Electrostatic Multilayer Deposition of a Gold−Dendrimer Nanocomposite

Poly(amidoamine) (PAMAM) dendrimers can be used as a polymeric template/stabilizer/reservoir to prepare stable gold−dendrimer nanocomposites by reducing PAMAM−tetrachloroaurate polysalts using hydrazine. In the gold−dendrimer nanocomposite, the presence of elemental gold is indicated by its characteristic plasmon absorption peak at 529 nm in aqueous solution and is visualized by transmission electron microscopy (TEM) equipped with energy-dispersive X-ray spectroscopy (EDXS). Electrostatic layer-by-layer assembly of the gold−dendrimer nanocomposite using poly(sodium 4-styrenesulfonate) (PSS) as the oppositely charged polyelectrolyte leading to nanoscale uniform multilayers of gold−dendrimer nanoclusters is reported. UV−vis absorption spectra from the consecutive multilayers indicated that each bilayer growth is regular, even though a 20 nm absorption bathochromic shift takes place in the film. TEM of PSS/gold−dendrimer nanocomposite film demonstrates that gold nanoparticles (5−20 nm) appear as aggregates within a gold−dendrimer nanocomposite monolayer, an observation borne out by crystalline gold electron diffraction patterns obtained from PSS/gold−dendrimer nanocomposite. Atomic force microscopy (AFM) of PSS/gold−dendrimer nanocomposite film indicates that the nanoclusters are arrayed with high uniformity at the nanometer scale.