Parametric study of the silver nanoparticles deposition on polyelectrolyte supporting layers.

Colloidal nanoparticles deposition on polyelectrolyte supporting layers is a widespread technique to achieve high density nanoparticle coatings, however the choice of the parameters is often not consistent and varies in different reports. Frequently the obtained films suffer from the aggregation and non-reproducibility. Here, we addressed the main variables in silver nanoparticles deposition - the immobilization time; concentration of the polyelectrolyte in the solution; the thickness of polyelectrolyte underlayer and overlayer; the concentration of salt in the polyelectrolyte solution during the formation of a underlayer. We report on the formation of the high-density silver nanoparticle films and ways to tune their optical density in the wide range using the immobilization time as well as the thickness of polyelectrolyte overlayer. Silver colloidal films with maximum reproducibility were obtained by adsorption of nanoparticles on 1 underlayer of 5 g/l polydiallyldimethylammonium chloride with 0.5M NaCl concentration. The results are promising for the fabrication of the reproducible colloidal silver films for multiple applications, such as plasmon enhanced fluorescent immunoassays and surface enhanced Raman scattering sensors.