Electrochemical, HR-XPS and SERS study of the self-assembly of biphenyl 4, 4'-dithiol on Au(111) from solution phase
E.M. EUTI; P. VÉLEZ; O. LINAREZ PÉREZ; G.RUANO; E.M.PATRITO; G.ZAMPIER; E.P.M. LEIVA; V.A. MACAGNO; F.P.COMETTO
ELSEVIER SCIENCE BV
Lugar: Amsterdam; Año: 2014 vol. 630 p. 101 - 108
We report a comparative study of 4,4′-biphenyldithiol adlayers grown on Au(111) substrates in solution phaseby different methods. Layers prepared by immersion in solutions of ethanol and n-hexane, with and withoutthe use of a disulfide reducing agent (tris-carboxyethyl phosphine, TCEP), were characterized by electroreductivedesorption, impedance spectroscopy, redox activity, high-resolution photoemission spectroscopy, and surface-enhanced Raman spectroscopy. It is shown that the simple immersion in an ethanolic solution leads to the for-mation of, at least, a bilayer with a high number of SS bonds. The use of n-hexane as solvent produces a drasticreduction of these undesired bonds, and a similar result is obtained if the substrates prepared in the ethanolicsolution are then washed with TCEP. The best results were obtained when the reducing agent was added intothe ethanol solution, in which case all the characterizations were coincident in the formation of a single layerof standing-up molecules free of SS bonds. The charge of the desorption peak and the relative intensity ofthe S2p and Au4f photoemission peaks both indicate a surface coverage θ ≈ 0.2. In the case of multilayers formedby immersion in pure ethanolic solutions, the Raman experiments indicate that intralayer SS bonds are notformed, and hence that all the SS bonds are of the interlayer type.