CdTe/CdS半导体量子点作为农药百草枯的高灵敏传感器

用硫普罗宁(Tiopronin,TP)作为稳定剂合成了水溶性的高荧光CdTe/CdS量子点.研究了该量子点与10种农药的相互作用.实验发现,当农药浓度为4.76×10-6mol/L时,农药百草枯(Paraquat)能显著猝灭CdTe/CdS量子点的荧光,使其荧光强度下降87.3%,而分别加入乙酰甲胺磷及辛硫磷等其它9种农药,仅能使CdTe/CdS量子点的荧光强度下降0.1%～5.1%,显示了该CdTe/CdS量子点对百草枯的特异性传感作用.采用吸收光谱和时间分辨荧光动力学研究了百草枯对CdTe/CdS量子点的荧光猝灭机理.计算得出荧光强度猝灭的Stern-Volmer常数K为2.03×106,而寿命猝灭的Stern-Volmer常数K为4.25×105.结果表明,百草枯对CdTe/CdS量子点的荧光猝灭主要为静态过程,而动态过程的贡献较小.利用二者的猝灭作用建立了对农药百草枯的高灵敏检测新方法,校正曲线的线性范围为9.90×10-9～1.50×10-6mol/L,检出限为6.35×10-9mol/L,R=0.999.用该方法对3种食品和3种水样中残留农药进行了检测,加标回收率均在82.2%～98.5%之间,其相对标准偏差为2.62%～8.35%.

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

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%.