Container to characterization: Impacts of metal oxide handling, preparation, and solution chemistry on particle stability

A study has been conducted to investigate the impact of experimental handling approaches on the state of model nanoparticles, from the container of dry particles to the characterization of suspended particles. Specifically, the effects of sonication, nanoparticle concentration, and ionic strength upon the size, electrophoretic mobility, and stability of the model metal oxides (TiO2, CeO2 and ZnO) were investigated. For initial breakup of dried nanoparticles in water, results indicate 30 min is the optimum sonication duration (120 W) all three metal oxide nanoparticles over the solution chemistry tested. Since aggregation is evident in metal oxide nanoparticles, sonication to achieve a proper dispersion of nanoparticles in solution is necessary prior to further experimentation. No more than 30 s sonication is needed for preparing well-dispersed test sample from the diluted stock suspension. Effects of nanoparticle concentration on the solution chemistry were also studied. TiO2 or CeO2 addition can reduce pH with increase of nanoparticle concentration; whereas pH increases with ZnO concentration. Consideration of these parameters (effects of sonication, nanoparticle concentration, and solution chemistry) is necessary to ensure successful subsequent toxicity and transport studies.