Crystalline materials are often formed via transient phases. Here we focus on ZnO as a widely used and investigated material for technological applications. Although the literature for the wet chemical synthesis of ZnO is extensive, its formation pathway using these strategies has gained limited attention so far and is poorly understood. To gain insight into these pathways, a HMTA-mediated ZnO synthesis protocol with a variety of zinc salts was employed using in situ pH measurements combined with discrete cryoTEM and SEM sampling studies, in addition to more typical pXRD and SEM product analysis. These results indicate a significant counter-ion effect on the reaction product. Using acetate, nitrate, chloride and sulphate as counter-ions all result first in the formation of a layered zinc hydroxy salt (LZHS), the exact composition of which depends on the counter-ion. Rather stable LZHSs are formed using chloride and sulphate, preventing the eventual formation of ZnO. Only acetate and nitrate result in the formation of ZnO. For acetate, ZnO is preferably grown in-dispersion, while for nitrate it is formed on exposed solid interfaces to the reaction medium (on-surfaces). For the latter the nucleation of its LZHS precursor requires an additional incubation time, resulting in heterogeneous nucleation instead.

中文翻译：

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抗衡离子对HMTA介导的ZnO形成机理的影响

晶体材料通常是通过过渡相形成的。在这里，我们将重点放在ZnO作为一种广泛用于技术应用且经过研究的材料上。尽管有关湿化学合成ZnO的文献非常广泛，但迄今为止使用这些策略的形成途径一直受到关注，并且了解甚少。为了深入了解这些途径，采用了原位采用HMTA介导的含多种锌盐的ZnO合成方案pH测量结合离散的cryoTEM和SEM采样研究，以及更典型的pXRD和SEM产品分析。这些结果表明对反应产物有显着的抗衡离子作用。首先使用乙酸根，硝酸根，氯离子和硫酸根作为抗衡离子，首先会形成层状羟基羟基锌盐（LZHS），其确切组成取决于抗衡离子。使用氯化物和硫酸盐可形成相当稳定的LZHS，从而防止最终形成ZnO。只有乙酸盐和硝酸盐会导致ZnO的形成。对于乙酸盐，ZnO优选在分散体中生长，而对于硝酸盐，它形成在暴露于反应介质的固体界面上（表面）。对于后者，其LZHS前体的核化需要额外的孵育时间，从而导致异质核化。