Catalytic effect of gold nanoparticles self-assembled in multilayered polyelectrolyte films

Multilayer films composed of poly(L-arginine) (pArg) and mercaptoundecanoic acid (MUA) stabilized gold nanoparticles (Au-MUA NPs) have been fabricated based on the electrostatic layer-by-layer self-assembly technique upon a gold electrode modified with a first layer of mercaptosuccinic acid (MSA). The formation of the pArg/Au-MUA NP self-assemblies as alternative multilayers was confirmed by UV-vis absorption spectroscopy and atomic force microscopy while their electrochemical properties were studied using cyclic voltammetry, square wave voltammetry, and electrochemical impedance spectroscopy. Charge transport through the multilayer was studied experimentally by using the redox pair [Fe(CN)(6)](3-/4-). It was found that these new assemblies have a high permeability to the probe ions. The presence of the Au-MUA NPs greatly improves the conductivity and the electron-transfer ability of the film which exhibited new electrical properties characterized by a low impedance response and enhanced electric current as more layers were added for both Au-MUA NP and pArg terminated multilayers. It is concluded that the behavior observed is based on two cumulative contributions: electron transfer mediated by the Au-MUA NPs layers and ionic diffusion favored by the poly(L-arginine) layers due to the Donnan inclusion. The films obtained showed high conductive properties which represent very promising features for the construction of electrochemical sensors or nanoelectronic devices.