Immobilization of methylene blue on self-assembled iodine monolayers on gold

The immobilization of methylene blue (MB) on iodine-covered Au(111) is studied by electrochemical techniques, scanning tunneling microscopy (STM), Auger Electron Spectroscopy (AES), and Raman spectroscopy. Results show that MB species are efficiently adsorbed on the root 3 x root 3 R30 degrees l lattice on Au(111). The electrochemical behavior of the adsorbed MB molecules is reversible, indicating a relatively fast electron transfer from the Au(111) surface to the immobilized MB species through the iodine layer. STM images with molecular resolution are consistent with adsorption of MB dimers on a root 3 x root 3 R30 degrees l lattice placed atop of the Au(111) substrate. Results are compared to those obtained for MB immobilized on Au(111) covered by S-n (n = 3-8) surface structures.