Techniques for controlling the size and/or distribution of a catalyst nanoparticles on a substrate are provided. The catalyst nanoparticles comprise any species that can be used for growing a nanostructure, such as a nanotube, on the substrate surface. Polymers are used as a carrier of a catalyst payload, and such polymers self-assemble on a substrate thereby controlling the size and/or distribution of resulting catalyst nanoparticles. Amphiphilic block copolymers are known self-assembly systems, in which chemically-distinct blocks microphase-separate into a nanoscale morphology, such as cylindrical or spherical, depending on the polymer chemistry and molecular weight. Such block copolymers are used as a carrier of a catalyst payload, and their self-assembly into a nanoscale morphology controls size and/or distribution of resulting catalyst nanoparticles onto a substrate.