Adsorption of Hydrophilic Silica Nanoparticles at Oil–Water Interfaces with Reversible Emulsion Stabilization by Ion Partitioning
Adsorption of Hydrophilic Silica Nanoparticles at Oil–Water Interfaces with Reversible Emulsion Stabilization by Ion Partitioning
复制标题
亲水性二氧化硅纳米颗粒在油水界面的吸附以及通过离子分配实现可逆乳液稳定
DOI：
10.1021/acs.langmuir.1c02919
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发表时间：
2022
期刊：
影响因子：
3.9
通讯作者：
Dinsmore, Anthony D.
中科院分区：
文献类型：
--
作者：
Keane, Robert K.;Hong, Wei;He, Wei;Teale, Sam;Bancroft, Robbie;Dinsmore, Anthony D.
颗粒在油-水界面处的吸附是皮克林乳液的基础，其在自然界和工业中是常见的。对于亲水性阴离子颗粒，静电排斥和润湿的缺乏抑制自发吸附并限制可用于乳液基应用的材料的范围。在这里，我们探讨如何添加离子，选择性地分配在两个流体相改变界面电位，并驱动颗粒吸附。我们将油溶性四丁基高氯酸铵（TBAP）添加到非极性相中，并将Ludox二氧化硅纳米颗粒或二氧化硅微粒添加到水相中。我们发现了一个明确的阈值TBAP浓度，高于该浓度乳剂可稳定数月。该阈值随着颗粒浓度和油的介电常数而增加。向水中加入NaClO 4盐会增加阈值，即使没有搅拌也会导致自发的颗粒解吸和液滴聚结。结果解释了基于泊松-玻尔兹曼理论的模型，该模型预测高氯酸根阴离子（ClO 4-）迁移到水相，并在油中留下净正电荷。我们的研究结果表明，一个大类的无机亲水性，阴离子纳米粒子可以用来稳定乳液在一个可逆的和刺激响应的方式，没有表面改性。
Adsorption of particles at oil–water interfaces is the basis of Pickering emulsions, which are common in nature and industry. For hydrophilic anionic particles, electrostatic repulsion and the absence of wetting inhibit spontaneous adsorption and limit the scope of materials that can be used in emulsion-based applications. Here, we explore how adding ions that selectively partition in the two fluid phases changes the interfacial electric potential and drives particle adsorption. We add oil-soluble tetrabutyl ammonium perchlorate (TBAP) to the nonpolar phase and Ludox silica nanoparticles or silica microparticles to the aqueous phase. We find a well-defined threshold TBAP concentration, above which emulsions are stable for months. This threshold increases with the particle concentration and with the oil’s dielectric constant. Adding NaClO4salt to water increases the threshold and causes spontaneous particle desorption and droplet coalescence even without agitation. The results are explained by a model based on the Poisson–Boltzmann theory, which predicts that the perchlorate anions (ClO4–) migrate into the water phase and leave behind a net positive charge in the oil. Our results show how a large class of inorganic hydrophilic, anionic nanoparticles can be used to stabilize emulsions in a reversible and stimulus-responsive way, without surface modifications.