ADSORPTION OF MANNITOL AND SORBITOL ON GOLD(111)

The adsorption of mannitol and sorbitol on Au(111) has been followed b y differential capacity measurements. Results obtained for the adsorpt ion of these polyalcohols in dilute solutions of HClO4 and NaClO4 show ed that the adsorption process could be described by a Frumkin isother m, the parameters of which were determined and discussed. The values o f the standard Gibbs energy of adsorption suggest physical adsorption of mannitol and sorbitol, without the existence of specific interactio ns of the adsorbed molecules with gold. The values of the interaction parameters are negative in both electrolytes, indicating a net attract ive interaction in the adsorbed layer. There are noticeable difference s between the values of the standard Gibbs energy of adsorption and of the interaction parameter for the two polyols, which have been interp reted in terms of the conformational properties of the two isomers in the adsorbed layer.