【作者】 刘琪；

【导师】 朱丽华；

【作者基本信息】 华中科技大学 ， 分析化学， 2015， 硕士

【摘要】 目前,量子点因具有优良的荧光性能而得到了广泛的关注,在无机离子检测、药物分析等领域应用广泛。本文合成了CdS量子点和碳点,并将其成功地应用于环境中污染物的检测。首先,实验发现,全氟辛酸(Perfluorooctanoic acid,PFOA)能选择性淬灭巯基丙酸修饰的CdS量子点荧光。其淬灭机理是PFOA的羧基和CdS量子点表面的羧基相结合后吸附至量子点表面,再通过PFOA的氟原子之间的相互作用(氟-氟亲和作用)使量子点团聚,导致其荧光发生淬灭。据此建立了检测PFOA的荧光新方法。在优化条件下,PFOA浓度在0.5~40μmol L-1范围内与体系的荧光淬灭效率(F/F0)之间存在良好的线性关系,检出限为0.3μmol L-1。采用此法对纺织品样品中PFOA的含量进行了测定,其加标回收率在95.0%~113.0%之间。其次,发现在pH为4.0的醋酸盐缓冲溶液中,Fe3+对以苯硼酸为前驱体合成的富含羟基的碳点的荧光有很明显的淬灭作用,而其它金属离子不能淬灭其荧光。研究表明,其淬灭过程包括动态和静态淬灭两种方式:Fe3+通过静电引力吸附到碳点表面,由于Fe3+是很强的电子接受体,吸附于碳点表面的Fe3+可接受碳点受光激发产生的光生电子而被还原为Fe2+,与此同时Fe3+又可与碳点表面的羟基结合使碳点团聚,这两种作用均导致碳点的荧光淬灭。据此建立了选择性测定铁的荧光方法。Fe3+浓度在1.0~250?mol L-1范围内与体系的荧光淬灭效率(ln[F0/F])有良好的线性关系,检出限为0.4?mol L-1。本法用于奶粉中铁含量的测定,结果令人满意。此外,根据Fe3+可大幅度淬灭碳点的荧光,而Fe2+不能淬灭碳点的荧光之特性,利用Feton反应,使用H2O2将Fe2+氧化为Fe3+,建立了一种基于Fe3+淬灭碳点荧光而间接测定H2O2的新方法。该方法的线性范围为0.7~500?mol L-1,检出限为0.2?mol L-1。采用此方法测定了一次性筷子中H2O2的残留量,结果与钛盐比色法的测定结果相符合。另外,还发现EDTA能淬灭碳点-Fe2+混合体系的荧光,据此建立了一种测定EDTA的新方法。该方法的线性范围为1.0~150?mol L-1,检出限为0.4?mol L-1。采用此法测定了自来水和湖水中EDTA的含量,其回收率在95.2%~106.5%之间。更多还原

【Abstract】 Quantum dots(QDs) developed in recent years as a kind of fluorescent nanomaterials. The research of QDs has become popular, and is widely applied to inorganic ion detection, drug analysis and biological field. In this paper, the water-soluble Cd S quantum dots and carbon(CDs) dots were synthesized which were applied to detection of PFOA, Fe3+, H2O2 and EDTA.The major research works are as follow:Firstly, it was observed that the addition of Perfluorooctanoic acid strongly quenched the fluorescence emission of the mercaptoacetic acid capped Cd S QDs because the adsorption of PFOA promotes the aggregation of Cd S QDs through a fluorine-fluorine affinity interaction. Under optimum conditions, the fluorescence intensity was observed to decrease linearly with an increase in the concentration of PFOA from 0.5 to 40 mmol L-1, with a detection limit of 0.3 mmol L-1. This new method was successfully implemented for the analysis of textile samples, with recoveries ranging from 95% to 113%.Then, using phenylboronic acid as precursor, synthesized CDs. Fluorescence quenching was observed between Fe3+ and the CDs in HAc-Na Ac buffer solution(p H 4.0), whereas many other metal ions could not quench its fluorescence. When Fe3+ ions are added into the CDs solution, they can be quickly adsorbed onto the surface of the negatively charged CDs through the electrostatic attractions. Because the outer electronic structure of Fe3+ is 4s23d5 and the 3d orbits are halffilled, the electrons at the conductive band of CDs will be easily transferred to the half-filled 3d orbits of Fe3+. Meanwile, Fe3+ had strong interaction with OH, it caused CDs aggregation. These two processes lead to the significant fluorescence quenching of CDs. Under optimum conditions, the relative fluorescence intensity ln[F/F0] was linearly proportional to the Fe3+ concentration in the range from 1 to 250 mmol L-1, with a detection limit of 0.4 mmol L-1. The proposed method was successfully applied to determine iron in milk powder. Besides, we found that Fe2+ didn’t quench the fluorescence of CDs, and H2O2 could oxidate Fe2+ to be Fe3+. Based on Fenton reaction, we developed a new system for H2O2 detection. Under optimum conditions, the relative fluorescence intensity ln[F/F0] was linearly proportional to the H2O2 concentration in the range from 0.7 to 500 mmol L-1, with a detection limit of 0.2 mmol L-1. The proposed method has been applied to the determination of H2O2 in throwaway chopsticks. The addition of EDTA in CDs-Fe2+ system caused a significant quenching of the CDs fluorescence intensity. Based on this phenomenon, we developed a new system for EDTA detection. Under optimum conditions, the relative fluorescence intensity ln[F/F0] was linearly proportional to the EDTA concentration in the range from 1.0 to150 mmol L-1, with a detection limit of 0.5 mmol L-1. The proposed method has been applied to the determination of EDTA in tap water and lake water with the recoveries of 95.2% to 106.5%.更多还原