Zilli Attilio, Langbein Wolfgang, Borri Paola
Cardiff University, School of Biosciences, Museum Avenue, Cardiff CF10 3AX, U.K.
Cardiff University, School of Physics and Astronomy, The Parade, Cardiff CF24 3AA, U.K.
ACS Photonics. 2019 Aug 21;6(8):2149-2160. doi: 10.1021/acsphotonics.9b00727. Epub 2019 Jul 21.
The scattering and absorption of light by nano-objects is a key physical property exploited in many applications, including biosensing and photovoltaics. Yet, its quantification at the single object level is challenging and often requires expensive and complicated techniques. We report a method based on a commercial transmission microscope to measure the optical scattering and absorption cross sections of individual nano-objects. The method applies to microspectroscopy and wide-field image analysis, offering fine spectral information and high throughput sample characterization. Accurate cross-section determination requires detailed modeling of the measurement, which we develop, accounting for the geometry of the illumination and detection as well as for the presence of a sample substrate. We demonstrate the method on three model systems (gold spheres, gold rods, and polystyrene spheres), which include metallic and dielectric particles, spherical and elongated, placed in a homogeneous medium or on a dielectric substrate. Furthermore, by comparing the measured cross sections with numerical simulations, we are able to determine structural parameters of the studied system, such as the particle diameter and aspect ratio. Our method therefore holds the potential to complement electron microscopy as a simpler and cost-effective tool for structural characterization of single nano-objects.
纳米物体对光的散射和吸收是许多应用中利用的关键物理特性，包括生物传感和光伏领域。然而，在单个物体层面上对其进行量化具有挑战性，并且通常需要昂贵且复杂的技术。我们报告了一种基于商用透射显微镜的方法，用于测量单个纳米物体的光学散射和吸收截面。该方法适用于显微光谱学和宽场图像分析，可提供精细的光谱信息和高通量的样品表征。准确的截面测定需要对测量进行详细建模，我们对此进行了开发，考虑了照明和检测的几何形状以及样品基板的存在。我们在三个模型系统（金纳米球、金纳米棒和聚苯乙烯纳米球）上演示了该方法，这些系统包括金属和介电粒子，有球形和细长形，放置在均匀介质中或介电基板上。此外，通过将测量的截面与数值模拟进行比较，我们能够确定所研究系统的结构参数，例如粒径和纵横比。因此，我们的方法有潜力作为一种更简单且经济高效的工具，补充电子显微镜用于单个纳米物体的结构表征。
