Controlling the interface between TiO₂ nanocrystals and ionic liquids is of high fundamental and applied interest for energy storage and conversion devices. Phase transfer of nanoparticles from a synthesis medium to a processing or an application medium plays a significant role in nanotechnology. Here we demonstrate that surface modification with phosphonic acids bearing cationic end-groups can trigger the phase transfer of TiO₂ nanoparticles from an aqueous sol to a typical water-immiscible ionic liquid, [Emim][NTf₂]. The transfer involves both the grafting of the phosphonic acid moiety and the exchange of the counter ion of the cationic end-group by NTf₂ anions, as demonstrated by solid-state NMR, elemental analysis and independent grafting and ion exchange experiments. Furthermore, the colloidal stability of the TiO₂ sols in [Emim][NTf₂] strongly depends on the hydrophobic character of the cationic end-groups.

中文翻译：

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膦酸接枝引发TiO ₂纳米粒子从水到离子液体的相转移

控制TiO ₂纳米晶体和离子液体之间的界面对于能量存储和转换装置具有重要的基础和应用意义。纳米颗粒从合成介质到加工或应用介质的相转移在纳米技术中起着重要作用。在这里，我们证明用带有阳离子端基的膦酸进行的表面改性可以触发TiO ₂纳米粒子从水性溶胶到典型的与水不混溶的离子液体[Emim] [NTf ₂ ]的相转移。转移既涉及膦酸部分的接枝，也包括NTf ₂对阳离子端基抗衡离子的交换。固态NMR，元素分析以及独立的接枝和离子交换实验所证实的阴离子。此外，[Emim] [NTf ₂ ]中TiO ₂溶胶的胶体稳定性强烈取决于阳离子端基的疏水性。