The development of a facile and reliable assay for arsenic (As) detection is crucial for its pollution control, which is a well-known heavy-metal pollutant in the environment. In this work, an efficient colorimetric method was established for As(V) detection based on a novel cuboid-shape Mn-Urea nanozyme (UMnzyme) with arsenic-enhanced oxidase-like activity. The UMnzyme was prepared through the coordination of Mn ions and carbonyl groups in urea, which possesses outstanding oxidase-like activity that can generate the superoxide anion free radical (O₂˙⁻) by catalyzing the dissolved O₂, triggering the 3,3′,5,5′-tetramethylbenzidine (TMB) chromogenic reaction. Furthermore, the free oxygen atoms in UMnzyme provide potential sites to bind with As, in which the formation of As–O will not destroy the morphology and structure of UMnzyme. The capture of As by UMnzyme results in the improvement of its oxidase-like activity; therefore, a colorimetric method for As(V) detection was developed with a linear range of 12.5–250 μg L⁻¹. The limit of detection was determined to be 2.4 μg L⁻¹ (S/N = 3), which is lower than the threshold (10 ppb) recommended by the World Health Organization. Moreover, the developed method was applied in the detection of As(V) in environmental water, and the recoveries are 89.5–103.6%. In short, this study provides an efficient and reliable strategy for As(V) detection based on a novel Mn-based nanozyme and a new idea for the reasonable design of Mn-based nanozymes with enhanced catalytic performance.

中文翻译：

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具有砷（V）增强氧化酶样活性的新型立方体锰尿素纳米酶的构建，作为选择性检测无机砷的比色探针

砷（As）是环境中众所周知的重金属污染物，开发一种简便可靠的砷（As）检测方法对其污染控制至关重要。在这项工作中，基于具有砷增强氧化酶样活性的新型长方体锰尿素纳米酶（UMnzyme），建立了一种有效的 As(V) 检测比色方法。 UMnzyme是通过Mn离子与尿素中的羰基配位制备而成，具有突出的类氧化酶活性，可通过催化溶解的O2产生超氧阴离子自由基(O2•−)，引发3,3',5, 5'-四甲基联苯胺（TMB）显色反应。此外，UMnzyme 中的自由氧原子提供了与 As 结合的潜在位点，其中 As-O 的形成不会破坏 UMnzyme 的形态和结构。 UMnzyme 对 As 的捕获导致其类氧化酶活性的提高，因此，开发了一种线性范围为 12.5-250 μg/L 的 As(V) 检测比色法。检测限确定为2.4 μg/L（S/N = 3），低于世界卫生组织推荐的阈值（10 ppb）。此外，将该方法应用于环境水中As(V)的检测，回收率为89.5%~103.6%。总之，该研究为基于新型锰基纳米酶的As(V)检测提供了一种高效可靠的策略，为合理设计具有增强催化性能的锰基纳米酶提供了新思路。