Atomistic Mechanisms of ZnO Aggregation from Ethanolic Solution: Ion Association, Proton Transfer, and Self-Organization

Abstract

We report on atomistic simulations related to the nucleation of zinc oxide nanocrystals from ethanolic solution. The underlying mechanisms are explored from the very initial stage of Zn²⁺ and OH⁻ ion association to the formation of nanometer-sized aggregates counting up to 250 ions. The embryonic aggregates consist of zinc and hydroxide ions, only. At later stages of aggregate growth, proton transfer reactions at the aggregate−solvent interface account for the formation of O²⁻ ions and induce the precipitation of zinc oxide. After the association of around 150 ions, ZnO domains were found to nucleate in the central region of the [Zn_x(OH)_yO_z]^2x-y-2z aggregates. In the course of further ion association and condensation reactions, progressive self-organization leads to an extended core in which the ions are arranged according to the wurtzite structure.