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Final Report on the physico-chemical characterisation of PROSPEcT engineered nanomaterials.

Tantra, R; Boyd, R; Cackett, A; Fry, A T; Gohil, D D; Goldberg. S,, ; Lee, J L S; Minelli, C; Peck, R; Quincey, P; Smith, S; Snowden, J; Spencer, S; Tompkins, J; Wang, J; Yang, L (2012) Final Report on the physico-chemical characterisation of PROSPEcT engineered nanomaterials. NPL Report. AS 68

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The PROSPEcT project represents the UK¿s contribution to an OECD WPMN (Organisation for Economic Co-operation and Development, Working Party on Manufactured Nanomaterials) sponsorship programme. The National Physical Laboratory (NPL) core activity relates to the physicochemical testing of manufactured CeO2 and ZnO nanomaterials. This is in support of the ecotoxicological investigations to study their potential risk in the damage of the aquatic environment, which will be commented in Chapter 1. The output of the core activity is reported in the main body of the report (Chapter 2), which consists of a summary of test results of the nanopowders; as received, when dispersed in one of four ecotox liquid media and when aerosolised. For the purposes of synchronisation and harmonisation, this data is also reported in the NAPIRA hub (www.nanohub.eu), a central European database. In acquiring the core data, trends were observed between the measured particle size and other parameters, such as; specific surface area, dispersion stability and dissolution kinetics. The ability to make such correlations is important as this means that the number of physicochemical parameters required for testing can be reduced in the future. However, without further evidence (namely. correlation with other data generated within the consortium and the ability to analyse the large amount of data objectively) it is difficult to deduce the most relevant physicochemical properties to complement the toxicity assessment.

In addition to the core activity, NPL was also involved in tackling various measurement issues (as detailed in the appendix) in :
a) understanding potential sources of variability in measurements, which can come by: not following a standard protocol, treating the measurement tool as a black box and thus not understanding their inherent limitations.
b) conducting homogeneity testing of samples (as organised by the Joint Research Centre (JRC); samples received have been subsampled using a spinning riffler by JRC. NPL's role was for the provision of data towards the assessment of the powders by JRC, for potential reference material development.
c) developing appropriate new technologies, which is necessary to improve future data reliability. New technological platforms under investigation to include: the use of an ozone based cleaning unit in order to remove background (to improve selectivity), Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS) as a potential tool to measure surface chemistry and subsequently perform depth profiles of adsorbents on the surface of nanomaterials, development of charge particle counter technology, protocols for the characterisation of the photocatalytic properties of nanomaterials and a microfluidic based technique for potential high throughput screening methods for the determination of solubility/ dissolution.. The ozone based cleaning unit involved the building and testing of the prototype, which was shown to be not fit for purpose. The latter four technologies are still under development stage.

Lastly, we have identified the knowledge gap:
a) need for better measurement tools
b) lack of suitable reference materials for testing
c) lack of experimental investigations that will have a direct impact on risk assessment.

If such issues are not dealt with, then questions surrounding nanotoxicity will forever remain inconclusive.

Item Type: Report/Guide (NPL Report)
NPL Report No.: AS 68
Subjects: Nanoscience
Nanoscience > Surface and Nanoanalysis
Last Modified: 02 Feb 2018 13:14
URI: http://eprintspublications.npl.co.uk/id/eprint/5442

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