Self-Assembled Monolayers of Mercaptoacetic Acid on Ag Powder: Characterization by FT-IR Diffuse Reflection Spectroscopy

The self-assembled monolayers (SAMs) of organic molecules on metal surfaces have been studied extensively in recent years.1-4 Both carboxylic acids and thiols are known to be adsorbed on Ag surfaces forming well packed monolayers;5,6 however, the competitive adsorption of thiols and carboxylic acids on Ag has not been reported much.7 To find out which group would be adsorbed preferentially on Ag surface when both thiol and carboxylic acid groups were present in the same molecule, we chose a bifunctional molecule, mercaptoacetic acid as the probe because it is the simplest molecule that contains both groups. Since the molecule has only one methylene unit, it would not have any interchain stabilization of the monolayer. The interaction between a head group and a metal substrate would be the main factor that controls the formation of the monolayer. W