Out of equilibrium self-assembly of Janus nanoparticles: steering it from disordered amorphous to 2D patterned aggregates

Solvent evaporation driven self-assembly of Janus nanoparticles (J-NPs) has been simulated employing lattice-gas models to investigate the possible emergence of new superlattices. Depending on the chemical nature of NP faces (hence solvophilicity and relative interaction strength), zebra-like or check-like patterns, and micellar agglomerates can be obtained. Vesicle-like aggregates can be produced by micelle-based corrals during heterogeneous evaporation. Patterns formed during aggregation appear to be robust against changes in evaporation modality (i.e. spinodal or heterogeneous) or interaction strengths, and they are due to a strictly nanoscopic orientation of single J-NPs in all cases. Due to the latter feature, the aggregate size growth law N(t)= t^α has its exponent α markedly depending on the chemical nature of the J-NPs involved in spite of the unvaried growth mechanism. We interpret such finding as connected to the increasingly stricter orientation pre-requirements for successful (binding) NP landing upon going from isotropic (α= 0.50), to zebra (α= 0.38), to check (α=0.23), and finally to micelle (α= 0.15-0.17) pattern forming NPs