Abstract：
In this study, we developed a new fluorescence \"on-off-on\" sensor utilizing water-soluble cobalt/zinc-nitrogen co-doped graphene quantum dots (Co/Zn-N-GQDs) to recognize quinalphos pesticide in vegetable and fruit samples. Primarily, the synthesis method employed a one-pot hydrothermal approach, using betel leaves as a natural precursor and cobalt (\"Co\"), zinc (\"Zn\"), and urea (\"N\") as dopant sources. The Co/Zn-N-GQDs probes underwent comprehensive analytical characterization. The Co/Zn-N-GQDs were synthesized with a remarkable luminescence yield of 31.49%, exhibiting excitation at 320 nm and emission peak at 393 nm. Interestingly, the luminescence of Co/Zn-N-GQDs was selectively \"Turned Off\" by Cu2+ via a static quenching setup. Remarkably, quenched fluorescence was surprisingly reactivated upon adding quinalphos to the quench setup, indicating a direct correlation between luminescence reactivation and quinalphos concentration. Briefly, this phenomenon is ascribed to the functional groups in quinalphos, such as quinoxalinyl and phosphorothioate, which chelate with Cu2+ ions, disrupting the nonfluorescent Cu2+-Co/Zn-N-GQDs complex. The design sensor demonstrated a limit of detection (LOD) of 0.11 μM and a broad linear span of 0.5 to 200 μM. In conclusion, Cu2+-Co/Zn-N-GQDs sensor showed immediate applicability, stability, and reproducibility, making it highly effective for quinalphos sensing in various samples.
摘要：
在这项研究中,我们开发了一种新的荧光“开-关”传感器，利用水溶性钴/锌-氮共掺杂石墨烯量子点（Co/Zn-N-GQDs）识别蔬菜和水果样品中的quinalphos农药。首先,合成方法采用一锅法，使用槟榔叶作为天然前体和钴(“Co”)，锌（“锌”），和尿素(“N”)作为掺杂剂源。Co/Zn-N-GQDs探针进行了全面的分析表征。合成了Co/Zn-N-GQDs，具有31.49%的显著发光率，显示激发在320nm和发射峰在393nm。有趣的是,Co/Zn-N-GQD的发光被Cu2通过静态猝灭设置选择性地“关闭”。值得注意的是,在将quinalphos添加到猝灭装置中时，猝灭的荧光令人惊讶地重新激活，表明发光再激活和quinalphos浓度之间存在直接相关性。简而言之，这种现象归因于quinalphos中的官能团，如喹喔啉和硫代磷酸酯，与Cu2+离子螯合，破坏非荧光Cu2+-Co/Zn-N-GQDs复合物。设计的传感器显示出0.11μM的检测极限（LOD）和0.5至200μM的宽线性跨度。总之,Cu2+-Co/Zn-N-GQDs传感器具有直接适用性，稳定性,和再现性，使其对各种样品中的quinalphos传感非常有效。
