Dynamics of silver nanoparticles at the solution/biofilm/mineral interface

International audienceThe extensive use of silver nanoparticles (AgNPs) is likely to result in their significant environmental release, and thus raises important concerns regarding their impact to ecosystems. In soils, bacterial biofilms can be found as mineral coatings, forming a complex interface that exhibits highly specific physico-chemical properties. As a result, this environmental compartment is likely to partly control the AgNPs fate. However, the interaction modes undergone by nanoparticles at this solution/biofilm/mineral are not yet well constrained. The dynamics of AgNPs interactions at a Shewanella oneidensis MR-1 biofilm-corundum (α-Al2O3) interface were investigated by Long Period-X-Ray Standing Waves-Fluorescence Yield Spectroscopy. Three different nanoparticle coatings of various properties (PVP, SiO2 and SiO2-NH2) were tested, showing important differences in AgNPs partitioning and stability at this complex interface. The behavior of the two AgNPs coated by an organic layer, but of opposite charge (SiO2 and SiO2-NH2), indicates that at first-order, electrostatic interactions control the AgNPs partitioning at the solution/biofilm/mineral interface. In addition, the comparative study of the organic PVP-coated and the inorganic SiO2-coated AgNPs, both negatively charged, highlights the controls imposed by the nanoparticles size and hydrophobic properties on their interactions with this complex interface