Department of Applied Physics, Chalmers University of Technology, 412 96 Göteborg, Sweden.
Nano Lett. 2011 Nov 9;11(11):4505-8. doi: 10.1021/nl1036116. Epub 2010 Dec 9.
The understanding of interaction forces between nanoparticles in colloidal suspension is central to a wide range of novel applications and processes in science and industry. However, few methods are available for actual characterization of such forces at the single particle level. Here we demonstrate the first measurements of colloidal interactions between two individual diffusing nanoparticles using a colorimetric assay based on plasmon hybridization, that is, strong near-field coupling between localized surface plasmon resonances. The measurements are possible because individual gold nanoparticle pairs can be loosely confined in an optical potential well created by a laser tweezers. We quantify the degree of plasmon hybridization for a large number of individual particle pairs as a function of increasing salt concentration. The data reveal a considerable heterogeneity at the single particle level but the estimated average surface separations are in excellent agreements with predictions based on the classical theory of Derjaguin, Landau, Verwey, and Overbeek.
胶体悬浮液中纳米颗粒相互作用力的理解是科学和工业中一系列新型应用和工艺的核心。然而，目前可用的实际表征方法很少能够在单颗粒水平上测量这种力。在这里，我们使用基于等离子体杂化的比色测定法首次测量了两个扩散纳米颗粒之间的胶体相互作用，即局域表面等离子体共振之间的强近场耦合。之所以能够进行测量，是因为可以将单个金纳米颗粒对松散地限制在由激光镊子产生的光阱中。我们量化了在增加盐浓度的情况下，大量单个颗粒对之间的等离子体杂化程度。数据显示在单颗粒水平上存在相当大的异质性，但估计的平均表面分离与基于德热纳、朗道、维韦和奥弗贝克的经典理论的预测非常吻合。
