Cysteine (Cys), homocysteine (Hcy), glutathione (GSH) and hydrogen sulfide (H₂S) are essential active substance in human body. The identification and detection of biothiols and H₂S are of great significance for the early diagnosis of certain diseases. In this paper, a new dual excitation and dual emission fluorescent probe, carbon quantum dot-O-7-nitrobenzo-2-oxa-1,3-diazole (CQDs-O-NBD), for the detection of biothiols and H₂S was synthesized. The carbon quantum dots (CQDs-OH) (λ_ex/em maxima = 377 nm/467 nm) were synthesized by a microwave-assisted method using hydroquinone as the carbon source. Through the reaction of the phenolic hydroxyl group of the carbon quantum dots and 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl), the CQDs-O-NBD was synthesized. Due to the static quenching (SQ) and the photo-induced electron transfer (PET) from CQDs to NBD, the fluorescence of the CQDs-O-NBD is very weak. After adding biothiols and H₂S, the ether bond of the CQDs-O-NBD was broken through nucleophilic substitution reaction, which led to the release of the CQDs-OH (channel 1 is turned on) and generation of a new compound NBD-thiols (channel 2). The CQDs-O-NBD as a probe shows the high selectivity and sensitivity for Cys/Hcy/GSH/NaHS (LOD of 0.24 μM/0.21 μM/0.19 μM/0.18 μM) over other aminos and ions by channel 1. The new formed compounds from NBD and Cys/Hcy have strong fluorescence under 470 nm wavelength light excitation (channel 2 is turned on), while the formed compounds from NBD and GSH/NaHS have no fluorescence (no channel 2), so the CQDs-O-NBD can discriminate Cys/Hcy (LOD: 0.07 μM/0.06 μM) from GSH/NaHS. In addition, the CQDs-O-NBD shows low toxicity and can be applied to the detection of Cys in fetal bovine serum and imaging in living cells.

半胱氨酸（Cys）、高半胱氨酸（Hcy）、谷胱甘肽（GSH）和硫化氢（H ₂ S）是人体必需的活性物质。生物硫醇和H ₂ S的鉴定和检测对于某些疾病的早期诊断具有重要意义。在本文中，一种新的双激发和双发射荧光探针，碳量子点-O-7-硝基苯并-2-氧杂-1,3-二唑（CQDs-O-NBD），用于检测生物硫醇和 H ₂ S被合成。碳量子点 (CQDs-OH) (λ _ex/emmaxima = 377 nm/467 nm）是通过微波辅助方法合成的，使用氢醌作为碳源。通过碳量子点的酚羟基与4-氯-7-硝基苯并-2-氧杂-1,3-二唑(NBD-Cl)反应，合成了CQDs-O-NBD。由于静态猝灭 (SQ) 和从 CQDs 到 NBD 的光诱导电子转移 (PET)，CQDs-O-NBD 的荧光非常弱。加入生物硫醇和 H _{2 后}S，CQDs-O-NBD 的醚键通过亲核取代反应断裂，导致 CQDs-OH 释放（通道 1 打开）并生成新化合物 NBD-硫醇（通道 2）。CQDs-O-NBD 作为探针显示出对 Cys/Hcy/GSH/NaHS（0.24 μM/0.21 μM/0.19 μM/0.18 μM）的高选择性和灵敏度，超过通道 1 的其他氨基和离子。新形成的NBD 和 Cys/Hcy 的化合物在 470 nm 波长光激发下有很强的荧光（通道 2 打开），而 NBD 和 GSH/NaHS 形成的化合物没有荧光（无通道 2），因此 CQDs-O-NBD可以区分 Cys/Hcy (LOD: 0.07 μM/0.06 μM) 和 GSH/NaHS。此外，CQDs-O-NBD具有低毒性，可应用于胎牛血清中Cys的检测和活细胞成像。