To prepare stock solutions of the polyelectrolyte polyallylamine hydrochloride (PAH, MW 17.5 kDa, Sigma-Aldrich), PAH was dissolved in ultrapure water and sonicated for 30 minutes. For further processing, 12 mL of the synthesized colloidal solution was centrifuged at 4,700 g for 40 minutes and redispersed in water, which removed most of the excess citrate. This step minimized the charge interference from citrate molecules, facilitating optimal deposition of the initial polycation layer (PAH). Subsequently, 12 mL of the centrifuged silver colloidal solution was added dropwise to 6 mL of a 5 g/L PAH solution under vigorous stirring in a glass vial.