Self‐Assembly of Strongly Amphiphilic Janus Nanoparticles into Freestanding Membranes

Abstract Amphiphilic nanoparticles can adsorb at interfaces between immiscible phases and form membranes. The ability to handle nanoparticle monolayers/bilayers as freestanding membranes independently from the interfaces on which they form can be of significant practical interest. Janus nanoparticles (JNPs) could generate membranes that have tunable pore size and are amphiphilic. Here it is shown how freestanding membranes from JNPs can be generated. First, strongly amphiphilic Janus nanoparticles that generate foams in surfactant‐free conditions are synthesized. Upon drying the foam lamellae remain as freestanding membranes consisting of perfectly oriented bilayers or monolayers of JNPs, thus providing direct evidence of structural organization of amphiphiles in foam lamellae. The wet foam lamellae can be picked up on grids and upon drying generate freestanding membranes. Sturdy freestanding membranes by transferring monolayers of JNPs from the air–water interfaces onto grids with fine openings are also prepared.