We present a novel method to produce crystalline oxide aerogels which is based on the cross-linking of preformed colloidal nanocrystals (NCs) triggered by propylene oxide (PO). Ceria and titania were used to illustrate this new approach. Ceria and titania colloidal NCs with tuned geometry and crystal facets were produced in solution from the decomposition of a suitable salt in the presence of oleylamine (OAm). The native surface ligands were replaced by amino acids, rendering the NCs colloidally stable in polar solvents. The NC colloidal solution was then gelled by adding PO, which gradually stripped the ligands from the NC surface, triggering a slow NC aggregation. NC-based metal oxide aerogels displayed both high surface areas and excellent crystallinity associated with the crystalline nature of the constituent building blocks, even without any annealing step. Such NC-based metal oxide aerogels showed higher thermal stability compared with aerogels directly produced from ionic precursors using conventional sol–gel chemistry strategies.

中文翻译：

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具有控制结晶度和胶体纳米晶体的环氧驱动交联作用的刻面的金属氧化物气凝胶

我们提出了一种新的生产结晶氧化物气凝胶的方法，该方法基于由环氧丙烷（PO）触发的预先形成的胶体纳米晶体（NCs）的交联。用氧化铈和二氧化钛来说明这种新方法。在油胺（OAm）的存在下，通过适当的盐分解，在溶液中产生了具有调谐的几何形状和晶面的二氧化铈和二氧化钛胶体NCs。天然表面配体被氨基酸取代，使NCs在极性溶剂中胶体稳定。然后通过添加PO使NC胶体溶液胶化，这会逐渐从NC表面剥离配体，从而触发缓慢的NC聚集。基于NC的金属氧化物气凝胶显示出高表面积和出色的结晶度，这些结晶度与构成基块的晶体性质有关，即使没有任何退火步骤。与直接使用常规溶胶-凝胶化学策略从离子前驱体生产的气凝胶相比，此类基于NC的金属氧化物气凝胶显示出更高的热稳定性。