“Figure/Ground” Study of Colloidal Silica Nanoparticles and Corresponding Microporous Xerogels

Abstract

A critical hurdle in the development of sol−gel techniques for the preparation of microporous inorganic materials is elucidating the effect of key synthesis and processing parameters on the structure of the resulting sols. Characterization of colloidal particles with diameters of less than approximately 10 nm is problematic using conventional techniques such as dynamic light scattering. Similarly, quantitative determination of pore size distribution in the resulting materials using gas adsorption isotherms is difficult in the microporous regime. The present work extends these traditional methods with the objective of obtaining information both on the particle size in an inorganic sol and on the pore size distribution in the resulting microporous xerogel. Silica sols synthesized at pH 3 and an H2O/TEOS ratio of r = 83 were shown by atomic force microscopy to have a distribution of particle diameters centered around approximately 4−6 nm. Nitrogen and molecular probe adsorption studies on xerogels derived fr...