Correlated membrane fluctuations in nanocrystal superlattices

Superlattices of organic monolayer-stabilized silver nanocrystals exhibit structural integrity at temperatures well above the melting point of the hydrocarbon capping ligands (i.e., the C-8, C-12, and C-16 alkanethiols used in this study). Temperature-dependent small angle x-ray scattering reveals that topological disordering occurs with spatially correlated domains of characteristic length xi that grow with increasing temperature until xi diverges at a critical temperature T-c, as xi similar to xi (0) (1 - T/T-c)(-0.67). A power law analysis of the scattering intensity with wave vector indicates that interactions between membranes due to thermal undulations control the topology below T-c.