Modelling the effect of water and zinc acetate concentrations on the size and morphology of ZnO nanoparticles obtained via the precipitation method

In a previous study, a model was proposed to explore the thermodynamic equilibrium involved in forming zinc oxide nanoparticles at specific conditions via precipitation, using zinc acetate and potassium hydroxide as precursors. In this current study, those parameters derived from the model that are theoretically affecting the particle size itself, such as water, zinc acetate, and potassium hydroxide concentrations, have been altered. Using data extracted from the model—including [Zn⁺²] concentration and pH—the trajectories of each reaction were plotted to ascertain the sizes of stable particles in equilibrium throughout the reaction's progression. Zinc oxide nanoparticles were experimentally obtained by varying reactant concentrations to validate the simulation outcomes. The resulting zinc oxide underwent morphological and structural characterization using transmission microscopy (TEM) and X-ray diffraction (DRX). A strong correlation was observed between the sizes predicted by the model and those observed in the micrographs, showcasing nanoparticles ranging between 15 and 40 nm. Increasing the water concentration from 1.5 to 12 M resulted in an increase in particle size from 15 to 30 nm. In contrast, there was no change in particle size due to the rise in zinc acetate concentration from 0.081 to 0.81 M. Furthermore, the rapid addition of KOH led to the production of smaller particles on the order of 3 nm, likely attributed to the reaction occurring away from equilibrium. Reactant concentrations also influenced morphology alterations, allowing for the formation of faceted spheres or rods under specific conditions.