Colloidal stability of nanoparticles stabilized with mixed ligands in solvents with varying polarity.

Colloidal stability of nanoparticles (NPs) strongly influences their synthesis, processing, and applications. For gold NPs stabilized with cetyl trimethylammonium bromide (CTAB) and polymer ligands we show that gradual increase in polarity of the water/aprotic solvent mixture leads to stabilization-aggregation-stabilization-aggregation transitions. We propose that these transitions are mediated by structural rearrangements of the CTAB layer on the NP surface.