Zirconia nanoparticles may be produced by challenging the fungus Fusarium oxysporum with aqueous ZrF₆ ²⁻ anions; extra-cellular protein-mediated hydrolysis of the anionic complexes results in the facile room temperature synthesis of nanocrystalline zirconia. Extracellular hydrolysis of the metal anions by cationic proteins of molecular weight around 24 to 28 kDa, which are rather similar in nature to silicatein, is shown to be responsible for the synthesis of zirconia nanoparticles, opening up the exciting possibility of large-scale biological synthesis of technologically important oxide materials.

The synthesis of inorganic materials by biological systems is characterized by processes that occur at close to ambient temperatures, pressures and neutral pH. This is exemplified by biosilicification in marine organisms such as diatoms while laboratory-based synthesis of silica involves extreme temperature and pH conditions. We show here that silica and titania particles may be produced by challenging the fungus Fusarium oxysporum with aqueous anionic complexes SiF₆ ²⁻ and TiF₆ ²⁻ respectively. Extra-cellular protein-mediated hydrolysis of the anionic complexes results in the facile room temperature synthesis of crystalline titania particles while calcination at 300 °C is required for crystallization of silica.