Xu Zhenying, Xie Hao, Ye Weixiang, Yang Yi, Ni Weihai
Jiangsu Key Laboratory of Thin Films, School of Physical Science and Technology, Soochow University, Suzhou, Jiangsu 215006, China.
Nanoscale. 2021 Jun 17;13(23):10335-10341. doi: 10.1039/d1nr02405a.
Instability problems encountered by Ag nanocrystals largely limit their use in practical applications. In AuAg bimetallic alloys, the stability of Ag can be greatly enhanced, whereas doping a high fraction of Au to the alloy usually leads to the loss of the superior properties of Ag and undesirable degradation of the quality factor of the plasmonic resonance. Herein, we provide experimental evidence that the atomically homogenous AuAg alloy nanocrystals with Au fraction as low as 4.9% (at%) possess comparable stability to pure Au, while the superior plasmonic properties of Ag are largely reserved. The study is based on the synthetic strategy developed for the overgrowth on the Au nanorods of atomically homogenous AuAg alloy shells with a tunable Au/Ag ratio but constant size and anisotropic shape. The stability of over 800 individual alloy nanocrystals in the absence of surfactants is simultaneously characterized at the single-particle level for over 10 h under light irradiation. The stability transition is explained in correlation with the charge redistribution of Ag occurring at the same critical Au fraction. We note that such bimetallic alloy nanocrystals with a low Au fraction possessing both high stability and high quality of resonance are preferred in fundamental researches and practical applications.
银纳米晶体遇到的稳定性问题在很大程度上限制了它们在实际应用中的使用。在金 - 银双金属合金中，银的稳定性可以大大提高，然而向合金中掺入高比例的金通常会导致银的优异性能丧失以及等离子体共振品质因数的不良降解。在此，我们提供实验证据表明，金含量低至4.9%（原子百分比）的原子均匀的金 - 银合金纳米晶体具有与纯金相当的稳定性，同时银的优异等离子体特性在很大程度上得以保留。该研究基于所开发的合成策略，即在具有可调金/银比但尺寸恒定且形状各向异性的原子均匀的金 - 银合金壳层在金纳米棒上进行外延生长。在光照下，在单粒子水平上同时对超过800个单独的合金纳米晶体在无表面活性剂的情况下的稳定性进行了超过10小时的表征。稳定性转变与在相同临界金含量下银发生的电荷重新分布相关联进行了解释。我们注意到，这种低金含量且兼具高稳定性和高共振品质的双金属合金纳米晶体在基础研究和实际应用中是优选的。
