ALKYL CHAIN DEPENDENT ALKANETHIOL SELF-ASSEMBLED ADSORPTION DYNAMICS

Abstract

The adsorption dynamics for the formation of self-assembled monolayer of alkanethiols has been investigated by electrochemical method, water contact angle and scanning tunneling microscopy. Thiols with three alkyl chains, including short chain hexanethiol, middle chain dodecanethiol, and long chain octadecanethiol are examined. The experimental results indicate that the adsorption of thiols onto Au substrate consists of two process, a rapid adsorption and a slow reorganization. The rapid adsorption process is demonstrated to follow the diffusion-controlled Langmuir model. The apparent adsorption rate constant is obtained from the slopes, which is related to the concentration. According to our results, the difference of activation energy per methylene unit is 89 J/mol.