Nanoparticle self-assembly onto polyelectrolyte-coated surfaces is exploited to produce dense nanoparticulate thin films on both planar and spherical substrates (the Figure shows a coated polystyrene sphere). A new type of ligand-stabilized gold nanoparticle is used to produce these films in a single step. An attractive feature of these nanoparticles is that the ligand can be removed by simply washing with water.