In this work charge enhanced dry impregnation (CEDI), a hybrid method of supported nanoparticle synthesis which combines the advantages of electrostatic adsorption—small particle size and tight size distributions—with the simplicity of incipient wetness impregnation, is demonstrated for four different metals (Pt, Pd, Co, and Ni) at multiple metal loadings over a common silica support. CEDI is achieved by basifying the impregnating solution sufficiently to charge the silica surface at the condition of incipient wetness. The electrostatic interactions induced between cationic ammine metal precursors and the deprotonated, negatively charged support result in smaller nanoparticles with tighter size distribution in comparison to those for incipient wetness impregnation (or dry impregnation, DI) with no pH adjustment. The method works best when the balancing ion of the precursor salt is hydroxide, such as platinum tetraammine hydroxide, (NH₃)₄Pt(OH)₂. Using the corresponding chloride salts with CEDI results in larger metal particles, but these are still smaller than DI-derived particles. Washing out the chloride results in very small nanoparticles without appreciable metal loss at metal loadings corresponding to one monolayer of precursor or below. Ammine complexes with nitrate as the counterion give small nanoparticles at lower but still relevant metal loadings (1 or 2 wt %) with no washing; in this way the CEDI synthesis procedure is completely parallel to incipient wetness impregnation but gives much better metal dispersion.

中文翻译：

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初湿浸渍法通过静电吸附法合成纳米颗粒

在这项工作中，电荷增强的干法浸渍（CEDI）对四种不同的金属（Pt ，钯，钴和镍）在普通二氧化硅载体上的多种金属负载下。通过在初始润湿条件下充分浸渗浸渍溶液以使二氧化硅表面带电，可以实现CEDI。与未经pH调节的初始湿法浸渍（或干法浸渍，DI）相比，阳离子氨基金属前体与去质子化的，带负电荷的载体之间产生的静电相互作用导致较小的纳米颗粒具有更紧密的尺寸分布。₃）₄ Pt（OH）₂。将相应的氯化物盐与CEDI一起使用会产生较大的金属颗粒，但这些颗粒仍小于DI衍生的颗粒。洗出氯化物会产生非常小的纳米颗粒，在对应于前驱体一层或以下的单层金属负载下，没有明显的金属损失。以硝酸盐为抗衡离子的氨配合物在不洗涤的情况下，在较低但仍具有相关金属负载量（1或2 wt％）的情况下产生小的纳米颗粒；这样，CEDI合成过程完全与初期湿润浸渍平行，但金属分散性更好。