| AVS 58th Annual International Symposium and Exhibition | |
| Surface Science Division | Tuesday Sessions |
| Session SS2-TuM |
| Session: | Self Assembled Monolayers and Networks |
| Presenter: | Stephanie Allen, The University of Nottingham, UK |
| Authors: | V.V. Korolkov, The University of Nottingham, UK S.A. Allen, The University of Nottingham, UK C.J. Roberts, The University of Nottingham, UK S.J.B. Tendler, The University of Nottingham, UK |
| Correspondent: | Click to Email |
Study of organic thiols adsorption on noble metals continues to be a subject of many research papers within the last three decades. Such steady interest arises mainly from the possibility to design metal surfaces with predefined chemical and physical properties that makes them suitable for a whole range of theoretical and applied studies.
Here we propose and investigate an idea that thiols with rigid or spherical hydrocarbon moieties should self-assemble on Au-surface much quicker than those with long-chain moieties. To support this idea we have investigated adsorption dynamics and monolayer structure for 1-adamantanethiol1 (AdSH) and [1,1’:4’,1’’-terphenyl]-4-thiol (TPT) molecules self-assembled on Au(111)-surface at 393K. We have demonstrated that both thiols form defect free and uniform SAMs almost instantly at elevated temperature. It takes ~1sec for AdSH to self-assemble on gold. In case of TPT ~90% of the monolayer forms within the first ~10 seconds of adsorption, and then it takes ~60 seconds to develop into a well-ordered structure. Both SAMs on Au were characterized with ambient STM up to a single-molecule level, X-ray photoelectron spectroscopy and spectroscopic ellipsometry. We were able to obtain near atomic resolved STM images for AdSH SAM on Au. They clearly showed that all AdSH molecules adsorbed in the same conformation with the molecular tilt and the twist angles being 1140 and 00 correspondingly. We have also demonstrated that most AdSH molecules are arranged in a head-to-tail orientation, with some molecules having a head-to-head orientation without forming a disulfide bond.
Molecular resolved STM images of TPT SAM/Au clearly demonstrated that within first seconds of adsorption the Au-surface is equally covered with two different phases (α- and β-). β-phase dominates on the Au-surface from ~10 sec of exposure and onwards. A closer inspection of the β-phase on a single molecule level allowed us to propose an upright conformation for TPT molecule on Au with the tilt angle of 0±5o. We also estimated the tilt angle for the α-phase to be within 10-20o. For both systems STM and XPS analysis suggest a high chemical and structural quality of the monolayers.
Overall we have proposed a simple and straightforward protocol for ultrafast fabrication of AdSH and TPT SAMs on Au-surface, which we believe can be readily extended for other similar molecular systems.
1Korolkov et al. J. Phys. Chem. C, Vol. 114, No. 45, 2010