A highly sensitive and rapid organophosphate biosensor based on enhancement of CdS - decorated graphene nanocomposite. Anal Chim Acta
ABSTRACT This work reports a rapid and sensitive organophosphates (OPs) amperometric biosensor based on acetylcholinesterase (AChE) immobilized on CdS-decorated graphene (CdS-G) nanocomposite. The as-prepared biosensor shows high affinity to acetylthiocholine (ATCl) with a Michaelis-Menten constant (K(m)) value of 0.24 mM. A rapid inhibition time (2 min) is obtained due to the integration of the CdS-G nanocomposite. Based on the inhibition of OPs on the enzymatic activity of the immobilized AChE, and used carbaryl as the model compound, the resulting biosensor exhibits excellent performance for OPs detection including good reproducibility, acceptable stability, and a reliable linear relationship between the inhibition and log[carbaryl] from 2 ng mL⁻¹ up to 2 μg mL⁻¹ with a detection limit of 0.7 ng mL⁻¹,which provides a new promising tool for analysis of enzyme inhibitors.
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ABSTRACT: CdS-reduced graphene oxide (RGO) composites are successfully synthesized via the microwave-assisted reduction of graphite oxide in a CdS precursor solution using a microwave synthesis system. The photocatalytic performances of CdS-RGO composites in the reduction of Cr(VI) are investigated. The results show that CdS-RGO composites exhibit enhanced photocatalytic performance for the reduction of Cr(VI) with a maximum removal rate of 92% under visible light irradiation as compared with pure CdS (79%) due to the increased light absorption intensity and the reduction of electron-hole pair recombination in CdS with the introduction of RGO.Chemical Communications 09/2011; 47(43):11984-6. DOI:10.1039/c1cc14875c · 6.72 Impact Factor
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ABSTRACT: This report presents a highly sensitive, rhodamine B-covered gold nanoparticle (RB-AuNP) -based assay with dual readouts (colorimetric and fluorometric) for detecting organophosphorus and carbamate pesticides in complex solutions. The detection mechanism is based on the fact that these pesticides can inhibit the activity of acetylcholinesterase (AChE), thus preventing the generation of thiocholine (which turns the RB-AuNP solutions blue and unquenches the fluorescence of RB simultaneously). The color of the RB-AuNP solution remains red and the fluorescence of RB remains quenched. By use of this dual-readout assay, the lowest detectable concentrations for several kinds of pesticides including carbaryl, diazinon, malathion, and phorate were measured to be 0.1, 0.1, 0.3, and 1 μg/L, respectively, all of which are much lower than the maximum residue limits (MRL) as reported in the European Union pesticides database as well as those from the U.S. Department Agriculture (USDA). This assay allows detection of pesticides in real samples such as agricultural products and river water. The results in detecting pesticide residues collected from food samples via this method agree well with those from high-performance liquid chromatography (HPLC). This simple assay is therefore suitable for sensing pesticides in complex samples, especially in combination with other portable platforms.Analytical Chemistry 04/2012; 84(9):4185-91. DOI:10.1021/ac300545p · 5.83 Impact Factor
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ABSTRACT: The widespread use of organophosphate pesticides (OPPs) in agriculture leads to residue accumulation in the environment, which is dangerous to human health and disrupts the ecological balance. This study reports results obtained by a standard chromatographic method (high performance liquid chromatography, HPLC) and an amperometric method for chlorpyriphos (CPF) determination in broccoli. Reversed-phase HPLC with UV–VIS detection was used for the separation, and the mobile phase was acetonitrile–water (75:25 v/v). The electrochemical experiments were performed in phosphate buffer solutions at pH = 7.4, with an incubation time of 10 min. The response of the sensor was a linear function of CPF concentration from 10− 10 to 10− 7 M with a corresponding equation: y = 0.1467x + 1.4472 (R2 = 0.9959) and a detection limit of 1.58 × 10− 10 M. The biosensor methodology was used to analyze CPF directly in broccoli that had been previously spiked with CPF solution.Materials Science and Engineering C 05/2012; 32(4):1001–1004. DOI:10.1016/j.msec.2012.01.009 · 3.09 Impact Factor