Copper (hydr)oxide nanomaterials are an important class of nanomaterials with various applications, including next-generation pesticides. The efficacy of these materials is largely affected by oxysulfidation, one of the most important transformation processes in the environment. Here, we show that the extent and route of oxysulfidation are facet-dependent for these materials. Specifically, oxysulfidation of Cu₂O_{100} and Cu₂O_{111}—two Cu₂O nanomaterials with predominantly exposed {100} and {111} facets—is fast and complete, with only a hollow shell left at the end of the experiment. In comparison, oxysulfidation of Cu₂O_{110}, a nanomaterial with {110} facet, is much less complete, in that, the end-product exhibits a yolk–shell structure with a large cuprite core. The varied degrees of oxysulfidation are attributable to the facet-dependent adsorption affinities of Cu₂O for both oxygen and sulfide ions, leading to the formation of different initial oxysulfidation products. Unlike the porous coatings of yarrowite on Cu₂O_{111} and a mixture of yarrowite and covellite on Cu₂O_{100}, the condensed layer of djurleite formed on Cu₂O_{110} passivates the material by sealing the surface of Cu₂O, hindering subsequent copper dissolution. Consequently, Cu ions released from Cu₂O_{100} and Cu₂O_{111} are 2.2 and 2.4 times higher than that from Cu₂O_{110}. These findings underline the important role of exposed facets in dictating the interfacial processes of soft metal-based nanomaterials, and have important implications for improving the efficiency of nanopesticides in redox dynamic rhizospheres to minimize the environmental impacts associated with the overuse of conventional pesticides.

中文翻译：

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Cu2O 纳米材料的刻面依赖性氧硫化：对提高纳米农药功效的影响


氧化铜（氢）氧化物纳米材料是一类重要的纳米材料，具有多种应用，包括下一代杀虫剂。这些材料的功效在很大程度上受氧硫化的影响，氧硫化是环境中最重要的转化过程之一。在这里，我们表明这些材料的氧硫化程度和途径是刻面依赖性的。具体来说，Cu₂O_{100} 和 Cu₂O_{111}（两种 Cu₂O 纳米材料，主要暴露{100}面和 {111} 面）的氧硫化反应快速而完整，实验结束时只剩下一个空壳。相比之下，Cu₂O_{110}（一种具有{110}面的纳米材料）的氧硫化作用要不完全得多，因为最终产物表现出具有大赤铜矿核的蛋黄壳结构。不同程度的氧硫化作用归因于 Cu₂O 对氧离子和硫化物离子的刻面依赖性吸附亲和力，导致形成不同的初始氧硫化产物。与 Cu₂O_{111}上的蓍草石多孔涂层以及 Cu₂O_{100}上的蓍草石和钝石混合物不同，在 Cu₂O_{110}上形成的蓍草石凝聚层通过密封 Cu₂O 的表面来钝化材料，从而阻碍随后的铜溶解。因此，Cu₂O_{100} 和 Cu₂O_{111}释放的 Cu 离子分别是 Cu₂O_{110} 释放的 2.2 倍和 2.4 倍。 这些发现强调了暴露面在决定软金属基纳米材料的界面过程中的重要作用，并对提高纳米农药在氧化还原动态根际中的效率以最大限度地减少与过度使用传统农药相关的环境影响具有重要意义。