基于NaGdF_4∶Eu纳米粒子的荧光猝灭测定痕量Cu^(2+)

Determination of Trace Copper(Ⅱ) Based on Fluorescence Quenching of NaGdF_4∶Eu Nanoparticles

采用水热法合成了柠檬酸盐修饰的水溶性NaGdF4∶Eu荧光纳米粒子,粒子溶液荧光强度稳定。实验发现,Cu2+对合成粒子的荧光有猝灭作用,据此可建立用NaGdF4∶Eu荧光探针测定痕量Cu2+的新方法。实验确定NaGdF4∶Eu的浓度为1.0×10-3mol·L-1,溶液的pH值为10.0。考察了其他常见离子对粒子荧光性能的影响,其中Fe3+使荧光发生猝灭,用三乙醇胺可消除Fe3+的干扰。标准曲线的线性回归方程为I=532-0.685c,相关系数r为-0.9984,线性范围为3.33×10-6～1.33×10-4mol·L-1,检出限为8.9×10-7mol·L-1,对浓度为6.0×10-5mol·L-1的Cu2+溶液平行测定11次,RSD为0.62%。以上结果表明,方法的线性范围较宽,灵敏度和精密度较高。测定了茶叶样品中铜含量,测定结果和原子吸收法测定结果相一致。分析Cu2+对粒子荧光猝灭的机理认为,Cu2+和粒子表面的柠檬酸根发生化学结合,改变了粒子表面的结构和组成,导致其荧光发生猝灭。

Water-soluble NaGdF4∶Eu fluorescent nanoparticles modified by citrate were synthesized by hydrothermal method with stable fluorescent properties. It was found that the fluorescence of the solution of as-prepared particles could be quenched by Cu^2＋,and thus a new mathod to determine trace Cu^2＋ using NaGdF4∶Eu as fluorescent probe was established. A pH 10.0 and the concentration 1.0×10^-3 mol·L^-1 of NaGdF4∶Eu were selected for measurement. Besides,the effect of some foreign ions on the fluorescence signals was investigated and the interference of Fe^3＋ was found,which was eliminated by adding triethanolamine. The regression equation of standard curve was I=532-0.685c with the correlation coefficient of -0.998 4 when the concentration of Cu^2＋ was in the range of 3.33×10^-6-1.33×10^-4 mol·L^-1,and the detection limit of 8.9×10^-7 mol·L^-1 and a RSD of 0.62% for 11 replicates of a 6.0×10^-5 mol·L^-1 Cu^2＋ solution were obtained,which suggest a wide linear analytical range,high sensitivity and high precision. Analytical applicability of the particles was demonstrated by tea sample analysis and the results of Cu^2＋ determination were in good agreement with those obtained by atomic absorption spectrometry. The reason for fluorescence quenching by Cu^2＋ can be explained in terms of combination of Cu^2＋ with citrate on the surface of NaGdF4∶Eu particles leading to a change in surface structure and the composition.