Soft-chemical exfoliation of RbSrNb_2O_6F into homogeneously unilamellar oxyfluoride nanosheets

摘要

Interlayer Rb~+ of the perovskite-type layered oxyfluoride RbSrNb_2O_6F was ion-exchanged with H~+, and the protonated phase was reacted with aqueous solution of tetrabutylammonium hydroxide to exfoliate it into nanosheets. The resulting nanosheet suspension exhibits Tyndall scattering of a laser beam, indicating its colloidal nature. Elemental composition of the nanosheet was estimated as Sr_(0.98)Nb _2O_6F_(0.97) ~(δ-), which was quite close to that of the layer unit of the precursor. The homogeneously unilamellar nature of this nanosheet was confirmed by atomic force and transmission electron microscopy observations and X-ray scattering results. The optical absorption edge of the nanosheet suspension was observed around at 293 nm, and two well-defined peaks with their maxima at 229 and 278 nm were observed. Furthermore, the aqueous suspension of the nanosheet exhibits fluorescence emission in the UV-blue region. These properties of the oxyfluoride nanosheets are quite different from those of its oxide analogues without F~-, such as LnNb_2O_7 ~- nanosheets (Ln = La ~(3+), Eu~(3+), Sm~(3+)), suggesting that anion-site replacement of oxide nanosheets can be utilized to optimize or induce various properties.