Mechanisms for Tungsten Oxide Nanoparticle Formation in Solvothermal Synthesis: From Polyoxometalates to Crystalline Materials
Mechanisms for Tungsten Oxide Nanoparticle Formation in Solvothermal Synthesis: From Polyoxometalates to Crystalline Materials
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DOI：
10.1021/acs.jpcc.8b12395
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发表时间：
2019-02-28
影响因子：
3.7
通讯作者：
Jensen, Kirsten M. O.
中科院分区：
文献类型：
--
作者：
Juelsholt, Mikkel;Christiansen, Troels Lindahl;Jensen, Kirsten M. O.
了解固体在原子尺度上的成核机制对于开发定制材料的新合成方法至关重要。在这里，我们使用原位x射线全散射来跟踪氧化钨形成过程中的结构重排，从溶液中的离子前体簇一直到最终的晶体纳米颗粒。为了研究溶剂对反应的影响，在水和油胺中进行了反应，在这两种情况下，前驱体溶液中存在的团簇都采用了众所周知的α - keggin多金属酸盐结构。然而，尽管前驱体团簇与最终结晶相相似，但反应路线高度依赖于溶剂，这为研究成核机制及其对最终氧化物结构缺陷的影响提供了新的思路。在水中，钨青铜纳米粒子结晶前，前驱体团簇部分重排为钨酸盐Y团簇，沿晶胞的c方向有较大程度的[WO6]无序。在油胺中，反应经历了几个步骤，包括非晶相和中间的焦绿盐结晶相，然后形成小而有序的钨青铜纳米颗粒。因此，溶剂不仅影响晶体大小，而且影响纳米颗粒的原子结构，我们将其与观察到的反应机理联系起来。
Understanding nucleation mechanisms of the solid state on an atomic scale is crucial in order to develop new synthesis methods for tailored materials. Here, we use in situ X-ray total scattering to follow the structural rearrangements that take place in the formation of tungsten oxide, all the way from the ionic precursor clusters in solution to the final crystalline nanoparticles. The reaction was performed in water and oleylamine to study the influence of solvent, and in both cases, the clusters present in the precursor solution adopted the well-known alpha-Keggin polyoxometalate structure. However, despite the similarity between precursor cluster and the final crystallographic phase, the reaction route is highly dependent on the solvent, shedding new light on nucleation mechanisms and their influence of defects in the final oxide structure. In water, the precursor cluster partly rearranges to the tungstate Y cluster before crystallization of tungsten bronze nanoparticles with a large degree of [WO6] disorder along the c direction of the unit cell. In oleylamine, the reaction goes through several steps, including an amorphous phase and an intermediate crystalline pyrochlore phase before forming small, ordered tungsten bronze nanoparticles. The solvent thus affects not only the crystallite size but also the atomic structure of the nanoparticles, which we link to the observed reaction mechanism.