Self-organization of nano-CdS particles in polystyrene can be observed by encapsulating the particles with ndodecyl mercaptan owing to a strong electron transfer interaction between the modified CdS nanoparticles and aliphatic carbons in polystyrene. Consequently, ultraviolet/visible absorption edge of the treated nanoCdS/polystyrene composites is further blueshifted in addition to the shift caused by the quantum size effect, and the fluorescence emission peak of the composite becomes redshifted and narrow.