Self-assembled structures of alkanethiols on gold-coated cantilever tips and substrates for atomic force microscopy : molecular organisation and conditions for reproducible deposition

Measurements of surface-liquid interactions (contact-angle goniometry) and tip-surface adhesion forces (atomic force microscopy) combined with infrared spectroscopic studies have been used to investigate surface-preparation and solution-deposition conditions for the reproducible formation of self-assembled molecular structures on gold-coated tips and substrates for atomic force microscopy. Preliminary data show that surface-saturated self-assembled monolayers form reproducibly on prolonged (> 20 h) exposure of gold-coated glass substrates to ethanolic solutions of omega-functionalised alkanethiols in the concentration range 80-160 mmol dm(-3). The data also show that exposure for 16 h to alkanethiol concentrations in the range 160-240 mmol dm(-3) promote bilayer formation whereas concentrations of 240-320 mmol dm(-3) result in the deposition of multilayers, the average orientation of which is parallel to that of the first molecular layer; the use of parent 1-undecanethiol solutions at concentrations of 1-80 mmol dm(-3) results in incomplete monolayer coverage. (C) 2009 Elsevier B.V. All rights reserved