US nanoparticles were prepared using polar functional polystyrene block copolymers. By modifying the polystyrene block copolymer with polar functional groups, the interaction between a polymer and nanoparticles could be improved, resulting in a higher fluorescence quantum yield of US nanoparticles. UV-Vis spectra and TEM images of CdS/polar functionalized block copolymer nanocomposites indicated the formation of nanoparticles with an average size of similar to5 nm.