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545 results on '"Fang, Yuzhi"'

185. Electrophoresis-chemiluminescence detection of phenols catalyzed by hemin.

Author

Shu, Lu, Zhu, Jinkun, Wang, Qingjiang, He, Pingang, and Fang, Yuzhi

Abstract

Based on the catalytic activity of hemin, an efficient biocatalyst, an indirect capillary electrophoresis–chemiluminescence (CE‐CL) detection method for phenols using a hemin–luminol–hydrogen peroxide system was developed. Through a series of static injection experiments, hemin was found to perform best in a neutral solution rather than an acidic or alkaline medium. Although halide ions such as Br− and F− could further enhance the CL signal catalyzed by hemin, it is difficult to apply these conditions to this CE‐CL detection system because of the self‐polymerization of hemin, as it hinders the CE process. The addition of concentrated ammonium hydroxide to an aqueous/dimethyl sulfoxide solution of hemin–luminol afforded a stable CE‐CL baseline. The indirect CE‐CL detection of five phenols using this method gave the following limits of detections: 4.8 × 10−8 mol/L (o‐sec‐butylphenol), 4.9 × 10−8 mol/L (o‐cresol), 5.4 × 10−8 mol/L (m‐cresol), 5.3 × 10−8 mol/L (2,4‐dichlorophenol) and 7.1 × 10−8 mol/L (phenol). Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Published
2014
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186. Determination of DNA and Thrombin by an Electrochemical Sensor Employing Aggregation of Crosslinked Gold Nanoparticles and Aptamer Segments.

Author

Chang, Zhu, Zang, Yunbo, Chen, Chen, He, Pingang, and Fang, Yuzhi

Subjects
THROMBIN, ELECTROCHEMICAL sensors, GOLD nanoparticles, APTAMERS, BIOMOLECULES, DNA probes, QUADRUPLEX nucleic acids
Abstract

In this study, a novel and ultrasensitive biosensor strategy based on gold nanoparticles and aptamer segments was designed to detect two biomolecule targets: DNA and thrombin. Two DNA probes were designed that included aptamer segments and nucleic acids. The aptamer segments assembled into a G-quadruplex structure in the presence of thrombin, and the nucleic acids formed a double helix structure with the target DNA. The two gold nanoparticle-labeled DNA probes were effectively aggregated by specific recognition of the target molecules. Methylene blue, a redox-active indicator of single-stranded DNA, was incorporated in the unrecognized segment of the probe on the gold nanoparticle aggregation. Furthermore, the gold nanoparticle aggregation not only provided an excellent conductive matrix for methylene blue, but also abundantly enriched the methylene blue molecule. Using this method, DNA and thrombin were detected in low concentration ranges with both probes. These gold nanoparticle aggregation-based electrodes were independently characterized using cyclic voltammetry, electrochemical impedance measurements, and scanning electron microscopy. The peak currents had a linear relationship with DNA concentration from 2.0 fM to 2.0 pM and with thrombin concentration from 2.0 pM to 2.0 nM. [ABSTRACT FROM AUTHOR]

Published
2014
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187. Direct Electrochemistry and Electrocatalysis of Hemoglobin on Aligned Carbon Nanotubes Based Electrodes Modified with Au Nanoparticles and SiO2 Gel.

Author

Yang, Jing, Xu, Ying, He, Pingang, and Fang, Yuzhi

Subjects
ELECTROCHEMISTRY, ELECTROCHEMICAL analysis, HEMOGLOBINOMETRY, CARBON nanotubes, CHEMICAL vapor deposition, FIELD emission electron microscopy, SCANNING electron microscopy
Abstract

Here we report on the preparation and characterization of new electrodes based on aligned carbon nanotubes (ACNTs) for hemoglobin (Hb) electrochemistry and electrocatalysis. The ACNTs are obtained by a thermal chemical vapor deposition method under normal pressure. Then the electrodes are elaborated by first sputtering a thin Au film (thickness of 200 nm) onto the top of the ACNTs, and then removing the Au layer/ACNTs from the quartz substrate with the aide of hydrofluoric acid (HF) treatment. Field emission scanning electron microscopy (FESEM) demonstrates that after nitric acid (HNO3) treatment, the nanotubes of the removed Au layer are totally tip-opened, purified and organized in a perfect vertically aligned architecture. The final ACNTs electrode is obtained by attaching the Au layer of ACNTs onto a glassy carbon electrode. Then the electrode was modified to act as a matrix for hemoglobin (Hb) immobilization and as an electrode for Hb electroanalysis by the assistance of Au nanoparticles (AuNPs) and SiO2 gel. Due to the individual specific effects of AuNPs, SiO2 gel and ACNTs, the resulting SiO2/Hb-AuNPs/ACNTs electrode showed good direct electrochemistry of Hb with an apparent MichaelisMenten constant of 0.44 mM. The electrode showed an excellent electrocatalytic activity towards H2O2, possessing a linear range from 40 µM to 4 mM and the detection limit was 22 µM based on a signal to noise ratio of 3. [ABSTRACT FROM AUTHOR]

Published
2013
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