Controllable assembly of colloid particles on the surface of polyelectrolyte multilayer films

Colloidal adsorption onto certain substrates is of great interest in both basic colloidal chemistry and colloidal lithography with a larger surface area. We studied the assembly of sulfonated polystyrene particles that have anionic charges on the surfaces of the polyelectrolyte multilayer(PEM) films composed of poly (diallyldimethylammonium chloride) (PDDA) and poly (sodium 4-styrenesulfonate) (PSS). The monolayer assembly of the colloid particles without three-dimensional aggregation could be observed by atomic force microscope (AFM) and scanning electron microscope (SEM), and. the number of colloids adsorbed per square micrometer was varied systematically from 2 to 7 by fine-tuning the fabrication and postfabrication of PEMs. Based on an electrostatic point of view, an approaching particle is attracted by the precursor film and repulsed by adsorbed particles, the balance between the attraction and repulsion is affected by alternation of surface property of PEMs. This method can provide a fabrication way of a wide range of dotted materials in which its feature size is the diameter of colloid particles.