The mechanical properties of interfacial nanostructures are highly relevant to the studies of chemical self-assembly and biological membranes, among other.  Previous studies revealed that self-assembled gold nanoparticle films at the air-water interface undergo, under compression, a rapid evolution from monolayer to a tri-layer, via intermediate phases characterized by the presence of macroscopic features.  However, traditional x-ray scattering techniques were not sufficiently fast to analyze the details of the transition.  Using the recently developed technique of grazing incidence X-ray off-specular scattering (GIXOS) made possible to overcome this difficulty and to record the evolution of the film’s normal structure with sub-minute time resolution.  An evidence for the presence of an interim bilayer phase has been obtained for the first time. 



Yeling Dai, Binhua Lin, Mati Meron, Kyungil Kim, Brian Leahy, Thomas A. Witten, and Oleg G. Shpyrko
Synchrotron X-ray Studies of Rapidly Evolving Morphology of Self-Assembled Nanoparticle Films under Lateral Compression
Langmuir 29 (46), 14050-14056 (2013).  Author affiliations:  University of California, San Diego, Center for Advanced Radiation Sources (CARS) and James Franck Institute, University of Chicago,Center for Advanced Radiation Sources (CARS), University of Chicago, Chicago, Cornell University, University of Chicago