Riedl J C, Akhavan Kazemi M A, Cousin F, Dubois E, Fantini S, Loïs S, Perzynski R, Peyre V
Sorbonne Université, Laboratoire PHENIX 4 place Jussieu, case 51 75005 Paris France
Laboratoire Léon Brillouin, UMR 12, CNRS-CEA, CEA-Saclay 91191 Gif-sur-Yvette France.
Nanoscale Adv. 2020 Jan 20;2(4):1560-1572. doi: 10.1039/c9na00564a. eCollection 2020 Apr 15.
The combination of ionic liquid and nanoparticle properties is highly appealing for a number of applications. However, thus far there has been limited systematic exploration of colloidal stabilisation in these solvents, which provides an initial direction towards their employment. Here, we present a new and comprehensive study of the key parameters affecting the colloidal stability in dispersions of oxide nanoparticles in ionic liquids. Twelve diverse and representative ionic liquids are used to disperse iron oxide nanoparticles. The liquid interface of these nanoparticles has been carefully tuned in a molecular solvent before transferring into an ionic liquid, without passing through the powder state. Multiscale-characterisation is applied, on both the micro and the nano scale, incorporating both small angle X-ray scattering and dynamic light scattering. The results show the surface charge of the nanoparticles to be a crucial parameter, controlling the layering of the surrounding ionic liquid, and hence producing repulsion allowing efficient counterbalancing of the attractive interactions. For intermediate charges the strength of the repulsion depends on the specific system causing varying levels of aggregation or even none at all. Several samples consist of sufficiently repulsive systems leading to single dispersed nanoparticles, stable in the long term. Thanks to the magnetic properties of the chosen iron oxide nanoparticles, true ferrofluids are produced, appropriate for applications using magnetic fields. The strength and breadth of the observed trends suggests that the key parameters identified here can be generalised to most ionic liquids.
离子液体和纳米颗粒特性的结合在许多应用中极具吸引力。然而，到目前为止，在这些溶剂中的胶体稳定性方面的系统探索还很有限，这为它们的应用提供了一个初步方向。在此，我们对影响氧化物纳米颗粒在离子液体中分散体胶体稳定性的关键参数进行了一项全新且全面的研究。使用了十二种不同且具有代表性的离子液体来分散氧化铁纳米颗粒。这些纳米颗粒的液体界面在转移到离子液体之前，已在分子溶剂中进行了精细调整，而无需经过粉末状态。采用了多尺度表征方法，涵盖微观和纳米尺度，包括小角X射线散射和动态光散射。结果表明，纳米颗粒的表面电荷是一个关键参数，它控制着周围离子液体的分层，从而产生排斥力，有效平衡吸引力。对于中等电荷，排斥力的强度取决于特定系统，导致不同程度的聚集甚至根本不聚集。几个样品组成了具有足够排斥力的系统，导致单分散纳米颗粒，长期稳定。由于所选氧化铁纳米颗粒的磁性，制备出了真正的铁磁流体，适用于使用磁场的应用。观察到的趋势的强度和广度表明，这里确定的关键参数可以推广到大多数离子液体。
