Layer-by-Layer Growth of Polymer/Nanoparticle Films Containing Monolayer-Protected Gold Clusters

Multilayer films of nanoparticles were grown in a systematic and controlled manner layer-by-layer by alternating exposures of suitably functionalized substrates (glass, Au) to either poly(allylamine) and carboxylic acid-functionalized nanoparticles or to poly(styrene sulfonate) and arylamine-functionalized nanoparticles. Electrostatic interactions comprise the dominant film growth factors. The rate of multilayer film growth depends on the polymer solution pH and other details of the solution exposures. Growth was followed by spectrophotometry of the Au nanoparticle cores, voltammetry of the Au core double layer charging, and film mass (quartz crystal microbalance). The first example is reported of quantized double layer charging of the Au cores in a layer-by-layer film that is composed of monolayer-protected clusters and a polyelectrolyte.