Bhattarai Badri, Zaker Yeakub, Atnagulov Aydar, Yoon Bokwon, Landman Uzi, Bigioni Terry P
Department of Chemistry , University of Toledo , Toledo , Ohio 43606 , United States.
School of Physics , Georgia Institute of Technology , Atlanta , Georgia 30332-0430 , United States.
Acc Chem Res. 2018 Dec 18;51(12):3104-3113. doi: 10.1021/acs.accounts.8b00445. Epub 2018 Nov 21.
Silver and gold molecular nanoparticles (mNPs) are a relatively new class of molecular materials of fundamental interest. They are high-nuclearity metal-organic compounds, with ligated metal cores, where the different character of bonding in the ligand shell and metal core gives rise to many of the unique properties of these materials. Research has primarily focused on gold mNPs, due to their good stability and the ease with which they may be synthesized and processed. To understand these materials as a general class, however, it will be necessary to broaden research efforts to other metals. Gold and silver are isoelectronic and have the same atomic radius, making the comparison of gold and silver mNPs attractive. The optical and chemical differences of the two metals provide useful contrasts, however, as well as a means to access a wider range of properties. In this Account, we focus on the synthesis, structure, and reactivity of silver mNPs. First, we review the origins and history of the field, from the ill-defined gas-phase metal clusters of the 1980s to the precisely defined mNPs of 1996 and onward. Next, we discuss the role of silver as a complement to gold mNPs in the effort to generalize lessons learned from either material and extend them into new metals. The synthesis of silver mNPs is covered in some detail, noting the choices made as the chemistry and the materials were developed. The importance of coordinating solvents and thermodynamic stability are also noted. The need to reduce solvent use is discussed and a new approach to achieving this goal is presented. Next, the structures of silver mNPs are discussed, including the Ag and Ag archetypes, and focusing on the successful de novo structure prediction of the latter. Structure and prediction of ligand shell motifs are also discussed. Finally, the postsynthetic chemistry and reactivity of silver mNPs are presented, including some of the first efforts to elucidate reaction mechanisms, beginning in 2012. Silver nanoparticles are gaining in popularity, particularly compared with gold, as the potential for silver to make a technological and economic impact is recognized. The superior optical properties of silver already make it a valuable material for plasmonics, but this may also translate to molecular species for nonlinear optics, sensors, and optoelectronics. The higher reactivity may also lead to a greater diversity of chemistry for silver compared to gold, including as an important broad-spectrum antimicrobial. Conversely, the "ultrastability" of the Ag archetype has already enabled unprecedented scale up with molecular precision, and may lead to the first industrial-scale production of metal mNPs. Clearly, silver mNPs are one of the most promising and significant new materials being studied today.
银和金分子纳米颗粒（mNPs）是一类相对较新的、具有重要基础研究价值的分子材料。它们是高核金属有机化合物，具有连接的金属核，其中配体壳层和金属核中不同的键合特性赋予了这些材料许多独特性质。由于金mNPs具有良好的稳定性以及易于合成和加工，研究主要集中在金mNPs上。然而，为了将这些材料作为一个整体类别来理解，有必要将研究工作扩展到其他金属。金和银是等电子体且具有相同的原子半径，这使得金和银mNPs的比较具有吸引力。不过，这两种金属的光学和化学差异不仅提供了有用的对比，还提供了一种获得更广泛性质的方法。在本综述中，我们重点关注银mNPs的合成、结构和反应性。首先，我们回顾该领域的起源和历史，从20世纪80年代定义不明确的气相金属簇到1996年及之后精确界定的mNPs。接下来，我们讨论银作为金mNPs的补充所起的作用，以便从这两种材料中总结经验教训并将其扩展到新的金属。我们详细介绍了银mNPs的合成，注意到在化学和材料发展过程中所做的选择。还提到了配位溶剂和热力学稳定性的重要性。讨论了减少溶剂使用的必要性，并提出了实现这一目标的新方法。接下来，我们讨论银mNPs的结构，包括Ag和Ag原型，并重点关注后者成功的从头结构预测。还讨论了配体壳层基序的结构和预测。最后，介绍了银mNPs的合成后化学和反应性，包括从2012年开始的一些阐明反应机制的初步努力。银纳米颗粒越来越受欢迎，特别是与金相比，因为人们认识到银具有产生技术和经济影响的潜力。银优越的光学性质已经使其成为等离子体学中的一种有价值的材料，但这也可能转化为用于非线性光学、传感器和光电子学的分子物种。与金相比，银更高的反应性也可能导致其化学性质更加多样化，包括作为一种重要的广谱抗菌剂。相反，Ag原型的“超稳定性”已经实现了前所未有的分子精度放大规模，并且可能导致金属mNPs的首次工业规模生产。显然，银mNPs是当今正在研究的最有前途和最重要的新材料之一。
