Spectroelectrochemical analysis of ion-transfer and adsorption of the PAMAM dendrimer at a polarized liquid|liquid interface

The interfacial behavior of the fourth generation polyamidoamine (G4 PAMAM) dendrimer at a water|1,2-dichloroethane (DCE) interface was studied by cyclic voltammetry and potential modulated fluorescence (PMF) spectroscopy. Irregular voltammetric responses were observed at positively polarized interfaces. The cyclic voltammogram was strongly dependent on pH and on the concentrations of the G4 PAMAM dendrimer and the organic supporting electrolyte. PMF spectroscopy was successfully used to analyze the interfacial mechanism of the dendrimer by adding an anionic porphyrin derivative as a fluorescent probe. The results of the PMF measurements demonstrated that the G4 PAMAM dendrimer was transferred across the interface, a process that was accompanied by an adsorption step at pH 7. In contrast, under alkaline conditions, the adsorption process did not seem to be involved in the interfacial behavior.