Preparation and characterization of ordered nanoparticle and polymer composite multilayers on colloids

Alternating nanoparticle/polymer composite multilayers have been assembled on submicrometer-sized polystyrene (PS) latex spheres by the sequential adsorption of silica nanoparticles (SiO2) and poly(diallyldimethylammonium chloride) (PDADMAC) from aqueous solutions. Growth of the composite multilayers on the PS latices was followed by electrophoretic mobility (EPM), single-particle light scattering (SPLS), scanning (SEM) and transmission (TEM) electron microscopy, and atomic force microscopy (AFM). EPM measurements revealed a reversal in zeta-potential with deposition of each SiO2 or PDADMAC layer; negative and positive values were observed for SiO2 and PDADMAC depositions, respectively. SPLS experiments showed a linear increase in SiO2/PDADMAC multilayer film thickness with deposition layer number; approximately one monolayer of nanoparticles was deposited with each SiO2 adsorption step. Both SEM and TEM provided direct evidence of stepwise multilayer growth, and AFM revealed a uniform covering of the PS colloids by the SiO2 nanoparticles. The thickness data from microscopy measurements for the SiO2/PDADMAC multilayers on the PS latices are in quantitative agreement with those obtained from SPLS. The fabrication of related composite multilayers on colloids is expected to produce novel particles with potential applications in various fields of materials science and biotechnology.