Long-term variation of capacitance of self-assembled alkanethiol films at polycrystalline Au electrode

Capacitance of a self-assembled hexadecanethiol monolayer (SAM) film increased in aqueous solutions and decreased in ethanol solutions with the time on a few hours scale. The increase and the decrease were demonstrated to be ascribed, respectively, to desorption and adsorption of hexadecanethiol. They obeyed approximately the firstorder rate law for the amount of the adsorbed thiol. The SAM is in equilibrium with the 5 mu M hexadecanethiol ethanol solution. The SAM becomes stable when it is immersed in deionized water for a long time or heated in the deionized water.