The preparation of cobalt-based nanozymes with high oxidase-like activity still needs more efforts. In this paper, we report the synthesis of a CoO/Co–tryptophan-functional graphene quantum dot hybrid (CoO/Co–Try-GQD). Firstly, cobalt ions coordinate with the indole nitrogen on Try-GQD to form a complex, followed by thermal reduction and oxidation. The resulting hybrid presents a three-dimensional network structure, and CoO/Co nanoparticles are uniformly dispersed on the graphene sheet with an average size of 10 ± 0.24 nm. This unique structure improved the oxidase-like activity of the hybrid, enabling it to catalyze the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to rapidly produce deep blue ox-TMB with a strong absorbance at 652 nm (A₆₅₂). A colorimetric method was developed for the highly sensitive determination of L-cysteine (L-cys) based on the inhibition of the hybrid's oxidase-like activity and low A₆₅₂ caused by the binding of L-cys with Co atoms on CoO/Co via the Co–S bond. The A₆₅₂ linearly decreased with increasing L-cys concentration in the range of 0.05–2 μM, and the detection limit was 0.032 μM. Further, the established method has been successfully applied to the determination of L-cys in milk.

中文翻译：

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CoO/Co-石墨烯量子点作为氧化模拟纳米酶用于 L-半胱氨酸的比色检测

具有高氧化酶活性的钴基纳米酶的制备仍需要更多努力。在本文中，我们报道了 CoO/Co-色氨酸功能石墨烯量子点杂化物（CoO/Co-Try-GQD）的合成。首先，钴离子与Try-GQD上的吲哚氮配位形成络合物，然后进行热还原和氧化。所得杂化物呈现三维网络结构，CoO/Co纳米颗粒均匀分散在石墨烯片上，平均尺寸为10±0.24 nm。这种独特的结构提高了杂化物的类氧化酶活性，使其能够催化无色3,3',5,5'-四甲基联苯胺（TMB）的氧化，快速产生深蓝色的ox-TMB，在652 nm处有强吸光度（一₆₅₂）。基于L -cys与 CoO/Co 上的 Co 原子结合抑制杂种氧化酶活性和低A ₆₅₂，开发了一种高灵敏度测定L - 半胱氨酸 ( L -cys ) 的比色方法。 Co-S 键。A 652在 0.05-2 μM 范围内随着L -cys_浓度的增加呈线性下降，检测限为 0.032 μM。此外，所建立的方法已成功应用于牛奶中L -cys的测定。