Temperature driven assembly of like-charged nanoparticles at non-planar liquid–liquid or gel–air interfaces

Gold nanoparticles (NPs) functionalized with 2-fluoro-4-mercaptophenol (FMP) ligands form densely packed NP films at liquid-liquid interfaces, including surfaces of liquid droplets. The process is driven by a gradual lowering of temperature that changes the solution's pH, altering both the energy of interfacial adsorption for NPs traveling from solution to the interface as well as the balance between electrostatic and vdW interactions between these particles. Remarkably, the system shows hysteresis in the sense that the films remain stable when the temperature is increased back to the initial value. The same phenomena apply to gel-air interfaces, enabling patterning of these wet materials with durable NP films.