This article reports an angle dependent X-ray photoemission investigation on the formation of a self-assembled monolayer of a small organic disulfide molecule (Naphtho[1,8-cd]-1,2-dithiole) on silver/platinum alloy surfaces. In addition to the S 2p signal normally associated with thiolate bond formation, a high binding energy S 2p signal was observed and is assigned to a sulfonic acid moiety. This is the first such report of sulfonic acid formation in disulfide systems and is quite similar to the process occurring on copper and silver surfaces for n-alkane thiols. The angle dependent intensities of the C 1s, S 2p and Ag 3d core levels were used to make a quantitative estimate of the surface composition and thus obtain information on the molecular orientation. The molecule was oriented almost normal to the silver/platinum alloy surface with the sulfonic acid moiety being closer to the monolayer-air interface than the thiolate sulfur which was very close to the alloy surface. This is explainedas arising due to steric effects associated with the larger sulfonic acid group.
|Number of pages||7|
|Journal||Journal of Electron Spectroscopy and Related Phenomena|
|Publication status||Published - Dec 1997|
- Alloy surfaces
- Aromatic organic disulfide
- Molecular assembly
- X-ray photoemission spectroscopy