Stability of metal oxide nanoparticles in aqueous solutions

摘要

The application of nanoparticles in the processes of making commercial products has increasednin recent years due to their unique physical and chemical properties. With increasing amountnof commercial nanoparticles released into nature, their fate and effects on the ecosystem andnhuman health are of growing concern. This study investigated the stability and morphology ofnthree metal oxide nanoparticles in aqueous solutions. The commercially available nanoparticles,nTiO2, ZnO, SiO2, aggregated quickly into micrometer-size particles in aqueous solutions, whichnmay not threaten human health. Their changes in morphology and characteristics were furthernexamined by dynamic light scattering (DLS) method and transmission electron microscopy (TEM).nAmong the several dispersion approaches, ultrasonication was found to be the most effective forndisaggregating nanoparticles in water. For these three selected nanoparticles, ZnO could notnremain stable in suspensions, presumably due to the dissolution of particles to form highnconcentration of ions, resulting in enhanced aggregation of particles. In addition, the existencenof dissolved organic matters stabilized nanoparticles in lake water and wastewater for severalnhours in spite of the high concentration of cations in these real-water samples. The fate ofnmetal oxide nanoparticles in natural water bodies would be determined by the type andnconcentration of cations and organic matters. Results obtained in this study revealed thatnthe stability of nanoparticles changed under different aqueous conditions and so did theirnfate in the environment.