Dynamics of adsorption and phase formation of p-nitrobenzoic acid at Au(111) surface in solution:: A combined surface-enhanced infrared and STM study

The adsorption of p-nitrobenzoic acid on Au(111) results in p-nitrobenzoate species bound to the surface through the carboxylate oxygen atoms with a bridging coordination. Potential step time-resolved infrared measurements revealed that the molecule is adsorbed randomly with a near flat orientation within a few milliseconds and then gradually reorients to a vertical orientation by forming ordered domains. The orientational phase transition is kinetically controlled and its rate increases as the applied potential increases. The ordered domains have a (3 x 5) stripe-like structure extending along the < 110 > directions of the underlying surface. We propose a model with two molecules per unit cell (surface concentration of 3 x 10(-10) mol cm(-2)) in which the carboxylate oxygen atoms locate in bridge sites.