Facile fabrication of hollow titania microparticles using wet yeast cells as templates

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Abstract Hollow titania microparticles were prepared using the bio-templating method with wet yeast cells as templates. Wet yeast cells were used to eliminate fixation or drying of as-cultured cells, and titania shells were formed on the cells via the sol–gel method with tetraisopropyl titanate (TTIP). When the citric acid was used to stabilize TTIP and catalyze TTIP hydrolysis, hollow titania microparticles with well-defined yeast cell morphologies were successfully synthesized. The diameter of the obtained particles was approximately 1.3 μm, and the crystal structure was anatase. The specific surface area and average pore diameter were 41.5 m2/g and 9.6 nm, respectively. Titania nanoparticles generated by homogeneous nucleation were rarely observed over a wide range of water concentrations, indicating that reaction on the biological cell surface, rather than monomer diffusion toward the surface, was rate-limiting. A significant advantage of our method is that the use of dry cultured cells is not required, in contrast to methods using powdered biological cell templates.