Joshi Chakra P, Bigioni Terry P
Department of Chemistry, The University of Toledo , Toledo, Ohio 43606, United States.
Langmuir. 2014 Nov 25;30(46):13837-43. doi: 10.1021/la503574s. Epub 2014 Nov 11.
Ionic surfactants are widely used for the phase transfer of nanoparticles from aqueous to organic phases; however, a model that can be used to select ionic surfactants based on the nanoparticle solution properties has yet to be established. Here, we have studied the phase transfer of a variety of nanoparticles and have identified hydrophobicity, steric repulsion, and interfacial tension as key factors in determining whether or not phase transfer will occur. Based on these studies, we have developed a simple model for phase transfer wherein the success of the surfactant depends only on three criteria. The phase transfer agents must (i) efficiently load onto or cross the interface, (ii) solubilize the nanoparticles in the receiving phase, and (iii) sterically stabilize the nanoparticles to prevent aggregation due to van der Waals forces between the inorganic cores. Using these criteria, the effectiveness of ionic surfactants could be predicted based on their molecular geometry and the properties of the nanoparticle solutions. These rules provide a basis for choosing surfactants for phase transfer of spherical nanoparticles up to 16 nm in diameter and advances the development of a general model of nanoparticle phase transfer, which would include all nanoparticle shapes, sizes, and solvents.
离子型表面活性剂被广泛用于纳米颗粒从水相到有机相的相转移；然而，一个可用于根据纳米颗粒溶液性质选择离子型表面活性剂的模型尚未建立。在此，我们研究了多种纳米颗粒的相转移，并确定了疏水性、空间排斥力和界面张力是决定相转移是否会发生的关键因素。基于这些研究，我们开发了一个简单的相转移模型，其中表面活性剂的成功仅取决于三个标准。相转移剂必须（i）有效地负载到界面上或穿过界面，（ii）在接收相中溶解纳米颗粒，以及（iii）在空间上稳定纳米颗粒以防止由于无机核之间的范德华力而导致聚集。使用这些标准，可以根据离子型表面活性剂的分子几何形状和纳米颗粒溶液的性质来预测其有效性。这些规则为选择用于直径达16 nm的球形纳米颗粒相转移的表面活性剂提供了基础，并推动了包括所有纳米颗粒形状、尺寸和溶剂的纳米颗粒相转移通用模型的发展。
