Adsorption characteristics of p-xylene-α,α′-dithol on gold and silver surfaces:: Surface-enhanced Raman scattering and ellipsometry study

被引:96
作者
Joo, SW
Han, SW
Kim, K [1 ]
机构
[1] Seoul Natl Univ, Dept Chem, Seoul 151742, South Korea
[2] Seoul Natl Univ, Ctr Mol Catalysis, Seoul 151742, South Korea
来源
JOURNAL OF PHYSICAL CHEMISTRY B | 1999年 / 103卷 / 49期
关键词
D O I
10.1021/jp992230+
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The adsorption behavior of p-xylene-alpha, alpha'-dithiol (p-XDT) on colloidal gold and silver surfaces has been investigated by means of surface-enhanced Raman scattering (SERS). p-XDT chemisorbed dissociatively on both the gold and silver surfaces but as mono- and dithiolate, respectively. Regardless of the bulk concentration of p-XDT, 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, p-XDT1-, 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 p-XDT was close to that required for a full-monolayer coverage limit, a band assignable to the S-S stretching vibration appeared at similar to 509 cm(-1) in the gold sol SER spectra. A separate ellipsometry measurement performed with vacuum-evaporated gold substrates revealed that up to trilayers could be assembled on gold in 1 mM n-hexane solution of p-XDT while only a monolayer formed in either methanol or ethanol solution. Although the exact causes were uncertain, such a difference in behavior seemed to have nothing to do with the oxygen species present in ethanol or methanol solution.
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页码:10831 / 10837
页数:7
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