Amide and ester surface attachment reactions for alkanethiol monolayers at gold surfaces as studied by polarization modulation Fourier transform infrared spectroscopy

Abstract

The modification of alkanethlol monolayers via amide and ester formation reactions is demonstrated as a methodology for attaching monolayer and submonolayer coverages of specific chemical species onto metal electrodes. A mono-layer of 1 I-mercaptoundecanolc acid (HSC,,H,,COOH) is used as a surface bifunctional linking agent on pdycrystailne goki swfaces. The reaction of these adsorbed molecules with gaseous thlonyl chloride converts the carboxylic acid group to an ackl chbrMe which can then be reacted further with an amine or alcohol to form an amide or ester linkage. The attachment of alkyl, aromatic, and electrochemically active species to the surface Is reported to demonstrate the versa-tility of this surface derivatlzation chemistry. Poiarlzatlon modulation Fourier transform infrared (PM-FTIR) spectros-copy Is employed as the primary method for monitoring the chemkai structure of the adsorbed monolayers, and additlonal X-ray photoelectron spectroscopy (XPS) and electrochemical measurements are used to verity the elemental composition, oxidation state, and surface coverage of the adsorbed mole-cules.