The enhancement effect of surface charges on forward and backward scattering of submicron polydisperse particles

Abstract

The existence of excess surface charges can change the complex refractive index and scattering properties of the submicron single particle. When charged submicron particles constitute a polydisperse particle system, the overall optical behavior will be affected by the number of particles, size distribution, surface charge density, and uneven complex refractive index. If the classical Mie theory based on electrically neutral particles is used to analyze such a particle system, it will inevitably lead to erroneous results. In this paper, the calculation model for scattering properties of charged spherical polydisperse particle systems is established, based on Mie theory. Considering the difference in the complex refractive index of the different size particles in the particle system, we analyzed the change characteristics of the optical properties of the submicron particle system before and after charged. Through calculation, it is found that the non-uniform particle size and complex refractive index in the polydisperse particle system have a certain buffer effect on the change of each optical coefficient, compared with the monodisperse particle system. Taking different Rosin-Ramler distributions as examples, we discussed the enhancement effect of surface charges on forward and backward scattering of submicron particle systems. It is found that the enhancement of forward scattering is more effective for particle systems with smaller median diameters. This means that the enhancement of charge helps to achieve visible light measurement of submicron or even nanometer particle systems.