Formation mechanism and morphology modulation of honeycomb hybrid films made of polyoxometalates/surfactants at the air/water interface

Porous hybrid films of surfactant-encapsulated polyoxometalates with different morphologies have been fabricated simply by water droplets as templating at the air/water interface. Highly ordered honeycomb hybrid films of nanometer-scale polyoxometalates and surfactants were fabricated by a simple solvent-evaporation method at the air/water interface. A good template by micrometer water droplets which are condensed from water vapor because of the quick evaporation of organic solvents plays an important role in the self-patterning of honeycomb films. The morphologies of the thin films can be modulated by the solvent volatility which can not only influence the pore size of the film but also determine whether or not a regular porous structure can be achieved at all. The faster the volatility of organic solvents, the smaller the pores of films. Higher hydrophobicity and larger surface coverage which are induced by the surface encapsulation of a polyoxometalate by cationic surfactants with longer double carbon chains are beneficial to the organization of porous structures. It is also found that the morphologies of the thin films can be changed when the thin films are dropped at different supporting solution interfaces. It is well demonstrated that the morphologies of the fabricated hybrid films are modulated by appropriate controls.