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Li Q.,Soochow University of China | Xu Z.,Soochow University of China | Tang W.,Soochow University of China | Wu Y.,Soochow University of China | Wu Y.,The Key Laboratory of Health Chemistry and Molecular Diagnosis of Suzhou
Analytical Letters | Year: 2015

A facile and green synthesis was employed to synthesize water-soluble carbon dots that were shown to be uniform monodisperse spheres with an average diameter of approximately 4 nanometers. Because of their strong adsorption, the carbon dots were assembled on a glassy carbon electrode without a bridging agent. The modified electrode was employed for the sensitive determination of dopamine. In 0.1 mole per liter phosphate buffer at pH 6.0, the peak currents of dopamine increased at the modified electrode. A calibration curve for dopamine was obtained from 1.5 × 10−7 to 1.5 × 10−4 mole per liter with a limit of detection of 2.6 × 10−8 mole per liter. The sensor was employed to determine dopamine in human plasma without interferences from uric acid and ascorbic acid. The carbon dot modified electrode also exhibited high stability and excellent precision. The results demonstrate the facile fabrication of a carbon dot-based sensor and a sensitive method for the determination of dopamine. © 2015, Copyright © Taylor & Francis Group, LLC. Source

Dai X.,Soochow University of China | Qiu F.,Jilin University | Zhou X.,Soochow University of China | Long Y.,Soochow University of China | And 3 more authors.
Analytica Chimica Acta | Year: 2014

This paper described a facile and direct electrochemical method for the determination of ultra-trace Cu2+ by employing amino-functionalized mesoporous silica (NH2-MCM-41) as enhanced sensing platform. NH2-MCM-41 was prepared by using a post-grafting process and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and fourier transform infrared (FTIR) spectroscopy. NH2-MCM-41 modified glassy carbon (GC) electrode showed higher sensitivity for anodic stripping voltammetric (ASV) detection of Cu2+ than that of MCM-41 modified one. The high sensitivity was attributed to synergistic effect between MCM-41 and amino-group, in which the high surface area and special mesoporous morphology of MCM-41 can cause strong physical absorption, and amino-groups are able to chelate copper ions. Some important parameters influencing the sensor response were optimized. Under optimum experimental conditions the sensor linearly responded to Cu2+ concentration in the range from 5 to 1000ngL-1 with a detection limit of 0.9ngL-1 (S/N=3). Moreover, the sensor possessed good stability and electrode renewability. In the end, the proposed sensor was applied for determining Cu2+ in real samples and the accuracy of the results were comparable to those obtained by inductively coupled plasma optical emission spectrometry (ICP-OES) method. © 2014 Elsevier B.V. Source

Wang K.,Soochow University of China | Wang K.,The Key Laboratory of Health Chemistry and Molecular Diagnosis of Suzhou | Wei X.,Soochow University of China | Wei X.,Shangqiu Normal University | And 2 more authors.
Microchimica Acta | Year: 2014

This paper reports on the synthesis of AuAg and PtAg alloy nanoclusters (NCs) and their enhancement effect on the electrochemiluminescence (ECL) of luminol. The conditions of synthesis were optimized, and the structure and properties of the NCs were characterized by X-ray diffraction, transmission electron microscopy, electrochemistry, and optical spectroscopy. The NCs are found to intensify (by up to 20 times) the ECL of luminol in solution of pH 8.5. This finding can largely extend the useful pH range of the ECL of luminol. The enhanced ECL is strongly affected by oxygen and hydrogen peroxide, and the mechanism of enhancement is attributed to the accelerated production of reactive oxygen species. The enhanced ECL is also affected by phenolic artificial estrogens, and this was used for their determination with detection limits as low as 700 pg L-1 (with AuAg) and 1.6 ng L-1 (with PtAg). The method was applied to the determination of such estrogens in egg samples using diethylstilbestrol as a reference substance. [Figure not available: see fulltext.] © 2014 Springer-Verlag Wien. Source

Zhang J.,Soochow University of China | Zhang J.,The Key Laboratory of Health Chemistry and Molecular Diagnosis of Suzhou | Cai F.,Soochow University of China | Cai F.,The Key Laboratory of Health Chemistry and Molecular Diagnosis of Suzhou | And 4 more authors.
Electroanalysis | Year: 2014

A rapid and ultrasensitive electrochemiluminescence (ECL) competitive immunoassay based on CdSe quantum dots (QDs) and the shorter chain as possible (cysteamine and glutaraldehyde) has been designed for the detection of salbutamol (SAL). Cysteamine and glutaraldehyde made coating antigen immobilize well on the gold electrode surface through the reaction between functional groups, which brought about the simplicity of the immunosensor to some extent. Transmission electron microscopy image, dynamic light scattering, photoluminescence, ultraviolet-visible absorption and electrochemical impedance spectra were used to characterize the prepared CdSe QDs and the cysteamine/glutaraldehyde/Ovalbumin-SAL/anti-SAL-QDs immunosensor. In the air-saturated PBS buffer containing 0.1M K2S2O8 and 0.1M KCl (pH9.0), a strong ECL emission of QDs can be observed which depended linearly on the logarithm of the salbutamol concentration with a wide range from 0.05ngmL-1 to 100ngmL-1, and a detection limit of 0.0056ngmL-1. The sensitivity, repeatability, and specificity of the ECL immunosensor have been evaluated. The sensor has been applied to real samples with satisfactory results. This work will open new ways of detecting food additive residue based on QDs ECL in immunoassays. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Tang Q.,Soochow University of China | Tang Q.,The Key Laboratory of Health Chemistry and Molecular Diagnosis of Suzhou | Cai F.,Soochow University of China | Cai F.,The Key Laboratory of Health Chemistry and Molecular Diagnosis of Suzhou | And 4 more authors.
Microchimica Acta | Year: 2015

We have designed an ul t r asensi t i v e electrochemiluminescence (ECL) immunoassay for the determination of the β-adrenergic agonist phenylethanolamine A (PA). It is based on the use of L-cysteine-capped CdSe quantum dots (QDs) immobilized on a glassy carbon electrode (GCE) with the help of chitosan. PA (the antigen) was linked to the surface of the GCE by using glutaraldehyde where it competes with the PA in the sample solution to bind to the antibody. Upon formation of the immunocomplex, a second antibody labeled with horseradish peroxidase was immobilized on the surface of the modified GCE. The ECL emission decreases due to steric hindrance by the immunocomplex which slows down the electron transfer rate of the reduction of dissolved oxygen, and this decrease can be strongly amplified by using an enzymatic cycle to consume the self-produced coreactant H2O2. Under optimal conditions, the ECL intensity measured in this competitive immunoassay is related to the concentration of PA over a range as wide as from 0.05 to 1,000 ng mL−1. The lower detection limit is 15 pg mL−1 at the S/N ratio of 3. This ECL immunoassay is rapid, sensitive, selective, acceptably precise, and extends the application of QDs-based ECL to immunoassays of β-agonists. © Springer-Verlag Wien 2014. Source

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