Abstract
One of the main challenges in nanoecotoxicological investigations is in the selection of the most suitable measurement methods and protocols for nanoparticle characterisation. Several parameters have been identified as being important as they govern nanotoxicological activity, with some parameters being better defined than others. For example, as a parameter, there is some ambiguity as to how to measure dispersion stability in the context of ecotoxicological investigations; indeed, there is disagreement over which are the best methods to measure nanoparticle dispersion stability. The purpose of this article is to use various commercially available tools to measure dispersion stability and to understand the information given by each tool. In this study, CeO2 was dispersed in two different types of media: de-ionised water and electrolyte-containing fish medium. The DLS mean particle size of freshly dispersed sample in DI water was ~200 nm in diameter. A visual sedimentation experiment showed that nanoparticle dispersion made in the fish medium was less stable compared to corresponding dispersion in de-ionised water. Stability of these dispersions was monitored using various techniques, for a period of 3 days. Our findings have shown that dispersion stability can be suitably assessed by monitoring: (a) surface charge, (b) sedimentation events and (c) presence of agglomerates, through time. The majority of techniques employed here (zeta potential, particle size via DLS, fluorescence and UV–Vis spectroscopy and SEM) were shown to provide useful, complementary information on dispersion stability. Nanoparticle Tracking Analysis (NTA) provides useful, quantitative information on the concentration of nanoparticles in suspension, but is limited by its inability to accurately track the motion of large agglomerates found in the fish medium.
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Notes
Certain trade names and company products are mentioned in the text or identified in illustrations in order to specify adequately the experimental procedure and equipment used. In no case does such identification imply recommendation or endorsement by National Institute of Standards and Technology, nor does it imply that the products are necessarily the best available for the purpose.
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Acknowledgments
This work was conducted as part of PROSPEcT, which is a public–private partnership between DEFRA, EPSRC and TSB and the Nanotechnology Industries Association (NIA Ltd.) and its members, and was administered by the DEFRA LINK Programme. Authors would like to thank Drs. Neil Harrison, Andrew Shaw and Alex Shard for useful discussions and continuing support and Mr. Jordan Tompkins for the initial handling and distribution of the nanomaterials. We acknowledge the use of instruments in the Biotechnology and Materials groups at NPL.
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Tantra, R., Jing, S., Pichaimuthu, S.K. et al. Dispersion stability of nanoparticles in ecotoxicological investigations: the need for adequate measurement tools. J Nanopart Res 13, 3765–3780 (2011). https://doi.org/10.1007/s11051-011-0298-y
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DOI: https://doi.org/10.1007/s11051-011-0298-y