Department of Chemistry, University of California, Riverside, California 92521, USA.
J Am Chem Soc. 2011 Nov 23;133(46):18931-9. doi: 10.1021/ja2080345. Epub 2011 Oct 31.
In this work we have carried out systematic studies and identified the critical role of hydrogen peroxide instead of the generally believed citrate in the well-known chemical reduction route to silver nanoplates. This improved understanding allows us to develop consistently reproducible processes for the synthesis of nanoplates with high efficiency and yields. By harnessing the oxidative power of H(2)O(2), various silver sources including silver salts and metallic silver can be directly converted to nanoplates with the assistance of an appropriate capping ligand, thus significantly enhancing the reproducibility of the synthesis. Contrary to the previous conclusion that citrate is the key component, we have determined that the group of ligands with selective adhesion to Ag (111) facets can be expanded to many di- and tricarboxylate compounds whose two nearest carboxylate groups are separated by two or three carbon atoms. We have also found that the widely used secondary ligand polyvinylpyrrolidone can be replaced by many hydroxyl group-containing compounds or even removed entirely while still producing nanoplates of excellent uniformity and stability. In addition to the general understanding of NaBH(4) as a reducing agent, it has also been found to act as a capping agent to stabilize the silver nanoparticles, prolong the initiation time required for nanoplate nucleation, and contribute to the control of the thickness as well as the aspect ratio of silver nanoplates. The improved insight into the specific roles of the reaction components and significantly enhanced reproducibility are expected to help elucidate the formation mechanism of this interesting nanostructure.
在这项工作中，我们进行了系统的研究，确定了过氧化氢而不是通常认为的柠檬酸在著名的化学还原途径制备银纳米板中的关键作用。这种改进的理解使我们能够开发出始终如一的、高效率和高产率的纳米板合成方法。通过利用 H(2)O(2)的氧化能力，各种银源，包括银盐和金属银，可以在适当的封端配体的辅助下直接转化为纳米板，从而显著提高合成的重现性。与之前认为柠檬酸是关键成分的结论相反，我们已经确定，具有选择性粘附在 Ag(111)面上的配体基团可以扩展到许多二羧酸和三羧酸化合物，其两个最近的羧基基团之间相隔两个或三个碳原子。我们还发现，广泛使用的二级配体聚乙烯吡咯烷酮可以被许多含有羟基的化合物取代，甚至可以完全去除，同时仍然可以生产出具有极好的均匀性和稳定性的纳米板。除了对 NaBH(4)作为还原剂的普遍理解之外，还发现它还可以作为一种封端剂来稳定银纳米颗粒，延长纳米板成核所需的起始时间，并有助于控制银纳米板的厚度和纵横比。对反应成分的具体作用的深入了解以及显著提高的重现性有望有助于阐明这种有趣的纳米结构的形成机制。
