Ultrathin multilayer polyelectrolyte films on gold: Construction and thickness determination .1.

Thin organic films fabricated by the successive deposition of the polyelectrolytes poly(allylamine hydrochloride) (PAH) and poly(styrenesulfonate) (PSS) have been successfully grown up to 24 layers on gold surfaces. These films are formed via electrostatic attraction between adjacent layers of opposite charge. Their construction has been examined using a quartz crystal microbalance (QCM), reflection spectroscopy (RS), surface plasmon resonance (SPR), and X-ray photoelectron spectroscopy (XPS). The thickness of the multilayer assemblies increases with the number of adsorbed layers, although a linear increase is observed only after the deposition of four polyelectrolyte layers ((PAH/PSS)(2)). The (PAH/PSS)(2) film facilitates regular, stepwise deposition of subsequent PAH and PSS layers. The thickness of (PAH/PSS)(2) on gold was determined independently by QCM, SPR, and XPS to be 7.9 +/- 0.6 nm. The PAH/PSS layer pair thickness after regular film growth was calculated to be 10.0 +/- 0.8 nm. The formation of these thin films on gold surfaces opens the possibility of constructing supramolecular assemblies for use in the areas of biological and chemical sensing.