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 °C. Scanning electron microscopy showed that under established optimum conditions the monoliths comprised well-aligned 30–50 µm 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.