Interfacial properties of silica-based materials in relation to their bioactivity studied through the adsorption of small (bio)molecules. Adsorption CH3OH

The adsorption of CH3OH at 303 K on a commercial sol-gel bioactive glass and on very simple model systems (either purely siliceous or prepared by introducing at the surface a controlled amount of calcium) has been studied in order to investigate the role of Ca species on the surface reactivity of bioactive glass 58S and of a Ca-doped silica (ACa8). The presence of calcium species has been found to induce a marked reactivity at the silica surface. The interaction of methanol is not fully vacuum reversible (neither at RT or at 423 K) on both calcium-containing systems (58S and ACa8), whereas it is almost completely reversible in the case of the all-silica system. The onset of a methoxylation process, besides SiOH/CH3OH H-bonding that is the only interaction operative at a pure silica surface, is suggested in the case of calcium-containing surfaces.