Stoppers and Skins on Clay Nanotubes Help Stabilize Oil-in-Water Emulsions and Modulate the Release of Encapsulated Surfactants
Stoppers and Skins on Clay Nanotubes Help Stabilize Oil-in-Water Emulsions and Modulate the Release of Encapsulated Surfactants
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DOI：
10.1021/acsanm.9b00469
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发表时间：
2019-06-01
影响因子：
5.9
通讯作者：
Bose, Arijit
中科院分区：
文献类型：
--
作者：
Ojo, Olakunle Francis;Farinmade, Azeem;Bose, Arijit
这项工作开发了颗粒稳定乳液的概念，使用管状天然粘土（称为埃洛石）附着在油-水界面上并稳定水包油乳液。这种埃洛石纳米管（HNT）用作表面活性剂的储存器，并且可以将表面活性剂递送到油-水界面，从而降低油-水界面张力。表面活性剂输送和颗粒稳定液滴的两步概念对溢油补救具有重要意义。然而，为了在水基溶剂浆料中递送负载表面活性剂的HNT，重要的是阻塞纳米管以防止表面活性剂的过早释放。这项工作的重点是使用一个环境友好的二维金属有机框架形成的协调铁（III）与多酚作为加塞剂。这种金属-酚网络（MPN）在HNT周围形成皮肤，从而提供了有效地螯合表面活性剂货物以用于受控释放的方式。低温扫描电子显微镜（Cryo-SEM）显示，这些HNT和HNT束附着在油-水界面上的侧上取向。倒滴张力测定法用于表征从HNT释放模型表面活性剂（吐温80）所产生的动态界面张力，并表明MPN塞子在中性pH值下长时间有效螯合表面活性剂货物。MPN在酸性pH值下分解触发的释放可以在输送到溢油点之前进行。这一过程的概念和可扩展性对溢油补救、提高石油采收率以及生物医学和制药应用具有重要意义。
This work develops the concepts of particle-stabilized emulsions using tubular natural clays known as halloysites to attach to the oil-water interface and stabilize oil-in-water emulsions. Such halloysite nanotubes (HNT) serve as reservoirs for surfactants and can deliver surfactants to the oil-water interface and thus lower the oil-water interfacial tension. This two-step concept of surfactant delivery and droplet stabilization by particles has significant implications to oil spill remediation. However, to deliver surfactant loaded HNTs in a water-based solvent slurry, it is important to stopper the nanotubes to prevent premature release of the surfactant. This work focuses on the use of an environmentally benign two-dimensional metal-organic framework formed by coordinating Fe(III) with a polyphenolic as a stoppering agent. Such metal-phenolic networks (MPN) form a skin around the HNTs, thus providing a way to effectively sequester surfactant cargo for controlled release. Cryo-scanning electron microscopy (Cryo-SEM) shows that these HNTs and HNT bundles attach to the oil-water interface with side-on orientation. Inverted drop tensiometry was used to characterize the dynamic interfacial tension resulting from the release of a model surfactant (Tween 80) from the HNTs and indicates that the MPN stoppers are effective in sequestering the surfactant cargo for extended periods at neutral pH values. Release triggered by MPN disassembly at acidic pH values can be performed just prior to delivery to oil spills. The concepts and scalability of this process have significant implications for oil spill remediation, enhanced oil recovery, and biomedical and pharmaceutical applications.