在人体内部环境中, 碘是合成甲状腺激素的关键原料之一, 而甲状腺激素主要功能是促进人体生长发育以及调节新陈代谢, 因此碘对人体内部环境正常运转起到至关重要的作用。 碘在人体内主要以碘化氨基酸的形式存在于甲状腺中, 对其常用的检测手段有很多种。 而这些方法虽然具有较高精度以及灵敏度高, 但检测过程较为复杂且检测周期较长。 因此, 发展一种成本较低、 操作简单、 快速准确的I^-检测方法具有应用意义。 研究设计一种简便且快速精准的I^-检测方法, 利用荧光“Off-On”传感体系对溶液中I^-进行定量检测。 以柠檬酸为碳源、 乙二胺为氮源, 通过水热法一步合成水溶性较好且具有良好荧光性质的碳点(CDs)。 利用荧光光谱仪以及紫外-可见光光谱仪对该CDs的光学性能进行表征。 通过分析CDs的光谱可知该CDs的激发波长为345 nm, 发射波长为470 nm。 另外, 通过傅里叶-红外光谱仪以及高分辨紫外光电子能谱对该CDs表面的官能团以及元素进行分析检测。 通过荧光光谱进行检测, 可以发现当CDs溶液中存在Hg²⁺时, CDs的荧光发生猝灭现象。 其原因是CDs与Hg²⁺的d轨道间非辐射电子转移或Hg²⁺与CDs表面的氨结合形成非荧光复合物, 导致CDs的荧光强度下降。 通过将最佳浓度的Hg²⁺与CDs溶液进行混合, 来制备Hg²⁺@CDs的荧光传感体系溶液。 分析Hg²⁺@CDs的荧光传感体系溶液的荧光光谱图可以发现, 当Hg²⁺@CDs的荧光传感体系溶液中存在I^-时, 体系荧光强度随着I^-浓度的上升而逐渐增强。 该原因可以归根于I^-与Hg²⁺之间存在较强的相互作用可将Hg²⁺从CDs表面脱附, 使CDs的荧光重新恢复, 从而实现I^-的荧光“Off-On”检测。 利用该方法来检测溶液中的I^-, 其检测范围在5.0~75 μmol·L^-1, 而检测限为0.25 μmol·L^-1。 实验最后还利用荧光光谱仪对Hg²⁺@CDs的荧光传感体系的选择性以及抗干扰能力进行分析, 结果显示该荧光传感体系对I^-具有较好的选择性以及良好的离子抗干扰性能。

In the human body, iodine is the key raw material for thyroid hormone. Moreover, thyroid hormone had a critical role in human growth and development and regulated metabolism, so iodine was played a vital role in the normal operation of the human body. The iodine was mainly in the form of iodinated amino acids presented in the thyroid gland. Furthermore, many methods were used to detect I^- with high precision and accuracy. However, most of the approaches lie in complicated operations and high detection cost. Therefore, it is of great significance to develop a method for detecting I^- with low cost, fast, accuracy and simple operation. In this study, a simple and convenient fluorescence “Off-On” detection method was used for I^- testing in solution. The carbon nanodots (CDs) were synthesized by a simple hydrothermal method, which citric acid and ethane diamine were used as the carbon source and the nitrogen source. The optical properties of the CDs were characterized by a fluorescence spectrometer and an ultraviolet-visible spectrometer, which emitted bright blue light at an excitation wavelength of 350 nm. Additionally, the groups on the surface of the CDs were characterized by the Fourier-infrared spectroscopy and high resolution ultraviolet photoelectron spectroscopy. The fluorescence of the prepared CDs can be pre-quenched by Hg²⁺. And the fluorescence quenching may be due to the non-radiative electron-transfer from the excited states to the d orbital of Hg²⁺. Another possible explanation is attributed to the Hg²⁺ ions combine with a large amount of nitrogen on the surface of the CDs to form a non-fluorescent complex, which leads to fluorescence quenching of CDs. The optimal concentration condition of Hg²⁺ was selected by analyzing the fluorescence spectrum of CDs solution with different concentration Hg²⁺. Once they meet I^- in the solution, Hg²⁺ on the surface of the CDs will be released due to the strong interaction between Hg²⁺ and I^-, and the fluorescence of CDs can be restored. Thus, I^- in the solution can be detectable by this fluorescent “Off-On” method, and the detection range is 5.0~75 μmol·L^-1 with the detection limit of 0.25 μmol·L^-1. Finally, the selectivity and anti-interference ability of Hg²⁺@CDs fluorescence sensing system were analyzed by fluorescence spectrum. And the results showed that the fluorescence sensing system had high selectivity to I^- and good ion anti-interference performance.