Adsorption of 1,4-Benzenedithiol on Gold and Silver Surfaces: Surface-Enhanced Raman Scattering Study

✍ Scribed by Sang Woo Joo; Sang Woo Han; Kwan Kim

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 113 KB
• Volume: 240
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.2001.7692

✦ Synopsis

The adsorption behavior of 1,4-benzenedithiol (1,4-BDT) on colloidal gold and silver surfaces has been investigated by means of surface-enhanced Raman scattering (SERS). 1,4-BDT chemisorbed dissociatively on both gold and silver surfaces but as mono-and dithiolate, respectively. Regardless of the bulk concentration of 1,4-BDT, only a monolayer was assembled on the silver surface with a flat orientation by forming two Ag-S bonds. On the gold surface, the monothiolate species,1,4-BDT -1 , appeared to assume a rather flat orientation at a very low surface coverage, but as the surface coverage was increased, the adsorbate took a perpendicular orientation. Furthermore, when the bulk concentration of 1,4-BDT was close to that required for a full-monolayer coverage limit, a band assignable to the S-S stretching vibration appeared at ∼ 536 cm -1 in the gold sol SERS spectra. A separate ellipsometry measurement performed with vacuum-evaporated gold substrates revealed that up to tetralayers could be assembled on gold in 1 mM n-hexane solution of 1,4-BDT while at best a bilayer formed in either methanol or ethanol solution. The different adsorbate structure of 1,4-BDT on gold and silver was overall quite comparable to that of p-xyleneα,α -dithiol.