In Situ Adsorption Investigation of Hexadecyltrimethylammonium Chloride on Self-assembled Monolayers by Surface Plasmon Resonance and Surface Enhanced Infrared Absorption Spectroscopy

摘要

In situ adsorption kinetics of hexadecyltrimethylammonium chloride (C_(16)TAC) on 1-dodecanethiol and 3-mercapto-1-propanol self-assembled monolayers (SAM) was investigated by surface plasmon resonance and surface enhanced infrared absorption spectroscopy. Adsorption from a dilute solution on 1-dodecanethiol SAM proceeded slow after initial fast increase. Adsorption from solutions at medium concentrations converged to a constant value through a maximum at the initial stage. Adsorption at a high concentration above critical micelle concentration became constant without through a maximum. These behaviors indicate the existence of two types of adsorption; one is faster bulk adsorption (physisorption), where excess accumulation sometimes occurs, and another is slower adsorption (chemisorption) being accompanied with rearrangement. Adsorption on 3-mercapto-l-propanol SAM was always slow over the wide C_(16)TAC concentration regions. This implies that the adsorption mechanism of C_(16)TAC depends on chemical structure of thiol.