Characterization of size, surface charge, and agglomeration state of nanoparticle dispersions for toxicological studies |
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Authors: | Jingkun Jiang Günter Oberd?rster Pratim Biswas |
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Institution: | (1) Aerosol and Air Quality Research Laboratory, Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA;(2) Department of Environmental Medicine, University of Rochester, Rochester, NY 14642, USA |
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Abstract: | Characterizing the state of nanoparticles (such as size, surface charge, and degree of agglomeration) in aqueous suspensions
and understanding the parameters that affect this state are imperative for toxicity investigations. In this study, the role
of important factors such as solution ionic strength, pH, and particle surface chemistry that control nanoparticle dispersion
was examined. The size and zeta potential of four TiO2 and three quantum dot samples dispersed in different solutions (including one physiological medium) were characterized. For
15 nm TiO2 dispersions, the increase of ionic strength from 0.001 M to 0.1 M led to a 50-fold increase in the hydrodynamic diameter,
and the variation of pH resulted in significant change of particle surface charge and the hydrodynamic size. It was shown
that both adsorbing multiply charged ions (e.g., pyrophosphate ions) onto the TiO2 nanoparticle surface and coating quantum dot nanocrystals with polymers (e.g., polyethylene glycol) suppressed agglomeration
and stabilized the dispersions. DLVO theory was used to qualitatively understand nanoparticle dispersion stability. A methodology
using different ultrasonication techniques (bath and probe) was developed to distinguish agglomerates from aggregates (strong
bonds), and to estimate the extent of particle agglomeration. Probe ultrasonication performed better than bath ultrasonication
in dispersing TiO2 agglomerates when the stabilizing agent sodium pyrophosphate was used. Commercially available Degussa P25 and in-house synthesized
TiO2 nanoparticles were used to demonstrate identification of aggregated and agglomerated samples. |
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Keywords: | Nanoparticle Toxicology Nanotoxicology Health Safety Ultrasonication Nanotechnology Environment |
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