2.2.2 Fabrication of Thin Films
Colloidal particles were deposited on the substrate by layer by layer
self-assembled multilayering using electrostatic interaction with
oppositely charged polyelectrolytes. Polydimethyldiallylammonium
chloride (PDAC), (Mw 100,000–200,000; 20% aqueous solution)
(Sigma‑Aldrich) was used as cationic polyelectrolytes). Magnetic polymer
colloidal dispersion of CSMPC with negative Zeta potential and size of
527 nm was employed as oppositely charges anionic solution. For a
predetermined time, LBL-SAMU thin films were fabricated in custom made
setup. Manually dipping the freshly cleaned glass slides (25.4mm ˟
76.2mm ˟ 1mm) (Fischer) into the desired solutions of the opposite
charge. Alternate layering was done to coat the prepared magnetic
colloids (polymer core-shell magnetic nanoparticles total solids 1%,
size 527 nm) in accordance to following steps; First adsorption stage: a
charged substrate generally of negative charge is immersed for 10
minutes into the positively charged solution to be adsorbed on the
surface of the slide for a known period, followed by first washing
cycles to wash out unbound particles as shown in Figure 1. Each stage in
the washing cycle takes about five minutes. Second adsorption stage:
oppositely charged particles of the first adsorption stage were adsorbed
on the substrate surface and then followed by the second washing cycle.
The whole process constitutes about 40 min to get one bilayer. Repeating
the protocol several times gives a multilayered structure for the
desired thickness. The fabricated films were characterized by different
techniques to study morphological properties and elemental composition,
including scanning electron microscopy (SEM) and energy dispersive
spectroscopy (EDS). (Jeol JSM 6490A) and optical microscopy (Optika
B-600MET).