Natural manganese (Mn) oxide coatings, resulting from the heterogeneous nucleation on foreign substances, have garnered interest based on their importance in the reaction with organic substances and in environmental systems. However, the heterogeneous nucleation of the natural Mn oxide coatings still remains elusive. Here, via fast photochemical oxidation of Mn²⁺(aq), we show that Mn(IV) oxide nuclei form and aggregate on quartz in three distinct successive stages: (i) a nanocrystalline film of unaligned grain forms, (ii) nanoislands develop on the film, and (iii) nanorods form on the nanoislands. Each stage has different crystalline structures and forms by aligned attachment of nanoscale precursors on the preceding surface. Crystal lattice analyses confirm the crystalline development, from the short-range order of the Mn oxide film to the long-range order of the nanorods. Also, the heterogeneous nucleation observed in this work produced groutellite-like tunnel structures of Mn oxide on quartz. This revealed pathway of the heterogeneous nucleation can offer a new perspective on the variety of poorly crystalline structures of natural Mn oxides found in the environment, which can affect elemental redox cycles, contaminant sequestration and removal, and soil carbon storage.

中文翻译：

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光照下隧道结构氧化锰在石英上异质成核的三个独特步骤


天然氧化锰 （Mn） 涂层是由异物质上的异质成核产生的，因其在与有机物质的反应和环境系统中的重要性而受到关注。然而，天然 Mn 氧化物涂层的非均相成核仍然难以捉摸。在这里，通过 Mn²⁺（aq） 的快速光化学氧化，我们表明 Mn（IV） 氧化物原子核在石英上形成并聚集在三个不同的连续阶段：（i） 形成未排列晶粒的纳米晶膜，（ii） 纳米岛在薄膜上形成，以及 （iii） 纳米棒在纳米岛上形成。每个阶段通过纳米级前驱体在前一个表面上的对齐连接而具有不同的晶体结构和形式。晶格分析证实了从 Mn 氧化物膜的短程有序到纳米棒的长程有序的晶体发育。此外，在这项工作中观察到的非均相形核在石英上产生了氧化锰的镁粒状隧道结构。这种揭示的非均相成核途径可以为环境中发现的天然 Mn 氧化物的各种不良结晶结构提供新的视角，这会影响元素氧化还原循环、污染物封存和去除以及土壤碳储存。