Approaches to Analysis of Depolarized Dynamic Light Scattering Data on Solutions of Elongated Particles

As a researcher studying nanoparticles in the sub-micron range in a Depolarized Dynamic Light Scattering (DDLS) experiment, accurately determining their size and shape is crucial. However, an analysis of collected intensity correlation data requires considering appropriate assumptions and various geometrical models, which can be challenging. Our project is aimed to provide researchers with efficient tools to analyze DDLS using two approaches and appropriate assumptions. Overall, we focused on three geometrical models: de la Torre's straight cylinder, Perrin's prolate ellipsoid, and Martchenko et's spherocylinder. In the first approach, we used a multiangle DDLS experiment to obtain translational and rotational diffusion coefficients from analysis of measured intensity correlation function at various angles and then solved for geometrical anisotropy of the particles using the geometrical models. In the second approach, we followed Glidden and Muschol to analyze single scattering angle correlation functions and then used the deduced decay rates to solve for particle dimensions using the same geometrical models. To make the complicated analysis more efficient, we created a Matlab graphical user interface program that utilizes both approaches and the three geometrical models to obtain the dimensions of elongated particles. The Matlab program was tested on our previously obtained DDLS data on aqueous solutions of elongated particles prepared at different concentrations. The deduced particle dimensions at extrapolated zero concentration are an important test of the models as they all rely on the assumption of infinite dilution.