表面活性剂-纳米颗粒相互作用与智能体系的构建（Ⅴ）相同电荷表面活性剂-纳米颗粒相互作用（i）——超低浓度纳米颗粒/表面活性剂构建新型乳状液及其稳定机制

Interactions between surfactants and nanoparticles and the construction of smart systems(V) Interactions between like-charged nanoparticles and ionic surfactants(i) Construction of novel emulsions using ultra-low concentration of nanoparticles/surfactants

利用无机纳米颗粒在水介质中带电以及带相反电荷的离子型表面活性剂对颗粒的可逆原位疏水化作用,可以构建具有多种触发机制的Pickering乳状液和Pickering泡沫等智能分散体系。令人惊奇的是,采用无机纳米颗粒与带相同电荷的离子型表面活性剂,亦可协同稳定O/W型乳状液,其特点是所需颗粒和表面活性剂浓度极低,分别可低至0.001%和0.001cmc,其中微量表面活性剂吸附于油/水界面控制液滴大小,而纳米颗粒并不吸附于油/水界面,而是分布于连续相水膜中,相关的稳定机理难以用经典的DLVO理论、位阻稳定理论以及Pickering稳定理论来解释。为此将这种由带相同电荷的离子型表面活性剂与无机纳米颗粒协同稳定的O/W型乳状液称为新型乳状液。本讲座将简单介绍这种新型乳状液的制备、表征、普适性以及初步探索的稳定机制。

By means of reversible hydrophobization of inorganic nanoparticles with the oppositely charged ionic surfactants in aqueous media, smart dispersion systems such as switchable or stimuli-responsible Pickering emulsions/foams with various triggers can be constructed. Surprisingly, like-charged inorganic nanoparticles and ionic surfactants can also co-stabilize O/W emulsions, in which the concentrations of both particles and surfactants required are extremely low, i.e., the minimum concentration required can be as low as 0.001% and 0.001 cmc, respectively. It is found that trace amount of surfactants adsorb at oil/water interface controlling droplet size, whereas the nanoparticles do not adsorb at oil/water interface but distribute in aqueous lamellae of the continuous phase. The O/W emulsions co-stabilized by like-charged nanoparticles and ionic surfactants are called novel emulsions since their stabilization mechanism can not be well interpreted by the classic DLVO, the steric and the Pickering stabilization theories. This lecture will discuss the formation, characterization, universality and preliminary stabilization mechanism of the novel O/W emulsions.