The interplay between nanoscale dipoles and ion screening drives the self-regulation of charged aqueous surfaces

We show that nanoparticle monolayers self-regulate their 2D organization to reach a common electrostatic steady state, characterized by a constant interfacial surface potential (ΔV ≈ 150 mV) and a fixed single-particle repulsive energy (U ≈ 2 × 10^-23 J), independently of ionic strength and ion identity. Variations in electrolyte composition instead control the nanoparticle surface excess, which adjusts to compensate changes in the interfacial dipolar strength. Further, both the interf