Jianzhi Huang

A highly sensitive metronidazole sensor based on a Pt nanospheres/polyfurfural film modified electrode

In this contribution, we combine the advantages of both Pt nanospheres and polyfurfural film and successfully develop a novel Pt nanospheres/polyfurfural film modified glassy carbon electrode (GCE) for electrochemical sensing of a nitro group containing pentatomic cyclic compound, metronidazole. In particular, the polyfurfural film and Pt nanospheres were handily obtained by a one-step electropolymerization method and a potential step method, respectively. Benefiting from their excellent synergistic catalytical properties, the Pt nanospheres/polyfurfural film/GCE shows significantly enhanced electrocatalytic activity towards metronidazole. A series of experimental parameters including the electropolymerization cycles of furfural, the deposition time of platinum, accumulation time, accumulation potential and pH of the supporting electrolyte for metronidazole was also investigated and optimized. The proposed sensor exhibited excellent selectivity, stability and reproducibility for the determination of metronidazole, providing a wide linear detection range from 2.5 to 500 μmol dm−3 and a low detection limit of 50 nmol dm−3 (S/N = 3) under optimal experimental conditions. When the proposed sensor was applied to determine metronidazole in real human serum samples, it gave a satisfactory result.

High sensitivity chlorogenic acid detection based on multiple layer-by-layer self-assembly films of chitosan and multi-walled carbon nanotubes on a glassy carbon electrode

A chlorogenic acid sensor based on a chitosan (CS) and multi-walled carbon nanotubes (MWCNTs) modified glassy carbon electrode (GCE) was fabricated via a layer-by-layer (LBL) self-assembly method. The prepared electrode exhibited excellent catalytic performance for chlorogenic redox reactions compared to the bare GCE. The effects of the number assembly layers, scan rate, pH of the supporting electrolyte and accumulation time on chlorogenic acid detection were optimized. Under the optimal conditions, the proposed sensor was significantly sensitive for the detection of chlorogenic acid and showed wide linear detection ranges at low concentrations from 2 × 10−8 to 1 × 10−7 mol dm−3 and at high concentrations from 1 × 10−7 to 2.25 × 10−4 mol dm−3. The detection limit was estimated to be 1.16 × 10−8 mol dm−3 (S/N = 3). Furthermore, the chlorogenic acid sensor exhibited excellent selectivity and stability and was utilized in practical applications, in particular, for the determination of human real samples.

Coordination matrix/signal amplifier strategy for simultaneous electrochemical determination of cadmium(II), lead(II), copper(II), and mercury(II) ions based on polyfurfural film/multi-walled carbon nanotube modified electrode

In this work, we firstly propose and confirm a novel coordination matrix/signal amplifier strategy to construct a highly sensitive lead(II) electrochemical sensor. Lead(II) ions can be efficiently accumulated and deposited on the electrode surface by strong coordination bonds between the unoccupied d-orbital of lead(II) ions and conjugated π-electron backbones of polyfurfural film (coordination matrix), and then the anodic stripping current can be significantly enhanced by multi-walled carbon nanotubes (MWCNTs, signal amplifier), finally realizing the highly sensitive determination of lead(II). The polyfurfural film/MWCNT modified glassy carbon electrode (GCE) sensor provided a wide linear detection range from 0.05 to 10 μg L−1 and a low detection limit of 0.01 μg L−1 (S/N = 3) for lead(II). Compared with a classical mercury film sensor (a classical and effective method for determining heavy metal ions), our proposed sensor was more sensitive and achieved better results. Moreover, based on the coordination matrix/signal amplifier strategy, the polyfurfural film/MWCNTs/GCE sensor was further successfully utilized for the simultaneous determination of Cd2+, Pb2+, Cu2+, and Hg2+, demonstrating a wide linear detection range for Cd2+ (0.5–15 μg L−1), Pb2+ (0.1–15 μg L−1), Cu2+ (0.1–12 μg L−1), and Hg2+ (1.5–12 μg L−1) and a low detection limit for Cd2+ (0.03 μg L−1, S/N = 3), Pb2+ (0.01 μg L−1, S/N = 3), Cu2+ (0.06 μg L−1, S/N = 3), and Hg2+ (0.1 μg L−1, S/N = 3). Finally, the proposed sensor was successfully applied to simultaneously determine Cd2+, Pb2+, Cu2+, and Hg2+ in real tap water samples. This work provides a novel and effective analytical strategy for constructing novel electrochemical sensors and shows broad application prospects in heavy metal ion determination for the future.

A highly sensitive morin sensor based on PEDT–Au/rGO nanocomposites modified glassy carbon electrode

In this work, we fabricated a sensitive electrochemical sensor based on a PEDT–Au/reduced graphene oxide nanocomposites (PEDT–Au/rGO) modified glassy carbon electrode (PEDT–Au/rGO/GCE) for electrochemical determination of morin. A facile, effective and high-efficiency one-pot method was employed to synthesize the PEDT–Au/rGO nanocomposites. The morphology and structure of as-prepared PEDT–Au/rGO nanocomposites were characterized by using a scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray spectroscopy (EDS), and its electrochemical characteristics were studied by EIS, CV and SWV. The PEDT–Au/rGO nanocomposites modified electrode exhibited excellent catalytic activities for morin oxidation, which was attributed to the synergistic catalytic effect that occurred at the interface of PEDT–Au and rGO layers. The effects of square wave voltammetry (SWV) parameters, accumulation time, accumulation potential and pH of the supporting electrolyte for morin were optimized. At the optimal experimental conditions, the PEDT–Au/rGO/GCE presented a high sensitivity of 0.0083 μmol dm−3 and a wide linear range from 1 to 150 μmol dm−3 toward morin oxidation with satisfactory selectivity and stability.

Application of Coal in Electrochemical Sensing

In this work, we first report a new application of coal as a novel modified electrode material in electrochemical sensing, achieving excellent electrochemical performance similar to graphene and making the utilization of coal become more multipurpose and more meaningful. Raw coal was first ball-milled, then centrifugated, and finally annealed, thus obtaining annealed coal that possesses lots of edge-plane-like defective sites, resulting in good electron-transfer efficiency and excellent electrocatalytic activity, which makes it promising when used as signal amplifier material and as a modified matrix in electrochemical sensing. And we also described an investigation into the electrochemical and spectroscopic properties of annealed coal samples and their application for the detection of electroactive redox molecules (rutin). Compared with other published carbon materials modified sensors, the annealed coal/chitosan/GCE sensor exhibited excellent electrocatalytic activity for the determination of rutin with good sensitivity, providing a wide linear detection range from 0.001 to 10 μmol dm-3 and a low detection limit of 0.2 nmol dm-3 (S/N = 3). Moreover, when the annealed coal/GCE sensor was applied for the determination of ascorbic acid, dopamine, uric acid, guanine, and adenine commonly contained in blood samples and urine samples, it also exhibited excellent detection performance with strong electrocatalytic activity. This research has opened up the application of coal in electroanalytical chemistry and held great promise for the sensing and biosensing application, which can be promising used as an alternative material of graphene.

High sensitivity simultaneous determination of myricetin and rutin using a polyfurfural film modified glassy carbon electrode

In this work, we successfully develop a simple electrochemical sensor based on a polyfurfural film modified glassy carbon electrode to realize the simultaneous electrochemical determination of myricetin and rutin. The proposed sensor exhibits superior electrocatalytic activity to both myricetin and rutin, simultaneously demonstrating a wide linear detection range of 0.05–10 μmol dm−3 with a low detection limit of 10 ± 0.5 nmol dm−3 (S/N = 3, α = 0.05, n = 3, type I error) for myricetin, and linear detection range of 0.001–10 μmol dm−3 with a low detection limit of 0.025 ± 0.004 nmol dm−3 (S/N = 3, α = 0.05, n = 3, type I error) for rutin. With favorable selectivity, stability and reproducibility, the proposed sensor was satisfied by applying for simultaneous determination of myricetin and rutin in real samples. It may provide a new strategy to simultaneously determine different kinds of polyphenolic compounds with polyfurfural film modified glassy carbon electrode in application of pharmaceutical and biological analysis in the future.

Rethinking Co(CO3)0.5(OH)·0.11H2O: a new property for highly selective electrochemical reduction of carbon dioxide to methanol in aqueous solution

Co(CO3)0.5(OH)·0.11H2O is usually acknowledged and used as a precursor to synthesize other nanomaterials. However, some important properties of Co(CO3)0.5(OH)·0.11H2O have not been discovered yet. Herein, we report an important new property of hollow urchin-like Co(CO3)0.5(OH)·0.11H2O for highly selective electrochemical reduction of carbon dioxide to methanol in NaHCO3 aqueous solution at −0.98 V versus saturated calomel electrode (SCE) with Faradaic efficiency of up to 97.0% under ambient conditions, which is superior to most of the electrocatalysts reported to date. Finally, this low-cost electrocatalyst shows great potential in CO2 conversion industry for practical application in the future.

Molecularly imprinted electrochemical sensor for advanced diagnosis of alpha-fetoprotein

In this study, a low-cost and easily prepared cancer biomarker sensor-alpha-fetoprotein (AFP) biosensor was successfully constructed on the surface of a glassy carbon electrode (GCE) by a surface imprinting procedure using available and cheap agents instead of antibodies. Under optimal detection conditions, the proposed biosensor showed specific recognition ability to free AFP by comparing with other comparative proteins and exhibited a wide linear detection range from 8.0 × 10−4 to 10 μg mL−1 for AFP with a low detection limit of 9.6 × 10−5 μg mL−1 (S/N = 3). Ultimately, the AFP imprinted sensor was applied to the determination of AFP in a human serum sample, giving satisfactory results.

Polyfurfural-Electrochemically Reduced Graphene Oxide Modified Glassy Carbon Electrode for the Direct Determination of Nitrofurazone

ABSTRACT An electrochemical sensor based on a polyfurfural-electrochemically reduced graphene oxide modified glassy carbon electrode has been developed for the sensitive and rapid determination of nitrofurazone. The morphologies and properties of the sensor were characterized by electrochemical impedance spectroscopy, scanning electron microscopy, cyclic voltammetry, and differential pulse voltammetry (DPV). In pH 7.0 Britton–Robinson buffer solution, the as-prepared polyfurfural-electrochemically reduced graphene oxide modified glassy carbon electrode shows excellent electrocatalytic performance for the electrochemical reduction of nitrofurazone, and the reduction peak current is about 9.45, 1.31, and 1.25 times higher than that of the bare glassy carbon electrode, polyfurfural modified glassy carbon electrode, and electrochemically reduced graphene oxide modified glassy carbon electrode, respectively. The DPV determination of nitrofurazone indicates that the linear range and detection limit of nitrofurazone are 1–50 and 0.25 µmol/dm3, respectively. In addition, this sensor exhibits high selectivity, reproducibility, stability, and also was successfully used to directly determine nitrofurazone in the commercial antibacterial lotion with comparative sensitivity to high-performance liquid chromatography, showing its promising application prospects.