Centre d’Élaboration de Matériaux et d’Etudes Structurales (UPR 8011)


Accueil > Recherche > Opérations Transverses > Thématiques

Unraveling the atomistic mechanisms of Ag+ release through a silica matrix for controlled anti-bacterial properties

 

Coordinators : M. Benoit (SINanO) et C. Bonafos (NeO)

Participants :
N. Tarrat (SINanO) et A. Mlayah (NeO)

 

Objectives

Silver nanoparticles (AgNPs) are widely used in health-care sector and industrial applications because of their outstanding antibacterial activity. In previous works carried out by the NeO team of CEMES, the toxic effect of small AgNPs (size < 20 nm) embedded in silica layers on algae photosynthesis has been demonstrated. This toxic effect is due to the release of Ag+ ions in the aqueous medium, which was shown to be highly dependent (i) on the distance at which the AgNPs are embedded beneath the silica free surface and (ii) on the structural properties of the silica matrix. Another turn should now be taken to allow a rational optimization of these promising nanocomposites with a “safe-by-design approach”. Indeed, to finely tune the Ag+ release rate by these nanocomposites, it is necessary to know the key factors controlling the ion diffusion inside the silica matrix. At the present time, these elementary mechanisms remain unknown. By modelling, at the DFT level of theory, the SiO2/Ag interface for different hydration rates and the diffusion of the chemical species involved in the Ag+ release processes, we intend to determine the elementary mechanisms of the diffusion through the silica matrix, i.e. the factors limiting or promoting these mechanisms, allowing a rational design of improved nanocomposites. In parallel, an experimental study of the AgNPs/SiO2 interface (bonding, faceting) will be held by HREM, STEM-EDX, STEM-EELS, XPS and FTIR on samples before and after water immersion. The effect of the silica cover layer porosity on Ag+ release will be probed by ICP-MS and the associated defects will be evidenced by ESR.

PNG - 167.7 ko

 

Planning (2017-2018)

Theory :

  • Study of the AgNPs/ SiO2 interface : interface preparation by classical molecular dynamics + interface refinement by DFT
  • Chemical species diffusion (H2O, OH-, H3O+, Ag+) through the silica matrix as a function of the hydration percentage by ab initio molecular dynamics

Experiments :

  • Study of the AgNPs/ SiO2 interface (bonding, faceting) by HREM, STEM-EDX, STEM-EELS, XPS and FTIR.
  • Study of the silica cover layer porosity on Ag+ release by ICP-MS
  • Characterization of defects in silica by ESR
  • TERS measurements

 

Involved platforms

  • Atom-tech and process (ion implantation),
  • Characterization (preparation, TEM, optics),
  • Engineering,
  • Common services (informatics),
  • Calculation centre CALMIP.

 

Financial supports

  • Projet interdisciplinaire du CNRS 2016-2017, Défi « InFIniTI » (MIRAGE)
  • PICS TANGO (CEMES/IPE –CSIC Zaragoza) 2015-2017.