Dispersion, fractionation and characterization of sub-100nm P25 TiO2 nanoparticles in aqueous media

Despite of the widespread use of manufactured nanomaterials and increasing concerns on their potential risk, only limited information is available on their physicochemical properties in toxicologically relavant aqueous media. Here, P25 TiO₂ (Evonik GmbH), one of the well-known and widely-used photocatalytic TiO₂, was dispersed and fractionated in aqueous media, and its physicochemical properties, especially for its sub-100 nm fraction, was carefullly studied. The colloidal properties of TiO₂ nanoparticles, such as ag]glomeration and sedimentation, were found strongly dependent on the physicochemical characteristics of nanoparticles (e.g., hydrodynamic size distribution, type of capping ligands and surface charge) as well as those of the aqueous media used (e.g., ionic strength and chemical compositions). This study has shown the importance of standardized dispersion and characterization protocol for toxicity tests, which is urgently needed for reliable, reproducible and impartial toxicity tests of manufactured nanomaterials.