Patterning of Magnetic
Bimetallic Coordination Nanoparticles
of Prussian Blue Derivatives by the Langmuir–Blodgett Technique
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Abstract
We report a novel method to prepare patterns of nanoparticles
over
large areas of the substrate. This method is based on the adsorption
of the negatively charged nanoparticles dispersed in an aqueous subphase
onto a monolayer of the phospholipid dipalmitoyl-l-α-phosphatidylcholine
(DPPC) at the air–water interface. It has been used to prepare
patterns of nanoparticles of Prussian blue analogues (PBA) of different
size (K<sub>0.25</sub>Ni[Fe(CN)<sub>6</sub>]<sub>0.75</sub> (NiFe),
K<sub>0.25</sub>Ni[Cr(CN)<sub>6</sub>]<sub>0.75</sub> (NiCr), K<sub>0.25</sub>Ni[Co(CN)<sub>6</sub>]<sub>0.75</sub> (NiCo), Cs<sub>0.4</sub>Co[Cr(CN)<sub>6</sub>]<sub>0.8</sub> (CsCoCr), and Cs<sub>0.4</sub>Co[Fe(CN)<sub>6</sub>]<sub>0.9</sub> (CsCoFe)). The behavior of DPPC
monolayer at the air–water interface in the presence of the
subphase of PBA nanoparticles has been studied by the compression
isotherms and Brewster angle microscopy (BAM) images. Atomic force
microscopy (AFM) of the transferred films on mica substrates shows
that patterns of the nanoparticles are observed for a 10<sup>–4</sup> M concentration of the subphase, based on the nanoparticle precursors,
at surface pressures between 1 and 6 mN/m and transfer velocities
from 10 to 80 mm/min. Vertical, horizontal, or tilted fringes of the
nanoparticles with respect to the transfer direction can be obtained
depending on the transfer velocity and surface pressure
