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Aging of TiO2 nanocomposites used in sunscreen. Dispersion and fate of the degradation products in aqueous environment |
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| Authors: | Jé rô me Labille,Jinghuan Feng,Daniel Borschneck,Magali Sammut,Mé lanie Auffan,Jé rô me Rose,Jean-Yves Bottero |
| Affiliation: | a CEREGE UMR 6635 CNRS/Aix-Marseille Université, Europôle de l'Arbois, 13545 Aix-en-Provence, France b International Consortium for the Environmental Implications of Nanotechnology iCEINT, Europole de l'Arbois, 13545 Aix en Provence, France c CP2M, Université d'Aix Marseille, Case 221, 13397 Marseille cedex 20, France |
| Abstract: | Aging in water of a TiO2-based nanocomposite used in sunscreen cosmetics has been studied as a function of light and time. It consisted initially in a TiO2 core, coated with Al(OH)3 and polydimethylsiloxane (PDMS) layers. Size measurement, coating alteration, and surface charge were followed by laser diffraction, TEM/EDS, ICP-AES and electrophoretic mobility measurement.The nanocomposite rapidly underwent progressive dispersion in the aqueous phase, enabled by the dissolution of the PDMS layer. A stable suspension of colloidal byproducts from 50 to 700 nm in size was formed. Their positively charged Al(OH)3 surface was evidenced with an isoelectric point around 7-8, controlling the dispersion stability. The critical coagulation concentrations measured with NaCl and CaCl2 was 2 × 10−2 and 8 × 10−3 M respectively. The presence of natural organic matter affected the colloidal stability according to the NOM/byproduct ratio. A 2 wt% ratio favored bridging flocculation, whereas a 20 wt% ratio induced sterical stabilization. |
| Keywords: | Nanoparticle Titanium dioxide Alteration Lifecycle Dispersion Aggregation Natural organic matter |
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