Reliable Langmuir Blodgett colloidal masks for large area nanostructure realization

Abstract

The fabrication of highly ordered nanostructures over large areas is key for many technologies and colloidal lithography using the Langmuir Blodgett technique appears a simple and straightforward way of reaching that goal. While this technique has been widely reported in the literature, its straightforward implementation to obtain well-ordered nanostructures over very large areas is far from obvious, since many key technical subtleties are rarely documented. Here, we describe an easily and highly reproducible recipe and detail aspects such as beads preparation, composition of the subphase, beads transfer method, influence of the spreading agent and the barrier compression rate, as well as monolayer transfer to the substrate. A drastic improvement in the polystyrene self-assembly at the air-water interface is observed after removing the common salt and surfactant molecules from commercial polystyrene beads suspensions. Similarly, an electrolyte free water subphase enhances the hexagonal arrangement of the beads and the long-range order. The beads sinking into the bulk of the water is reduced by dispensing the beads using a glass slide and the polystyrene suspension prepared using water and ethanol at 1:1 mitigates repulsive and attractive forces, leading to excellent hexagonal close packed arrangement. By following the recipe shown here, the reader should easily fabricate lattice-like colloidal masks for producing nanostructures over larger areas.