We describe a green new method for the synthesis of water-soluble photoluminescent carbon dots (CDs) that were functionalized with methimazole (MTZ) and applied to determine Hg²⁺ based on the fluorescence extinction. Starch obtained from rice was used as a natural source for the production of CDs by hydrothermal treatment. Also, it was proposed a factorial design to optimize the parameters for CD synthesis and the results showed that the luminescence intensity is a function of temperature and not of the heating time in the hydrothermal process. The synthesized CDs were characterized using fluorescence techniques, Fourier transform infrared spectroscopy (FTIR), and UV–Vis spectroscopy. Through transmission electron microscopy (TEM) and dynamic light scattering (DLS), it was found the formation of CDs on a nanometer scale with an average size of 11 nm. The functionalization with MTZ, eliminated all interferences from other metals, indicating a selective response to Hg²⁺ ions. The method was applied to Hg²⁺ determination in waters. Under optimal conditions, was obtained a limit of detection of 1.8 × 10⁻⁷ mol L⁻¹ with a linear range from 3.3 × 10⁻⁷ to 50.0 × 10⁻⁶ mol L⁻¹. Therefore, the proposed method can be considered a simple, selective, and precise alternative that minimizes the number of reagents used for Hg²⁺ determination in natural waters, and can be applied on a large scale in environmental analyzes.

我们描述了一种绿色的新方法，该方法用于合成由甲基苯并咪唑（MTZ）功能化并用于确定Hg ²⁺的水溶性光致发光碳点（CD）基于荧光消光。从稻米中获得的淀粉被用作通过水热处理生产CD的天然来源。此外，有人提出了析因设计来优化CD合成的参数，结果表明，发光强度是温度的函数，而不是水热过程中加热时间的函数。使用荧光技术，傅立叶变换红外光谱（FTIR）和UV-Vis光谱对合成的CD进行表征。通过透射电子显微镜（TEM）和动态光散射（DLS），发现形成了纳米级CD，平均尺寸为11 nm。使用MTZ进行功能化，消除了来自其他金属的所有干扰，表明对Hg ²⁺的选择性反应离子。该方法用于水中Hg ^2+的测定。在最佳条件下，获得的检出限为1.8×10 ^-7 mol L ^-1，线性范围为3.3×10 ^-7至50.0×10 ^-6 mol L ^-1。因此，所提出的方法可以被认为是一种简单，选择性和精确的替代方法，该方法可最大程度减少天然水中用于测定Hg ²⁺的试剂数量，并可大规模应用于环境分析。