title: 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.affiliation: Department of Chemistry and Environmental Sciences, University of Texas at Brownsville, Brownsville, Texas 78520, United States. henry.moore@utb.edu
authors.forename: H Justin
authors.initials: HJ
authors.lastname: Moore
authors.forename: Ramon
authors.initials: R
authors.lastname: Colorado
authors.forename: Han Ju
authors.initials: HJ
authors.lastname: Lee
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Jamison
authors.forename: T Randall
authors.initials: TR
authors.lastname: Lee