Enzymes have catalytic turnovers. The field of nanozyme endeavors to engineer nanomaterials as enzyme mimics. However, a discrepancy in the definition of “nanozyme concentration” has led to an unrealistic calculation of nanozyme catalytic turnovers. To date, most of the reported works have considered either the atomic concentration or nanoparticle (NP) concentration as nanozyme concentration. These assumptions can lead to a significant under- or overestimation of the catalytic activity of nanozymes. In this article, we review some classic nanozymes including Fe₃O₄, CeO₂, and gold nanoparticles (AuNPs) with a focus on the reported catalytic activities. We argue that only the surface atoms should be considered as nanozyme active sites, and then the turnover numbers and rates were recalculated based on the surface atoms. According to the calculations, the catalytic turnover of peroxidase Fe₃O₄ NPs is validated. AuNPs are self-limited when performing glucose-oxidase like activity, but they are also true catalysts. For CeO₂ NPs, a self-limited behavior is observed for both oxidase- and phosphatase-like activities due to the adsorption of reaction products. Moreover, the catalytic activity of single-atom nanozymes is discussed. Finally, a few suggestions for future research are proposed.

中文翻译：

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Nanozyme 催化周转和自限性反应

酶具有催化周转。纳米酶领域致力于将纳米材料设计为酶模拟物。然而，“纳米酶浓度”定义的差异导致对纳米酶催化转化的计算不切实际。迄今为止，大多数报道的工作都将原子浓度或纳米颗粒 (NP) 浓度视为纳米酶浓度。这些假设可能导致对纳米酶催化活性的严重低估或高估。在本文中，我们回顾了一些经典的纳米酶，包括 Fe ₃ O ₄、CeO ₂和金纳米粒子（AuNPs），重点是报道的催化活性。我们认为只应将表面原子视为纳米酶活性位点，然后根据表面原子重新计算周转次数和速率。根据计算，验证了过氧化物酶 Fe ₃ O ₄ NPs的催化转化。AuNPs 在执行类似葡萄糖氧化酶的活动时是自限性的，但它们也是真正的催化剂。对于 CeO ₂ NPs，由于反应产物的吸附，氧化酶和磷酸酶样活性均观察到自限行为。此外，还讨论了单原子纳米酶的催化活性。最后，对未来的研究提出了一些建议。