Direct modification of a gold electrode with aminophenyl groups by electrochemical reduction of in situ generated aminophenyl monodiazonium cations

Aminophenyl groups were electrochemically grafted at the surface of a gold electrode by reduction of in situ generated aminophenyl monodiazonium cations. The in situ aminophenyl monodiazonium cations were generated by reaction of 1 equiv of p-phenylenediamine with 1 equiv of sodium nitrite in 0.5 M HCl, and their formation was confirmed by gas chromatography-mass spectrometry. The presence of aminophenyl groups at the surface of the gold electrode was demonstrated by electrochemistry and infrared and X-ray photoelectron spectroscopies. The formation of an inhomogeneous multilayered film was also evidenced by atomic force microscopy. Furthermore, grafted aminophenyl groups present at the gold electrode surface reacted with trifluoroacetic acid anhydride in dry tetrahydrofuran with a reaction yield of about 75% for the trifluoroacetylation of the amine groups.