Silica xerogel–hydrogen peroxide composites: Their morphology, stability, and antimicrobial activity

Hydrogen peroxide was incorporated into silica xerogel matrix over the concentration range from 3.8 to 68.0 wt% via the sol–gel route. The obtained composites were characterized by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The release rates of H2O2 from the composites into the aqueous phase were examined. In most cases, a 90% release was attained after ca. 10 min, and it was only slightly dependent on H2O2 concentration and particle size. The antimicrobial activity of the composite containing 3.59% H2O2 was evaluated against Escherichia coli and Micrococcus luteus. A comparative assay was carried out for aqueous solution of H2O2 of the same concentration. The results demonstrated a potent microbicidal efficacy of the composite. Furthermore, diffusion range of the hydrogen peroxide from the solid composite into an agar medium matched that of the H2O2 in aqueous solution. The stability tests with the xerogels containing 3.8, 26.4, and 68.0% of H2O2 showed that after 63 days respective losses of the H2O2 at 3 °C were 8.8, 9.7, and 6.2%. Both the DSC results and the stability tests have shown that the molecular water present in the pores stabilizes the composite, probably through improving the binding of the H2O2 molecules onto the silica surface.