Structure of silver-containing sol-gel hybrid materials and its performance as biocide coatings

Full text: Development of thin biocide coatings is acquiring higher meaning since it brings the possibility to functionalize surfaces exposed to biologic contamination and, therefore, to inhibit the spreading of contagious infections provoked by different microorganisms. In this work, hybrid organic-inorganic sol-gel materials were functionalized with silver ions in order to analyze the relationship between the hybrid structures, silver ion stability and biocide effect as a function of the organic component and densifying thermal treatments. Hybrid silica-methyl and silica-epoxy coatings were synthesized, through the sol-gel method, by hydrolytic condensation of tetraethoxysilane (TEOS), methyl-trimethoxysilane (MTES) and glycidoxypropyltrimethoxysilane (GPTMS) under acidic conditions. Silver ions were added in the sol stage by a silver nitrate solution. Stable and colorless sols were obtained. Through dip-coating at a constant withdrawal rate, homogeneous and cracks-free coatings were obtained and thermally treated at 50, 100, 150 and 200 ◦C in air and oxygen atmospheres. Hybrid structures and thermal evolution of silver nanoparticles were analyzed by Small Angle X-ray Scattering (SAXS) at the SAXS1 beamline of LNLS. A spinodal-like phase separation was resolved in each one of the hybrid matrixes. Analysis of SAXS curves were compared with results from Fourier Transformed Infrared Spectroscopy (FTIR), UV-visible spectroscopy and Transmission Electron Microscopy (TEM). Biocide effect was evaluated, against Escherichia coli, through the inhibition halo in agar diffusion tests. (author)