Influence of the nature of the alkanethiol terminal group on the electrochemical stability and blocking ability of self-assembled nanofilms on Au electrode

Abstract

We studied the effect of the nature of the terminal group of thiols with the same chain length HS (CH2)8 – R (R: -CH3, -CH2OH, -NH2) on the electrodesorption behaviour of well-formed SAMs (the self-assembled monolayers), their stability and blocking ability using voltammetry and chronoamperometry. The nature of the terminal functional group determines the surface properties of SAM and provides the basis for subsequent interactions (for example, with peptides, proteins, DNA) in order to create sensors and bioagents. For the studied thiols, the hydrophilicity of the end groups increases in the series -CH3<< -NH2 ≤ -CH2OH; they also differ in polarity and the possibility of protonation of the amino group. For thiols with -CH3 and -CH2OH groups, an increase in the hydrophilicity of the terminal group leads to the formation of less stable and less ordered films. The replacement of carbon by nitrogen with approximately the same hydrophilicity of the groups (-CH2OH and -NH2) leads to the formation of a more stable film consisting of molecules in the same energy state, butwith poorer insulatingproperties.