Sticking probabilities in adsorption from liquid solutions: Alkylthiols ongold

The sticking probability, defined as the rate of adsorption per molecular c ollision with the surface, directly expresses the difficulty encountered by a molecule in scaling the barrier to adsorption. Its prior use has been re stricted to adsorption of gases. A method extending this concept to adsorpt ion from liquid solutions is applied to transient measurements of alkylthio l adsorption onto Sold from ethanol solutions. The initial sticking probabi lity increases from similar to 10(-8) to similar to 10(-6) with alkyl chain length, implying a stabilization of the transition state by similar to 0.6 5 kJ/mol per CH2. Since their sticking probabilities in the gas phase are s imilar to 1.0, the solvent increases the activation free energy by similar to 40 kJ/mol.