systematically investigated the effect of the excess ligands on film formation to show that a certain excess ligand concentration inhibits the wrinkling and folding of the film during compression, which is beneficial to the film quality. Also, the interparticle distance slightly increases with increasing excess ligand concentration, Figure ). For nanoparticles stably dispersed only in polar solvents, Nie et al. provided a solution by demonstrating that nanoparticles dispersed even in a polar phase (PVP coated Au nanoparticles in ethanol) can spread over a water surface without mixing when the nanoparticles are introduced as an aerosol by electro-spraying, Figure ). After nebulization, the solvent in the tiny colloid droplets evaporates rapidly resulting in trapping of the nanoparticles at the air-water interface.