Spectroscopic evidence for the origin of odd–even effects in self-assembled monolayers and effects of substrate roughness. Issue 10 (28th February 2017)

• Record Type: Journal Article
• Authors: Chen, Jiahao; Liu, Jian; Tevis, Ian D.; Andino, Richard S.; Miller, Christina M.; Ziegler, Lawrence D.; Chen, Xin; Thuo, Martin M.
• Is Part Of: Physical chemistry chemical physics. Volume 19:Issue 10(2017)
• Page Start: 6989
• Page End: 6995
• Publication Date: 2017-02-28
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c6cp07580k
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : This paper reports the effects of substrate roughness on the odd–even effect in n -alkanethiolate self-assembled monolayers (SAMs) probed by vibrational sum frequency generation (SFG) spectroscopy. Abstract : This paper reports the effects of substrate roughness on the odd–even effect in n -alkanethiolate self-assembled monolayers (SAMs) probed by vibrational sum frequency generation (SFG) spectroscopy. By fabricating SAMs on surfaces across the so-called odd–even limit, we demonstrate that differentiation of the vibrational frequencies of CH3 from SAMs derived from alkyl thiols with either odd (SAM O ) or even (SAM E ) numbers of carbons depends on the roughness of the substrate on which they are formed. Odd–even oscillation in SFG susceptibility amplitudes was observed for spectra derived from SAM E and SAM O fabricated on flat surfaces (RMS roughness = 0.4 nm) but not on rougher surfaces (RMS roughness = 2.38 nm). In addition, we discovered that local chemical environments for the terminal CH3 group have a chain-length dependence. There seems to be a transition at around C13, beyond which SAMs become "solid-like".