Roemling Lukas J, De Angelis Gaia, Mauch Annika, Amstad Esther, Vogel Nicolas
Friedrich-Alexander-Universität Erlangen-Nürnberg, Institute of Interfaces and Particle Technology, 91058, Erlangen, Germany.
Soft Materials Laboratory, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, 1015, Switzerland.
Small. 2025 Jun;21(22):e2411772. doi: 10.1002/smll.202411772. Epub 2025 May 2.
The properties of clusters of colloidal particles, often termed supraparticles, are determined by the arrangement of the primary particles. Therefore, controlling the structure formation process is of key importance. While buckled morphologies can result from fast drying kinetics as found in spray drying, controlling the morphology under slow drying conditions remains a challenge. The final morphology of a supraparticle formed from an emulsion droplet can be controlled by manipulating particle-surfactant interactions. Water/oil emulsions are used to template supraparticle formation. The interactions of negatively charged colloidal particles with the surfactants stabilizing the water/oil-interface are tailored via the local pH within the aqueous droplet. At low pH, protonation of the anionic headgroup of the surfactant decreases electrostatic repulsion of the particles, facilitates interfacial adsorption, and subsequently causes buckling. The local pH of the aqueous droplet phase continuously changes during the assembly process. The supraparticle formation pathway can therefore be controlled by determining the point in time at which interfacial adsorption is enabled by adjusting the initial pH. Consequently, the final supraparticle morphology can be tailored at will, from fully buckled structures, via undulated surface morphologies to spherically rough and spherically smooth supraparticles and crystalline colloidal clusters.
胶体颗粒簇（通常称为超颗粒）的性质由初级颗粒的排列方式决定。因此，控制结构形成过程至关重要。虽然如喷雾干燥中发现的那样，快速干燥动力学可导致弯曲形态，但在缓慢干燥条件下控制形态仍然是一个挑战。由乳液滴形成的超颗粒的最终形态可通过操纵颗粒 - 表面活性剂相互作用来控制。水/油乳液用于模板化超颗粒的形成。带负电的胶体颗粒与稳定水/油界面的表面活性剂之间的相互作用通过水滴内的局部pH值进行调整。在低pH值下，表面活性剂阴离子头基的质子化降低了颗粒的静电排斥力，促进了界面吸附，并随后导致弯曲。在组装过程中，水滴相的局部pH值会持续变化。因此，通过调整初始pH值来确定界面吸附开始的时间点，可以控制超颗粒的形成途径。因此，可以随意调整最终超颗粒的形态，从完全弯曲的结构，到起伏的表面形态，再到球形粗糙和球形光滑的超颗粒以及结晶胶体簇。
