Mechanism of Formation of Monodispersed Colloids by Aggregation of Nanosize Precursors

TL;DR

This paper presents a kinetic model explaining how monodispersed colloids form through nucleation and aggregation of nanosize precursors, validated by experiments with gold particles.

Contribution

It introduces a new kinetic model that accounts for the formation of narrow size distribution colloids via aggregation of primary particles, supported by numerical simulations and experimental validation.

Findings

Model accurately predicts average particle size

Distribution width matches experimental data

Time scale of formation aligns with observations

Abstract

It has been experimentally established in numerous cases that precipitation of monodispersed colloids from homogeneous solutions is a complex process. Specifically, it was found that in many systems nuclei, produced rapidly in a supersaturated solution, grow to nanosize primary particles (singlets), which then coagulate to form much larger final colloids in a process dominated by irreversible capture of these singlets. This paper describes a kinetic model that explains the formation of dispersions of narrow size distribution in such systems. Numerical simulations of the kinetic equations, with experimental model parameter values, are reported. The model was tested for a system involving formation of uniform spherical gold particles by reduction of auric chloride in aqueous solutions. The calculated average size, the width of the particle size distribution, and the time scale of the process, agreed reasonably well with the experimental values.