Exfoliation was achieved by dilution of the 0.5% GO dispersion (1 mL) with deionized water (24 mL), followed by 15 min
sonication. The resulting homogeneous yellow-brown sol,which contained 0.2 g/L GO, was stable for a period of months and was used for film preparation.
An aqueous solution (0.01 M) of poly(allylamine hydrochloride),PAH, (Aldrich, MW ) 50 000-65 000) was adjusted to pH 7 with NH3 and was used for growth of polycation layers