CaTiO3 nanobricks prepared from anodized TiO2 nanotubes

Bioactive CaTiO3 nanobricks were synthesized using a two-step anodization–hydrothermal treatment. TiO2 nanotubes (TNTs) on the Ti substrate surface were first prepared by anodization in a glycerol electrolyte with 0.5% NH4F. Two percent H2O in the electrolyte was required to obtain highly ordered TNTs; the regularity of TNTs was indispensible for further formation of CaTiO3 nanostructures. The TNTs were then hydrothermally treated in saturated Ca(OH)2 solution at 150 °C for 12 h. The TNTs were transformed to crystalline CaTiO3 nanobricks of width 45–75 nm and length 125–275 nm. A transformation mechanism was proposed based on a combination of dissolution–precipitation and Ostwald ripening. The bioactivity of the CaTiO3 nanobricks was evaluated using simulated body fluid immersion tests. A hydroxyapatite layer with high coverage was formed within 7 days, showing the potential for biomedical applications.

► The AHT process enables the nanotemplates-free synthesis of perovskite nanostructures.
► We found that anodized TiO2 nanotubes are better starting materials than other titanium-based oxide nanomaterials.
► Well-arranged CaTiO3 nanostructures were fabricated by AHT for the first time.
► Crystalline CaTiO3 nanobricks show excellent apatite-forming abilities.