Deposition of Bioactive Titania Layers on Non-Metallic Substrates under Ambient Conditions due to Hydrolysis of Titanium Oxysulfate Solution

Abstract

Titania layer is deposited on polyethylene substrates when they are soaked in TiOSO4/H2O2 solution and aged in hot water. The aging in hot water promoted the precipitation of anatase and rutile in the surface layer, indicating that cleavage and recombination of the Ti-O-Ti bond took place. The Ti-OH functional groups were rearranged and emerged accompanying the structure relaxation in the layer. Moreover, the aging in hot water enhanced crystalline of titania and then obtained well apatite-forming ability on the polyethylene substrates in SBF. This was accounted for by the removal of residual impurities due to TiOSO4/H2O2 treatment. They had an anatase/rutile dual layer microstructure: the dense bottom layer predominantly consisted of rutile, while the upper layer consisted of loosely packed aggregation of anatase particles. The titania deposition was the results of compromise among two conflicting processes: 1) hydrolysis of titanium oxysulfate to yield either soluble titanol-complexes or titania, 2) dissolution of the titania under the presence of hydrogen peroxide to yield similar complexes or compounds. Various soaking periods were carried out to investigate the dissolution-deposition equilibrium in the solution. Anatase/rutile dual layers were thus deposited on titanium and polyethylene substrates when they were soaked in TiOSO4/H2O2 solution and aged in hot water. The proper soaking time in the treating solution is the other key factors to control the formation of dense titania layers. The resulted titania layers have apatite-forming ability.