Biocatalytic synthesis of a nanostructured and crystalline bimetallic perovskite-like barium oxofluorotitanate at low temperature

Silicatein, an enzymatic biocatalyst from the marine sponge Tethya aurantia, is demonstrated to catalyze and template the hydrolysis/condensation of the molecular precursor BaTiF(6) at low temperature to form nanocrystalline BaTiOF(4), an orthorhombic oxofluorotitanate. The kinetics of hydrolysis and growth were studied in-situ via pH profiling and quartz crystal microbalance (QCM) techniques. The composition and structure of the resulting BaTiOF(4) microstructures on the silicatein surface were characterized using FT-IR spectroscopy, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction. The silicatein-mediated hydrolysis/condensation of BaTiF(6) generates nanocrystalline BaTiOF(4) (a high temperature intermediate to BaTiO(3)) at 16 degrees C without any added acid or base, and the growth is templated along the protein filaments into floret microstructures. The unique combination of silicatein and the single-source molecular precursor has allowed a multimetallic perovskite-like material to be biocatalytically synthesized, in vitro, for the first time.