Synthesis, characterization, and relative stabilities of self-assembled monolayers on gold generated from bidentate n-alkyl xanthic acids.

Abstract

A series of self-assembled monolayers (SAMs) on gold were generated by the adsorption of n-alkyl xanthic acids (NAXAs) having the general formula CH3(CH2)nOCS2H (n = 12-15). The structural features of these SAMs were characterized by optical ellipsometry, contact angle goniometry, polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), and X-ray photoelectron spectroscopy (XPS). This series of xanthate SAMs were compared to SAMs generated from the corresponding n-alkanethiols and aliphatic dithiocarboxylic acids (ADTCAs). The collected data indicate that the NAXAs generate densely packed and well-ordered monolayers. The contact angles of hexadecane on the xanthate monolayers exhibited a large "odd-even" effect similar to that produced by the ADTCA SAMs. The relative stability of these bidentate xanthate SAMs was evaluated by monitoring the changes in ellipsometric thicknesses and wettability as a function of time under various conditions. The results demonstrate that SAMs formed from NAXAs are much less stable than analogous n-alkanethiolate and ADTCA SAMs.

• Authors: H Justin Moore, Ramon Colorado Jr, Han Ju Lee, Andrew C Jamison, T Randall Lee
• Journal: Langmuir : the ACS journal of surfaces and colloids (Langmuir) Vol. 29 Issue 34 Pg. 10674-83 (Aug 27 2013) ISSN: 1520-5827 [Electronic] United States
• PMID: 23875580 (Publication Type: Journal Article)