Regulation of Interparticle Forces Reveals Controlled Aggregation in Charged Nanoparticles

Abstract

The ability to control interparticle forces not only improves the existing nanoparticle (NP) functionalities but paves the way for newer properties as well. A proof of concept in this direction is presented here, wherein the regulation of interparticle forces—revealing controlled aggregation—has been successfully translated into the trapping and scavenging of toxic ions. A perfect balance between the attractive and repulsive forces is achieved by tuning the [+] and [−] ligands on the surface of heterogeneously charged metal NPs. The NP–ion aggregates are stable for ∼2 days, with a visible color change (Δλmax = 12–15 nm), which makes them available for scavenging from the site of action. The incorporation of “potent” forces like repulsions, rather than a mere dilution of attractive forces, is necessary to ensure the formation of controlled aggregates. The net surface charge of NPs is conveniently modified to trap ions irrespective of their charge and binding strength. More importantly, the regulation of interparticle forces imparts a new function of selectivity toward trapping of toxic ions in a carboxylate functionalized NP system. Thus, the present work introduces a conceptually unprecedented approach to impart long-term stability (∼2 days) to NP–ion aggregates by controlling the interparticle forces.