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Zaijun L.,Jiangnan University | Zhongyun W.,Jiangnan University | Xiulan S.,Jiangnan University | Yinjun F.,Zhejiang Zanyu Technology Co. | Peipei C.,Jiangnan University
Talanta | Year: 2010

The paper describes a sensitive and highly stable label-free electrochemical impedance immunosensor for the determination of aflatoxin B1 (AFB1), which is based on the formation of silica gel-ionic liquid biocompatible film on the glassy carbon electrode. The electrochemical performances of the sensor were investigated by electrochemical impedance spectroscopy using a Fe(CN)6 3-/4- phosphate buffer solution as base solution for test. As new ionic liquid, 1-amyl-2,3-dimethylimidazolium hexafluorophosphate, offers a very biocompatible microenvironment for AFB1 antibody, the sensor exhibits good repeatability (RSD = 1.2%), sensitive electrochemical impedance response to AFB1 in the range of 0.1-10 ng ml-1 and lowers the detection limit of AFB1 (0.01 ng ml-1). The electron-transfer resistance change of the sensor after and before incubation with AFB1 of 2.0 ng ml-1 can retain 95% over a 180-day storage period at 4 °C. The results present a remarkable improvement of sensitivity (2-fold) and long-term stability (190-fold) when compared to classical silica gel sensor. Moreover, proposed sensor has a high selectivity to AFB1 alone with no significant response to AFB2, AFG1, AFG2 and AFM1 as single substrates, it has been successfully applied to the determination of trace AFB1 in bee pollen samples with a spiked recovery in the range of 96.0-102.5%. © 2009 Elsevier B.V. All rights reserved.


Gu Z.,Jiangnan University | Yang S.,Jiangnan University | Li Z.,Jiangnan University | Sun X.,Jiangnan University | And 3 more authors.
Electrochimica Acta | Year: 2011

The paper reported an ultrasensitive electrochemical biosensor for glucose which was based on CdTe-CdS core-shell quantum dot as ultrafast electron transfer relay between graphene-gold nanocomposite and gold nanoparticle. Since efficient electron transfer between glucose oxidase and the electrode was achieved, the biosensor showed high sensitivity (5762.8 nA nM-1 cm-2), low detection limit (S/N = 3) (3 × 10-12 M), fast response time (0.045 s), wide calibration range (from 1 × 10 -11 M to 1 × 10-8 M) and good long-term stability (26 weeks). The apparent Michaelis-Menten constant of the glucose oxidase on the medium, 5.24 × 10-6 mM, indicates excellent bioelectrocatalytic activity of the immobilized enzyme towards glucose oxidation. Moreover, the effects of omitting graphene-gold nanocomposite, CdTe-CdS core-shell quantum dot and gold nanoparticle were also investigated. The result showed sensitivity of the biosensor is 7.67-fold better if graphene-gold nanocomposite, CdTe-CdS core-shell quantum dot and gold nanoparticle are used. This could be ascribed to improvement of the conductivity between graphene nanosheets due to introduction of gold nanoparticles, ultrafast charge transfer from CdTe-CdS core-shell quantum dot to graphene nanosheets and gold nanoparticle due to unique electrochemical properties of the CdTe-CdS core-shell quantum dot and good biocompatibility of gold nanoparticle for glucose oxidase. The biosensor is of best sensitivity in all glucose biosensors based on graphene nanomaterials up to now and has been satisfactorily applied to determination of the glucose in human saliva samples. © 2011 Elsevier Ltd. All rights reserved.


Yan L.,Jiangnan University | Li R.,National University of Ireland, Maynooth | Li Z.,Jiangnan University | Liu J.,Jiangnan University | And 3 more authors.
Electrochimica Acta | Year: 2013

The paper reported a three-dimensional activated reduced graphene oxide nanocup/nickel aluminum layered double hydroxides composite (3D-ARGON/NiAl-LDH) with super high electrochemical and capacitance performances. Graphene oxide was reduced by hydrazine in ammonia medium to form three-dimensional reduced graphene oxide nanocup using polystyrene colloidal particle as sacrificial template. The nanocup was then activated by the alkali corrosion and thermal annealing. The 3D-ARGON/NiAl-LDH was finally fabricated by the hydrothermal synthesis via in situ growth of ultrathin NiAl-LDH nanoflakes on the 3D-ARGON in an ethanol medium. The study demonstrated that the composite offers special 3D architecture with a macropore on the rim of a cup and large mesoporous structure on the wall of a cup, which will greatly boost the electron transfer and mass transport during the faradaic redox reaction, and displays excellent electrochemical and capactance performances, including high specific capacitance and rate capability, good charge/discharge stability and long-term cycling life. Its maximum specific capacitance was found to be 2712.7 F g-1 at the current density of 1 A g-1, which is more than 7-fold that of pure NiAl-LDH, 3-fold that of common reduced graphene oxide/NiAl-LDH and 1.8-fold that of two-dimensional activated reduced graphene oxide/NiAl-LDH. The specific capacitance can remain 1174 F g-1 when the current density increases up to 50 A g-1. After 5000 cycles at the current density of 30 A g-1, the capacitance can keep at least 98.9%. This study provides a promising approach for the design and synthesis of graphene-based materials with largely enhanced supercapacitor behaviors, which can be potentially applied in energy storage/conversion devices. © 2013 Published by Elsevier Ltd.


Yulian N.,Jiangnan University | Ruiyi L.,National University of Ireland, Maynooth | Zaijun L.,Jiangnan University | Yinjun F.,Zhejiang Zanyu Technology Co. | Junkang L.,Jiangnan University
Electrochimica Acta | Year: 2013

High-performance supercapacitors materials (a-GNS/NiAl-LDH) was fabricated via in situ growth of NiAl-layered double hydroxide (NiAl-LDH) nanoflakes on well-activated graphene nanosheets (a-GNS). Graphene oxide was exfoliated and reduced using the microwave irradiation, alkali corrosion and thermal annealing in sequence. The resulting a-GNS is of large BET surface area of up to 3026 m2 g-1 and excellent conductivity. The as-prepared a-GNS/NiAl-LDH was characterized by scanning electron microscope, transmission electron microscope, X-ray diffraction and infrared spectrum. The results indicated NiAl-LDH nanoflakes are well dispersed on the wrinkled graphene nanosheets. Further, the apparent electron transfer rate constant (k s) and electrochemical performance of a-GNS/NiAl-LDH as electrode material for supercapactiors were also investigated. The ks value was found to be 0.0885 cm s-1, which is more than 2.5-fold that of pure NiAl-LDH. The a-GNS/NiAl-LDH provides a maximum specific capacitance of 1730.2 F g-1 at current density of 0.1 A g-1. The specific capacitance can remain 790 A g-1 when the current density increase to 10 A g-1, which is more than 6- and 3-fold that of pure NiAl-LDH (116.3 F g-1) and common GNS/NiAL-LDH (260.6 F g-1) made from the graphene produced by the chemical reduction of graphene oxide, respectively. The capacitance can keep at least 99.2% at current density of 5 A g-1 after 500 cycles. These demonstrated that the use of a-GNS obviously improve the specific capacitance, high-current capacitive behavior and cycle stability. © 2012 Elsevier Ltd. All rights reserved.


Zhilei W.,Jiangnan University | Zaijun L.,Jiangnan University | Xiulan S.,Jiangnan University | Yinjun F.,Zhejiang Zanyu Technology Co. | Junkang L.,Jiangnan University
Biosensors and Bioelectronics | Year: 2010

The paper describes an ingenious approach for the fabrication of a promising glucose sensor, GOx/C60-Fc-CS-IL, that exploits the synergistic beneficial characteristics of fullerene (C60), ferrocene (Fc), chitosan (CS) and ionic liquid (IL) for glucose oxidase (GOx). Cyclic voltammetry, impedance spectroscopy and chronoamperometry were used to evaluate performance of the biosensor, respectively. Since efficient electron transfer between GOx and the electrode was achieved, the biosensor exhibits a high sensitivity (234.67 nA nM-1 cm-2), low detection limit (S/N = 3) (3 × 10-9 M), fast response time (0.752 s), wide calibration range (from 1 × 10-8 M to 1 × 10-5 M) and excellent long-term stability (30 weeks). The apparent Michaelis-Menten constant (KM) of GOx on the composite medium, 0.03 mM, shows high bioelectrocatalytic activity of immobilized enzyme toward glucose oxidation. Due to low operating potential (100 mV), the biosensor is relatively insensitive to electroactive interfering species in human blood such as ascorbic acid, and uric acid, which are commonly found in blood samples. Excellent electrochemical reversibility, high sensitivity and stability, technically simple and possibility of preparation at short period of time are of great advantages of these glucose biosensors. © 2009 Elsevier B.V. All rights reserved.


Tao Y.,Jiangnan University | Ruiyi L.,University of Birmingham | Zaijun L.,Jiangnan University | Yinjun F.,Zhejiang Zanyu Technology Co.
Electrochimica Acta | Year: 2014

There is a great need to develop high-performance electroactive materials for supercapacitors. The study reported a facile and scalable strategy for synthesis of size-tunable NiCo2O4 with nanocoral-like architecture. Cobalt nitrate and nickel nitrate were dissolved in a tertbutanol solution and heated to reflux state under microwave radiation. The amounts of ammonia was dropped into the mixed solution to form nickel/cobalt double hydroxides. The reaction can complete within 15 min with the productivity of 99.9%. The obtained double hydroxides display flowercluster-like ultrathin nanostructure. The double hydroxide was calcined into different NiCo 2O4 products using different calcination temperature, including 400 °C, 500°C, 600°C and 700°C. The resulting NiCo2O4 is of nanocoral-like architecture. Interestingly, the size of coral can be easily controlled by adjusting the temperature. The NiCo2O4 prepared at 400°C gives a minimum building block size (10.2 nm) and maximum specific surface area (108.8 m 2·g-1). The unique structure will greatly improve faradaic redox reaction and mass transfer, the NiCo2O4 electrode exhibits excellent electrochemical performances for supercapacitors. Its maximum specific capacitance was 870.7 F g-1 at the current density of 1A g-1. The specific capacitance can remain 805.8 F g -1 at the current density of 10 A g-1, which offers an increase of about 4.6% after 1500 cycles. Moreover, the study also provides prominent approach to fabricate various size-adjustable nano-materials with three-dimensional network framework for supercapacitors, Li-ion batteries and other energy storge devices. © 2014 Published by Elsevier Ltd.


Linting Z.,Jiangnan University | Ruiyi L.,National University of Ireland, Maynooth | Zaijun L.,Jiangnan University | Qianfang X.,Jiangnan University | And 2 more authors.
Sensors and Actuators, B: Chemical | Year: 2012

The paper described an immunosensor for aflatoxin B 1 with an enhanced electrochemical performance based on graphene/conducting polymer/gold nanoparticles/the ionic liquid composite film. Graphene oxide, 2,5-di-(2-thienyl)-1-pyrrole-1-(p-benzoic acid) and gold nanoparticles, in this order, were electrodeposited on gold electrode surface. The graphene was characterized and its apparent heterogeneous electron transfer rate constant determined to be 28.55 ± 0.17 cm s -1 which is better than that of a bare gold electrode. An electrochemical immunoassay for aflatoxin B 1 was developed by immobilizing the respective antibody on the conducting polymer film, and a solution containing ionic liquid and chitosan was then dropped onto this electrode. The presence of graphene and gold nanoparticles warrant fast electron transfer, and the ionic liquid provides a benign microenvironment for the antibody. The method displays a good sensitivity, detection limit (at S/N = 3) as low as 1 fM, a dynamic range from 3.2 fM to 0.32 pM, and an excellent long-term stability (over 26 weeks). This immunoassay represents a remarkable improvement in terms of sensitivity, repeatability and stability when compared to other method for the determination of aflatoxin B 1. It was successfully applied to the determination of aflatoxin B 1 in spiked food samples, with recoveries in the range from 96.3% to 101.2%. © 2012 Elsevier B.V.


Zaijun L.,Jiangnan University | Xiulan S.,Jiangnan University | Qianfang X.,Jiangnan University | Ruiyi L.,National University of Ireland, Maynooth | And 3 more authors.
Electrochimica Acta | Year: 2012

The paper described a green and controllable strategy to fabricate well-dispersed graphene-gold nanocomposite film. To prepare graphene-gold nanocomposite film, graphene and gold nanoparticles were alternately electrodeposited on the surface of glassy carbon electrode. Since electrochemical technique offers control over reaction parameters and excellent repeatability, the amounts of graphene and gold nanoparticles for the each layer can be pre-determined by controlling concentrations of graphene oxide and chlorauric acid. The as-prepared graphene-gold nanocomposite film was characterized by infrared spectrum, scanning electron microscope, Raman spectrum and X-ray diffraction, and its electrocatalytic activity was estimated by Laviron's model. The apparent heterogeneous electron transfer rate constant of 37.67 ± 0.19 cm s-1 was obtained, indicating fast electron transfer of Fe(CN)6 4- to the electrode. Further, the film was investiaged as sensing materials for synchronously detection of hydroquinone and resorcinol. When the cencentrations are in the ranges of 1.6 × 10-8 to 1.2 × 10-4 mol l-1 for hydroquinone and 1.0 × 10-8 to 2 × 10-6 mol l-1 for resorcinol, differential pulse voltammetric peak current of the sensor linearly increases. The sensitivities of differential pulse voltammetric response are 30.5 μA μM-1 cm-2 for hydroquinone and 117.83 μA μM-1 cm-2 for resorcinol. The detection limits were found to be 5.2 × 10-9 mol l -1 for hydroquinone and 2.2 × 10-9 mol l -1 for resorcinol (S/N = 3). Proposed method is simple, sensitive and selective, it has been applied to the determination of hydroquinone and resorcinol in real water samples with a spiked recovery in the range of 96.0-103.4%. © 2011 Elsevier Ltd.


Zhiguo G.,Jiangnan University | Shuping Y.,Jiangnan University | Zaijun L.,Jiangnan University | Xiulan S.,Jiangnan University | And 3 more authors.
Analytica Chimica Acta | Year: 2011

We first reported an ultrasensitive hydrogen peroxide biosensor in this work. The biosensor was fabricated by coating graphene-gold nanocomposite (G-AuNP), CdTe-CdS core-shell quantum dots (CdTe-CdS), gold nanoparticles (AuNPs) and horseradish peroxidase (HRP) in sequence on the surface of gold electrode (GE). Cyclic voltammetry and differential pulse voltammetry were used to investigate electrochemical performances of the biosensor. Since promising electrocatalytic synergy of G-AuNP, CdTe-CdS and AuNPs towards hydrogen peroxide was achieved, the biosensor displayed a high sensitivity, low detection limit (S/N=3) (3.2×10 -11M), wide calibration range (from 1×10 -10M to 1.2×10 -8M) and good long-term stability (20 weeks). Moreover, the effects of omitting G-AuNP, CdTe-CdS and AuNP were also examined. It was found that sensitivity of the biosensor is more 11-fold better if G-AuNP, CdTe-CdS and AuNPs are used. This could be ascribed to improvement of the conductivity between graphene nanosheets in the G-AuNP due to introduction of the AuNPs, ultrafast charge transfer from CdTe-CdS to the graphene sheets and AuNP due to unique electrochemical properties of the CdTe-CdS, and good biocompatibility of the AuNPs for horseradish peroxidase. The biosensor is of best sensitivity in all hydrogen peroxide biosensors based on graphene and its composites up to now. © 2011.


Xiang Y.,Zhejiang University of Technology | Xiang Y.,Free University of Colombia | Kong L.,Zhejiang University of Technology | Kong L.,Zhejiang Zanyu Technology Co. | And 4 more authors.
Industrial and Engineering Chemistry Research | Year: 2014

Carbon nanotube (CNTs) and activated carbon (AC) supported Pd and Ni catalysts were prepared for the (in situ) hydrogenation of phenol to cyclohexanone and cyclohexanol. The hydrophobic/hydrophilic properties of the catalysts were tailored by pretreating the carbonaceous support with HNO 3 at various conditions and characterized by X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption (TPD), and transmission electron microscopy (TEM). The catalytic results suggested that Pd and Ni supported on CNTs show significantly higher activity than that supported on ACs. Pretreating the CNTs with HNO3 increases the local hydrophilicity of the active phase (by introducing oxygenated groups), which result in an increase in the cyclohexanone selectivity and strongly decrease the phenol conversion. The first-principles density functional theory calculation suggested that the adsorption/desorption behaviors of phenol, methanol, H2O, and cyclohexanone on the catalysts might be influenced highly by the hydrophobic/hydrophilic properties. The hydrophilic catalysts show high selectivity in cyclohexanone by lower conversion in phenol or vice versa. © 2014 American Chemical Society.

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