Herein, a simple and green “ON-OFF-ON” sensing system was developed using ultrasonic-exfoliated g-C₃N₄ nanosheets (CNNS) for the determination of a thiol-based ionic liquid (THIL), which was prominently different from common organic or biothiol molecules in terms of physico-chemical properties. After addition of THIL ([HSBMIM]Br used as an example), the Ag⁺-quenched CNNS fluorescence (“OFF” state) was recovered to the “ON” state due to reaction between THIL and Ag⁺ that led to functional group activation on CNNS surfaces. This phenomenon can be explained by competition of THIL with Ag⁺ because of the strong and specific affinity of –SH groups in THIL for Ag⁺ and by the reversibility of the Ag⁺-CNNS coordination reaction. Relevant factors influencing fluorescent recovery were rigorously optimized, including solution pH, incubation time as well as CNNS and THIL concentrations. THIL-recovered fluorescence intensities increased with increasing THIL concentrations providing a linear range of 15–360 nM and limit of detection (LOD) of 4.28 nM (1.07 μg L⁻¹). Testing a series of conventional imidazole-based ionic liquids indicated high specificity for the target analyte and negligible interference effects for the determination of nM-level THIL. The proposed fluorescent sensing method demonstrated excellent feasibility for trace THIL determination in real-world fresh and marine water matrices with high extraction recovery (90.3–107.9%) and high inter- and intra-day precisions (2.3–5.6% relative standard deviations). As far as our information goes, it is the first report on the development of g–C₃N₄–based “ON-OFF-ON” sensing platform for fast, sensitive and cost-effective determination of nM-level ionic liquids in natural waters.

本文中，使用超声剥落的gC ₃ N ₄纳米片（CNNS）开发了一种简单而绿色的“ ON-OFF-ON”感测系统，用于测定基于硫醇的离子液体（THIL），这与普通有机溶剂明显不同。就理化性质而言，还是生物硫醇分子。加入THIL（以[HSBMIM] Br为例）后，由于THIL与Ag ⁺之间的反应导致官能团活化，Ag ⁺猝灭的CNNS荧光（“ OFF”状态）恢复为“ ON”状态。在CNNS表面上。这种现象可以用THIL与Ag ⁺的竞争来解释，因为THIL中–SH基团对Ag ⁺有很强的特异性亲和力。以及Ag ⁺ -CNNS配位反应的可逆性。严格优化了影响荧光恢复的相关因素，包括溶液的pH值，孵育时间以及CNNS和THIL的浓度。THIL回收的荧光强度随THIL浓度的增加而增加，提供的线性范围为15–360 nM，检测限（LOD）为4.28 nM（1.07μgL ^-1）。对一系列常规的咪唑基离子液体进行测试表明，它们对目标分析物具有很高的特异性，而对于nM级THIL的测定，其干扰作用却可以忽略不计。所提出的荧光传感方法证明了在现实世界的淡水和海水矩阵中进行痕量THIL测定的极佳可行性，具有很高的提取回收率（90.3–107.9％）和日间和日内精度（相对标准偏差为2.3–5.6％）。就我们所掌握的信息而言，这是基于g–C ₃ N ₄的“ ON-OFF-ON”感测平台开发的第一份报告，该平台可快速，灵敏且经济高效地测定天然nM级离子液体水域。