Polarized imaging dynamic light scattering for simultaneous measurement of nanoparticle size and morphology

Abstract

The performance of nanoparticles is often affected by particle size and morphology. Currently, electron microscopy or atomic force microscopy is typically utilized to determine the size and morphology of nanoparticles. However, there are issues such as difficult sample preparation, long processing times, and challenges in quantitative characterization. Therefore, it is of great significance to develop a fast, accurate, and statistical method to measure the size and morphology of nanoparticles. In this study, a new method, called polarized imaging dynamic light scattering (PIDLS), is proposed. The nanoparticles are irradiated with a vertical linearly polarized laser beam, and a polarization camera collected the dynamic light scattering images of particles at four different polarization directions (0°, 45°, 90°, and 135°) at a scattering angle of 90°. The average particle size and distribution are obtained using the imaging dynamic light scattering method at 0° polarization direction, and the morphology of the particles is obtained based on the depolarization patterns of the scattered light. The optical sphericity Ф is defined based on the degree of linear polarization (DoLP). It is also implemented for the quantitative evaluation of the sphericity of the nanoparticles, including spherical, octahedral, nanoplate, nanorod, and linear ones. Together with the Poincaré sphere parameter ψ, the morphology of the nanoparticles can be roughly identified. In addition, PIDLS enables the measurement of particle size and morphology distributions simultaneously for evaluating the uniformity of particles. The effectiveness of PIDLS is verified by the measurement of five kinds of industrial titanium dioxide as well.