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Stability and aggregation kinetics of TiO2 nanoparticles

Wide range of possibilities for application of nanoparticles, from industry, cosmetics, pharmacy to environmental engineering, has resulted in large increase in necessary fundamental investigations.[1] Special interest exists for exploring nanoparticle stability in variety of experimental conditions (especially of those close to environmental) and understanding their possible toxicity.[2, 3] Here, we investigated TiO2 nanoparticle properties by dynamic and electrophoretic light scattering. Special emphasis we put on the preparation of stable suspensions and, in some critical experimental conditions, we performed the aggregation kinetics experiments.[4, 5] We investigated the influence of pH, concentration and salt type on the stability of nanoparticles. Also, we explored the influence of two added polyelectrolytes as potential stabilizers[6] which could improve nanoparticle stability, i.e. resistance to aggregation with change of pH or addition of monovalent salts. The results showed that there is no significant aggregation of nanoparticles at low ionic strengths in the pH range around isoelectric point when the polyelectrolyte, either polycation (poly(diallyldimethylammonium)) or polyanion (poly(styrenesulfonate)), was present. Also, the higher concentration of added salt at constant pH values was necessary for the aggregation in the presence of polyelectrolyte compared to polyelectrolyte free case. There was also noted difference between polycation- and polyanionmodified particles. In the presence of polycation the aggregation started at significantly lower concentration than in the presence of polyanion.

TiO2 nanoparticles, aggregation kinetics, polylelectrolytes

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