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arXiv 0902.4163physics.opticsphysics.ins-det
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用倾斜Laser显微镜表征纳米颗粒:近场背散射测量

Nanoparticle characterization by using Tilted Laser Microscopy: back scattering measurement in near field

D. Brogioli, D. Salerno, V. Cassina, F. Mantegazza

摘要:

通过使用近场散射技术,显微镜可以很容易地变成测量静态和动态光散射的设备,这对于表征纳米颗粒分散体非常有用。到目前为止,基于显微镜的技术仅限于前向散射,最大可达30度。在本文中,我们提出了一种新的光学方案,克服了这一限制,扩展检测范围的角度大于90度(后向散射)。我们的光学方案是基于一个显微镜,一个宽的数值孔径物镜,和激光照明,与准直光束定位在一个大的角度相对于物镜的光轴(倾斜激光显微镜,TLM)。本文将通常只适用于傍轴散射的近场散射理论推广到强离轴情况。我们用几种不同直径的校准球形纳米粒子测试了我们的仪器和计算,进行了高达110度的静态和动态散射测量。测量的静态光谱和衰减时间与Mie理论和斯托克斯-爱因斯坦方程提供的扩散系数兼容。这种修改后的显微镜进行背散射测量的能力开辟了新的应用散射在近场技术的测量系统具有强烈的角度依赖性散射的方式。

英文摘要:

By using scattering in near field techniques, a microscope can be easily turned into a device measuring static and dynamic light scattering, very useful for the characterization of nanoparticle dispersions. Up to now, microscopy based techniques have been limited to forward scattering, up to a maximum of 30 degrees. In this paper we present a novel optical scheme that overcomes this limitation, extending the detection range to angles larger than 90 degrees (back-scattering). Our optical scheme is based on a microscope, a wide numerical aperture objective, and a laser illumination, with the collimated beam positioned at a large angle with respect to the optical axis of the objective (Tilted Laser Microscopy, TLM). We present here an extension of the theory for near field scattering, which usually applies only to paraxial scattering, to our strongly out-of-axis s ituation. We tested our instrument and our calculations with calibrated spherical nanoparticles of several different diameters, performing static and dynamic scattering measurements up to 110 degrees. The measured static spectra and decay times are compatible with the Mie theory and the diffusion coefficients provided by the Stokes-Einstein equation. The ability of performing backscattering measurements with this modified microscope opens the way to new applications of scattering in near field techniques to the measurement of systems with strongly angle dependent scattering.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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