Time-Resolved and Space-Resolved Study of Iron Oxide Nanoparticle Self-Assembly on Liquid Surfaces by Using In-Situ Small Angle X-Ray Scattering

Real time in-situ synchrotron small-angle X-ray scattering (SAXS) is used to follow the formation of ordered monodisperse iron oxide nanoparticle (NP) monolayers (MLs) at multiple positions after an NP heptane dispersion is drop-cast on diethylene glycol (DEG). One and only one close-packed hexagonal ML is formed at the heptane/DEG interface before the heptane totally evaporates, while the remaining NPs are still dispersed in the heptane bulk. Optical reflection is also used to monitor ML formation.