To improve the sensitivity and selectivity for S and Fe detection in complex agricultural products, ultra-small nano CeO/CuO doped carboxylated chitosan fibers (CeO/CuO CCF) was constructed under microwave-assisted conditions. Not only did CeO/CuO CCF possess suitable BET specific surface area, superior stability and synergistic-enhancement oxidase-like activity, trace S or Fe could selectively change its oxidase-like activity accompanying with visible color changes. Under the optimized conditions, there express specific double ratiometric colorimetric linear relationships between lg(/)/lg() and or with large linear ranges. When applied for visual monitoring of S and Fe in real agricultural products, the detection limits were low to 3.5 × 10 mol·L and 9.4 × 10 mol·L respectively, far below the permitted values in drinking water by World Health Organization. The mechanisms for synergistic-enhancement oxidase-like activity for CeO/CuO CCF to selectively recognize S and Fe were proposed. This work will provide an efficient way for visual monitoring of multiple analytes in complex agricultural products.

中文翻译：

---

超小型纳米 CeO2/CuO 掺杂羧化壳聚糖纤维，用于农产品中 S2− 和 Fe2+ 的高性能氧化酶模拟视觉监测

为了提高复杂农产品中硫和铁检测的灵敏度和选择性，在微波辅助条件下构建了超细纳米CeO/CuO掺杂羧化壳聚糖纤维（CeO/CuO CCF）。 CeO/CuO CCF不仅具有合适的BET比表面积、优异的稳定性和协同增强的类氧化酶活性，而且微量的S或Fe可以选择性地改变其类氧化酶活性并伴随可见的颜色变化。在优化条件下，lg(/)/lg()之间表现出特定的双比例比色线性关系，或具有较大的线性范围。应用于实际农产品中S、Fe的目视监测，检出限分别低至3.5×10 mol·L和9.4×10 mol·L，远低于世界卫生组织饮用水中的允许值。提出了 CeO/CuO CCF 选择性识别 S 和 Fe 的协同增强类氧化酶活性的机制。这项工作将为复杂农产品中多种分析物的视觉监测提供一种有效的方法。