Fang Yinjun

An ultrasensitive hydrogen peroxide biosensor based on electrocatalytic synergy of graphene–gold nanocomposite, CdTe–CdS core–shell quantum dots and gold nanoparticles

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(-11) M), wide calibration range (from 1×10(-10) M to 1.2×10(-8) M) 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.

Synergistic contributions of fullerene, ferrocene, chitosan and ionic liquid towards improved performance for a glucose sensor

The paper describes an ingenious approach for the fabrication of a promising glucose sensor, GOx/C(60)-Fc-CS-IL, that exploits the synergistic beneficial characteristics of fullerene (C(60)), 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) (3x10(-9) M), fast response time (0.752 s), wide calibration range (from 1x10(-8) M to 1x10(-5) M) and excellent long-term stability (30 weeks). The apparent Michaelis-Menten constant (K(M)) 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 V), 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.

A sensitive and highly stable electrochemical impedance immunosensor based on the formation of silica gel–ionic liquid biocompatible film on the glassy carbon electrode for the determination of aflatoxin B1 in bee pollen

The paper describes a sensitive and highly stable label-free electrochemical impedance immunosensor for the determination of aflatoxin B(1) (AFB(1)), 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 AFB(1) antibody, the sensor exhibits good repeatability (RSD=1.2%), sensitive electrochemical impedance response to AFB(1) in the range of 0.1-10 ng ml(-1) and lowers the detection limit of AFB(1) (0.01 ng ml(-1)). The electron-transfer resistance change of the sensor after and before incubation with AFB(1) of 2.0 ng ml(-1) can retain 95% over a 180-day storage period at 4 degrees 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 AFB(1) alone with no significant response to AFB(2), AFG(1), AFG(2) and AFM(1) as single substrates, it has been successfully applied to the determination of trace AFB(1) in bee pollen samples with a spiked recovery in the range of 96.0-102.5%.