Yongjin Zou

Prussian Blue electrodeposited on MWNTs-PANI hybrid composites for H2O2 detection

A Prussian Blue (PB)/polyaniline (PANI)/multi-walled carbon nanotubes (MWNTs) composite film was fabricated by step-by-step electrodeposition on glassy carbon electrode (GCE). The electrode prepared exhibits enhanced electrocatalytic behavior and good stability for detection of H(2)O(2) at an applied potential of 0.0V. The effects of MWNTs thickness, electrodeposition time of PANI and rotating rate on the current response of the composite modified electrode toward H(2)O(2) were optimized to obtain the maximal sensitivity. A linear range from 8x10(-9) to 5x10(-6)M for H(2)O(2) detection has been observed at the PB/PANI/MWNTs modified GCE with a correlation coefficient of 0.997. The detection limit is 5x10(-9)M on signal-to-noise ratio of 3. To the best of our knowledge, this is the lowest detection limit for H(2)O(2) detection. The electrode also shows high sensitivity (526.43muAmuM(-1)cm(-2)) for H(2)O(2) detection which is more than three orders of magnitude higher than the reported.

Amperometric glucose biosensor based on ultrafine platinum nanoparticles

Abstract In the present paper the ultrafine and highly dispersed platinum nanoparticles (average size 3 nm) were used for the construction of a glucose biosensor in a simple method. An excellent response to glucose has been obtained with a high sensitivity (137.7 µA mM−1 cm−2) and fast response time (5 s). The biosensor showed a detection limit of 5 µM (at the ratio of signal to noise, S/N=3) and a linear range form 0.2 to 3.2 mM with a correlation coefficient r=0.999. The apparent Michaelis–Menten constant (k m) and the maximum current were estimated to be 9.36 and 1.507 mA mM−1 cm−2, respectively. In addition, effects of pH value, applied potential and the interferents on the amperometric response of the sensor were investigated and discussed.

Synthesis of N-doped hierarchical carbon spheres for CO2 capture and supercapacitors

N-doped hierarchical carbon spheres have been synthesized via a soft template and hydrothermal method using melamine as a nitrogen source. The obtained carbon spheres possess a high nitrogen content and well-developed porosity. These carbon spheres are examined as absorbents for CO2 capture and as electrode materials for supercapacitors. Due to the high nitrogen content and hierarchical pore size distribution, the carbons show high CO2 uptakes of 2.2–4.4 mmol g−1 at 298 K and 1 bar. Furthermore, we observe that the carbon spheres exhibit excellent performance as supercapacitor electrodes with a high specific capacitance of 356 F g−1 at a current density of 0.2 A g−1. These carbon spheres as promising materials will exhibit excellent performance in various fields.

A novel sensor based on electrochemical polymerization of diglycolic acid for determination of acetaminophen

Diglycolic acid (DA) polymer was coated on glassy carbon (GC) electrode by cyclic voltammetry (CV) technique for the first time. The electrochemical performances of the modified electrode were investigated by CV and electrochemical impedance (EIS). The obtained electrode showed an excellent electrocatalytic activity for the oxidation of acetaminophen (ACOP). A couple of well-defined reversible electrochemical redox peaks were observed on the ploy(DA)/GC electrode in ACOP solution. Compared with bare GC electrode, the oxidation peak potential of ACOP on ploy(DA)/GC electrode moved from 0.289 V to 0.220 V. Meanwhile, the oxidation peak current was much higher on the modified electrode than that on the bare GC electrode, indicating DA polymer modified electrode possessed excellent performance for the oxidation of ACOP. This kind of capability of the modified electrode can be enlisted for the highly sensitive and selective determination of ACOP. Under the optimized conditions, a wide linear range from 2 × 10(-8) to 5.0 × 10(-4)M with a correlation coefficient 0.9995 was obtained. The detection limit was 6.7 × 10(-9)M (at the ratio of signal to noise, S/N=3:1). The modified electrode also exhibited very good stability and reproducibility for the detection of ACOP. The established method was applied to the determination of ACOP in samples. An average recovery of 100.1% was achieved. These results indicated that this method was reliable for determining ACOP.

Fabrication and characterization of a novel nanoporous Co–Ni–W–B catalyst for rapid hydrogen generation

A highly active nanoporous Co–Ni–W–B alloy has been prepared using chemical reduction in an ethanol solution and tested as a novel catalyst for hydrolysis of ammonia borane. Compared with the alloy prepared in an aqueous solution, the as-prepared alloy shows a much higher surface area and hydrogen generation rate.

Synthesis of three-dimensional graphene aerogel encapsulated n-octadecane for enhancing phase-change behavior and thermal conductivity

We prepared a series of three-dimensional graphene aerogel (3D-GA) encapsulated n-octadecane (OD) composite phase change materials (PCMs) through both solution and vacuum impregnation to ensure that a homogeneous dispersion of OD in the porous structure of 3D-GA was present. At the same time, we also investigated the micro-structure, thermal storage properties, and thermal conductivity of the composite PCMs. We used scanning electron microscopy and Fourier transform infrared spectroscopy to demonstrate that OD was encapsulated effectively in the porous structure of 3D-GA and that the composite PCMs were prepared successfully. Differential scanning calorimetry (DSC) results confirmed that the composite PCMs possess good phase change behavior, fast thermal-response rates and excellent thermal cycling stability. The melting enthalpy and crystallization enthalpy can reach 195.70 J g−1 and 196.67 J g−1, respectively, and have almost no change for 60 DSC thermal cycles. Temperature–time curves suggested that the composite PCMs have excellent thermal regulation properties, and their temperature can be maintained in the range of 21–27 °C for about 640 s in a heating procedure. Thermal conductivity analysis indicated that the thermal conductivities of the composite PCMs are improved significantly by the highly thermally conductive 3D-GA. All these results demonstrated that the composite PCMs possess good comprehensive properties that can be used widely in energy storage systems.

Simple synthesis of graphene-doped flower-like cobalt–nickel–tungsten–boron oxides with self-oxidation for high-performance supercapacitors

In this study, we devised an easy and simple approach to synthesize a composite of flower-like cobalt–nickel–tungsten–boron oxides (Co–Ni–W–B–O) that were doped with reduced graphene oxide (rGO); the composite was designed for supercapacitor applications. A Co–Ni–W–B alloy was first deposited on rGO through one-pot chemical reduction in an ethanol solution at room temperature. The resulting Co–Ni–W–B alloy self-oxidized in air on the rGO surface. The Co–Ni–W–B–O/rGO composites resembled three-dimensional flowers with a high surface area; they also exhibited superior electrochemical performance when compared to most previously reported electrodes based on nickel–cobalt oxides. Furthermore, the Co–Ni–W–B–O/rGO composite prepared in an ethanol solution showed much higher electrochemical performance than the composite prepared in water. The Co–Ni–W–B–O/rGO electrode showed an ultrahigh specific capacitance of 1189.1 F g−1 at 1 A g−1 and exhibited a high energy density of 49.9 W h kg−1 along with remarkable cycle stability (10 000 cycles with 80.7% capacitance retention at 15 A g−1), which is promising for its application in energy storage devices.

Direct Electron Transfer of Horseradish Peroxidase and Its Biosensor Based on Gold Nanoparticles/Chitosan/ITO Modified Electrode

Abstract Gold nanoparticles/chitosan modified indium tin oxide (ITO) coated glass electrode was prepared by a simple layer-by-layer self-assembly technique. Horseradish peroxidase (HRP) was successfully immobilized on the modified electrode by electrostatic adsorption. Direct electrochemistry and electrocatalysis of HRP were investigated. The composite film showed an obvious promotion for the direct electron transfer between HRP and the underlying electrode. The immobilized HRP exhibited an excellent electrocatalytic activity toward the reduction of H2O2. The catalysis currents increased linearly to the H2O2 concentration in a wide range of 2.0 × 10−5 to 6.5 × 10−3 M with a low detection limit of 3.5 × 10−6 M. The calculated apparent Michaelis-Menten constant (K ) was 4.43 mM.

Organic carbon gel assisted-synthesis of Li1.2Mn0.6Ni0.2O2 for a high-performance cathode material for Li-ion batteries

Lithium-rich layered oxide Li1.2Ni0.2Mn0.6O2 with a stable network flake structure has been synthesized through a facile resorcinol–formaldehyde (RF) organic carbon gel-assisted method. The as-prepared sample used as a cathode material in lithium ion batteries (LIBs) was characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and electrochemical measurements. The stable network flake structure is assembled through a dense stack of nanoparticles with an average size of 50–200 nm. As an active material for LIB cathodes, the Li1.2Ni0.2Mn0.6O2 sample shows excellent rate capacities and cycling stability, and delivers a high initial discharge capacity of 273.3 mA h g−1 at 0.1C (1C = 200 mA g−1) between 2.0 V and 4.8 V. When the discharge rate is increased to 2C, an initial capacity of 196.7 mA h g−1 is obtained. After 150 cycles, a discharge capacity of 183.7 mA h g−1 and a high capacity retention of 93.4% are yielded at a rate of 2C.

Light metal borohydrides/amides combined hydrogen storage systems: composition, structure and properties

The implementation of a future economy based on hydrogen-related energy needs an urgent development of efficient, safe, and economic solid-state hydrogen-storage materials. During the search process for novel materials for storing hydrogen, research interests in the past few decades have been intensively focused on light metal borohydrides and amides as two representative chemical complex hydrides with high hydrogen capacities. Recently, a large number of studies have reported new borohydride/amide combined systems that expand the scope of hydrogen-storage materials. Here, we review the interaction between light metal borohydrides and amides for storing hydrogen, with a special emphasis on the synthetic strategies and structural, physical, and chemical properties, which reveal a correlation between the composition, structure, and dehydrogenation properties and also provide general principles to the design of new combined systems with tailored functionality. This review also demonstrates the current progress on the dehydrogenation kinetic improvement of borohydride/amide combined systems.