title: Transmission X-ray scattering as a probe for complex liquid-surface structures.
abstract: The need for functional materials calls for increasing complexity in self-assembly systems. As a result, the ability to probe both local structure and heterogeneities, such as phase-coexistence and domain morphologies, has become increasingly important to controlling self-assembly processes, including those at liquid surfaces. The traditional X-ray scattering methods for liquid surfaces, such as specular reflectivity and grazing-incidence diffraction, are not well suited to spatially resolving lateral heterogeneities due to large illuminated footprint. A possible alternative approach is to use scanning transmission X-ray scattering to simultaneously probe local intermolecular structures and heterogeneous domain morphologies on liquid surfaces. To test the feasibility of this approach, transmission small- and wide-angle X-ray scattering (TSAXS/TWAXS) studies of Langmuir films formed on water meniscus against a vertically immersed hydrophilic Si substrate were recently carried out. First-order diffraction rings were observed in TSAXS patterns from a monolayer of hexagonally packed gold nanoparticles and in TWAXS patterns from a monolayer of fluorinated fatty acids, both as a Langmuir monolayer on water meniscus and as a Langmuir-Blodgett monolayer on the substrate. The patterns taken at multiple spots have been analyzed to extract the shape of the meniscus surface and the ordered-monolayer coverage as a function of spot position. These results, together with continual improvement in the brightness and spot size of X-ray beams available at synchrotron facilities, support the possibility of using scanning-probe TSAXS/TWAXS to characterize heterogeneous structures at liquid surfaces.
authors.affiliation: National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY 11973, USA.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Fukuto
authors.affiliation: National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY 11973, USA.
authors.forename: Lin
authors.initials: L
authors.lastname: Yang
authors.affiliation: Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973, USA.
authors.forename: Dmytro
authors.initials: D
authors.lastname: Nykypanchuk
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439, USA.
authors.forename: Ivan
authors.initials: I
authors.lastname: Kuzmenko
keywords: SAXS; WAXS; air/water interface; liquid surface scattering; transmission X-ray scattering