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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Polyhedral Oligomeric Silsesquioxane (POSS)-Stabilized Pd Nanoparticles: Factors Governing Crystallite Morphology and Secondary Aggregate Structure
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Polyhedral Oligomeric Silsesquioxane (POSS)-Stabilized Pd Nanoparticles: Factors Governing Crystallite Morphology and Secondary Aggregate Structure

机译：多面体低聚倍半硅氧烷（POSS）稳定的Pd纳米颗粒：控制微晶形态和二级聚集体结构的因素

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摘要

Polyhedral oligomeric silsesquioxane (POSS)-based amine ligands are used as capping agents in the reductive growth of Pd nanocrystallites, and the effects of the specific form of the ligand on the structure of both the secondary aggregate and the primary metal nanoparticle are explored. Secondary aggregates of the ligand capped Pd particles are seen to form a uniform structure only if (a) the POSS ligand is totally functionalized with amine groups and (b) the amine groups are in the hydrochloride form. By casting these results in the context of density functional theory calculations, we show that the morphology of Pd core-shell nanomaterials is determined by the ratio of self-interaction potentials of the ligands to their interaction with solvent. The structures of the primary metal crystallites are also shown to be sensitive to the amine ligand in the hydrochloride form. Our results further show that the POSS versions of a ligand will frequently form precipitating capped metal nanoparticle structures, where the discrete molecular forms produce no isolable metal nanoparticles at all on the time scale of the experiments. A study of the diffusion rates of the reactive species in the Pd/ POSS-ligand system shows a correlation between the growth of observable metal crystallites and sufficiently slow ligand diffusion kinetics. Finally, we illustrate through a TEM time series that Pd nucleation seems to happen without a prior formation of observable self-assembled POSS ligand templates.
机译：多面体低聚倍半硅氧烷（POSS）基胺配体在Pd纳米微晶的还原生长中用作封端剂，并探讨了配体特定形式对次级聚集体和初级金属纳米颗粒结构的影响。仅当（a）POSS配体被胺基团完全官能化并且（b）胺基团呈盐酸盐形式时，才能看到配体封端的Pd颗粒的二级聚集体形成均匀的结构。通过在密度泛函理论计算的上下文中铸造这些结果，我们表明，Pd核-壳纳米材料的形貌由配体的自相互作用电位与其与溶剂相互作用的比率决定。还显示出初级金属微晶的结构对盐酸盐形式的胺配体敏感。我们的结果进一步表明，配体的POSS版本将经常形成沉淀的带帽金属纳米颗粒结构，其中离散的分子形式在实验时间范围内根本不会产生可分离的金属纳米颗粒。对Pd / POSS-配体系统中反应性物种扩散速率的研究表明，可观察到的金属微晶的生长与足够慢的配体扩散动力学之间存在相关性。最后，我们通过TEM时间序列说明，在没有事先形成可观察到的自组装POSS配体模板的情况下，似乎发生了Pd成核。

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