Department of Chemistry and Richard E. Smalley Institute for Nanoscale Science and Technology, Rice University, 6100 Main Street, Houston, Texas 77005, United States.
Anal Chem. 2013 Feb 5;85(3):1337-41. doi: 10.1021/ac303713z. Epub 2013 Jan 15.
A new method is described for measuring the short-wave infrared (SWIR) emission wavelengths of numerous individual nanoparticles without using a dedicated spectrometer. Microscope objectives designed for use at visible wavelengths often show severe axial chromatic aberration in the SWIR. This makes coplanar objects emitting at different SWIR wavelengths appear to focus at different depths. After this aberration has been calibrated for a particular objective lens, the depth at which an emissive nanoparticle appears brightest and best focused can be used to deduce its peak emission wavelength. The method is demonstrated using a dilute, structurally polydisperse sample of single-walled carbon nanotubes deposited onto a microscope slide. Discrete emission centers in this sample have different peak wavelengths corresponding to specific nanotube structural species. A set of images was recorded at stepped focus settings and analyzed to find the sharpest focus depth of each nanotube. The chromatic aberration calibration curve converted these depths into peak emission wavelengths with a spectral resolution better than 3 nm, allowing identification of each nanotube's structure. Chromatic aberration spectroscopy is a practical tool for using existing microscopic equipment to extract significant spectral information on coplanar nanoparticle samples that emit or scatter light.
描述了一种新的方法，用于测量大量单个纳米粒子的短波红外 (SWIR) 发射波长，而无需使用专用光谱仪。专为可见光设计的显微镜物镜在 SWIR 中通常会出现严重的轴向色差。这使得在不同 SWIR 波长处发射的共面物体似乎聚焦在不同的深度。在为特定物镜校准了这种像差之后，可以使用发射纳米粒子最亮和聚焦最好的深度来推断其峰值发射波长。该方法使用沉积在显微镜载玻片上的单壁碳纳米管的稀松、结构多分散样品进行了演示。该样品中的离散发射中心具有对应于特定纳米管结构种类的不同峰值波长。在逐步聚焦设置下记录了一组图像，并对其进行了分析，以找到每个纳米管的最清晰焦点深度。色差校准曲线将这些深度转换为峰值发射波长，其光谱分辨率优于 3nm，从而可以识别每个纳米管的结构。色差光谱学是一种实用工具，可用于利用现有的显微镜设备从发射或散射光的共面纳米粒子样品中提取重要的光谱信息。
