The immobilization of titania nanoparticles on hyaluronan films and their photocatalyticproperties

Abstract

We have developed a method to bind titania nanoparticles onto hyaluronic films (HA)photoimmobilized on silanized glass. Titania nanoparticles were deposited on the HAfilms from commercially available dispersions by casting and dip-coating methodsat various pH values. XPS was used to monitor the deposition of titania andto estimate the surface coverage of the nanoparticles. The topography of thetitania-modified HA films was investigated by means of AFM. XPS results indicatethat the titania surface coverage depends on the preparation method and thepH of the dispersion. We found that the maximum titania nanoparticle surfacecoverage was obtained by the casting method with the formation of aggregates andmultilayers of particles. The titania surface coverage for the surfaces prepared bythe dip-coating method is pH-dependent. The surfaces prepared at pH 2 show asurface coverage of 65% and a rather uniform distribution of particles. We foundthat titania nanoparticles are anchored in a stable way to the HA substrate in aphosphate buffer solution (PBS) and that the interaction between the HA andthe titania is through the carbonyl group of carboxylates and amidic groups ofthe polymer. AFM images clearly show that titania nanoparticles are uniformlydistributed over the HA films. By measuring the average diameter and the averageheight of the nanoparticles deposited on HA films it appears that the particles arepartially embedded in the polysaccharide films. The results of the study on thephotobleaching of methylene blue indicate that the characteristic photocatalytic activity oftitania is maintained when the nanoparticles are anchored to the HA substrate.