While the reverse emulsion methods traditionally only give core–shell nanostructures, we show that Janus nanostructures could be readily obtained by introducing salt solutions. Given the isolated pockets of reverse emulsion, the salt solutions could reach extreme concentrations, up to 700 times higher than what is possible via the Stöber method. Both the increasing amount of the doped cations in the silica and the decreasing cationic radius would enhance the interactions with the negatively charged silica precursor, resulting in poorer “wetting” of the silica domain on the Fe₃O₄ nanoparticles. In other words, with increasing strength of the internal interactions, the growth domain would have a higher tendency to curl up and reduce its unfavorable interfaces, leading to poorer wetting. The tuning of the solid–solid wetting is of great significance for the design and synthesis of Janus nanoparticles, in particular their precise structural modulation. We believe that our new means of structural modulation beyond the interface itself would open new synthetic routes at the nanoscale.

中文翻译：

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通过内能调制在反相乳液中部分包封 Fe3O4 纳米颗粒

虽然传统上反乳液方法只给出核壳纳米结构，但我们表明，通过引入盐溶液可以很容易地获得 Janus 纳米结构。鉴于反向乳液的孤立口袋，盐溶液可能达到极端浓度，比通过 Stöber 方法可能达到的浓度高 700 倍。二氧化硅中掺杂阳离子量的增加和阳离子半径的减小都会增强与带负电的二氧化硅前体的相互作用，导致二氧化硅域在 Fe ₃ O ₄上的“润湿”较差纳米粒子。换句话说，随着内部相互作用强度的增加，生长域将有更高的卷曲趋势并减少其不利的界面，导致润湿性变差。固-固润湿的调节对于 Janus 纳米粒子的设计和合成具有重要意义，特别是它们的精确结构调制。我们相信，我们超越界面本身的结构调制新方法将在纳米尺度上开辟新的合成路线。