Hydrothermal Synthesis of Single-Crystalline Perovskite PbTiO_3 Nanosheets with Dominant (001) Facets

摘要

Single-crystalline tetragonal perovskite lead titanate (PbTiO_3) nanosheets with dominant (001) facets have been successfully synthesized by employing layered K_2Ti_6O_(13) nanofibers as titanium sources. The as-prepared PbTiO_3 nanosheets were characterized by means of X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, and selected-area electron diffraction. In order to understand the formation mechanism of the PbTiO_3 nanosheets, a series of time-dependent experiments were performed. Because of the substitution of Pb~(2+) ions for K~+ ions, the TiO_6 octahedral lamellas exfoliate from the layered K_2Ti_6O_(13) crystal structure. Then the exfoliated TiO_6 octahedral lamellas as templates transform to lamellar PbTiO_3 species by reacting with the dehydrated Pb~(2+) ions. With hydrothermal treatment prolongation, the lamellar PbTiO_3 species crystallize to single-crystalline PbTiO_3 nanosheets. Moreover, the thickness of the synthesized single-crystalline PbTiO_3 nanosheets can be tailored in the range of 10-50 nm by controlling the hydrothermal treatment time. In addition, the band gap and the optoelectronic properties of the single-crystalline PbTiO_3 nanosheets are investigated by UV-vis absorption and photoluminescence.