Hydrothermal synthesis and formation mechanism of the single-crystalline Bi4Ti3O12 nanosheets with dominant (010) facets

Abstract

Single-crystalline bismuth-layered perovskite Bi₄Ti₃O₁₂ nanosheets with a thickness of about 20 nm and a lateral size over several micrometers have been synthesized by a PVA assisted hydrothermal route. The as-prepared Bi₄Ti₃O₁₂ nanosheets were characterized by means of X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy (TEM) and high-resolution TEM. The as-prepared Bi₄Ti₃O₁₂ nanosheets have (010) dominated surface facets. Time-dependent experiments reveal that the layered K₂Ti₆O₁₃ nanofibers formed in the initial stage of the hydrothermal treatment play a key role in the synthesis of Bi₄Ti₃O₁₂. In the proceeding hydrothermal treatment, the Bi³⁺ ions substitute for the K⁺ ions in the layered K₂Ti₆O₁₃ and peel off the TiO₆ octahedron lamellae from the lattice of K₂Ti₆O₁₃, which then serves as a template for the formation of lamellar Bi₄Ti₃O₁₂ by reaction with the dehydrated Bi³⁺ ions. Finally, the lamellar Bi₄Ti₃O₁₂ species crystallize and grow to single-crystalline Bi₄Ti₃O₁₂ nanosheets under the effect of the preferential adsorption of PVA on the (010) planes. In addition, the band gap and the optoelectronic properties of the single-crystalline Bi₄Ti₃O₁₂ nanosheets were investigated by measuring their UV-vis absorption and photoluminescence spectra, respectively.