Self-Assembled Monolayers on Gold Generated from Alkanethiols with the Structure RNHCOCH2SH

Suk Wah Tarn-Chang, Hans A. Biebuyck, George M. Whitesides, Nooli Jeon, Ralph G Nuzzo

Research output: Contribution to journalArticle

Abstract

This paper outlines a general synthetic route to alkanethiols useful in forming self-assembled monolayers (SAMs) starting from amines, RNH2, and converting them, via α-chloroamides RNHCOCH2Cl, to thiols having the structure RNHCOCH2SH. The wettabilities (estimated from contact angles of water and hexadecane) and the thicknesses (as measured by ellipsometry and X-ray photoelectron spectroscopy, XPS) of SAMs having an amide moiety β to Au/thiolate were similar to those of SAMs of alkanethiols with similar backbone length on gold. The internal amide group present in SAMs prepared from CF3CH2-NHCOCH2SH increases their stability against desorption or exchange with hexadecanethiol in ethanol relative to SAMs from CF3(CH2)3SH. The desorption of SAMs from CF3(CH2)3SH was first order in the alkanethiolate and had a half-life of ∼2 h at 10-9 Torr; SAMs from CF3CH2NHCOCH2SH, by contrast, showed no loss after 48 h at ∼ 10-9 Torr. The rate of exchange of a SAM from CF3CH2NHCOCH2SH with hexadecanethiol in ethanol was 102-103 times slower than the SAMs from CH3(CH2)3SH or from CF3(CH2)3-SH. The susceptibility of a SAM prepared from a short-chain alkanethiol (e.g., CH3(CH2)3SH or CF3-CH2NHCOCH2SH) to damage by UV was 10 times greater than that observed for a SAM prepared from hexadecanethiol (as measured by XPS). UV damage of SAMs derived from CF3CH2NHCOCH2SH, followed by protection of the UV-damaged SAM by replacement with hexadecanethiol and etching, gave gold patterns with minimum feature sizes of 5 μm; these sizes were limited by the lithographic procedure used and do not reflect the true edge resolution of this photolithographic method.

Original languageEnglish (US)
Pages (from-to)4371-4382
Number of pages12
JournalLangmuir
Volume11
Issue number11
DOIs
StatePublished - Nov 1 1995

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ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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