Synthesis of layered tantalate nanocrystals by aqueous process at room temperature

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

“…Metalate nanosheets have been prepared via the fabrication of layered metalates with bulky organic cations, i.e., N­(CH 3 ) 4 + (tetramethylammonium ion; TMA + ) and N­(C 4 H 9 ) 4 + , as interlayer cations. − For such layered metalates, swelling and exfoliation occur when they are placed in aqueous solutions due to the intercalation of water molecules into the interlayer, thus yielding metalate nanosheets. We have been studying the bottom-up synthesis of metalate nanosheets by aqueous solution processing. − For our synthetic method, layered metalates with bulky organic cations are synthesized in aqueous sols by taking advantage of the acid–base reactions between protic metal oxides and hydroxides of bulky organic cations, such as N­(CH 3 ) 4 OH (TMAOH). For example, titanium isopropoxide Ti­[OCH­(CH 3 ) 2 ] 4 and TMAOH aqueous solution are mixed at room temperature, and then the mixture is diluted with water, resulting in the formation of transparent aqueous sols of flake-like titanate nanosheets. , The acid–base reaction between TMAOH and protic titanium oxide Ti­(OH) 4 that was formed by the hydrolysis of Ti­[OCH­(CH 3 ) 2 ] 4 , yields a layered tetramethylammonium titanate.…”

“…We have prepared metalate nanosheets with only one type of metal ion, i.e., titanate nanosheets. − Metalate nanosheets with layered perovskite-type structures are representative of those having more than two types of metal ions. , Li et al and Wang et al reported that layered perovskite-structured metalate nanosheets (Ca 2 Nb 3 O 10 – ) have superior dielectric properties over that of titanate nanosheets. Moreover, if metalate nanosheets with more than two types of metal ions are synthesized in aqueous sols by a bottom-up process, the number of metalate nanosheets that can be synthesized by our bottom-up method would increase significantly.…”

Temperature-controlled reversible exfoliation-stacking of titanate nanosheets in an aqueous solution containing tetraalkylammonium ions

“…8 Briefly, the liquid TTIP was added to an aqueous solution of tetraalkylammonium hydroxide (R4N + OH -, R = methyl (TMA + ), ethyl (TEA + ), propyl (TPA + ), or butyl (TBA + )), followed by heating with gentle shaking at 60 o C for 2 h. The obtained solutions (named as R4N + -TiOx hereafter) were colorless and transparent at room temperature independent of alkyl chain length of R4NOH. 9,10 In the present study, the molar ratio of R4N + to titanium was fixed to 1.4. Raman scattering measurement (Fig.…”

Bottom-up synthesis of titanophosphate nanosheets by the aqueous solution process

“…Alternatively, we have formed metalate nanosheets by a bottom-up synthesis in aqueous solution. [12][13][14][15][16][17][18] The chemical reactions in the sols form layered metalates with bulky cations in their interlayers. These layered metalates are exfoliated, yielding metalate nanosheets as highly water-dispersible colloidal particles, which can be applied as coating sols for thin lm fabrication by solution processes.…”