Hydrothermal Synthesis of Layered Perovskite-Structured Metal Oxides and Cesium Tungstate Nanosheets

Abstract

The synthesis of layered metalates consisting of metalate layers with two types of metal ions and interlayer organic cations via an aqueous solution process was studied for the preparation of metalate nanosheets. First, layered perovskite Cs[Sr2Nb3O10] was synthesized hydrothermally and featured Cs+ ions, but not organic cations, as interlayer cations; the formation of a strontium niobate layer required a high hydrothermal temperature (≥150 °C). Next, bulky organic interlayer cations N(CH3)4+ and C16H33N(CH3)3+ were used. However, bulky cations inhibited the formation of layered compounds at high temperature due to their thermal vibration. Then, layered cesium tungstates were hydrothermally synthesized using alkylamines at a temperature ≥150 °C. Alkylamines NH2CnH2n+1 with a long alkyl chain n ≥ 10 provided a robust layered structure at ≥150 °C, yielding layered cesium tungstates with interlayer organic cations. Upon dispersing the product in acetone solvent, cesium tungstate nanosheets [Cs4W11O36]2– were...