Diffusivity control in nanoporous membrane through organic-inorganic hybridization

Nanoporous inorganic materials have attracted great interest due to their potential application as nanofilters, drug delivery carriers and adsorbents. In order to control the molecular passage through nanopores, we have modified the pore channel of inorganic materials with organic moieties and investigated the diffusion pattern of small molecules. The surface was modified by octyltriethoxysilane (OTS) by refluxing in toluene for 12 h. The water contact angle of OTS modified zirconia membrane was observed ∼110° showing hydrophobic surface. Contact angles to various solvents were also examined to verify the self-assembled monolayer of octyl chains on the inorganic membrane. The molecular passage patterns of both pristine and modified nanoporous membrane were evaluated by means of the diffusivity of small dye molecule, azobenzene. The diffusion coefficients of azobenzene on both membranes were measured in various solvents on the basis of Fick's diffusion law. The diffusivities in various solvents for pristine and its modified zirconia membrane were determined. The diffusivity was observed to be influenced by surface energy of both membrane and solvent as well as the polarity of solvents.