We present a route for the functionalization of gold nanoparticles (AuNP) based on phase transfer functionalization in order to optimize the stability and the potential for self-assembly. Depending on the desired size, different ligand exchanges have to be employed: The maximum AuNP size that can be stabilized without concentration loss is 46 nm for polystyrene-based ligands with 5 and 10 kDa. Small particles <12 nm are better stabilized by smaller ligands. We are able to demonstrate that well ordered close packed monolayers of 28 nm AuNP covering at least 400 mu m(2) are possible with a potential for much larger areas. Such monolayers are of great interest for various fundamental experiments in the context of plasmonics and SERS and for sensor applications.