Department of Chemistry, Dankook University , 152 Jukjeon-ro, Suji-gu, Yongin, Gyeonggi 448-701, Korea.
ACS Nano. 2015 Dec 22;9(12):12292-300. doi: 10.1021/acsnano.5b05568. Epub 2015 Oct 20.
The control of nanogaps lies at the heart of plasmonics for nanoassemblies. The plasmon coupling sensitively depends on the size and the shape of the nanogaps between nanoparticles, permitting fine-tuning of the resonance wavelength and near-field enhancement at the gap. Previously reported methods of molecular or lithographic control of the gap distance are limited to producing discrete values and encounter difficulty in achieving subnanometer gap distances. For these reasons, the study of the plasmon coupling for varying degrees of interaction remains a challenge. Here, we report that by using light, the interparticle distance for gold nanoparticle (AuNP) dimers can be continuously tuned from a few nanometers to negative values (i.e., merged particles). Accordingly, the plasmon coupling between the AuNPs transitions from the classical electromagnetic regime to the contact regime via the nonlocal and quantum regimes in the subnanometer gap region. We find that photooxidative desorption of alkanedithiol linkers induced by UV irradiation causes the two AuNPs in a dimer to approach each other and eventually merge. Light-driven control of the interparticle distance offers a novel means of exploring the fundamental nature of plasmon coupling as well as the possibility of fabricating nanoassemblies with any desired gap distance in a spatially controlled manner.
纳米间隙的控制是纳米组装体等离子体学的核心。等离子体耦合对纳米颗粒之间的纳米间隙的大小和形状非常敏感，允许对共振波长和间隙处的近场增强进行微调。以前报道的分子或光刻控制间隙距离的方法仅限于产生离散值，并且在实现亚纳米间隙距离方面遇到困难。由于这些原因，对不同程度相互作用的等离子体耦合的研究仍然是一个挑战。在这里，我们报告说，通过使用光，可以将金纳米粒子 (AuNP) 二聚体的粒子间距离从几纳米连续调节到负值（即合并的粒子）。因此，AuNP 之间的等离子体耦合通过亚纳米间隙区域中的非局部和量子区域从经典电磁区域过渡到接触区域。我们发现，紫外辐照诱导的烷二硫醇链接物的光氧化解吸导致二聚体中的两个 AuNP 彼此靠近并最终合并。光驱动的粒子间距离控制为探索等离子体耦合的基本性质以及以空间控制方式制造具有任意所需间隙距离的纳米组装体提供了一种新方法。
