Sugaya Takeshi, Ozaki Masahiko, Guégan Régis, Idota Naokazu, Sugahara Yoshiyuki
Department of Chemical Science and Technology, Faculty of Bioscience and Applied Chemistry , Hosei University , 3-7-2 Kajino-cho , Koganei-shi, Tokyo 184-8584 , Japan.
Kagami Memorial Research Institute for Materials Science and Technology , Waseda University , 2-8-26 Nishiwaseda , Shinjuku-ku, Tokyo 169-0051 , Japan.
Langmuir. 2019 May 21;35(20):6594-6601. doi: 10.1021/acs.langmuir.8b03923. Epub 2019 Apr 22.
Oleyl phosphate-modified HLaNbO· xHO nanosheets (OP_HLaNb nanosheets) were prepared via phase transfer from an aqueous phase, comprising a dispersion of HLaNbO· xHO (HLaNb) nanosheets, formed through the intercalation of tetrabutylammonium ion (TBA) in the interlayer space of HLaNb and subsequent delamination, to a cyclohexane phase containing oleyl phosphate (OP, a mixture of monoester and diester). The modification of HLaNb nanosheets with OP was essentially completed within 3 days at a pH value of 2 or 4. Both infrared and solid-state C cross-polarization and magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of the OP_HLaNb nanosheets showed the presence of OP and/or related species and TBA on the HLaNb nanosheet surface. The solid-state P MAS NMR spectra of OP_HLaNb nanosheets exhibited new signals at -2 and 0 ppm, the former of which indicates the formation of Nb-O-P bonds. These whole data set obtained by complementary techniques clearly point out the modification of the HLaNb nanosheet surface by OP moieties causing a phase transfer. OP_HLaNb nanosheets showed higher dispersibility in cyclohexane than the OP_HLaNb_interlayer nanosheets, which were prepared via stepwise substitution reactions in the interlayers of HLaNb to achieve surface modification with OP and subsequent exfoliation in cyclohexane. The presence of TBA on the HLaNb nanosheets and the use of a liquid-liquid biphasic system were likely to improve the dispersibility. These results show that the preparation of OP-modified HLaNb nanosheets which could be well-dispersed in the cyclohexane phase was successful because of the use of a liquid-liquid biphasic system.
油磷酸酯修饰的HLaNbO·xH₂O纳米片（OP_HLaNb纳米片）是通过从水相进行相转移制备的。水相中包含通过四丁基铵离子（TBA）插入HLaNb的层间空间并随后剥离形成的HLaNbO·xH₂O（HLaNb）纳米片分散体，将其转移至含有油磷酸酯（OP，单酯和二酯的混合物）的环己烷相。在pH值为2或4时，OP对HLaNb纳米片的修饰在3天内基本完成。OP_HLaNb纳米片的红外光谱以及固态¹³C交叉极化和魔角旋转（MAS）核磁共振（NMR）光谱均表明HLaNb纳米片表面存在OP和/或相关物种以及TBA。OP_HLaNb纳米片的固态³¹P MAS NMR光谱在-2和0 ppm处出现新信号，前者表明形成了Nb - O - P键。通过互补技术获得的这些完整数据集清楚地表明，OP部分对HLaNb纳米片表面的修饰导致了相转移。与通过在HLaNb层间进行逐步取代反应以实现用OP进行表面修饰并随后在环己烷中剥离制备的OP_HLaNb层间纳米片相比，OP_HLaNb纳米片在环己烷中表现出更高的分散性。HLaNb纳米片上TBA的存在以及液 - 液双相体系的使用可能提高了分散性。这些结果表明，由于使用了液 - 液双相体系，成功制备了可在环己烷相中良好分散的OP修饰的HLaNb纳米片。
