Bridging Interactions and Selective Nanoparticle Aggregation Mediated by Monovalent Cations

Abstract

Selective aggregation and precipitation of like charged nanopartcles (NPs) covered with carboxylate ligands can be induced by different monovalent cations. The ordering of critical concentrations required for NP precipitation is Cs(+) >> K(+) > Li(+) > Na(+) > Rb(+) and does not correlate with the size of hydrated cations M(+), nor can it be predicted by the Hofmeister series. On the other hand, different anions have no effect on the precipitation trends. These observations are rationalized by a theoretical model combining the elements of the DLVO theory with molecular level calculations. The key component of the model is the cation specific binding of various metal cations to the carboxylate ligands.