Silica nanoparticles were functionalized with amine and quaternary ammonium groups using a two-step chemical surface modification, to allow coating with anionic polymers for emulsion stabilization. This strategy proved to render high colloidal stability in aqueous dispersions and strong electrostatic interactions with polyacrylic acid and poly(sodium 4-styrene sulfonate), over a wide pH range. These hybrid nanoparticles stabilized Pickering emulsions at very low concentrations (0.01 wt%), without added surfactants. Most stable emulsions were obtained with nanoparticles coated with polyacrylic acid, due to synergy of strong interfacial adsorption of nanoparticles enhanced by the long polymeric chains and the weak polyelectrolyte character of the polymer. These nanoparticles were able to prevent diffusion of N,N′-diethyl- m -toluamide (DEET), a common insect repellent, from oil-in-water emulsions into a model media. The release profile followed typical zero-order kinetics, demonstrating the potential of using the polymer-coated nanoparticles developed in this work in DEET formulations to achieve extended repellent action. Graphical abstract

中文翻译：

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用于缓释 Pickering 乳液的聚合物包覆阳离子二氧化硅纳米粒子

二氧化硅纳米粒子使用两步化学表面改性用胺和季铵基团进行功能​​化，以允许用阴离子聚合物涂层以稳定乳液。事实证明，该策略在水分散体中具有高胶体稳定性，并在很宽的 pH 范围内与聚丙烯酸和聚（4-苯乙烯磺酸钠）产生强静电相互作用。这些混合纳米粒子在非常低的浓度 (0.01 wt%) 下稳定了 Pickering 乳液，无需添加表面活性剂。最稳定的乳液是用涂有聚丙烯酸的纳米粒子获得的，这是由于长聚合物链增强了纳米粒子的强界面吸附和聚合物的弱聚电解质特性的协同作用。这些纳米颗粒能够阻止 N,N'-二乙基-间-甲苯甲酰胺 (DEET) 的扩散，一种常见的驱虫剂，从水包油乳液到模型介质。释放曲线遵循典型的零级动力学，证明了在避蚊胺配方中使用在这项工作中开发的聚合物涂层纳米粒子来实现扩展的驱虫作用的潜力。图形概要