Herein, we describe pH-responsive Pickering emulsions stabilized by a sodium carboxylate-derived selenium surfactant (C₁₀-Se-C₁₀·(COONa)₂) in combination with positively charged alumina nanoparticles. Unlike other bola-type carboxylate surfactants (e.g., disodium eicosanoate), C₁₀-Se-C₁₀·(COONa)₂ is soluble in water with a low Krafft temperature (36.1 °C). The emulsions are sensitive to pH variations, and efficient demulsification can be achieved by a pH trigger. The carboxylic sodium group in the C₁₀-Se-C₁₀·(COONa)₂ structure can be reversibly cycled between its anionic and nonionic states (carboxylic acid), resulting in a pH-controlled electrostatic attraction between the surfactant and alumina. The Pickering emulsion can be reversibly switched between “on” (stable) and “off” (unstable) states by pH at least four times. Compared with the emulsions stabilized by specially synthesized stimuli-responsive particles or surfactants, the method reported here is much easier to implement and requires very low concentrations of the surfactant and nanoparticles, with potential applications in the fields of biomedicine, drug delivery, and cosmetics.

中文翻译：

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含硒表面活性剂和氧化铝纳米颗粒稳定的 Pickering 乳液的 pH 响应行为

在此，我们描述了由羧酸钠衍生的硒表面活性剂（C ₁₀ -Se-C ₁₀ ·(COONa) ₂）与带正电荷的氧化铝纳米粒子组合稳定的 pH 响应性 Pickering 乳液。与其他bola 型羧酸盐表面活性剂（例如，二十烷酸二钠）不同，C ₁₀ -Se-C ₁₀ ·(COONa) ₂可溶于低克拉夫特温度（36.1 °C）的水中。乳液对 pH 值变化很敏感，通过 pH 触发可以实现有效的破乳。C ₁₀ -Se-C ₁₀ ·(COONa) _{2 中}的羧基钠基结构可以在其阴离子和非离子状态（羧酸）之间可逆地循环，从而在表面活性剂和氧化铝之间产生 pH 控制的静电吸引力。Pickering 乳液可以通过 pH 在“开”（稳定）和“关”（不稳定）状态之间可逆地切换至少四次。与通过特殊合成的刺激响应粒子或表面活性剂稳定的乳液相比，这里报道的方法更容易实施，并且需要非常低浓度的表面活性剂和纳米粒子，在生物医学、药物输送和化妆品领域具有潜在应用。