CJCU

Chem. J. Chinese Universities ›› 2010, Vol. 31 ›› Issue (6): 1118.

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CdTe/CdS Semiconductor Quantum Dots as a Highly Sensitive Sensor for Pesticide Paraquat

BIAN Qian-Qian, LIU Ying-Fan, YU Jun-Sheng*   

  1. Key Lab of Analytical Chemistry for Life Science, Ministry of Education, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China
  • Received:2009-12-21 Online:2010-06-10 Published:2010-06-10
  • Contact: YU Jun-Sheng. E-mail: jsyu@nju.edu.cn
  • Supported by:

    国家自然科学基金(批准号: 20875045)和国家自然科学基金委创新研究群体科学基金(批准号: 20821063)资助.

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Abstract:

The highly fluorescent water-soluble CdTe/CdS quantum dots(QDs) have been synthesized with tiopronin(TP) as a stabilizer and thioacetamide(TAA) as a sulfur source. The interaction of as-prepared CdTe/CdS QDs with the ten kinds of pesticides demonstrates that QDs fluorescence could be strongly quenched by paraquat at room temperature. When ten kinds of 4.76×10-6 mol/L pesticides were added to 6.0×10-4 mol/L CdTe/CdS QDs solution, respectively, maximum quenching observed was 87.3% for paraquat and 0.1%—5.1% for other nine kinds of pesticides, such as acephate, phoxim, triadimefon, acetochlor, dichlorvos, cypermethrin, acetamiprid, glyphasate-isopropylammonium and malathion. The result shows that the CdTe/CdS QDs is highly sensitive sensor for paraquat. The quenching mechanism of the CdTe/CdS quantum dots by paraquat has been investigated by absorption spectroscopy and time-resolved luminescence technique. The intensity Stern-Volmer plot for quenching by paraquat shows clear upward curvature with K=2.03×106. The lifetime Stern-Volmer plot is linear with K=4.25×105 , and shows less quenching than the intensity data. It is clear that the fluorescence intensity of QDs is decreased by both complex formation with paraquat as well as collisional quenching by paraquat. A highly sensitive fluorimetric method for the determination of paraquat is established by using CdTe/CdS QDs as a sensor. The calibration curve is linear over the concentration range of 9.90×10-9—1.50×10-6 mol/L with a correlation coefficient of 0.999, and a limit of detection of 6.39×10-9 mol/L. The proposed method has been applied to the determination of paraquat residues in rice, wheat-flour, lettuce leaves and waste-water samples with standard addition recoveries of 82.2%—98.5% and RSD of 2.62%—8.35%.

Key words: CdTe/CdS core-shell quantum dot; Paraquat; Fluorescent sensor

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