Using l-cysteine as the precursor, carbon dots with nitrogen and sulfur heteroatoms co-doped (N, S-CDs) were synthesized via a simple hydrothermal method. The doped N and S atoms enhance the fluorescence intensity, and the modified functional group on N, S-CDs facilitate the coordination interaction between N, S-CDs and Co²⁺. Thus, the prepared N, S-CDs can be used as fluorescence probe to detect Co²⁺ with excellent selectivity and sensitivity. Moreover, various interferences displayed unobvious effect on the sensing of N, S-CDs to Co²⁺. This probe provided a rapid, visual method to monitor Co²⁺ with a wide monitoring range to Co²⁺ (1–50 μM) and a low detection limit of 26 nM. More interestingly, the quenched fluorescence (turn-off) of N, S-CDs induced by Co²⁺ could be recovered (turn-on) with the addition of H₂O₂ or EDTA. The fluorescence quenching mechanism is a static quenching, accompanied with electron transfer by forming the complex between Co²⁺ and functional groups of N, S-CDs.

以1-半胱氨酸为前体，通过简单的水热法合成了共掺杂有氮和硫杂原子的碳点（N，S-CDs）。掺杂的N和S原子增强了荧光强度，N，S-CDs上修饰的官能团促进了N，S-CDs和Co ²⁺之间的配位相互作用。因此，所制备的N，S-CDs可以用作荧光探针，以优异的选择性和灵敏度检测Co ²⁺。而且，各种干扰对N，S-CD对Co ²⁺的感测显示出明显的影响。该探针提供了一种快速，直观的方法来监测Co ^2+，并具有广泛的Co ²⁺监测范围（1–50μM）和26 nM的低检测限。更有趣的是，可以通过添加H ₂ O ₂或EDTA来恢复（打开）Co ²⁺诱导的N，S-CD的猝灭荧光（关闭）。荧光猝灭机制是静态猝灭，通过在Co ²⁺和N，S-CDs的官能团之间形成络合物来伴随电子转移。