Silver doped silica-methyl hybrid coatings. Structural evolution and antibacterial properties

In this work, the effect of silver doping on the organic–inorganic hybrid structure of sol–gel coatings and its performance as bactericidal materials was analyzed. Coatings were synthesized through the hydrolytic condensation of tetraethoxysilane (TEOS) and methyl-triethoxysilane (MTES); silver nitrate was used as a source of Ag+ ions. The structural analysis, performed through Small Angle X-ray Scattering (SAXS) with synchrotron light, Fourier Transformed Infrared (FTIR) and UV–visible spectroscopies, revealed the complex scenario developed as the network crosslinking rises during the thermal treatment. The matrix structure works as a size-selective membrane where only the smaller silver clusters and ions are released to the surface while the higher nanoparticles remain trapped inside. Finally, bacteriologic analysis, performed with Escherichia coli cultures, confirmed a tight correlation between silver lixiviation and the inhibition halos observed in agar diffusion tests.