Trimodal charge transport in polar liquid-based dilute nanoparticulate colloidal dispersions

Abstract

The dominant modes of charge transport in variant polar liquid-based nanoparticulate colloidal dispersions (dilute) have been theorized. Theories formulating electrical characteristics of colloids have often been found to over- or under-predict charge transport in dilute suspensions of nanoparticles in polar fluids owing to grossly different mechanistic behaviors of concentrated systems. Three major interacting modes with independent yet simultaneous existence have been proposed and found to be consistent with analyses of experimental data. Electric double layer (EDL) formation at nanoparticle–fluid interface-conjugated electrophoresis under the influence of the electric field has been determined as one important mode of charge transport. Nanoparticle polarization due to short-range field non-uniformity caused by the EDL with consequent particle motion due to inter-particle electrostatic interactions acts as another mode of transport. Coupled electro-thermal diffusion arising out of Brownian randomization in the presence of the electric field has been determined as the third dominant mode. An analytical model based on discrete interactions of the charged particle–fluid domains explains the various behavioral aspects of such dispersions, as observed and validated from detailed experimental analysis. The analysis is also predictive of the dominance and behavior of the three modes with important nanocolloidal parameters such as temperature and concentration.