Revealing the Interfacial Self-Assembly Pathway of Large-Scale, Highly-Ordered, Nanoparticle/Polymer Monolayer Arrays at an Air/Water Interface

The pathway of interfacial self-assembly of large-scale,
highly
ordered 2D nanoparticle/polymer monolayer or bilayer arrays from a
toluene solution at an air/water interface was investigated using
grazing-incidence small-angle scattering at a synchrotron source.
Interfacial-assembly of the ordered nanoparticle/polymer array was
found to occur through two stages: formation of an incipient randomly
close-packed interfacial monolayer followed by compression of the
monolayer to form a close-packed lattice driven by solvent evaporation
from the polymer. Because the nanoparticles are hydrophobic, they
localize exclusively to the polymer–air interface during self-assembly,
creating a through thickness asymmetric film as confirmed by X-ray
reflectivity. The interfacial self-assembly approach can be extended
to form binary NP/polymer arrays. It is anticipated that by understanding
the interfacial self-assembly pathway, this simple evaporative procedure
could be conducted as a continuous process amenable to large area
nanoparticle-based manufacturing needed for emerging energy technologies.