Effect of Directional Movement on Dynamic Light Scattering

Guiqiong Huang,Bingquan Xu,Li Peng,Kaiqing Luo,Jian Qiu,Peng Han,Dongmei Liu

doi:10.1109/jphot.2021.3083611

Guiqiong Huang, Bingquan Xu + Show 5 more

Open Access

https://doi.org/10.1109/jphot.2021.3083611

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Abstract

Dynamic light scattering is a standard technique of nano-particle sizing in colloid systems. However, it is difficult to measure the particle size accurately in the flowing dispersion, which is inevitable in many applications, such as on-line measurement. In this paper, we present that the wave vector of the scattered light, which is averaged to a constant in traditional technique, varies with time when the particles undergoing not only the random motion but also the directional movement. This variation results in an additional term of sinc function to the traditional intensity autocorrelation function of the scattered light, thus affect the final particle size determination, especially for large velocity of the directional movement. The experimental results agree well with our derivation. We believe this will facilitate the extension of the technique of the dynamic light scattering to a wider range of application, especially of the on-line measurement in the flowing dispersion.

Highlights

Dynamic light scattering (DLS) is one of the main methods for size measurement of the nanometer and submicron particles in colloid systems [1]-[6]
We present that the change of the scattering wave vector should be included in the autocorrelation function (ACF) when particles undergo random motion and directional movement simultaneously
In contrast to the traditional ACF that is a superposition of weighted exponential functions, there is an additional term of sinc function related

Summary

Introduction

Dynamic light scattering (DLS) is one of the main methods for size measurement of the nanometer and submicron particles in colloid systems [1]-[6]. Some researchers attribute this difference to the Gaussian incident light field Chowdhury and his colleagues following the work of Edwards et al [26], have discussed the theory of DLS for a flowing dispersion of Brownian particles. They assumed a spherically symmetric Gaussian incident beam with a plane wave front in the scattering volume [27]. Weber et al developed an analytical expression for the homodyne autocorrelation function of laser light scattered by a laminar flow of a polydisperse particle-fluid system [29] Overall, these published works assume that the profile of the actual incident light follows the Gaussian distribution, so the scattered light will change when the particles move in the direction not parallel with the incident light. We believe our model can describe the dynamic light scattering from particle systems more accurately, and will facilitate the extension of the application of the DLS, especially for the on-line measurement in the flowing dispersion

Principle and method

Findings

Experimental and discussion

Conclusions