Dispersion of ZnO Nanoparticles in Aqueous Solutions Using Polyvinylamine as the Dispersant

Dispersion of inorganic solids, such as ZnO nanoparticles, at nanoscale in aqueous suspension is one of the important issues in nanotechnological processes. In this study, we have prepared the nano- ZnO aqueous suspensions using polyvinylamine (PVAm) as the dispersant. The dispersion efficiency was evaluated by the sedimentation test and the optical absorption intensity of the dispersion solution. The zeta potential measurement was used to study the effect of PVAm on the surface chargaes of ZnO nanoparticles. In the absence of PVAm, ZnO nanoparticles in water precipitate very quickly in several hours, resulting in large ZnO macro-aggregates in the size of 2 ~ 3 μm. This is because that ZnO nanoparticles do not carry enough surface charges. By introduction of PVAm into suspension as the dispersant, the stability of nano-ZnO aqueous suspensions increases significantly, and it could be evidenced by the small amount of precipitation for several days. In the presence of polymer, the zeta potentials of ZnO nanoparticles exceeds + 30 mV and can be up to + 70 mV. Additionally, the stability of nano-ZnO aqueous suspensions closely relates to the pH of suspension, and the most stable suspension occurs at pH = 7 to 11.