Radiolabelling of silver and titania nanoparticles as a tool for sensitive detection of nanoparticle release from surface coatings

Engineered nanoparticles (NPs) such as silver and titania are widely used in consumer products e.g. as functional additives in surface coatings. Due to aging or abrasion of these nanocomposites, particle release becomes likely and further transport e.g. in environmental systems could be assumed. For conventional nanocomposites, accurate and sensitive detection and quantification of NP release is still a challenge due to the fact that released fractions might be small but nevertheless significant. The application of radiotracers provides the excellent option of “visibility”, traceability and quantification of NPs in complex media. Therefore, different radiolabelling strategies for engineered nanopowders (TiO₂ P 25, Evonic Industries, dp = 21 nm; Ag⁰, Sigma Aldrich, dp < 100 nm) were established using a diffusive introduction of ^110mAg radionuclides (t_1/2 = 250 d) into Ag⁰-NPs (Hildebrand & Franke, 2012) and ⁴⁴Ti radionuclides (t_1/2 = 63 a) into TiO₂-NPs through a low-temperature annealing procedure. Another radiolabelling strategy is the direct activation of Ag⁰ and TiO₂ nanopowders that was done via proton irradiation using a Scanditronix MC40 cyclotron (Abbas et al. 2010, Holzwarth et al. 2012).
Both methods were tested with respect to radiolabelling yield, achievable activity concentration, pH-dependent stability of the radiolabelling and the influence on NP properties. Results obtained show an appropriate selection of radiolabelling methods suitable for different experimental conditions for NP release studies.

Abbas K, Cydzik I, Del Torchio R, Farina M, Forti E, Gibson N, Holzwarth U, Simonelli F, Kreyling W (2010) J Nanopart Res 12:2435–2443.
Holzwarth U, Bulgheroni A, Gibson N, Kozempel J, Cotogno G, Abbas K, Simonelli F, Cydzik I (2012) J Nanopart Res 14:880.
Hildebrand H and Franke K (2012) J Nanopart Res 14:1142.