Functionalization of polycrystalline gold through the electroreduction of aryldiazonium salts in ionic liquids

In this work the electrochemical functionalization of polycrystalline gold with a nitro-phenyl layer has been studied. The surface modification has been performed by cyclic voltammetries through the electroreduction of 4-nitrobenzenediazonium salt (NBD) using as solvent the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl) imide ([BMP][TFSA]). The presence of phenyl groups on the electrode surface was studied by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The barrier propriety of nitro-phenyl modified gold surfaces were characterized by EIS using Fe(CN)6 3- / Fe(CN)6 4- as a redox probe. The results indicate that nitro-phenyl groups are present on gold surface. The increase in the scan rate during the reduction of NBD in ionic liquid leads to a less covered surface as indicated by a decrease in the charge transfer resistance for the redox probe. Moreover, using the ionic liquid as solvent, lower amount of the attached molecules and a less dense layer are obtained.