Rarely polymer-grafted nanoparticles are shown to be able to self-assemble into stable nanostructures of different morphologies. The driving force for the assembly is a competition between a short-range attraction of the nanoparticles and long-range repulsion of the grafted chains. Effects of the solvent quality for the nanoparticles, grafting density and the length of the chains are studied. We have shown that non-spherical vesicles resembling a monocrystal can be stable in dilute solution. In them, the wall represents a sheet of hexagonally packed nanoparticles which sharply bends to become closed forming facets and edges. Improving solvent quality leads to a cascade of transitions: vesicles - tubes - perforated sheets - threads. Adsorption of the nanoparticles on a solvophobic surface can result in their 2D self-assembly. We have predicted ordering of the nanoparticles into a hexagonal network similar to the structure of graphene sheets. Schematic diagrams of states in 2D and 3D are constructed. (C) 2018 Elsevier Ltd. All rights reserved.