The interaction of charged nanoparticles at interfaces

We study charged nanoparticles adsorbed onto surfactant bilayers using small-angle scattering of synchrotron radiation. The in-plane interaction of the particles is well described by a DLVO component (measured independently in solution) and a repulsive dipolar interaction due to the presence of the interface, with an amplitude close to the theoretical prediction. We prove that charged nanoparticles at soft interfaces are well described by the classical model of Poisson-Boltzmann and van der Waals terms; as a corollary, they do not experience the like-charge attraction reported in the literature for some systems of micron-sized spheres at interfaces.