Hongyan Wang

Design and fabrication of a graphene/carbon nanotubes/activated carbon hybrid and its application for capacitive deionization

In this work, graphene/carbon nanotubes (CNTs)/activated carbon (AC) (GTAC) hybrids were designed and fabricated by combing graphene, CNTs with AC into one new type of hybrid and applied as capacitive deionization (CDI) electrodes. The morphology, structure and electrochemical performance of the GTAC were characterized by scanning electron microscopy, nitrogen adsorption–desorption, cyclic voltammetry and electrochemical impedance spectroscopy. The results show that the GTAC with 72 wt% CNTs, 8 wt% graphene and 20 wt% AC exhibits the best electrochemical performance among all the samples. When used as a CDI electrode, GTAC exhibits a higher electrosorption capacity of 2.30 mg g−1 than those of optimized graphene/AC (1.10 mg g−1), graphene/CNTs (1.06 mg g−1) and CNTs/AC (0.96 mg g−1) in this work. The higher electrosorption capacity of GTAC can be ascribed to the superiority of the “plane-to-line-to-point” (graphene-to-CNTs-to-AC) conducting network. This result demonstrates that GTAC should be a promising candidate as a CDI electrode.

A label-free electrochemical DNA sensor based on ZrO2/poly(thionine)/CNT modified electrode and its application for detecting CaMV35S transgene gene sequence

A label-free electrochemical sensor for detecting the CaMV35S transgene gene sequence was reported based on a ZrO2/poly(thionine)/multiwalled carbon nanotubes modified glassy carbon electrode (ZrO2/PTH/MWCNTs/GCE). Probe oligonucleotides (p-ssDNA) were immobilized on the ZrO2 thin films via the strong affinity between the phosphate groups and ZrO2. Differential pulse voltammetry (DPV) was used to monitor DNA hybridization. Upon hybridization electrochemical signal changes were generated at the PTH-solution interface. Compared with noncomplementary target ssDNA, an obvious decrease in the peak current was observed upon p-ssDNA hybridization with complementary target ssDNA. The sensor exhibited an excellent selectivity for distinguishing three-mismatched with complementary target ssDNA and a high sensitivity for detecting complementary target ssDNA with the detection limit of 0.34 pM (S/N = 3). In addition, the sensor showed an excellent reproducibility and stability, and applied to determine the CaMV35S transgene gene sequence in samples with satisfactory results.

Facile synthesis of porous Co3O4 nanoplates for supercapacitor applications

Porous tricobalt tetraoxide (Co3O4) nanoplates with large aspect ratio have been obtained by annealing Co(OH)2 precursor nanoplates synthesized by a facile reflux method without the need for any template or surfactant. After the heat treatment, the as-obtained phase-pure Co3O4 nanoplates with a well-retained structure were applied as the electrode material for supercapacitors, and the sample exhibits excellent performance with a high specific capacitance of 225 F g−1 after 2000 charge–discharge cycles at 2 A g−1, corresponding to a retention of 97% of the initial capacitance.

Microwave assisted synthesis of MoS2/nitrogen-doped carbon shell–core microspheres for Pt-free dye-sensitized solar cells

In this work, novel MoS2/nitrogen-doped carbon shell–core microspheres (MNCS) have been designed and prepared through the microwave-assisted method, and used as counter electrodes for platinum-free dye-sensitized solar cells (DSSCs). The results show that as-prepared shell–core composite microspheres possess low charge transfer resistance and high electrocatalytic activity. When used as a counter electrode for DSSCs, the powder conversion efficiency of an as-prepared cell with optimized MNCS reaches 6.2% under standard light illumination, which is comparable to cells with a conventional Pt counter electrode.

Visible light photocatalytic degradation of rhodamine B by Bi2WO6 prepared via microwave-assisted method

A series of Bi2WO6 have been synthesized via microwave-assisted method and used as photocatalysts for the photocatalytic degradation of rhodamine B (RhB). The results indicate that sample synthesized at pH value of 1 shows an optimal photocatalytic performance in degradation of RhB under visible light irradiation. The photocatalytic performance improvement can be attributed to enhanced light absorption and reduced electron–hole pair recombination.

Simultaneous voltammetric detection of dopamine, ascorbic acid and uric acid using a poly(2-(N-morpholine)ethane sulfonic acid)/RGO modified electrode

A poly(2-(N-morpholine) ethane sulfonic acid)/reduced graphene oxide (RGO) modified glassy carbon electrode (GCE) was prepared using an electropolymerization method, and was characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The electrochemical behaviors and simultaneous detection of ascorbic acid (AA), dopamine (DA) and uric acid (UA) at this electrode were studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Tests showed that this electrode exhibited excellent electrocatalytic activity towards the oxidation of AA, DA and UA. The oxidation peak currents of AA, DA and UA were proportional with their concentrations in the ranges 1.0 μM–30 μM (30 μM–100 μM), 0.05 μM–100 μM and 0.1 μM–100 μM, with detection limits of 0.43 μM, 0.0062 μM and 0.056 μM, respectively. In addition, this electrode exhibited an excellent selectivity, reproducibility and stability, and has been successfully used to determine real samples with satisfactory results.

Label-free impedimetric sensing platform for microRNA-21 based on ZrO2-reduced graphene oxide nanohybrids coupled with catalytic hairpin assembly amplification

Herein, a sensitive electrochemical impedance sensor was constructed based on ZrO2-reduced graphene oxide (RGO)-modified electrode coupled with the catalytic hairpin assembly signal amplification strategy. Electrochemical impedance spectroscopy (EIS) was used to detect microRNA (miRNA) using the change in electron transfer resistance (ΔRet) originated from nucleic acid hybridization on the electrode surface. MiRNA-21 was used as a model to verify this strategy. The results indicated that ΔRet exhibited a good linear relationship with the concentration of miRNA-21 in the range from 1.0 × 10−14 mol L−1 to 1.0 × 10−10 mol L−1 with a detection limit of 4.3 × 10−15 mol L−1 (S/N = 3). Additionally, this sensor exhibited good selectivity, and it could be applied to detect miRNA-21 in human serum samples and measure the expression levels of miRNA-21 in human breast cancer cell lines (MCF-7); thus, this sensor has great potential in cancer diagnosis.

Co9S8 nanotubes: facile synthesis and application in the catalytic reduction of 4-nitrophenol

Co9S8 nanotubes have been successfully synthesized via a facile two-step solvothermal method without the assistance of any template or surfactant, using cobalt sulphate (CoSO4⋅7H2O), urea and sodium sulphide (Na2S⋅9H2O) as starting reactants, and deionized water and glycol as the reactive medium. The phase and the morphology of the as-obtained product were characterized by means of powder X-ray diffraction, energy dispersive spectrometry and scanning electron microscopy. The result displays that the Co9S8 nanotubes have hexagonal cross-sections, the diameter of the nanotubes is about 200 nm and the wall thickness is of 50 nm. The experiments showed that the Co9S8 nanotubes could be used as new-type catalysts for the reduction of 4-nitrophenol. It was found that the as-obtained Co9S8 nanotubes contributed to the best catalytic activity.