Paper NS+NC-TuA9
Temperature Effects on the Formation of Thioether Self-Assembled Monolayers on Au(111)

Tuesday, October 21, 2008, 4:20 pm, Room 311

Self-assembled monolayers (SAMs) offer many potential advantages to science and industry in the form of parallel nanostructure fabrication, lubricants for MEMS, corrosion protection and sensing. As such, being able to synthesize stable SAMs from different starting materials in a larger number of configurations will enable greater control over the systems for each of these applications. Due to the stability of metal-sulfur bonds, thiol (H-S-R) SAM formation has been studied extensively. In the case of thioethers (R-S-R), it has recently been shown that at temperatures up to 298 K in both ambient¹ and ultra-high vacuum² conditions, that the molecules still self-assemble on metal surfaces and exhibit long-range ordering, despite a weaker binding to the surface than thiols. Due to the presence of the additional hydrocarbon tail, thioethers form SAMs with a dramatically different geometry²; additionally, the weaker bonding reduces the stability of these systems relative to that of thiol SAMs. In this study it was found that in the Au(111)-(C₁₈H₃₇)₂S system, stability may be increased by elevation of the sample temperature to moderate values (400 K) during the monolayer formation. Furthermore, the gold surface reconstruction associated with increased adsorbate-substrate bond strength changes the ordering of thioether SAMs. This strong temperature dependence on the stablility of the thioether SAM’s structure suggests that temperature may be an easily controllable parameter in the design and tuning of self-assembled monolayers for specific applications.

¹ Jaegeun Noh, Tomohide Murase, Ken Nakajima, Haiwon Lee, and Masahiko Hara, Journal of Physical Chemistry B, 2000, 104, 7411 -7416;
² Stephen C. Jensen, A. E. Baber, H. L. Tierney and E. Charles H. Sykes ACS Nano, 2007, 1, 1, 22-29.