Fabrication of ice-templated macroporous TiO2-chitosan scaffolds for photocatalytic applications

Higher-ordered 3D macroporous TiO2-functionalized chitosan scaffolds were prepared by ice segregation induced self-assembly (ISISA), in which homogenous dispersions of 6, 27 or 200 nm sized TiO2 nanoparticles and chitosan cross-linked with glycidoxypropyltrimethoxysilane were unidirectionally frozen at -196 degrees C. Scanning electron microscopy showed that under established optimum conditions the monoliths comprised well-aligned 30-50 mu m sized micro-channels running parallel to the direction of ice growth. The surface morphology of the internal wall structure was influenced by the size of the titania nanoparticles. Scaffolds prepared in the presence of 6 nm sized anatase particles showed featureless walls with concealed/embedded nanoparticles, whereas larger TiO2 particles remained exposed at the surface of the channel walls. Mechanical properties of the composite scaffolds were studied under compressive loads and stress-strain measurements obtained, and the effect of particle size on the elastic properties of the macroporous constructs determined. The hybrid scaffolds were shown to be reusable substrates for the photocatalytic degradation of methylene blue and Orange II dye molecules.