Amine-Rich Polyelectrolyte Multilayer Nanoreactors for in Situ Gold Nanoparticle Synthesis

Abstract

In situ synthesis of inorganic clusters in polyelectrolyte multilayers (PEMs) has typically relied on free carboxylic acid groups as the binding sites, limiting the scheme to the loading of cationic precursor reagents. The use of amine groups for similar purposes has not been demonstrated because of the challenge of incorporating free amine groups that are not paired with the oppositely charged groups residing on the polyanion of the PEM. In this paper, we use specific PEM assembly conditions to produce ultrathin conformal films of PAH/PAA (poly(allylamine hydrochloride)/poly(acrylic acid)) and PAH/PSS (poly(styrene sulfonate)) that upon suitable postassembly treatment undergo substantial molecular rearrangements that generate free amine groups in the films. These PEMs are capable of binding anionic precursors including complexes widely used for the synthesis of gold nanoparticles. On the basis of our understanding of the gold binding mechanisms, we demonstrate systematic control over the size and spatial distribution of gold nanoparticles in the films by changing the PEM assembly and postassembly treatment conditions.