a process for producing polymer - supported metal nanoparticles involves confinement of metal nanoparticles in polymeric nanotubes or nanosheets in an aqueous environment using hydrophobic reactants . metal nanoparticles supported in the polymeric nanotubes or nanosheets are substantially monodisperse and have an average particle size of 4 nm or less . the polymer - supported metal nanoparticles are useful in fuel cells , sensors , bioanalysis , biological labeling or semi - conductors , especially as catalysts .