Physico-chemical characterization of ferrocenyl-modified hyperbranched poly(ethylenimine) self-assembled multilayers

In this work, we characterize the electrochemical behavior of a new ferrocenyl-modified, hyperbranched poly(ethylenimine) (HBPei-Fc). The effects of the ionic strength, pH and the nature of the anion of the supporting electrolyte on the electrochemical behavior of the redox polymer were studied using cyclic voltammetry and an electrochemical quartz crystal microbalance. The interactions of the polymer with the anions of the supporting electrolyte, which was incorporated during the redox process, determined the electrochemical behavior that was observed. The polymer was employed for the construction of layer-by-layer-assembled multi-composite films using thiolated gold surfaces with HBPei-Fc as the polycation and citrate-stabilized gold nanoparticles or glucose oxidase (GOx) as the negative polyelectrolyte. The self-assembled multilayers were characterized using UV–Vis spectrophotometry and electrochemical techniques to follow the signal of the ferrocene groups of the polymer. The adsorption of the polymer and GOx was analyzed using surface plasmon resonance to determine the surface coverage and the kinetic properties of the process. The results demonstrated that the ferrocenyl-modified polymer is an efficient platform for the immobilization of both inorganic materials, such as metallic nanoparticles, and biomolecules.