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 approximately 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).