Octanethiol Self-assembled Monolayers Research Articles

A SEXAFS investigation of self-assembled monolayers on silver

Sulfur K-edge surface extended X-ray absorption fine structure (SEXAFS) measurements have been carried out on self-assembled monolayers (SAMs) of alkylthiols adsorbed onto evaporated silver surfaces. By using the Auger yield method, it was found that adequate data could be obtained to allow a preliminary determination of the adsorption site of the S head groups on the predominantly (111) Ag surface. For SAMs of butanethiol and octanethiol, the three-fold hollow site was identified as the most probable position for the S atom. In addition to studies of as-prepared monolayers, the evolution of the NEXAFS spectra of octanethiol SAMs on silver which were progressively photo-oxidised was also investigated. The results supported the model derived for this process from other techniques.

Self-assembled monolayer gold electrode for surfactant analysis

A gold electrode coated with a self-assembled monolayer of octane-thiol (SAM/Au) has been used as an amperometric detector for the determination of surfactants. This detector operated in the presence of a high percentage of organic solvent and was adapted to an HPLC System. At the SAM/Au, the electrochemical response of an electroactive tracer (potassium ferricyanide) was completely inhibited, but, in the presence of a cationic surfactant, the electrochemical reduction was progressively restored. In flow injection analysis, using the SAM/Au in an amperometric flow-through detector polarised at 0.0 V vs Ag/AgCl, a linear response (i=f{[surfactant]}) was observed for cationic surfactants e.g. cetylpyridinium chloride in the concentration range 2 × 10−6–1 × 10−3 M. The electrochemical data along with the determination of the ion pair stoichiometry between the redox tracer and the surfactant suggest an electrochemical response related to ion pair formation and governed by electron transfer by tunneling effect.