title: Increased mobility of metal oxide nanoparticles due to photo and thermal induced disagglomeration.
abstract: Significant advances have been made on our understanding of the fate and transport of engineered nanomaterials. One unexplored aspect of nanoparticle aggregation is how environmental stimuli such as light exposure and temperature variations affect the mobility of engineered nanoparticles. In this study, TiO(2), ZnO, and CeO(2) were chosen as model materials for investigating the mobility of nanoparticles under three external stimuli: heat, light and sonication. Sunlight and high power sonication were able to partially disagglomerate metal oxide clusters, but primary particles bonded by solid state necks were left intact. A cycle of temperature increase from 25°C to 65°C and then decrease back was found to disagglomerate the compact clusters in the heating phase and reagglomerate them as more open fractal structures during the cooling phase. A fractal model summing the pair-wise DLVO interactions between primary particles within two fractal agglomerates predicts weak attractions on the order of a few kT. Our study shows that common environmental stimuli such as light exposure or temperature variation can disagglomerate nanoparticle clusters and enhance their mobility in open waters. This phenomenon warrants attention since it is likely that metal oxide nanoparticles will experience these natural stimuli during their transport in the environment.
authors.affiliation: Bren School of Environmental Science and Management and University of California Center for Environmental Implications of Nanotechnology, University of California Santa Barbara, Santa Barbara, California, United States of America.
authors.forename: Dongxu
authors.initials: D
authors.lastname: Zhou
authors.forename: Samuel W
authors.initials: SW
authors.lastname: Bennett
authors.forename: Arturo A
authors.initials: AA
authors.lastname: Keller
mesh_terms: D002586:Cesium / Q000737:chemistry; D017709:Fractals; D008027:Light; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D008956:Models, Chemical; D009038:Motion; D010316:Particle Size; D013010:Sonication; D013696:Temperature; D014025:Titanium / Q000737:chemistry; D014867:Water / Q000737:chemistry; D015034:Zinc Oxide / Q000737:chemistry
chemical_list: D014867:Water; C009495:titanium dioxide; D002586:Cesium; D014025:Titanium; D015034:Zinc Oxide