Comparative Study of the Adsorption of Thiols and Selenols on Au(111) and Au(100)

ARISNABARRETA, NICOLÁS; RUANO, GUSTAVO D.; LINGENFELDER, MAGALÍ; PATRITO, E. MARTÍN; COMETTO, FERNANDO P.

LANGMUIR

AMER CHEMICAL SOC

Año: 2017

0743-7463

The effect of the Au crystalline plane on the adsorption of different thiols and selenols is studied via reductive desorption (RD) and X-Ray Photoelectron Spectroscopy (XPS) measurements. SAMs using aliphatic (ATs) and aromatic thiols (ArTs) on both Au (111) and Au (100) were prepared. The electrochemical stability of these SAMs on both surfaces is evaluated by comparing the position of the RD peaks. The longer the AT?s chain the more stable the SAM on Au (100) when compared to Au (111). By means of XPS measurements, we determine that the binding energy (BE) of the S 2p signal corresponding to the S atoms in the thiol/Au interface, commonly assigned at 162.0 eV, shifts 0.2 eV from Au (111) to Au (100) for SAMs prepared using thiols with the C* (C atom bonded to S) in sp3 hybridization; such as ATs. However, when the thiol presents the C* with a sp2 hybridization, such as in the case of ArTs, the BE remains at 162.0 eV regardless the surface plane. Selenol-based SAMs were characterized comparatively on both Au (100) and Au (111). Our results show that selenol SAMs become even more electrochemically stable on Au (100) with respect to Au (111) than the analog sulphur-based SAM. According to our results, we suggest that the electronic distribution around Au-S/Se bond, could be responsible for the different structural arrangements reported in literature (gold adatoms, etc.), which should be dependent on the crystalline face and the chemical nature of the environment of the adsorbates (sp3-C* vs. sp2-C* and vs. ).