Preparation of ZnO Nanoparticles with High Dispersibility Based on Oriented Attachment (OA) Process

Understanding nanoparticle growth mechanisms is crucial for the synthesis of nanocrystals with desired biological and chemical properties. Growth of nanocrystals by oriented attachment (OA) is frequently reported as a method supplementary to the classical growth by Ostwald ripening (OR) process. In this work, ZnO nanoparticles (NPs) were prepared by wet chemical method. Size/shape evolution of ZnO NPs in ethanol solution was systematically studied using transmission electron microscopy (TEM), dynamic light scattering (DLS), and X-ray diffraction (XRD). In addition, a detailed process of the nanoparticle growth-based OA mechanism is discussed. Results revealed that reaction conditions affect size/shape of NPs and change their surface structure: prior to OA, the surface of adjacent particles transformed into their "rough" states. We proved that stability of the solution was significantly improved in this state. Such a state is important to design nanoparticles with high stability and as nano-suspensions with special physical and/or chemical properties. This state is a critical step in enhancing OA process.