Pickering emulsions are increasingly applied in the production of medicines, cosmetics, and in food technology. To apply Pickering emulsions in a rational manner it is insufficient to examine properties solely on a macroscopic scale, as this does not elucidate heterogeneities in contact angles (θ) of individual particles, which may have a profound impact on stability and microstructure. Here, we apply the super-resolution technique iPAINT to elucidate for the first time the microscopic origins of macroscopically observed emulsion phase inversions induced by a variation in particle size and aqueous phase pH. We find θ of single carboxyl polystyrene submicron particles (CPS) significantly decreases due to increasing aqueous phase pH and particle size, respectively. Our findings confirm that θ of submicron particles are both size- and pH-dependent. Interestingly, for CPS stabilized water-octanol emulsions, this enables tuning of emulsion type from water-in-oil to oil-in-water by adjustments in either particle size or pH.

中文翻译：

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阐明亚微米粒度和表面化学性质对界面位置和Picker乳液类型的影响。

Pickering乳液越来越多地应用于药物，化妆品和食品技术的生产中。要以合理的方式使用Pickering乳液，仅在宏观尺度上检查性能是不够的，因为这无法阐明单个颗粒的接触角（θ）的不均匀性，而这可能会对稳定性和微观结构产生深远影响。在这里，我们应用超分辨率技术iPAINT首次阐明了由粒径和水相pH值变化引起的宏观观察到的乳液相转化的微观起源。我们发现，单个羧基聚苯乙烯亚微米颗粒（CPS）的θ分别由于水相pH和粒径的增加而显着降低。我们的发现证实，亚微米颗粒的θ既取决于尺寸，又取决于pH。