Silver nanoparticles (AgNPs) because of their strong biocide activity are widely used in health-care sector, food industry and various consumer products. As their use may involve risks and hazards, we have performed an assessment of the biocide properties of small (<20 nm) AgNPs embedded in silica layers. Two physical approaches were used to elaborate these nanocomposites : (i) low energy ion beam synthesis at CEMES and (ii) combined silver sputtering and plasma polymerization at LAPLACE laboratory in Toulouse. These techniques allow elaboration of a single layer of AgNPs embedded in silica films at defined nanometer distances (from 0 to 7 nm) beneath the free surface with complementary size and surface fraction. The silver release from the nanostructures after immersion in buffered water was measured by inductively coupled plasma mass spectrometry. For assessing the short-term toxicity of Ag we used an original method implying green algae, Chlamydomonas reinhardtii, as biosensors. Embedding AgNPs reduces their interactions with the buffered water, protecting the AgNPs from fast oxidation. The release of bio-available silver (impacting on the algal photosynthesis) is controlled by the depth at which AgNPs are located for the given host silica matrix. This provides a procedure to tailor the biocide effect of nanocomposites containing AgNPs and paves the way towards “safe by design” AgNPs based nanocomposites.
This work is performed in collaboration with LAPLACE Laboratory in Toulouse (Kremena Makasheva) and Instituto Pirenaico de Ecología of CSIC in Zaragoza (Enrique Navarro) in the framework of the PICS “TANGO” project (2015-2017).
- Fluorescence Yield of the algae dispersed into the solution in which the specimen with AgNPs has been embedded, as function of the released silver from the embedded AgNPs, for different samples fr which the distance between the AgNCs and the surface is tuned (cross-sectional TEM images). This yield is proportional to the number of algae with photosynthesis system active. Closer are the AgNCs to the surface larger is the biocide effect.
- © CEMES-CNRS
Contact : caroline.bonafos chez cemes.fr