Ion-induced reversibility in the aggregation of hydrophobic colloids

Experimental evidence of a fully reversible aggregation process due to ionic specificity is presented for the first time. The results indicate the existence of repulsive structural forces between particles coming from the specific accumulation of poorly hydrated ions around hydrophobic surfaces. This result emphasizes the key role that ion-water structure near interfaces plays in Hofmeister effects, as recently suggested by molecular dynamics simulations.