Real-time tracking of superparamagnetic nanoparticle self-assembly.
The spontaneous self-assembly process of superparamagnetic nanoparticles in a fast-drying colloidal drop is observed in real time. The grazing-incidence small-angle X-ray scattering (GISAXS) technique is employed for an in situ tracking of the reciprocal space, with a 3 ms delay time between subsequent frames delivered by a new generation of X-ray cameras. A focused synchrotron beam and sophisticated sample oscillations make it possible to relate the dynamic reciprocal to direct space features and to localize the self-assembly. In particular, no nanoparticle ordering is found inside the evaporating drop and near-surface region down to a drop thickness of 90 microm. Scanning through the shrinking drop-contact line indicates the start of self-assembly near the drop three-phase interface, in accord with theoretical predictions. The results obtained have direct implications for establishing the self-assembly process as a routine technological step in the preparation of new nanostructures.
Siffalovic
P
P
Institute of Physics, Slovak Academy of Sciences, Dubravska cesta 9, 84236 Bratislava, Slovakia. peter.siffalovic@savba.sk
Majkova
E
E
Chitu
L
L
Jergel
M
M
Luby
S
S
Capek
I
I
Satka
A
A
Timmann
A
A
Roth
S V
SV
D008855:Microscopy, Electron, Scanning; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D014961:X-Ray Diffraction