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Diversity of TiO2 nanopowders’ characteristics relevant to toxicity testing

  • Saša Novak
  • Martina Lorenzetti
  • Anja Drame
  • Janja Vidmar
  • Janez Ščančar
  • Metka Filipič
Research Paper

Abstract

In this study, the physicochemical properties of several commercial ultrafine TiO2 powders and their behaviour in the as-received form and colloidal suspensions were analysed. Besides the particle size, the morphology and agglomeration state of the dry powders, dispersibility, ζ-potential and sedimentation in water and in phosphate-buffered saline (PBS) were studied. Also, leaching of ions from the powders during ageing in physiological solution and the ability of the photoactivated powders to decompose organic substances were evaluated. The examined TiO2 powders revealed diversified characteristics when dispersed in water. In general, while in dry conditions the particle size appeared in the nano-range (down to 32 nm), the particles were agglomerated in aqueous suspensions at pH ~7 and only a minor amount showed dimensions below 200 nm, but none below 100 nm. The inherent pH of the 3 % suspensions varies from 3.7 to 7.5 and the surface charge at these pH values varied from highly positive to highly negative values. In PBS, the surface charge is negative and relatively low for all the samples, which resulted in agglomeration. Five out of six powders exhibited significant photocatalytic activity when exposed to UV irradiation. This also includes one cosmetic-grade powder. Furthermore, during the immersion in aqueous media at physiological temperature, the powders released foreign ions, which might also contribute to the results of cytotoxicity tests. The results revealed the major role of the particle surface charge and its impact on particle dispersion or agglomeration. Due to the high ionic strength in the liquids relevant for cell-surface interaction tests, for all the examined titania powders the nanoparticulate character was lost. However, the presence of impurities and photocatalysis might further contribute to the results of cytotoxicity tests.

Keywords

Nanoparticles TiO2 Suspensions ζ-potential Solubility Photoactivation Environmental and health effects 

Notes

Acknowledgments

This work was financially supported by the Slovenian Research Agency within the programme Nanostructured Materials, No. P2-0084, and by the EU FP7 programme within ISO-FOOD ERA Chair (FP7-REGPOT, grant agreement no. 621329). The authors wish to thank Petra Jenuš for TEM observation of the powders.

Supplementary material

11051_2016_3437_MOESM1_ESM.docx (17 kb)
Supplementary material 1 (DOCX 17 kb)

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Copyright information

© Springer Science+Business Media Dordrecht 2016

Authors and Affiliations

  • Saša Novak
    • 1
    • 2
  • Martina Lorenzetti
    • 1
  • Anja Drame
    • 1
    • 2
  • Janja Vidmar
    • 2
    • 3
  • Janez Ščančar
    • 2
    • 3
  • Metka Filipič
    • 4
  1. 1.Department for Nanostructured MaterialsJožef Stefan InstituteLjubljanaSlovenia
  2. 2.Jožef Stefan International Postgraduate SchoolLjubljanaSlovenia
  3. 3.Department for Environmental ScienceJožef Stefan InstituteLjubljanaSlovenia
  4. 4.National Institute for BiologyLjubljanaSlovenia

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