Xuechou Zhou

Electrochemical sensor of 4-aminobutyric acid based on molecularly imprinted electropolymer

A simple and effective procedure based on a molecularly imprinted polymer (MIP) was developed for preparing a selective 4-aminobutyric acid (4-ABA) sensor. The sensitive layer was prepared by electropolymerization of o-phenylenediamine (o-PD) on a gold electrode in the presence of 4-ABA, which acts as a template. Cyclic voltammetry (CV), differential pulse voltammetry (DPV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) measurements were used to monitor the process of electropolymerization. The molecularly imprinted sensor was tested by CV as well as DPV to verify the changes of redox currents of hexacyanoferrate. The concentration of 4-ABA in the range of 0.2–20.0 μmol L−1 can be determined with a detection limit of 0.08 μmol L−1 (defined as S/N = 3) under the optimum conditions. The MIP sensor shows high selectivity, sensitivity and reproducibility. The results from sample analysis indicate that the MIP-4-ABA sensor can be used for quantitative analysis.

Highly sensitive determination of lead( ii ) and cadmium( ii ) by a large surface area mesoporous alumina modified carbon paste electrode

Nanosized mesoporous γ-alumina (M-γ-Al2O3) was first prepared and then modified into a carbon paste to fabricate a novel modified carbon paste electrode. The prepared alumina has pores with an amorphous wall and large surface area. The electrochemical behavior of the modified carbon paste electrode was investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods. The modified carbon paste electrode was employed to determine Pb2+ and Cd2+ simultaneously by a differential pulse voltammetry (DPV) method. Amperometric determination was carried out in 0.1 mol L−1 NaAc–HAc buffer solution (pH 6.0) after enriching for 360 s at −1.0 V. The oxidation peak currents of Pb2+ and Cd2+ were proportional to their concentration in the range of 0.001–10 μmol L−1 and 0.01–10 μmol L−1, respectively. The detection limits of Pb2+ and Cd2+ were 0.20 nmol L−1 and 2.0 nmol L−1 (S/N = 3), respectively. The modified carbon paste electrode shows good stability, repeatability and sensitivity. The proposed method was applied to the determination of Pb2+ and Cd2+ in water samples with satisfactory results.

A hydrogen peroxide biosensor based on horseradish peroxidase/poly(L-leucine)/polydopamine modified glassy carbon electrode

A simple and practical sensor of hydrogen peroxide (H2O2) was designed successfully. The mixture of horseradish peroxidase (HRP) and chitosan (Chit) are effectively immobilized on the surface of poly-L-leucine/polydopamine modified glassy carbon electrode (PL-LEU/PDA/GCE). Under the optimum conditions, the biosensor based on HRP exhibits a fast amperometric response (within 3 s) to H2O2. The linear response range of the sensor is 0.5–952.0 μmol L–1, with the detection limit of 0.1 μmol L–1 (S/N = 3) and the sensitivity of 0.23 A L moL–1 cm–2. The apparent Michaelis–Menten constant (kMapp) of the biosensor is evaluated to be 0.12 mmol L–1, which suggests that the HRP-Chit/PL-LEU/PDA/GCE shows a higher affinity for H2O2. The sensor exhibits good sensitivity, selectivity, stability and reproducibility. The proposed method has been successfully applied to the determination of H2O2 in practical samples.