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).