utilized to develop an advanced electrochemical sensing platform with multifunctional applications ranging from voltammetric sensing to amperometric sensing and DNA sensing. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a cobalt hexacyanoferrate/large-mesopore carbon modified glassy carbon electrode (CoHCF–LMC/GC) was simply fabricated by electrodepositing CoHCF film on LMC. The electrochemical behaviors of L-dopa at this modified electrode have been studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and amperometry. The results show that the CoHCF–LMC modified electrode exhibits efficiently electrochemical activity for L-dopa oxidation in 0.1M PBS (pH=7.4), and the quantitative determination of L-dopa is unperturbed by the ascorbic acid (AA). Amperometry results depict that the proposed sensor provides excellent performance towards the determination of L-dopa with a low detection limit of 1.7×10−8 M in the wide concentration range from 1.0×10−7 to 1.9×10−3 M at +0.20V versus Ag/AgCl. Moreover, the studied composite electrode exhibits a good reproducibility and long-term stability. Determination of L-dopa in commercial tablets and human blood serum with satisfying results was also investigated by the proposed composite electrode. [Copyright &y& Elsevier]

Designing low-cost, high-efficiency and non-noble metal-based electrocatalysts is fairly essential for the commercial utilization of electrochemical sensors and energy conversion devices. Low-cost CuFe 2 O 4 spinel has been widely researched as an electrocatalyst in electrochemical sensors and catalysis. Nevertheless, the low utilization of active sites in bulk CuFe 2 O 4 and the poor electro conductivity of CuFe 2 O 4 invariably restrict its upgrade in catalytic efficiency. Herein, by utilizing the facile electrospinning technique and without involving any template or surfactant, we successfully design three-dimensional (3D) hierarchically porous architecture woven by abundant ultrafine CuFe 2 O 4 crystal-coupled porous carbon nanowires (denoted as CuFe 2 O 4 /PCFs). Characterization results verify the 3D net-like textural structures of CuFe 2 O 4 /PCFs. Especially, the hierarchically porous structure, high surface area, and abundant carbon edges boost the uniform dispersion of tiny CuFe 2 O 4 crystals; these obviously promote the amounts of electrochemically available CuFe 2 O 4 active sites while decreasing the mass transport resistance of CuFe 2 O 4 /PCFs in electrocatalytic processes. Meanwhile, introducing carbon matrices can drastically enhance the electrical conductivity of CuFe 2 O 4 /PCF nanowires. All these advances in structural and physical performances truly make tremendous progress for CuFe 2 O 4 /PCFs for H 2 O 2 reduction and oxygen evolution reaction (OER) catalysis compared with bulk CuFe 2 O 4. For instance, the CuFe 2 O 4 /PCF catalyst exhibits a high sensitivity of 69.18 μA mM−1 cm−2, low detection limit of 1.20 μM and wide linear range of 0.11–22.0 mM for H 2 O 2 sensing. Meanwhile, the CuFe 2 O 4 /PCF catalyst just needs a potential value of 1.589 V (vs. reversible hydrogen electrode) to achieve the OER catalysis current density of 10 mA cm−2 in 1.0 M KOH, it only shows a small Tafel slope of 89.34 mV dec−1 for the OER as well. Our catalyst design strategy of CuFe 2 O 4 /PCF nanowires not only demonstrates the successful design of a novel high-efficiency non-noble-metal catalyst for both OER and H 2 O 2 reduction catalysis but also affords a new methodology for boosting the electrocatalytic abilities of spinel-type hybrid materials by designing a 3D structure and improving conductivity. Image 1 • Ultrafine CuFe 2 O 4 nanocrystallines coupled porous carbon nanowires. • The 3D hierarchical porous net-like architecture consist of CuFe 2 O 4 /PCFs nanowires. • Riched catalytic active sites and excellent electroconductibility for electrocatalysis. • Wide linear range (0.11–22.0 mM) and high sensitivity (69.18 μA mM−1 cm−2) toward H 2 O 2 sensing. • A negative OER E 10 value of 1.589 V vs. RHE and a low Tafel slope of 89.34 mV dec−1. [ABSTRACT FROM AUTHOR]