Particle size of nanoparticles (NPs) influences not only their environmental transport but also their toxicity. In natural aquatic or subsurface systems, the aggregation of NPs leads to reduced mobility due to sedimentation, deposition, and filtration; while NPs with strong resistance to clustering tend to remain suspended and travel long distance. To date, studies have investigated the effects of solution chemistry on NPs aggregation, while little has been done to reveal the influence of material properties on NPs aggregation. In this study, the aggregation of four titania (TiO2) NPs with different morphologies (spheres, dots, wires, and rods), size, crystal structure (anatase, rutile, and amorphous) are being investigated. Results to date have shown distinct charging behavior and aggregation kinetics of TiO2 with different morphologies. The aggregation of rod shape TiO2 is more resistant to salt concentration change than the other three TiO2. The diffusion limited doublet formation rate (k11) of TiO2 wires was much higher than dots and rods, possibly due to wires' aligned attachment along the long axis. Size's role in controlling TiO2 aggregation was also pronounced that bigger particles aggregate faster with the same ionic strength. The ongoing work is to identify the diffusion-limited aggregation regime and reaction-limited aggregation regime and to determine the fractal dimension of the aggregates.

Role of material properties in controlling nanoparticle aggregation

243rd National Meeting (2012)

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