Phase separation of alkanethiol self-assembled monolayers during the replacement of adsorbed thiolates on Au(111) with thiols in solution

Takashi Kakiuchi, Kimiharu Sato, Minehiko Iida, Daisuke Hobara, Shin Ichiro Imabayashi, Katsumi Niki

研究成果: Article査読

92 被引用数 (Scopus)

抄録

Replacement of self-assembled monolayers (SAM) of hexadecanethiol (HDT) on the Au(111) surface with 12-mercaptododecanoic acid (MDDA) in ethanol solution has been studied using voltammetry of the reductive desorption and scanning tunneling microscopy (STM). The exchange of adsorbed HDT molecules with MDDA dissolved in ethanol proceeds domainwise, that is, not in a random fashion. Two well-separated peaks, corresponding to the desorption of MDDA-rich domains and HDT-rich domains, appear in a voltammogram over the replacement process. The peak potential associated with the desorption of HDT-rich domains remains unchanged in the course of the replacement, indicating that the solubility of MDDA in HDT-rich domains is very small. STM imaging of the substrate shows that domains whose sizes are greater than 15 nm2 are predominant and occupy 85% of the area of HDT-rich domains. The entire exchange process is pseudo-first-order with the rate constant being 9.1 × 10-3 h-1 in 1 mmol dm-3 MDDA in ethanol at 31°C. The reverse process, i.e., the replacement of adsorbed MDDA with dissolved HDT in ethanol, is much slower, suggesting the stabilization of MDDA monolayers by lateral hydrogen bonding. A significant shift in the peak potential of MMDA-rich domains during the replacement indicates the considerable dissolution of HDT in MDDA domains.

本文言語English
ページ(範囲)7238-7244
ページ数7
ジャーナルLangmuir
16
18
DOI
出版ステータスPublished - 2000 9 5
外部発表はい

ASJC Scopus subject areas

  • 材料科学(全般)
  • 凝縮系物理学
  • 表面および界面
  • 分光学
  • 電気化学

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