Epitaxial transfer through end-group coordination modulates the odd-even effect in an alkanethiol monolayer assembly

Nanoscale. 2014 Apr 7;6(7):3496-502. doi: 10.1039/c3nr05671f.

Abstract

Short spacer length and high end-group coordination lead to the top network acting as a template for the buried sulfur-gold interface of n-alkanethiols (SH-(CH2)n-OH or SH-(CH2)n-CH3) on gold {111}. Annealing and templating both drive toward a higher sampling of the spatially favorable bridge adsorption sites. The hydrogen-bonded network increases in strength by increasing the number of hydrogens participating per oxygen, from 1.75 to 1.98 for n = 14-30. Higher n leads to better packing (five times for hydroxyl-terminated and seven times for methyl-terminated for n = 14-30) and stability of monolayers, while lower n results in better epitaxial transfer (transfer coefficient ratio = 13.5 for {SH-(CH2)14-OH}/{SH-(CH2)30-CH3}) and actuation. Odd values of n for the hydroxyl-terminated n-alkanethiols lead to lattice spacing of an average of 0.04 ± 0.01 Å higher than even values. There is a structural transition in properties around spacer length n = 24-27. Characterization of monolayer assembly through correlation between adatom and network layers provides recursive design principles for actuation and sensing applications.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.