pH-dependent intercalation of gold nanoparticles into a synthetic fluoromica modified with poly(allylamine)

The intercalation of poly(allylamine) (PAA) into a synthetic fluoromica (Na-TSM) was studied in order to understand the subsquent process of gold nanoparticle intercalation into the interlayer galleries. The composition and structure of the PAA intercalation compound (PAA/Na-TSM) was strongly influenced by the pH of its synthesis. At pH 3.0, the fully protonated form of the polymer was intercalated as a single layer (d = 1.42-1.46 nm), accompanied by 0.2-0.4 chloride ions per PAA monomer unit. The role of chloride appears to be to screen the electrostatic repulsion of polycations within the gallery. At pH 12.0, a partially protonated form of PAA intercalates as an expanded layer (d = 1.50-1.61 nm) with no chloride ions. From equilibrium PAA adsorption data, the standard free energy for PAA intercalation at pH 12.0 was -35 kJ/mol. At pH 3.0 and low PAA loading, the corresponding ΔGo is -64 kJ/mol, consistent with the stronger interaction of protonated PAA chains with the anionic clay sheets. Au nanoparticles (